Rydberg sensing-based navigation receiver systems

Abstract

In a general aspect, a Rydberg sensing based navigation receiver (RSNR) system is presented. In some implementations, a vapor cell sensor system senses navigation signals from satellites of two or more distinct satellite constellations. Sensor data are generated by the vapor cell sensor system based on the navigation signals, and navigation data are generated by processing the sensor data. The navigation data may include position information, timing information, and other information.

Description

Rydberg Sensing-Based Navigation Receiver SystemsCROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority to U.S. Provisional Application No. 63 / 748,609, filed January 23, 2025, entitled " Rydberg Sensing-Based Navigation Receiver Systems." The above-referenced priority document is incorporated herein by reference.TECHNICAL FIELD

[0002] The following description relates to Rydberg sensing-based navigation receiver (RSNR) systems.BACKGROUND

[0003] Navigation systems use satellite-based signals to determine a receiver’s position, velocity, or orientation. For example, navigation systems have been developed to use satellite-based signals from global navigation satellite systems (GNSS) such as GPS, Galileo, GLONASS, or BeiDou. By analyzing timing, phase, or signal strength parameters of these signals, a receiver can calculate its location relative to known references. These systems are widely used in personal, transportation, autonomous, and defense applications.BRIEF DESCRIPTION OF THE DRAWINGS

[0004] FIG. 1 is a schematic diagram showing multiple types of satellite orbits.

[0005] FIG. 2 is a block diagram showing aspects of an example Rydberg sensing-based navigation receiver (RSNR) system.

[0006] FIG. 3 is a block diagram showing aspects of an example vapor cell sensor system.

[0007] FIGS.4A-4C are schematic diagrams of example electron energy level structures for two-photon and three-photon measurements using the example RSNR system in FIG. 2 based on Cs atoms in a vapor state.

[0008] FIG. 5 is a flow chart showing aspects of an example process to operate the example RSNR system in FIG. 2.

[0009] FIG. 6 is a flow chart showing aspects of an example process to operate the example RSNR system in FIG. 2.DETAILED DESCRIPTION

[0010] In some aspects, Rydberg sensing-based navigation receiver (RSNR) systems are configured to sense navigation signals and to determine position and timing information. An RSNR system may include a vapor cell sensor system having one or more Rydberg atom-based vapor cell sensors and a laser system configured to interrogate the vapor cell sensors. The RSNR system may be implemented as the RSNR system 200 of FIG. 2 or in other configurations. In some instances, an RSNR system is configured to detect and decode navigation signals at multiple frequencies over a broad range of frequencies, for example spanning tens of gigahertz, either simultaneously or sequentially. An RSNR system may receive spread-spectrum encoded navigation signals from satellites belonging to multiple satellite constellations. For example, an RSNR system may receive navigation signals from satellite constellations in low Earth orbit (LEO), medium Earth orbit (MEO), geosynchronous Earth orbit (GEO), or other orbits.

[0011] In some implementations, a vapor cell sensor is omnidirectional and selfcalibrating, with a wide carrier bandwidth that enables detection of ultra-broadband signals, for example over a range from about 0.1 GHz to about 100 GHz, without reconfiguration of the vapor cell sensor. Such bandwidth can allow the RSNR system to use signals of opportunity, including signals outside designated GNSS bands, to support navigation. Multiple vapor cell sensors can additionally be engineered for directionality and / or amplification, for example by using photonic crystal receivers. Multiple vapor cell sensors can be arranged as an array to perform angle-of-arrival (AoA) or other measurements. The vapor cell sensors may be disposed at different locations on a platform, such as on wingtips, a nose, and a tail of an aircraft, to enable spatial diversity and improved angular resolution.

[0012] In some instances, the RSNR system is configured to detect multiple navigation signals of different frequencies on multiple channels at the same time. The vapor cell sensor system may operate across several bands, for example in S, X, Ku, and Ka bands, using a common optical front-end rather than separate RF antennas for each band. In some implementations, a photonic circuit routes coupling laser signals at one or more wavelengths to different vapor cell sensors and permits agile switching of the sensing frequency, enabling rapid tuning between navigation signals or multichannel operation in which multiple navigation signals are read out simultaneously. In some cases, an RSNR system can decode the navigation signals and compute the position and timing information of the platform based on the decoded navigation data.

[0013] In some examples, RSNR systems use matched filtering or other correlation techniques to read out and decode the navigation signals from the optical output of the vapor cell sensors. The navigation signals can be code-division multiple-access-type (CDMA-type) signals in which a fast chip channel is encoded with a phase relationship, for example approximately 90 degrees out of phase with a data channel. The quantum readout can be implemented using one or more techniques, including transient phase readout, radiofrequency (RF) heterodyne readout, RF and optical heterodyne readout, or optical phase readout.

[0014] The systems and techniques described here can provide several technical advantages and improvements for position, navigation, and timing (PNT). For example, RSNR systems may enable ultra-broadband detection of multiple navigation signals from diverse satellite constellations and maintain operation in challenging environments, including GNSS-denied areas. In some instances, RSNR systems are inherently resistant to jamming and spoofing because generating convincing spoofing and jamming signals across multiple widely separated frequency bands and constellations is technically complex and costly. RSNR systems may use redundancy across constellations, frequencies, and angles-of-arrival to detect anomalous signals, increase navigation accuracy, and reduce reliance on high-accuracy inertial sensors such as precision accelerometers, gyroscopes, and clocks.

[0015] In addition, RSNR systems may reduce or eliminate the need for active RF frontend electronics such as low-noise amplifiers and narrowband filters, thereby mitigating high filter losses, out-of-band interference, transmitter-induced jamming of reception, and crosstalk between antennas and GNSS receivers. The use of optically read out Rydberg vapor cell sensors can provide electromagnetic transparency and low probability of interception while remaining compatible with other RF and electronic systems on the platform. In some implementations, RSNR systems can be realized with low size, weight, power, and cost (SWaP-C), for example occupying a compact volume, operating at power levels suitable for medium or smaller unmanned platforms, and supporting deployment on unmanned and manned aerial, terrestrial, maritime, and space vehicles. In some cases, a combination of these and potentially other advantages and improvements may be obtained.

[0016] FIG. 1 is a schematic diagram showing aspects of a navigation environment 100. The navigation environment 100 includes multiple types of satellite orbits around Earth and an RSNR system 106. In the example shown, the RSNR system 106 communicates with multiple satellites in a low earth orbit (LEO) 102 and multiple satellites in a medium earth orbit (MEO) 104. LEO 102 includes an orbit with an altitude in a range of 180-2000 kilometers (km); and MEO 104 includes an orbit with a higher altitude than LEO 102 which is in a range of 2000-35786 km. In some instances, satellites in the LEO 102 (e.g., LEO satellites) are closer to Earth than those in MEO 104 (e.g., MEO satellites) and have highspeed and low-latency communication but smaller coverage area. MEO satellites positioned in MEO 104 have broader coverage with more latency than LEO satellites positioned in LEO 102. In some instances, there are other types of satellite orbits around Earth that can communicate with the RSNR system 106. In some implementations, a satellite constellation includes multiple satellites in a common orbit or set of orbits within a given orbital regime, and the satellites within the constellation cooperatively provide navigation signals that can be used by navigation receivers (e.g., by the RSNR system 106) on or near the Earth’s surface. In some implementations, the RSNR system 106 can communicate with different satellite constellations in distinct orbits 102, 104. In some instances, the RSNR system 106 may be implemented as the RSNR system 200 shown in FIG. 2 or in another manner.

[0017] In some implementations, the RSNR system 106 is configured to receive and process navigation signals from two or more distinct satellite constellations. Satellite constellations may be considered distinct, for example, when they operate in different orbital regimes (e.g., LEO vs. MEO), operate at different carrier frequencies, are operated by different entities, or employ different encoding schemes. For example, a first satellite constellation may comprise LEO satellites operating in the Ku-band, while a second distinct satellite constellation may comprise MEO satellites operating in the L-band (e.g., GPS constellation). In some implementations, the RSNR system 106 is used in conjunction with a satellite-based navigation infrastructure that includes a collection of satellites from distinct constellations configured to transmit navigation signals from space toward the RSNR system 106 on or near the surface of the Earth. The satellite-based navigation infrastructure can also include one or more ground stations configured to provide information such as atmospheric data, clock corrections, or orbit-related data to the satellites or to other elements of the infrastructure. In some instances, the RSNR system 106 includes a vapor cell sensor system (e.g., the vapor cell sensor system 300 shown in FIG. 3) that receives and senses navigation signals from at least a minimum number of satellites sufficient to solve for a navigation solution, and that determines position, velocity, and time based on the received navigation signals.

[0018] In some instances, the navigation signals from the satellite constellation in MEO 104 can be weak and may be subject to jamming and spoofing by an adversary. The navigation signals can also be affected by weather and interference which may cause the loss of navigation signals. In some instances, jamming or other interfering signals, which may reside outside the desired operational frequency band, can affect the desired in-band navigation signal. In some instances, operating frequencies of the RSNR system 106, where there is sufficient transmission through the atmosphere, can be selected from a broad frequency range, e.g., ~1-100 GHz. Jamming in this case becomes prohibitively expensive since the jammer(s) have to cover all operating frequencies in the broad frequency range. Spoofing would become practically impossible because all the received navigation signals from the combination of satellite constellations in LEO 102 and MEO 104 would have to be spoofed, requiring fooling the navigation receiver of the navigation system simultaneouslyat all the operating frequencies including spoofing the angle of arrival of the navigation signals. In some implementations, the RSNR system 106 is more robust to weather and interference because of the stronger signals from the satellite constellation in LEO 102 and the different ways that the atmosphere and geography affect the different frequencies. By diversifying the navigation signals from distinct satellite constellations, the RSNR system 106 can become more robust. In some instances, the RSNR system 106 based on multiple distinct satellite constellations can help to mitigate hand-off between satellites.

[0019] In some instances, the RSNR system 106 includes a vapor cell sensor system configured to sense navigation signals from satellites of two or more distinct satellite constellations. In some implementations, a vapor cell sensor system includes a probe laser system, one or more coupling laser systems, one or more Rydberg-atom-based vapor cell sensors, one or more optical detectors, a signal processor, and a control system. The probe and coupling laser systems are configured to generate optical frequency combs and / or narrow-linewidth optical signals that are stabilized to one or more frequency references and routed, via dispersive elements, switches, and frequency shifters, to the vapor cell sensors. Within each vapor cell sensor, a vapor (e.g., a vapor of Rydberg atoms or molecules in a sealed dielectric cell) is interrogated on one or more optical transitions to and from a Rydberg state, and electromagnetic radiation in a radiofrequency or microwave band couples an additional transition, thereby modifying the optical transmission through the vapor. The optical detectors convert the resulting electromagnetically induced transparency (EIT)- or Electromagnetically induced absorption (EIA)-based or related optical signals into electrical signals, which are digitized by the signal processor. The signal processor is configured to analyze the digitized data (e.g., via Fourier or other transforms, matched filtering, and spectral estimation) to determine properties of the incident electromagnetic radiation such as frequency, amplitude, phase, and, in some arrangements, AoA or other parameters.

[0020] In some examples, the vapor cell sensor system further includes photonic-integrated frequency comb generators, frequency separators, and frequency shifters that enable rapid, agile tuning across a wide sensing bandwidth while maintaining laser stabilization, as well as optical amplifiers to provide sufficient power per comb tooth orfrequency component. The vapor cell sensors can be arranged in an array and coupled to the laser systems and detectors via optical waveguides or free-space optics, allowing different vapor cell sensors to cover different frequency ranges, support off-resonant measurements, or form long baselines for angle-of-arrival determination. The vapor cell sensor may include a control system configured to coordinate operation of the lasers, comb generators, switches, and processing pipelines, implement feedback for laser locking and system calibration, configure scan ranges, dwell times, and sensing modes, and interface with user or external systems for diagnostics, reconfiguration, and timing and geolocation support. Together, these features enable wideband, self-calibrated, high-sensitivity electromagnetic sensing using Rydberg-atom-based vapor cells. In some instances, the vapor cell sensor system may be implemented as the vapor cell sensor system 202 shown in FIG. 2, the vapor cell sensor system 300 shown in FIG. 3, or in another manner.

[0021] In some instances, the vapor cell sensor system is configured to generate sensor data based on sensing the navigation signals. The RSNR system 106 also includes one or more processors that can be configured to process the sensor data from the vapor cell sensor system and generate navigation data which includes position and timing information. In some instances, the RSNR system 106 may further include other components or subsystems. For example, the RSNR system 106 may include memory unit which stores instructions and data, an interface which communicates with other RSNR systems or external systems, and a power unit for supplying power to the components and subsystems of the RSNR system. In some instances, the RSNR system 106 may be implemented as the RSNR system 200 shown in FIG. 2 or in another manner.

[0022] FIG.2 is a block diagram showing aspects of an example RSNR system 200. The example RSNR system 200 operates as a navigation receiver. The example RSNR system 200 may operate by sensing navigation signals from multiple distinct satellite constellations, for example, satellite constellations that operate in MEO and LEO or other satellite constellations operating in other orbits. In some implementations, the RSNR system 200 is configured to receive and process satellite-based navigation signals. As shown in FIG. 2, the example RSNR system 200 includes a vapor cell sensor system 202, one or more processors 204, a memory unit 206, an interface 208, and a power unit 210.The vapor cell sensor system 202 is configured to receive electromagnetic navigation signals transmitted from a plurality of navigation satellites positioned in different orbitals (e.g., LEO 102 and MEO 104 shown in FIG. 1), filter, amplify, and process the received navigation signals to one or more intermediate or baseband frequencies, and the one or more processors 204 are configured to generate navigation data (e.g., position, timing, etc.) based on the sensor data produced by the vapor cell sensor system 202. In some examples, the RSNR system 200 can be integrated into a mobile platform, such as an unmanned or manned aerial, terrestrial, or maritime vehicle, or can be implemented as a standalone unit communicatively coupled to other control or payload systems. In some instances, the example RSNR system 200 may include additional or different features, and the components of the example RSNR system 200 may operate as described with respect to FIGS. 2-5 or in another manner.

[0023] In some implementations, the vapor cell sensor system 202 operates based on a vapor comprising Rydberg states (e.g., a vapor of Rydberg atoms or Rydberg molecules). The vapor cell sensor system 202 may include one or more Rydberg vapor cell sensors. In some implementations, multiple laser signals from an agile laser system can be routed and shifted so that different vapor cell sensors can be assigned to different navigation signals. In some instances, the vapor cell sensor system 202 includes at least one first vapor cell sensor configured to sense a first subset of navigation signals from a first satellite constellation (e.g., operating in LEO); and at least one second vapor cell sensor configured to sense a second subset of navigation signals from a second satellite constellation (e.g., operating in MEO) that is distinct from the first satellite constellation. In some instances, the vapor cell sensor system 202 includes at least one third vapor cell sensor configured to sense a third subset of navigation signals from a third satellite constellation (e.g., operating in GEO).

[0024] In some examples, a master clock laser of the vapor cell sensor system 202 can be used to generate a frequency comb signal electro-optically using a photonic integrated circuit modulator, e.g. thin-film lithium niobate (TFLN). Frequency comb lines closest to the relevant Rydberg states of the vapor in a vapor cell sensor can be selected using a dispersive element. The vapor cell sensor system 202 may include an agile laser systemconfigured to provide dynamic frequency hopping between different navigation signals from different satellite constellations (e.g., MEO, LEO, and GEO) or to sense a number of navigation signals with different carrier frequencies in a more static configuration. In some instances, dynamic selection using photonic integrated circuit switches, e.g., drop-out filters or electro-optic switching, can be used. Once the laser light of the agile laser system (acting as the coupling laser in the Rydberg vapor cell sensor) is selected it can be shifted using photonic integrated circuit IQ modulators, for example based on TFLN, to frequency shift the light into resonance with the necessary Rydberg transition. Once shifted the light can be directed to the respective vapor cell sensors. In some instances, the RSNR system 200 can be carried by a vehicle platform and the multiple vapor cell sensors of the vapor cell sensor system 202 may be placed around the vehicle platform to determine the angle of arrival configured to distinguish navigation signals coming from satellite constellations as opposed to ground-based spoofing and jamming signals. In an angle-of-arrival configuration, the multiple vapor cell sensors may operate at the same frequency. In some instances, various amplifiers to increase the optical signals and modulations using the TFLN modulators for signal processing can be included in the vapor cell sensor system 202 as needed.

[0025] In some instances, the vapor cell sensor system 202 may include two or more lasers for sensitivity and phase detection, both coherent and incoherent. For example, the vapor cell sensory system may be configured to perform measurements according to the examples shown in FIGS. 4A, 4B and 4C. FIG.4A is a schematic diagram of example electron energy level structures for a two-photon measurement 400 using a probe laser and a coupling laser. FIG. 4B is a schematic diagram of example electron energy level structures for a three-photon measurement 420 using a probe laser, a first coupling laser and a second coupling laser. FIG.4C is a schematic diagram for a four-photon measurement 440 using a probe laser, first, second and third coupling lasers and based on Cs atoms in a vapor state. In some instances, a vapor cell sensor system 202 configured for the three-photon measurement 420 can be Doppler free and can overcome residual Doppler shifts in the atom-laser field interaction that limits the spectral linewidth to ~3.5 MHz in the 2-photon case shown in FIG.4A.

[0026] High coherence enables phase changes of the electromagnetic field to be determined through the transient response of the system. The 3-photon measurement scheme 440 shown in FIG. 4C forms a closed loop that includes the transition of the target electromagnetic field to facilitate all-optical phase and amplitude detection. This configuration is directly sensitive to the phase of the target electromagnetic field provided the phases of the laser fields forming the loop are sufficiently stable, e.g., stable compared to the phase resolution required for a particular application. A vapor cell sensor system with four lasers configured to perform the four-photon measurement 440 as shown in FIG.4C can be used for coherent sensing of navigation signals for decoding QPSK as well as other possible encoding schemes. The readout can utilize a comb or a single frequency probe laser. The readout can be heterodyne, or a single or small number of frequency probe laser lines. The lasers can be detuned for off-resonant electromagnetic field sensing. In some instances, the three-photon configuration shown in FIG.4C can provide superior phase sensitivity for QPSK-encoded navigation signals.

[0027] In some implementations of the two-photon configuration of FIG.4A, the vapor cell contains cesium atoms at a temperature of 0-60 °C and a buffer gas pressure of 1-50 Torr. The probe laser is tuned near the D2 transition at 852 nm and is intensity-stabilized and focused to a beam waist of 50-200 μm through the vapor cell. The coupling laser is tuned near a 6P->nD Rydberg transition (for example, around 510-520 nm for n~40-60) and overlapped with the probe beam in a counter-propagating geometry. Typical probe and coupling powers are in the range of 1-500 μW and 1-500 mW, respectively, producing an EIT window whose splitting depends on the incident RF field amplitude. In the three-photon configuration of FIG.4B, an additional coupling laser is introduced to drive a second Rydberg transition (e.g., nD->n’P in the 2-3 pm band), forming a ladder that cancels first-order Doppler shifts and narrows the effective linewidth below a few hundred kHz. In the closed-loop configuration of FIG. 4C, a third coupling laser (for example at 480-500 nm) closes an optical loop that includes the RF-driven transition; the relative optical phases are stabilized using optical-frequency references and RF phase modulators so that changes in the phase of the RF navigation signal appear directly as changes in the optical interferencecondition of the loop, enabling high-fidelity amplitude and phase readout of QPSK-encoded carriers.

[0028] In some instances, the vapor cell sensor system 202 may be implemented as described in U.S. Patent No. 12,372,849 and in the publications " A Three-Photon Rydberg Atom-Based Radio Frequency Sensing Scheme with Narrow Linewidth" by Bohaichuk et al. (Physical Review Applied 20, L061004, 2023) and " Phase-sensitive RF detection in a nonequilibrium interferometric setup using Rydberg atoms," by Schmidt et al. (Physical Review Letters, 093602, 2025). In some instances, the vapor cell sensor system 202 includes devices and components that allow the construction of the exemplary laser configurations shown in FIGS.4A-4C. These differ in sensitivity and the ability to detect phase. Other configurations based on other atomic or molecular systems may also be used. In some implementations, the RSNR system 200 includes an agile laser system, which has the capability to scan over a broad range of frequencies, e.g., ~1-100 GHz. In some instances, an agile laser system would also be configured to produce several output frequencies in order to continuously address navigation signals of different frequencies, e.g., from different GNSS systems or from a combination of MEO and LEO satellites. Such agile laser system may be implemented, for example, as described in the publication " Stable, narrowlinewidth laser system with a broad frequency tunability and a fast switching time," by Liu et al. (Optics Letters 49, 399, 2024) or in another manner. In some instances, the vapor cell sensor system 202 can include photonic integrated circuits, e.g., drop-out filters and on-chip electro-optic modulators, potentially constructed from thin film lithium niobate (TFLN) for fine tuning the laser frequency and modulating the laser signals. In some instances, two agile laser systems may be required for looped atomic configurations for simultaneous IQ readout. In some instances, multiple Rydberg vapor cell sensors may be configured as an array for operating at different laser wavelengths (or frequencies). In some cases, it may be advantageous to distribute the vapor cell sensors on a vehicle platform, e.g., to better determine the angle of arrival. In these situations, several vapor cell sensors may be assigned to a specific frequency, e.g., there are sub-sections of the array of vapor cell sensors that sense particular navigation signals or other electromagnetic signals(e.g., jamming or interference signals). The detection can utilize adaptive scanning or adaptive readout of several different electromagnetic signals at the same time.

[0029] In some implementations, the vapor cell sensor system 202 includes an optical detector to detect output laser signals from the vapor cell sensors. The optical detector senses changes in the transmission input optical laser signals through the vapor cell sensor in the presence of the navigation signals and other interference, spoofing or jamming signals. Output optical signals from the vapor cell sensors received at the optical detector are converted to digital signals that can be processed on the one or more processors 204. The one or more processors 204 of the RSNR system 200 can store, in the memory unit 206, the digital signals as a function of time and run them through multiple matched filters to identify the data from the satellites, including data that can be derived from the navigation signals and timing information that is not explicitly contained in the navigation signals. The RSNR system 200 can record jamming or interference signals when they are detected, in the memory unit 206. The output optical signals can be averaged together over time or acquired in real-time. The digital signals can be subjected to Fourier transform analysis or another transformation analysis in the FPGA or signal processor. The data can be used to locate the incoming signals that vary in time and space and calculate derivative information based on the measurements, such as the angle of arrival of an electromagnetic signal (e.g., a navigation signal or a jamming or interference signal) using multiple vapor cell sensors. The data may be made available in whole or in part to a user via a user interface. The digital signals can be stored in the memory unit 206 of the RSNR system 200 for future evaluation in whole or in part, including the calculated data.

[0030] In some instances, the vapor cell sensors produce output optical signals based on sensing navigation signals from distinct satellite constellations, and the output optical signals are converted to data that can be further processed by operation of the one or more processors 204. In certain examples, signals from distinct satellite constellations can be compared to each other and used to increase the accuracy of the position and timing, or detect interference, spoofing or jamming. For example, if 3 out of 4 signals give a position that is different from one of the signals, a spoofing warning can be triggered. The RSNR system 200 can track the position and time trajectories from the different navigationsignals to identify when the anomaly occurred, helping to identify whether it is a system malfunction or an adversary attempting to redirect the vehicle. Similarly, the angle of arrival can be used to provide more information.

[0031] In some implementations, the vapor cell sensor system 202 includes multiple vapor cell sensors, and each vapor cell sensor can sense a different frequency from a specific satellite constellation. Vapor cell sensors can be distributed over a vehicle sensing the same frequency to determine angle of arrival - in some cases, the longest baseline is an optimal configuration. In some instances, the multiple vapor cell sensors may not have the same geometry and can use the vapor cell sensor to enhance the signal; and signal size can be increased by adding signals together without increasing interference. In some instances, the vapor cell sensor system 202 can produce sensor data based on the navigation signals received at the one or more vapor cell sensors. In some instances, sensor data may include digital data generated and output by the vapor cell sensor system 202 that is suitable for subsequent processing by the one or more processors 204 to determine properties of electromagnetic signals detected by the system. The sensor data can be derived from output optical signals produced by one or more vapor cell sensors in response to incident electromagnetic radiation (e.g., navigation signals, navigation interference signals, etc.) and can include, for example, time-series digital samples of photodetector outputs, complex in-phase and quadrature (I / Q) samples obtained via heterodyne detection, and / or frequency-or comb-indexed amplitude and phase values representing an optical spectrum. In certain examples, this sensor data is provided to the one or more processors 204, which analyzes the sensor data to determine characteristics of the detected electromagnetic signals, such as frequency, amplitude, spectrum, modulation, Doppler shift, and, in navigation applications, pseudo-random noise code correlations, navigation messages, and position and timing information.

[0032] In certain examples, navigation data may include position and timing information from each navigation frequency or from each satellite constellation, position and timing information on GNSS drop-outs, and position and timing information on handover between different satellites. In some instances, the navigation data produced by the RSNR system 200 may include other information. The RSNR system 200 can be configuredto interface with computers and other systems on a vehicle including dead-reckoning and other inertial measurement equipment. The RSNR system 200 can be used to correct these devices in real-time so that in the unlikely case where all navigation signals are denied the dead reckoning system can be used to hold-over the navigation system. The RSNR system 200 can be programmed to hand over each navigation signal as the vehicle moves. For satellite constellations operating in LEO, this is important as the handovers are more frequent. In some instances, the diversity of navigation signals from the satellite constellations in LEO can be used to aid hand-off between satellites in a LEO satellite constellation by bootstrapping the information from the other satellite constellations. Because of the adaptability and dynamic nature of the RSNR system 200, it can also derive information from other signals of opportunity such as Starlink as well as other constellations and ground platforms (such as beacons). Other signals of opportunity include OrbComm, Iridium, Globalstar, Kuiper, OneWeb, Telesat and Pulsar.

[0033] In some instances, the vapor cell sensor system 202 based on the 3-photon and 4-photon schemes (as shown in FIGS. 4B and 4C) can be configured to readout differential phase shift encoding - either through phase changes or absolute phase measurements referenced to a clock. The looped configuration for Rydberg atom sensing shown in FIG.4C can be used for QPSK schemes. The LI signal can be represented as,sL1(t)= / 2Pcdct')c(t') cos(wt + 0) + 2Ppdp(t)p(t) sin(a>t + 0)where Pcand Ppare the in-phase and quadrature powers, dcand dpare the respective data in each respective channel arriving at 50 Hz, c(t) is the C / A encoding (identification), and p(t) is the p-code encoding. Ppis around 3 dB less than Pc. c(t) includes 1023 bits referred to as chips transmitted at 1.023 MHz. The C / A code is used to pick out the signals from each MEO satellite through the use of correlations (e.g., the Gold codes). The p-code is a longer code including 23.5 k chips at 10.23 MHz. The p-code is primarily for military applications and is encrypted with higher accuracy than the C / A code. The C / A code is the civilian GPS signal. A y-code can be used in place of the p code, operating similarly, to defend against spoofing. The L2 signal only has p-code and can be represented as,sL2(t) = ^2Pp dp(t)p(t) cosQot + 0)

[0034] In some examples, the data is transmitted at 50 Hz. The signal processing gain from the use of the C / A code and p code is a ratio of the chip rate to the bit rate (50 Hz). The signal processing gain for the C / A code is 43dB (20,460) while for the p-code the signal processing gain is 53 dB (204,600). These gains are referenced to the respective bandwidth necessary to capture the C / A code and p code respectively. Other types of encoding schemes are possible, such as binary offset carrier (BOC) modulation.

[0035] Other spread spectrum signals are possible to use. Here, phase shift changes (differential phase shift encoding) rather than absolute phase shifts can be used to encode the information. It is also possible that two signals would not be encoded on the same carrier. For example, encoding schemes are closer to L2 for the C / A code than LI where a QPSK method is used.

[0036] It is unlikely that L2-type encoding would be necessary for a system operating at multiple frequencies and with multiple satellite constellations. A differential phase shift encoding is also referred to as incoherent phase shift encoding while the standard phase shift encoding is referred to as coherent encoding.

[0037] In some instances, the navigation signals that can be detected by the RSNR system 200 may be encoded using spread spectrum BPSK and QPSK, or based on other spread spectrum encoding schemes. The navigation signals can be encoded using differential (incoherent) or coherent methods. Spread spectrum encoding is currently used because of its robustness and resistance to jamming and interference. The navigation signals can be encoded with chip rates up to 10 MHz. The bandwidth of the RSNR system 200 is currently 10 MHz. In some instances, the navigation signals can be encoded up to 35 MHz using M-sequences - a form of encoding with large Hamming separations. In some instances, the RSNR system 200 may include comb readout for larger spectral bandwidths. For QPSK, heterodyning is possible as is the all-optical loop configuration. For the differential encoding, a closed loop as shown in FIG.4C may not be required for BPSK. In some instances, a combination of encoding schemes could be used, even employing aselection of chip rates, to make it more robust and resilient to jamming, spoofing and interference. Carrier frequencies at L, S, C and X-band are particularly attractive, but other frequencies are possible.

[0038] The number of satellites and hand-off between satellites for navigation depend on the orbits of the satellite constellation. The RSNR system 200 can adapt to the frequencies available or be constructed to use a fixed, e.g., built-in, set of frequencies. The satellites in the navigation system can use CDMA with BPSK or QPSK. In some instances, it is also conceivable that incoherent CDMA can be utilized by using differential phase encoding. Other types of modulation like binary offset carrier (BOC) modulation can also be used. Several different types of modulation can be used on a single satellite system or different satellite systems may use different types of modulation. Hand-off between LEO satellites happens more often, in minutes rather than hours for MEO satellites. LEO satellites are more dynamic, making the acquisition and hand-off by the GNSS receiver occur more often and also complicates Doppler measurements.

[0039] In some implementations, navigation signals transmitted from the satellites in different satellite constellations can be encoded using spread-spectrum techniques, such as code division multiple access (CDMA), in which different satellites are distinguished by respective spreading codes while sharing a common frequency band. Such spreadspectrum encoding can provide robustness against interference, jamming, and multipath. In some instances, the navigation signals can employ modulation schemes such as binary phase-shift keying (BPSK), quadrature phase-shift keying (QPSK), or other digital modulation formats. The RSNR system 106 is configured to receive, detect, and decode the encoded navigation signals using one or more Rydberg-atom-based vapor-cell sensors and associated optical readout techniques.

[0040] In some instances, the vapor cell sensor system 202 can be configured to perform coherent sensing. In certain examples, the multiple laser systems of the vapor cell sensor system 202 may be configured as described by the energy diagram shown in FIG. 4C. In some instances, coherent sensing can be accomplished using a loop configuration for Rydberg sensors described in " Phase-sensitive RF detection in a non-equilibriuminterferometric setup using Rydberg atoms," by Schmidt et al. (Physical Review Letters, 093602, 2025). A heterodyne signal can also be used to obtain the in-phase and quadrature signals of the carrier. Some signals like the L2 do not have to be decoded in this manner as there isn’t a quadrature signal. In some instances, during coherent sensing, the vapor cell sensor system is configured to perform operations in which both amplitude and phase information of the incident navigation signals are preserved and measured, for example through heterodyne or homodyne optical detection methods that produce in-phase (I) and quadrature (Q) signal components. In contrast, during incoherent sensing, the vapor cell sensor system is configured to perform operations in which primarily amplitude or power information is measured, without necessarily preserving the absolute phase of the carrier signal.

[0041] In some cases, it may be more convenient to encode the navigation signals in the phase changes because it is ideal for Rydberg atom sensors. The RSNR system 200 can use differential phase encoding to more ideally mesh with the broad bandwidth Rydberg sensor. The 3-photon method represented by FIG.4B can sense phase changes without a loop configuration. The 2-photon method as shown in FIG.4A can also sense phase changes, however, the effect is not as pronounced as in the 3-photon setup because of Doppler shifts of the atoms.

[0042] In some instances, a GPS system operates at specific frequencies in the L-band (1575.42 MHz) of the electromagnetic spectrum from communication between satellites and receivers. The bandwidth of the GPS signal is 2 MHz for acquisition using BPSK encoding. 50 Hz is the bandwidth for the civilian data signal (50 bps).

[0043] In some instances, the power of a GPS transmitter on a satellite may be 25 W (14 dBW) and satellite antenna gain may be 13.5 dBi. A typical path loss is -0.5 dB due to atmospheric propagation while a -1.25 dB loss can be anticipated from the transmitter path. Satellite Effective isotropic radiated power (EIRP) of the navigation signals is about 400 W (26.0 dBW). For a l m2patch the intensity at the surface of the Earth is given by 1 E2(.£'fiP.1 g22 3T7W4nR22 120 n m2

[0044] In some instances, GPS Orbit Intensity and E-Field can be determined by 400W / ( / ?) = - — — — — - — — = 8 x 1014Wm2,and4TT(2 x 107m)2E = V2 x 377 x 8 x 10“14V m“x= 8 gVm-1.

[0045] To detect this field in a 50 Hz bandwidth, a sensitivity can be determined,£-= = 1 LiVm’1Hz-1 / 2.VHzIn some instances, the sensitivity may be in a range of 1-3.3 gV m-1Hz-1 / 2or in a range greater than 3.3 gV m-1Hz-1 / 2. When a signal-to-noise ratio (SNR) of 5-10 is required, the sensitivity may need to be better by a factor of ~10.

[0046] In some instances, the LEO Orbit Intensity and E-Field are400 W / Q?) = = 8 x 10-12Wm’2, andV 74TT(2 x 106m)2E = V2 x 377 x 8 x 10“14V m-1= 80 gV m-1.To detect this field in a 50 Hz bandwidth a sensitivity of£—= = 11 gV m-1Hz-1 / 2VHzis needed. In some instances, the sensitivity may be about 33 gV m-1Hz-2.

[0047] The sensitivities of a 2-photon Rydberg vapor cell sensor as shown in FIG.4A is around£-= = 250 gV m-1Hz-1 / 2Hz

[0048] The sensitivity of a 3-photon Rydberg vapor cell sensor is around£-= = 30 gV m-1Hz-1 / 2.Hz

[0049] For a Heterodyne system, the sensitivity is around£— = 10 pV m-1Hz-1 / 2.'Hz

[0050] When a SNR of around 10 is required, the sensitivity required for GPS reception can be determined to be around -^= = 0.1 pV m-1Hz-1 / 2(0.3 pVm-1Hz-1 / 2) and the Hzsensitivity for a satellite constellation operating in the LEO can be determined to be around -^= = 1 pV m-1Hz-2 (3.3pV m-1Hz-1 / 2).V Hz

[0051] In some instances, a signal processing gain, which is equal to the square root of the ratio of the PN rate to the data rate, can be calculated for a GPS system using11.023 MHzPG = — - - = 143.J 50 Hz

[0052] With signal processing gain, the sensitivity is around -^= = 1.7 pV m1Hz1 / / 2for HzE / E 2-photon systems; -== = 0.2 pV m-1Hz-1'2for 3-photon systems, and^= =VHz VHz 0.07 pV m-1Hz-1 / 2for Heterodyne, which have a narrow bandwidth.

[0053] In some instances, these numbers can be further improved using a dish or collecting optic to meet the conditions necessary for the detection of navigation signals from satellite constellations operating in the LEO and MEO even with current Rydberg atom-based sensing technology. A gain of 10-20 dB is sufficient. It is also possible to use a vapor cell sensor like a photonic crystal vapor cell sensor. Averaging over the period of the signals can be used in some cases.

[0054] In some instances, position information in the navigation data is determined using the principle of trilateration by operation of the one or more processors 204, with an augmentation (a fourth satellite) for timing synchronization. The position measurement is a passive endeavor as the RSNR system 200 does not send any communications to the satellite. The satellite does receive corrections to its own clock and position measurements from ground stations.

[0055] The position of the RSNR system 200 is determined by the time that it takes the navigation signals from the known positions of the satellites to reach the RSNR system 200.The four signals are used to determine the position and timing at the RSNR system 200. Knowledge of the satellite positions is critical. Each satellite communicates what time it is on the satellite, the position of the satellite, information on atmospheric conditions, and satellite status and identification information. The information is included in the navigation message. The RSNR system 200 receives the time at GPS time and also information from the satellites to convert GPS time to coordinated universal time (UTC). The position referred to as the ephemeris is contained in the navigation message. Information called the almanac contains data that enables the RSNR system 200 to find the satellites once the data from a single satellite has been processed. The signal from the satellite also includes data on the satellite health, e.g. health of the clock and other breakdowns of the satellite. The signals are decoded by running the signals through matched filters corresponding to the satellite pseudo-random noise (PRN) codes. The matched filter can also be used to determine the time-of-arrival of the signal. The chip signals can be used for timing to increase the accuracy. The carrier signal phase can also be used if the phase sensitive detection method of the looped configuration is used. Doppler shifts can be detected, for example, as described in U. S. Patent No. 12,306,237 and the publications " Transient Phase Sensing in a Three-Photon Rydberg Ladder Scheme", by Bohaichuk et al. (arXiv:2508.13132 [physics. atom-ph]) or " Phase-sensitive RF detection in a non-equilibrium interferometric setup using Rydberg atoms," by Schmidt et al. (Physical Review Letters, 093602, 2025).. Signals from the different frequencies can be combined using algorithms like Kalman filtering to improve the position accuracy.

[0056] The one or more processors 204 of the RSNR system 200 can be configured to determine parameters such as frequency, amplitude, modulation type, direction-of-arrival of the navigation signals, navigation messages, and position and timing information based on processing the sensor data. The RSNR system 200 can also provide interference detection metrics and spectral information to the one or more processors 204 of the RSNR system 200, which can use this information to adapt receiver operating parameters, generate interference alerts, or adjust the trajectory of the mobile platform to mitigate the effects of the navigation interference. In some instances, the vapor cell sensor system 202 may be implemented as the vapor cell sensor system 300 shown in FIG. 3 or in anothermanner. The signal processors can include one or more microprocessors, microcontrollers, digital signal processors (DSPs), field-programmable gate arrays (FPGAs), applicationspecific integrated circuits (ASICs), or any combination thereof. The signal processing system can be configured to perform operations such as digital filtering, code and carrier correlation, code and carrier tracking, navigation message decoding, and computation of pseudo-ranges, Doppler shifts, and position, velocity, and time (PVT) solutions. In some instances, the one or more processors 204 can be configured to perform operation 506 in the example process 500.

[0057] In some examples, the one or more processors 204 maybe further configured to execute algorithms that fuse GPS-based measurements with measurements obtained from other sensors, such as inertial sensors. The one or more processors 204 may implement one or more sensor fusion algorithms, such as Kalman filters or particle filters, to generate a combined navigation solution and to detect, classify, or mitigate navigation interference. The one or more processors 204 can also be configured to generate control signals that adjust the operating parameters of the vapor cell sensor system 202 based on detected interference conditions.

[0058] In some implementations, the memory unit 206 is configured to store instructions used by the one or more processors 204 and data obtained from the vapor cell sensor system 202. The memory unit 206 can include one or more types of memory devices, such as volatile memory (e.g., random-access memory (RAM)), non-volatile memory (e.g., flash memory, EEPROM, or magnetic storage), or any combination thereof. In certain instances, the memory unit 206 can store program code for execution by the one or more processors 204, configuration data for the vapor cell sensor system 202, satellite ephemeris and almanac data, and other data.

[0059] In some examples, the memory unit 206 can further store navigation data, including raw and processed sensor data, position and timing information, interference detection metrics, vapor cell sensing measurements, and historical logs of system operation. The stored data can be used for real-time navigation, post-processing, performance analysis, machine-learning-based interference classification, or forgenerating diagnostic reports. In some implementations, the memory unit 206 can be logically partitioned to separate safety-critical data from non-critical data and can support secure storage and access mechanisms to protect proprietary algorithms and sensitive navigation information.

[0060] In some implementations, the interface unit 208 is configured to provide communication between the RSNR system 200 and external systems. The interface unit 208 can include wired interfaces, such as Ethernet, serial (e.g., RS-232, RS-422), USB, or CAN bus interfaces, and / or wireless interfaces, such as Wi-Fi, Bluetooth, or other radiofrequency communication links. The interface unit 208 can be configured to transmit navigation data, interference detection alerts, sensing data, and status information to a vehicle control system, ground control station, or other external devices.

[0061] In some examples, the interface unit 208 also supports reception of configuration commands, software updates, and external reference information, such as differential corrections, assisted-GNSS data, or mission profiles. The interface unit 208 can implement one or more communication protocols, including standardized or proprietary protocols, and can include security mechanisms such as encryption, authentication, and access control to ensure secure communication. In certain implementations, the interface unit 208 can provide a user interface, such as a graphical user interface (GUI) or commandline interface, that allows an operator to configure the RSNR system 200 and to visualize navigation and interference data in real time.

[0062] In some implementations, the power unit 210 is configured to supply electrical power to the vapor cell sensor system 202, the one or more processors 204, the memory unit 206, and the interface unit 208. The power unit 210 can include one or more energy storage devices, such as rechargeable or non-rechargeable batteries, supercapacitors, or fuel cells, and one or more power conversion circuits, such as voltage regulators, DC-DC converters, inverters, and power distribution circuits. The power unit 210 can be configured to receive power from an external power source, such as a vehicle power bus or an external AC or DC power supply, and to condition the received power for use by the various subsystems. In some examples, the power unit 210 may include monitoring andcontrol circuitry configured to monitor parameters such as input voltage, output voltage, current consumption, temperature, and remaining energy capacity, and to generate status signals indicative of the power unit state. The monitoring and control circuitry can be configured to selectively enable or disable one or more subsystems, adjust power distribution, or implement power-saving modes based on the operating conditions of the mobile platform or navigation system.

[0063] FIG. 3 is a block diagram showing aspects of an example vapor cell sensor system 300. As shown in FIG. 3, the example vapor cell sensor system 300 includes a probe laser system 302, a coupling laser system 304, one or more vapor cell sensors 306, one or more optical detectors 308, a signal processor 310, and a control system 320. The example vapor cell sensor system 300 may include additional or different features, and the components of the example vapor cell sensor system 300 may operate as described with respect to FIG. 3 or in another manner. For another example, the example vapor cell sensor system 300 may include a user interface to communicate with other components or devices of an RSNR system, to allow a user to modify values of control parameters of the control system 320, values of processing parameters of the signal processor 310, or values of other parameters. In some cases, a user interface may include a computer-readable code that can be run on the control system 320 and changed by the user to control the laser systems 302, 304 and the signal processor 310. The code is capable of controlling switches, modulators, and mode of operation, for example, enabling the reconfiguration of devices and components. In some instances, reconfiguration may include updating the sensing regions, the dwell times, the scan speed, frequency range of interest, or other parameters. The user interface may also run diagnostics to monitor the health of the example vapor cell sensor system 300. In some instances, the user interface may include a wired or wireless communication module to, for example wirelessly or optically, communicate with a remote computing system or other RSNR systems at nearby geographic locations.

[0064] In some instances, the example vapor cell sensor system 300 can be used for detecting radio frequency (RF) electromagnetic radiation. In some implementations, the example vapor cell sensor system 300 uses an electro-optical comb for Rydberg atombased electrometry with EIT-based or EIA-based transmission spectra. In someimplementations, the example vapor cell sensor system 300 can perform self-calibrated absolute power measurements by measuring the frequency splitting of a spectral line shape. The spectral line shape is based on the precise electronic transitions of a vapor, and as such, measurements based on its features (e.g., the frequency splitting) may be selfcalibrated. In these implementations, the example vapor cell sensor system 300 may experimentally measure the value of the frequency splitting, such as by operation of an optical detector. The example vapor cell sensor system 300 may then use this measured value to determine the electric field strength of electromagnetic radiation interacting with the vapor. In certain instances, the example vapor cell sensor system 300 may be used in other types of applications and measurements. In some instances, the example vapor cell sensor system 300 may be operated according to the example process 500, 600 shown in FIGS. 5-6, or in another manner.

[0065] In some implementations, the probe laser system 302 of the example vapor cell sensor system 300 includes a probe laser 312 and a first comb generator 314. In some instances, the probe laser system 302 is configured to generate a first frequency comb signal 316 to the one or more vapor cell sensors 306 based on a direct probe laser output signal 313.

[0066] In some implementations, the probe laser 312 is a semiconductor laser. In some instances, the probe laser 312 may include other types of lasers, such as a fiber laser, a distributed feedback (DFB) laser, or a Bragg reflector (DBR) laser. For example, fiber lasers can be thermally or piezoelectrically tuned but need to be stabilized against a reference to eliminate laser frequency fluctuations. DFB and DBR lasers can be tuned electrically or thermally but may also need to be stabilized against a frequency reference. In some instances, the probe laser 312 may include a narrow spectral bandwidth laser. In certain examples, the probe laser 312 may need to re-acquire a lock signal for frequency stabilization once it approaches its new target frequency.

[0067] In the example shown in FIG. 3, the first frequency comb signal 316 is an optical signal produced by the first comb generator 314; and has a comb-shaped frequency profile that is defined by comb lines at respective comb frequencies. In some implementations, thefirst comb generator 314 may be part of a photonic integrated circuit system; and may be made of thin film lithium niobate for electro-optic comb generation. In some instances, the first comb generator 314 may be based on a mode-locked laser, an optical micro-resonator, a nonlinear optical fiber, an acousto-optic modulator, or another type of optical comb generator.

[0068] As shown in FIG. 3, the coupling laser system 304 includes a coupling laser 322, a second comb generator 328, a frequency separator 330, and a frequency shifter 334. The coupling laser system 304 is configured to generate a second frequency comb signal 336 and output one or more selected frequency components 336 of the second frequency comb signal 329 to the one or more vapor cell sensors 306. For example, one vapor cell sensor 306 may receive all the selected frequency components 336 from the coupling laser system 304 either in multiple sets of beam paths, or in a single beam path. In certain examples, each vapor cell sensor 306 may be configured to receive a respective subset of frequency components of the second frequency comb signal 336 from the coupling laser system 304.

[0069] In some instances, the coupling laser 322 of the example coupling laser system 304 may be a continuous wave (CW) laser; and the coupling laser signal 323 may be a frequency-locked output of the CW laser by operation of a laser stabilizer. In some cases, the coupling laser 322 may include a narrow-linewidth tunable laser. Narrow-linewidth tunable lasers can be constructed using external cavity diode laser (ECDL) technology, which allows for cheap and compact diode lasers capable of producing emissions in the violet to midinfrared spectral regime. With optical feedback from an external cavity, the narrow-linewidth tunable laser can also be achieved using a Fabry-Perot (FP) diode laser and / or gain chips. In this case, the ECDL may include a laser and a wavelength selection component (such as grating or interference filter). The FP diode laser’s wavelength can be coarsely tuned over its wide gain bandwidth by rotating the angle between the laser beam and the grating / interference filter. Mode hops may occur when the tuning range exceeds a free spectral range of the external cavity, which in certain cases, can be around a few GHz, a few tens of GHz, exceeding 100 GHz, or in another range. In some instances, changes to the frequency can be made by adjusting temperature, or mechanically moving an element of the laser system (e.g., an optical element such as a mirror or lens).

[0070] Fluctuations in the temperature and injection current of the ECDL can cause the wavelength to drift. Meanwhile, acoustic noise and other unwanted perturbations of the laser cavity can broaden the spectral bandwidth to greater than 1 MHz, and possibly to 10 MHz. To compensate for these effects, an active feedback loop can be applied to lock the diode laser’s frequency to a stable frequency reference, such as atomic or molecular transition, an FP cavity, or an optical frequency comb. The bandwidth of the feedback loop may be greater than 5 MHz, with about 1 MHz being possible for semiconductor lasers (e.g., ECDLs) due to their inherent noise characteristics.

[0071] In some instances, the coupling laser 322 is a semiconductor laser. In some instances, the coupling laser system 304 of the vapor cell sensor system 300 in FIG. 3 can enable fast switching between different Rydberg states because the coupling laser 322 does not need to be tuned and relocked. In some instances, the coupling laser 322 may include other types of lasers, such as a fiber laser, a distributed feedback (DFB) laser, or a distributed Bragg reflector (DBR) laser. For example, when the coupling laser 322 includes a fiber laser, it can be thermally or piezoelectrically tuned; and needs to be stabilized against a reference to eliminate laser frequency fluctuations. When the coupling laser 322 includes a DFB or DBR laser, it can be tuned electrically or thermally; and needs to be stabilized against a reference. When the coupling laser 322 includes a narrow spectral bandwidth laser, it may need to re-acquire a lock signal for frequency stabilization once a new target frequency is approached.

[0072] In some implementations, the coupling laser system 304 includes other types of lasers having an output frequency that is locked to a frequency (absolute or approximately absolute) reference using a laser stabilizer. In certain instances, the coupling laser 322 can operate analogously to an optical frequency reference. In some examples, the frequency reference may be an interferometer (e.g., an FP cavity) or a molecular or atomic spectral feature that does not change over time. A cesium (Cs) clock is referenced to the frequency separating the two ground hyperfine states of a Cs atom (or ensemble thereof) and can be used to stabilize an optical frequency comb and the coupling laser by using the laser -optical frequency comb beat signal. Many optical clocks use narrow bandwidth atomic or ionic transitions for their reference transitions. With such a reference transition, thecoupling laser 322 can generate a spectroscopic signal such as an atomic absorption that can be used to frequency lock the coupling laser 322. Fast electronics may then be used to generate an error signal from the atomic signal that is fed back to an actuator in the coupling laser 322 to correct its frequency.

[0073] In some implementations, the coupling laser 322 is configured to measure the derivative signal of an atomic spectral line. Taking the derivative of the signal (e.g., via frequency modulated spectroscopy) can produce an electrical signal with an approximately linear slope around the spectral line peak. If the direct coupling laser output signal 323 drifts away from its resonance, an electrical signal can be produced to correct the frequency of the direct coupling laser output signal 323. For example, the electrical signal may be a voltage signal whose sign indicates the direction of the laser frequency error. The fundamental frequency of the coupling laser signal 323 can be tuned relative to the reference by modulating the coupling laser signal 323- or alternatively, some fraction of its output after separating the fraction from the main laser output - to create a sideband at a desirable offset frequency and locking the sideband to the reference. The tuning can be precise since the sideband frequency is generated by a radio frequency source that can be locked to a clock, such as an ovenized (or thermally stabilized) crystal oscillator or even an atomic clock. Sub-hertz performance is possible. In many implementations of the coupling laser system 104, such offset tuning is used to align the optical frequency comb to dispersive elements (e.g., in the frequency separator 330), such as an arrayed waveguide grating. In some instances, the direct probe and coupling laser output signals 313, 323 generated by the probe and coupling lasers 312, 322 are both locked to a stable, narrow bandwidth reference such as a frequency comb, interferometer, atomic or molecular absorption line, or another type of reference.

[0074] In some examples, the coupling laser 322 may only have to lock to a single stable reference and the coupling laser 322 does not have to be relocked to its reference when the example coupling laser system 304 is switched between different outputs, which improves the robustness and repeatability of the system. In these configurations, the coupling laser system 304 may also extend the selection range of the wavelength. In some instances, thecoupling laser 322 can have a spectral bandwidth less than 1 MHz, less than 1 kHz, less than 1 Hz, or another value.

[0075] As shown in FIG. 3, the direct coupling laser output signal 323 produced as the output of the coupling laser 322 can be used to generate the second frequency comb signal 336 spanning the desired wavelength range by the second comb generator 328. In the example shown in FIG. 3, the second frequency comb signal 336 has a comb-shaped frequency profile that is defined by comb lines at respective comb frequencies. In some implementations, the second comb generator 328 is part of a photonic integrated circuit system; and made of thin film lithium niobate for electro-optic comb generation. In some instances, the second comb generator 328 may be based on a mode-locked laser, an optical micro-resonator, a nonlinear optical fiber, an acousto-optic modulator, or another type of optical comb generator. The second comb generator 328 may be implemented as the first comb generator 314 or in another manner.

[0076] In some implementations, the example vapor cell sensor system 300 allows frequency comb spectroscopy in which the probe and coupling lasers 312, 322 do not have to be tuned. Enough power can be allocated to each comb line in the first frequency comb signal 316 to measure virtually all practical de-tunings simultaneously. Moreover, large laser fluctuations of up to 10 MHz can be compensated by signal processing, and as such, in some instances, the probe and coupling lasers 312, 322 are not precisely locked. In some instances, only one of the probe and coupling lasers 312, 322 is locked to a reference frequency. The reference frequency may be different for the frequency of the probe and coupling lasers 312, 322.

[0077] In some instances, the frequency separator 330 includes one or more dispersive elements and one or more optical switches. For example, the one or more dispersive elements may be configured to separate different frequency components (e.g., comb lines) in the second frequency comb signal 336; and the one or more optical switches can be configured to receive the separated frequency components of the second frequency comb signal 336. In some instances, the frequency separator 330 of the coupling laser system 304 may include a network of drop-out filters as part of a photonic integrated circuit systemtuned near each frequency component of the second frequency comb signal 336. In this case, the outputs of the drop-out filters may be combined, in whole or in part. The output of the coupling laser system 304 (e.g., one or more selected frequency components of the second frequency comb signal 336) can then be determined by which drop-out filters are tuned so that they are activated. Tuning of the drop-out filters can be accomplished with micro-heaters or by using piezoelectric elements.

[0078] In some implementations, each frequency shifter 334 includes one or more fine-tuning elements for shifting the one or more selected frequency components of the second frequency comb signal 336 before the one or more selected frequency components are recombined or transmitted independently to one or more vapor cell sensors 306. In some instances, frequencies of the selected frequency components of the second frequency comb signal can be fine-tuned by operation of the frequency shifter 334. In some instances, each fine-tune element of the frequency shifter 334 may include an electro-optic modulator (EOM), to shift the frequency of a frequency component to a desired value. In some instances, an electro-optic modulator can be configured as an IQ modulator (e.g., in a Mach-Zehnder configuration), which can allow for modulation of a single sideband suppressed carrier (SSB-SC). In some instances, the comb spacing is less than the spectral range of the frequency shifter 334 to ensure continuous coverage. For example, the frequency components in the second frequency comb signal 329 may be separated from each other by a common frequency spacing, by operation of the frequency separator 330. In some instances, the frequency shifter 334 may be configured to shift the frequencies of the selected frequency components by a frequency magnitude no less than the common frequency spacing. In some instances, the probe laser system 302 may also include a frequency shifter with one or more fine-tuning elements configured to shift one or more frequencies of the frequency components in the first frequency comb signal 316.

[0079] In some instances, the switching speed of the coupling laser system 304 may also be affected by the frequency relock time of a radio frequency oscillator driving the one or more fine-tuning elements in the frequency shifter 334. Moreover, the spectral linewidth may be determined by the spectral bandwidth of the optical clock, which can be less than 1 Hz in certain cases. Many atomic physics applications require laser light with a spectralbandwidth of less than 1 MHz. In some instances, such as when the coupling laser system 304 switches, its spectral bandwidth may be limited by a product of time and bandwidth. For example, if the switching time is 1 ps then the coupling laser system 304 may dwell for 10 ps to achieve a spectral bandwidth of 100 kHz. However, such a dwell time can be faster than the unlocking and relocking of a conventional laser. In some instances, the coupling laser system 304 may include one or more optical amplifiers at its output to achieve the desired output power that is necessary for injection into the vapor cell sensors 306.

[0080] In some implementations, each vapor cell sensor 306 includes a Rydberg atombased vapor cell sensor. In some instances, each vapor cell sensor 306 includes a vapor in an enclosed volume (e.g., in a vapor cell). The vapor is used as a medium to interact with electromagnetic radiation. The vapor cell sensor 306 may include Rydberg atoms in a vapor state (e.g., vaporized87Rb or133Cs) that alter an optical transmission in response to the electromagnetic radiation. The optical transmission may be influenced by optical transitions of the atoms in the vapor state. In some instances, the vapor cell sensor 306 may be implemented as a metrology vapor cell, a glass vapor cell, a microelectromechanical system (MEMS) vapor cell, or another type of engineered vapor cell based on metamaterial or photonic crystal principles.

[0081] In some implementations, the vapor of the vapor cell sensor 306 is hermetically sealed and packaged in an electromagnetically transparent dielectric material, such as polylactic acid (PLA) plastic materials and other dielectric materials. In some implementations, the vapor cell sensor 306 is formed at least in part (wholly or partially formed) of a dielectric material that is transparent to the electromagnetic radiation. The vapor cell sensor 306 may be, for example, of the type described in the publication " Microwave electrometry with Rydberg atoms in a vapor cell using bright atomic resonances," by J. A. Sedlacek, et al. (Nature Physics 8, 819-824, 2012), or in U. S. Patent No.10,859,981 entitled " Vapor Cells Having One or More Optical Windows Bonded to a Dielectric Body." Other types or configurations of the vapor cell sensor 306 may be used in some cases. The dielectric material may define a window for the vapor cell sensor 306, through which electromagnetic radiation is received. Examples of the dielectric material include silicon, silicate-based glasses, borosilicate glass, and quartz.

[0082] In some implementations, the direct probe laser output signal 313 from the probe laser 312 has a probe frequency matched to a first optical electronic transition from the ground state to an excited state of a vapor in the one or more vapor cell sensors 306; and the direct coupling laser output signal 323 from the coupling laser 322 has a coupling frequency matched to a second optical electronic transition from an excited state to a Rydberg state of the vapor in the one or more vapor cell sensors 306. The first optical electronic transition may share an energy level in common with the second optical electronic transition. For example, the vapor may include first, second, and third electron energy levels that are each progressively higher in energy. The first optical electronic transition may be defined by a first energy gap between the first and second electron energy levels; and the second optical electronic transition may be defined by a second energy gap between the second and third electron energy levels. However, other arrangements of electron energy levels may be possible (e.g., an arrangement in which one or more subsequent electron energy levels are lower than a starting electron energy level).

[0083] In some implementations, electromagnetic radiation (e.g., RF pulses or other forms of electromagnetic radiation) are received by the vapor cell sensors 306. The electromagnetic radiation may be generated by an antenna or another apparatus that is located remote from the example RSNR system. The electromagnetic radiation may be generated by any source of electromagnetic radiation (e.g., an unknown source, a remote source, etc.). If the electromagnetic radiation is received by the vapor cell sensors 306, the signal processor 310 may determine properties of the electromagnetic radiation.

[0084] In some implementations, the atoms in the vapor state include an RF electronic transition that is configured to alter, in response to absorbing electromagnetic radiation, an absorption of light by one or both the first and second optical electronic transitions. The RF electronic transition may correspond to an electronic transition that is defined by a pair of electron energy levels, at least one of which is different from the first, second, and third electron energy levels. The RF electronic transition may have a third energy gap that is smaller in magnitude than the first and second energy gaps of, respectively, the first and second optical electronic transitions. In some instances, the vapor cell sensor system 300 may include one or more additional laser systems which are configured to generate lasersignals in addition to the probe and coupling laser signals 313, 323, the additional laser signals may have respective frequencies that are matched to different optical electronic transitions of the vapor. In certain cases, the absorption of light by these optical electronic transitions may also be altered by the RF electronic transition. For example, the vapor cell sensor system 300 may include a third laser system which may include a third laser (e.g., an auxiliary coupling laser which can produce an auxiliary coupling laser for resonant with other transitions. In some instances, the example vapor cell sensor system 300 may include a fourth laser system which may include a fourth laser and an associated frequency comb generator for phase and amplitude fast scanning. In some instances, the vapor cell sensor system 300 may further include other optical devices or components.

[0085] In some instances, the vapor cell sensor 306 can be omni-directional and selfcalibrated. In some instances, the vapor cell sensor 306 can be implemented with a wide carrier bandwidth so that the vapor cell sensor 306 does not need to be changed in order to detect the electromagnetic radiation. In some instances, each vapor cell sensor 306 may include a narrow bandwidth vapor cell sensor, e.g., a photonic crystal receiver.

[0086] In some instances, each of the vapor cell sensors 306 is communicably coupled through waveguides, e.g., fiber optic cable, to the probe laser system 302, the coupling laser system 304, and the optical detectors 308. Additionally, a mounting system for the vapor cell sensors 306 can be included, such as a plastic tripod mount and a plastic mount for the vapor cell sensor configured to attach to the mount, plastic aerials, etc. The vapor cell sensors 306 can be removed from a backpack so that they can be positioned around the backpack with the control system 320 and the laser systems 302, 304. An array of vapor cell sensors 306 can be configured in a regular array by fixing the vapor cell sensors 306 into a form, made of plastic, or another dielectric material. The vapor cell sensors 306 can be detached; or the array can be disassembled, and the arrangement of the array can be reconfigured, such as a long baseline antenna for angle of arrival determination. The laser systems 302, 304 may be shared by the multiple vapor cell sensors 306 using a system of light splitters, switches, a photonic integrated circuit, or in another manner. In some instances, each vapor cell sensor 306 may include collection and focusing elements such as lenses or other optical components.

[0087] In some instances, an output optical signal 346 from a vapor cell sensor 306 can be generated based on EIT or EIA when frequency components from the first and second frequency comb signals 316, 329 are resonantly coupled to atomic states of a vapor in the vapor cell sensor. In some implementations, a sub-Doppler method is useful for higher spectral resolution in the Autler-Townes regime and higher sensitivity. The output optical signal 346 is received by one or more optical detectors 308. In some implementations, the optical detector 308 is configured to receive a set of optical signals from the vapor cell sensors and convert the set of optical signals to analog electrical signals. The signal processor 310 is in communication with the optical detector 308. The signal processor 310 is configured to receive the analog electrical signals from the optical detector 308; to convert the analog electrical signals to digital signals; to process the digital signals; and to detect (e.g., measure) the properties of an optical spectrum at one or more of the comb frequencies of the second frequency comb signal 336. The signal processor 310 is configured to generate data representing the properties of the optical spectrum at the one or more comb frequencies of the second frequency comb signal 336.

[0088] The example vapor cell sensor system 300 may further include a memory unit configured to store instructions for the signal processors 344 in the signal processor 310. The instructions, when executed by the one or more signal processors 344, may be configured to perform operations such as determining, based on the data, the properties of the electromagnetic radiation received at the vapor cell sensors 306. As shown in FIGS. 3, the signal processor 310 includes analog-to-digital converters (ADCs) 342 configured to convert analog signals generated by the optical detectors 308 to digital signals. The digital signals can then be communicated to the signal processors 344 configured to process and analyze the digital signals. In some instances, the signal processor 344 may include Field Programmable Gate Arrays (FPGAs) where a Fourier transformation on the digitized data, to obtain a frequency spectrum. In some instances, the signal processors 344 may be configured to perform other transformation operations such as Laplace, wavelet, etc. If electromagnetic radiation is present at the vapor cell sensor 306, a change in the transmission of the probe laser signal at an RF frequency detuning can be detected in the frequency spectrum. The EIT / EIA spectrum (e.g., properties of off-resonance peaks) can beused to determine the properties of the electromagnetic radiation received at the vapor cell sensor 306. In some instances, the wavelength / frequency of the frequency component 138 can be rapidly changed to shift the RF sensing window.

[0089] In some implementations, the control system 320 is configured to communicate control signals to the laser systems 302, 304, the signal processor 310, and other components or devices of the example vapor cell sensor system 300. In some instances, the control system 320 is configured to provide feedback to control the probe and coupling lasers 312, 322, including feed forwards. For example, the control system 320 includes FPGAs, analog electronics, custom RF electronics (e.g., RFSoC), or another processor-based system that can be controlled through a user interface and through autonomous control layers operating in different types of processors. In some instances, the vapor cell sensor system 300 can be configured to scan several different bands simultaneously. In some implementations, the signal processor 310 and the control system 320 may be part of an integrated system-on-chip (SoC) for control and digital signal processing. For example, the signal processor 310 may include a specialized FPGA board with a CPU processor.

[0090] For example, if the bandwidth of the first frequency comb signal 316 is 100 MHz then the first frequency comb signal 316 might be up-shifted by 120 MHz so that the full bandwidth of the beat frequencies can be detected by the optical detectors 308. In some instances, the signal processor 310 may be a swept frequency spectrum analyzer, a realtime spectrum analyzer, or another type of spectrum analyzer. At frequencies less than 5 GHz, real-time digital signal processing solutions can be convenient. In the amplitude regime, where the amplitude of the optical spectrum is used to deduce the electromagnetic field amplitude, the method can still be useful since the entire line shape can be measured, reducing noise since small frequency fluctuations of the peak center can be observed and compensated. Analogous principles can be used to carry out comb spectroscopy using a three-photon process by modulating the probe laser signal 113.

[0091] In some instances, the vapor cell sensor system 300 includes multiple coupling laser systems 304, for example, at different frequencies to provide closed loop systems for reading out phase optically. For example, the vapor cell sensor system 300 includes twocoupling laser systems 304 (e.g., 636 nm and 2260 nm) for performing operation shown in FIG.4B. For another example, the vapor cell sensor system 300 includes three coupling laser systems 304 (e.g., 636 nm, 2260 nm and 496 nm) for performing operation shown in FIG.4C. In some instances, other multi-photon detection schemes may be possible.

[0092] In some instances, the example vapor cell sensor system 300 includes multiple vapor cell sensors 306 configured in an array with a reconfigurable topology. In some instances, each vapor cell sensor 306 can be configured to sense a respective frequency range enabling faster scanning of multiple frequency bands and concentration on specific frequency bands. The multiple vapor cell sensors 306 can be distributed over a large area. In some instances, an array of vapor cell sensors 306 can be configured to sense different electromagnetic frequencies; determine angle of arrival; and other functions. The multiple vapor cell sensors 306 in an array can be configured to have a longer baseline increasing the angle resolution for angle of arrival detection; and signal size can be increased by adding signals together without increasing interference.

[0093] The example vapor cell sensor system 300 can allow for different subsets of an array of vapor cell sensors 306 to simultaneously sense electromagnetic radiation with different frequencies. The vapor cell sensor system 300 can also enable a single vapor cell sensor 306 to simultaneously detect electromagnetic radiation at different frequencies. By taking advantage of the Doppler shifts of the moving atoms, different atomic velocity groups can sense electromagnetic radiation at different frequencies in the same vapor cell sensor 306, allowing off-resonance measurement, in which the frequency components in the first frequency comb signal 316 from the probe laser system 302 is near the resonance of an atomic transition. In other words, in the off-resonance measurement, the frequency components of the first frequency comb signal 316 are not tuned exactly to the resonance of the atomic transition but slightly detuned from the resonance.

[0094] In some instances, the vapor cell sensor system 300 may further include optical waveguide circuits, fiber optics, free-space optics, optical test benching, and other optical circuits and devices. In some examples, the example vapor cell sensor system 300 includes a GPS receiver or another type of location detection system which is configured to providegeolocation data associated with each of the vapor cell sensors 306. For reducing any perturbation caused by the GPS receiver, the GPS receiver is included in the control system 320, for example with a control package. In certain cases, the control system 320 also includes a clock configured to provide timing data. In some instances, the timing data is associated with the detected output optical signal generated by the optical detector 308 upon receiving the output optical signals from the vapor cell sensors. For example, the clock may be an atomic clock, thermally stabilized crystal oscillator, or another type of clock. In certain instances, the clock can be steered by the GPS timing signal. The example vapor cell sensor system 300 can be battery powered for remote field testing, plugged into wall power, or both. Some remote testing can allow for power supplied by a generator, such as a vehicle engine running an alternator to charge a battery and supply DC power.

[0095] In some instances, the vapor cell sensor system 300 can meet the challenges of wide bandwidth spectrum sensing. In some cases, the system can simultaneously be used to calibrate and configure other equipment for electronic protection and force spectrum management. In some examples, the vapor cell sensor system 300 can be hardened (e.g., structurally reinforced to endure environmental stress) to meet deployment specifications, e.g., requirement standard specified in MIL-STD-810 (U. S. Department of Defense Test Method Standard, Environmental Engineering Considerations and Laboratory Tests). The vapor cell sensor system 300 can be designed to be field-portable when it has to be carried by a 5G-6G field technician or by soldiers to characterize the electromagnetic spectrum at different sites in order to predict phenomena such as interference. The vapor cell sensor system 300 can be configured to operate in all types of weather and be covert and passive. The vapor cell sensor system 300 can operate in a large frequency range, for example, spanning around 0.1-100 GHz, UHF to W-band to gather intelligence for planning and operations in electronic warfare. In some implementations, the example vapor cell sensor system 300 has a sensing bandwidth of 0.1-100 GHz, a RF transition switching time of 50 ps; a dwell time of 1 ms, an on-resonance sensitivity of greater than -130 dBm / Hz, an off-resonance sensitivity of greater than -100 dBm / Hz, and a time to scan 100 GHz of 0.5 s. In some instances, the example vapor cell sensor system 300 may have other characteristics of other values.

[0096] The coupling laser system 304 includes a coupling laser 322, a first amplifier 324, a frequency doubler 326, a second comb generator 328, a frequency separator 330, a second amplifier 332, and a frequency shifter 334. The example vapor cell sensor system 300 may include additional or different features, and the components of the example vapor cell sensor system 300 may operate as described with respect to FIG. 3 or in another manner. In some instances, the example vapor cell sensor system may be operated according to the process 500 shown in FIG. 5 or in another manner.

[0097] As shown in FIG. 3, the direct coupling laser output signal 323 can be amplified by the first amplifier 324; and the amplified direct coupling laser output signal can be used to generate the second frequency comb signal 328 spanning the desired wavelength range by the second comb generator 328.

[0098] In some implementations, each of the first and second amplifiers 324, 332 is an optical amplifier which may include a semiconductor optical amplifier, a tapered amplifier, a fiber amplifier, or another type of amplifier. In some instances, the second amplifier 332 may have a broad enough spectral bandwidth to amplify an optical signal at each comb tooth of the second frequency comb signal 329. The amplification may be the same for each comb tooth. In some variations, the second amplifier 332 may be seeded by the power of an output from the fine-tuning element. If the power of the output from the fine-tuning element is too small, then amplification at intermediate stages can be implemented. For example, the output from the second comb generator 328 or the optical switch of the frequency separator 330 can be amplified to compensate for loss or lower comb tooth power. It is valuable to have enough seed power for the final amplification because if the power from the weakest fine-shifted comb tooth is above the saturation point of the amplifier, the output power can be more uniform across the entire system spectral bandwidth. In these variations, the first amplifier 324 may amplify only at the center frequency of the CW laser of the coupling laser 322. The second amplifier 332, in many cases, will be strong enough to increase the power per comb tooth as the amplified power can be distributed amongst many comb teeth.

[0099] As shown in FIG. 3, the amplified direct coupling laser output can be split after operation of a frequency doubler 326. One portion of the output of the frequency doubler 326, serving as a frequency reference for heterodyne readout, can be communicated to the frequency reference 318. The other portion can be communicated to the second comb generator 328 and used to generate the second frequency comb signal 329. In some implementations, the frequency doubler 326 is configured to perform a process of doubling the frequency of the amplified coupling laser signal. In some instances, the frequency doubler 326 includes a device or system that achieves second harmonic generation, e.g., nonlinear crystals such as lithium niobate, beta barium borate, or potassium titanyl phosphate, that allows the incoming fundamental light to convert into its second harmonic. In some instances, the frequency doubler 326 may be configured to perform a nonlinear optical process to achieve the second harmonic generation. In some instances, the frequency doubler 326 includes an amplifier, where the doubling crystal is included in the amplifier to perform intracavity doubling.

[0100] The second frequency comb signal 329 includes multiple comb lines with frequency spacings in a range of ~10 kHz -1 MHz. The second frequency comb signal 329 with a bandwidth up to 1 GHz can then be communicated to the one or more vapor cell sensors 306. The one or more frequency components 336 of the second frequency comb signal 329 are communicated through the vapor cell sensors 306 in the presence of the first frequency comb signal 316 (e.g., counter or co-propagating); and is directed to the one or more optical detectors 308 where it is mixed with a reference optical signal 338 from the frequency reference 318. In some instances, each vapor cell sensor 306 may receive the same frequency components 336 of the second frequency comb signal 329. In certain examples, different vapor cell sensors 306 may receive respective subsets of frequency components 336 of the second frequency comb signal 329. In some instances, multiple different frequency components 336 can be routed to the same vapor cell sensor 306.Different combinations of these extremes may be enabled by operation of the frequency shifter 334.

[0101] After the frequency separator 330, the multiple frequency components can be recombined into a unified output and then amplified to the desired optical output power byoperation of the second amplifier 332. In some instances, the multiple frequency components may be separately amplified before being recombined. In some instances, the multiple frequency components may not need to be combined prior to being amplified. In some instances, frequencies of the amplified frequency components of the second frequency comb signal 329 can be fine-tuned by operation of respective frequency shifters 334. In some instances, the example vapor cell system 300 may include optical amplifiers throughout the system to boost optical signals. In some instances, each frequency shifter 334 may include an electro-optic modulator (EOM), to shift the frequency of a frequency component to a desired value. In some instances, an electro-optic modulator can be configured as an IQ modulator (e.g., in a Mach-Zehnder configuration), which can allow for modulation of a single sideband suppressed carrier (SSB-SC). In some instances, the comb spacing is less than the spectral range of the frequency shifter 334 to ensure continuous coverage. For example, the frequencies of the frequency components in the second frequency comb signal 329 may be separated from each other by a common frequency spacing. As such, the frequency shifter 334 may be configured to shift the frequency of the selected frequency component by a frequency magnitude no less than the common frequency spacing. In some implementations, the frequency shifter 334 includes a photonic integrated circuit for electro-optic frequency shifting and switching. In some instances, the photonic integrated circuit may include thin film materials such as silicon nitride, tantalum pentoxide, lithium niobate, or other materials for filtering, routing and laser stabilization.

[0102] In some implementations, the probe laser 312 is chosen as the optical source for the first frequency comb signal 316 because it may be necessary to resolve the optical transmission associated with each comb line or detuning from resonance. To do so, the first frequency comb signal 316 after passing through the vapor cell sensor 306 may be beat (or combined) with the reference optical signal 338 (or local oscillator) from the frequency reference 318. As shown in FIG. 3, the reference optical signal may be a second portion of the probe laser signal 313. In some instances, the reference optical signal may be obtained in another manner. The output optical signal 346 and the reference optical signal 338 form a heterodyne optical spectrum, which is based on a fundamental frequency of the probelaser signal 313 but shifted by a frequency such that a bandwidth of the optical spectrum can be detected by the optical detectors 308 and the signal processor 310.

[0103] As shown in FIG. 3, the example vapor cell sensor system 300 includes a clock 348 that is in communication with the signal processor. An accurate clock is necessary for the vapor cell sensor system 300. In some instances, the clock 348 can be an atomic clock, an ovenized quartz oscillator, or another type of clock.

[0104] FIG. 5 is a flow chart showing aspects of an example process 500. In some instances, the example process 500 can be performed by operation of the example RSNR system 200 shown in FIG. 2 or in another manner. The example process 500 can be configured to utilize signals across all or part of the RF spectrum of navigation signals. The example process 500 may include additional or different operations, including operations performed by additional or different components, and the operations maybe performed in the order shown or in another order.

[0105] At 502, navigation signals from satellites are sensed. In some implementations, navigation signals from satellites of multiple constellations (e.g., LEO or MEO in FIG. 1) are sensed by the vapor cell sensor system of the RSNR system. In some implementations, the control system of the vapor cell sensor system configures the probe and coupling laser systems to direct one or more optical frequency combs and / or narrow-linewidth optical signals to a set of Rydberg-atom-based vapor cell sensors, each vapor cell sensor being assigned to a particular frequency, navigation band, or constellation (for example, a first subset of sensors tuned to receive signals from a LEO constellation and a second subset tuned to receive signals from a MEO constellation). As the satellites in the different constellations transmit spread-spectrum navigation signals toward the RSNR system, the electromagnetic fields associated with the navigation signals couple RF or microwave transitions of the Rydberg atoms in the vapor cells. This interaction perturbs the optical transmission or phase response of the vapor, producing EIT / EIA-based or related signatures at the optical output of each vapor cell sensor that are indicative of the incident navigation signals, including their carrier frequencies, modulation, and time-varying code structure.

[0106] In some cases, different vapor cell sensors in an array are spatially distributed around a platform to provide angular diversity, so that navigation signals from the different constellations can be sensed concurrently with sensitivity to angle-of-arrival. In some implementations, the angle of arrival of a navigation signal is determined using a plurality of vapor cell sensors operated at a common sensing frequency. The vapor cell sensors are mounted at known positions along a baseline of length d (for example, on the wingtips of an aircraft), and each sensor produces a complex baseband representation of the received signal. The signal processor estimates a phase difference Δφ between the baseband signals from two sensors and computes an angle of arrival θ using a relation of the form θ = arcsin(Δφ λ / (2π d)), where λ is the wavelength corresponding to the RF carrier frequency. For arrays with more than two vapor cell sensors, the one or more processors can apply conventional beamforming or other algorithms to the sensor outputs to obtain a direction-of-arrival estimate in one or more angular dimensions. These AoA estimates can be associated with specific satellites based on their predicted positions and used both to improve geometry-based navigation solutions and to distinguish satellite-borne signals from ground-based spoofing or jamming sources.

[0107] In some examples, operation 502 further includes adaptively scanning or hopping among different navigation frequencies within and across constellations. The control system of the vapor cell sensor system may command the agile laser system and associated photonic-integrated comb generators, frequency separators, and frequency shifters to step or hop the Rydberg transitions through a sequence of operating points that correspond to carrier frequencies used by different satellite constellations. Multiple vapor cell sensors can be configured so that different subsets of the array simultaneously cover distinct frequency ranges or constellations, thereby enabling parallel acquisition of navigation signals from satellites occupying different orbits and frequency allocations.

[0108] At 504, sensor data is obtained. In some implementations, sensor data produced by the vapor cell sensor system during operation 502 is obtained and prepared for processing. In some implementations, the optical detectors receive output optical signals from the vapor cell sensors (for example, optical signals whose transmission or phase is modified by the incident navigation signals) and convert the output optical signals intoanalog electrical signals. The signal processor of the vapor cell sensor system digitizes these analog signals using one or more analog-to-digital converters to obtain time-series digital samples representing the optical response of each vapor cell sensor as a function of time and frequency (e.g., comb index). The resulting digital sensor data may include, for example, sampled photodetector outputs, complex in-phase and quadrature (I / Q) samples obtained via optical or electrical heterodyne detection, and / or comb-indexed amplitude and phase values that describe the optical spectrum at the comb frequencies.

[0109] In certain examples, the sensor data obtained at 504 is formatted and routed to the one or more processors of the RSNR system as data for each satellite channel, each frequency, and each constellation. The signal processor of the vapor cell sensor system can perform preliminary signal processing on the sensor data, such as digital filtering, spectral analysis, and downconversion to one or more baseband representations. For coherent sensing modes, the sensor data includes I / Q streams suitable for correlation with locally generated PRN replicas to recover code phase and Doppler; for incoherent sensing modes, the sensor data may include magnitude or power-versus-time traces that encode envelope variations associated with different PRN codes and data symbols. In either case, the sensor data obtained at 504 provides a digital representation of the interaction between the navigation signals from the various satellite constellations and the Rydberg vapor cell sensors, which can then be processed in subsequent operations (e.g., at 506) to obtain PRN codes, navigation messages, Doppler shifts, and ultimately position and timing information.

[0110] At 506, navigation data is generated. In some instances, the navigation data is generated by operation of the one or more processors of the RSNR system based on the sensor data produced by the vapor cell sensor system. The navigation data may include position and timing information derived from some or all of the satellite signals obtained at 502. In some cases, the position and timing information represent a detected position of the RSNR system and a time associated with the detected position. Additional or different types of navigation data may be generated.

[0111] In some implementations, generating the navigation data includes acquiring and decoding spread-spectrum satellite signals. For instance, spread-spectrum satellite signalsmay be decoded in a manner that is analogous to a conventional GPS receiver. In some cases, a plurality of PRN codes associated with respective satellites in each satellite constellation are obtained, and digital or analog correlators search over code phase and Doppler frequency. The sensed signals can be correlated with locally generated PRN replicas to obtain code lock for a plurality of satellites in each constellation, thereby identifying the PRN codes present in the received signals. Once code lock is achieved, the corresponding spread-spectrum signals can be demodulated to obtain navigation messages associated with at least a subset of satellites in each constellation. From these navigation messages, satellite information, such as ephemeris parameters, clock correction terms, and health / status flags can be extracted, and at least four satellites in each constellation that satisfy a selection criterion (for example, health, geometry, and signal quality) can be selected for use in computing a navigation solution. For example, GPS positioning requires 4 satellites with readable signals and a desire to maximize the time between hand-offs.

[0112] In some instances, the PRN codes and navigation messages can be obtained by configuring the vapor cell sensor system for coherent sensing, in which the in-phase (I) and quadrature (Q) components of the received satellite signals are recovered. In these implementations, the vapor cell sensor system is configured to operate in a phase-sensitive readout mode. In a phase -sensitive readout mode, the probe and coupling lasers are configured, for example via a heterodyne or homodyne optical detection scheme, to preserve the phase of the RF or microwave navigation signals incident on the vapor. The optical detectors produce electrical signals that encode both amplitude and phase information of the received navigation signals at baseband, and the one or more processors can convert these baseband signals to I / Q representations for each satellite channel. The I / Q data are then used to perform coherent correlation with the locally generated PRN replicas, enabling fine code-phase tracking, precise Doppler estimation, and coherent demodulation of the navigation messages with improved carrier-to-noise performance. In some examples, certain aspects may utilize techniques described in the publication " Phasesensitive RF detection in a non-equilibrium interferometric setup using Rydberg atoms," by Schmidt et al., (Physical Review Letters, 093602, 2025).

[0113] In other implementations, the navigation signals can be obtained by configuring the vapor cell sensor system for incoherent sensing, particularly when the navigation signals are encoded using distinct phase encodings. In these cases, the vapor cell sensor system may be operated in an amplitude-detection regime, in which the primary observable is a change in optical transmission or absorption amplitude as the RF navigation signals interact with the Rydberg states of the vapor. The system can sequentially or simultaneously tune across signal bands and measure envelope variations corresponding to different PRN codes and data symbols without preserving the absolute RF phase. The vapor cell sensor system can perform incoherent or differential detection, such as energy detection over short integration intervals, to distinguish between distinct phase-encoded navigation symbols and to reconstruct the PRN codes and navigation messages for each satellite channel. This incoherent mode can simplify certain aspects of the receiver architecture while enabling reliable code acquisition and data demodulation in environments where coherent phase recovery is challenging.

[0114] In some implementations, the method further includes leveraging the vapor cell sensor system to determine respective Doppler shifts of navigation signals from the selected satellites and using those Doppler shifts to refine the navigation solution. Once at least four satellites are selected in each constellation, the signal processor estimates the Doppler frequency offset for each selected satellite signal, for example by tracking the carrier frequency in the coherent I / Q domain or by tracking spectral line shifts in the Rydberg-based optical response. The estimated Doppler shifts are used to augment the navigation messages by updating or refining satellite range-rate information, correcting for residual frequency offsets, and improving estimates of relative satellite-receiver motion. The one or more processors then calculate position and timing information based on the Doppler-augmented navigation messages from the selected satellites, for example by solving a set of navigation equations that incorporate both code-based pseudo-ranges and Doppler-derived range rates. In some cases, the Doppler-augmented data can also be used to enhance velocity estimation, detect anomalous motion indicative of spoofing, or improve clock estimation, thereby increasing the accuracy and robustness of the operation.

[0115] In some implementations, generating the navigation data further includes organizing the recovered measurements into per-satellite navigation data records for use in subsequent navigation processing. For each satellite for which PRN code lock and data demodulation are maintained, the one or more processors can determine and store one or more navigation observables, such as code phase, carrier phase, Doppler frequency, carrier-to-noise density ratio, and associated time stamps referenced to a system clock. The one or more processors can combine these observables with satellite information obtained from the navigation messages, including ephemeris parameters, clock correction terms, and satellite health / status indicators, to form a navigation data set for each visible satellite in each constellation. Based on one or more selection criteria — such as signal quality, satellite geometry, and constellation diversity -the signal processor can select at least a minimum number of satellites from one or more constellations and flag the corresponding navigation data records for use in position and timing computations and, in some implementations, for interference and spoofing detection in later operations of the process.

[0116] In some implementations, operation 506 further includes detecting the presence of navigation interference (e.g., signals that interfere with navigation signals) while obtaining the navigation data from the sensor data. The one or more processors can analyze the sensor data and the derived PRN correlations to identify signals that are inconsistent with expected satellite information, for example by detecting energy in frequency bands or code channels not assigned to any known satellite, by identifying PRN-like sequences that do not match valid codes, or by recognizing anomalous code-phase, carrier-phase, or Doppler behavior relative to the ephemeris data. In some examples, interference detection is augmented by measurements from multiple constellations and, optionally, by detecting and comparing AoA or spectral information obtained from the vapor cell sensor system, so that signals whose apparent direction, spectrum, or timing are inconsistent with the predicted satellite positions can be classified as candidate spoofing, jamming, or other non-navigation signals.

[0117] In some instances, the one or more processors can detect navigation interference by comparing navigation data derived from two or more distinct satellite constellations. For example, constellation-specific position fixes and measurementresiduals can be evaluated against a predetermined tolerance to flag outliers and exclude suspect signals from the navigation solution. In addition, Doppler, carrier-phase consistency, and / or AoA checks across constellations can be used to corroborate interference detection and generate an integrity alert. Signals identified as navigation interference can be excluded from satellite selection when forming the navigation data for subsequent position, velocity, and timing computations.

[0118] FIG. 6 is a flow chart showing aspects of an example process 600 for operating the RSNR system 200 shown in FIG. 2. An RSNR system may include a vapor cell sensor system (e.g., the vapor cell sensor system 202) which includes a probe laser and a coupling laser. The probe and coupling lasers of the example RSNR system can be locked to a stable reference; and the RSNR system includes an agile laser with an array of vapor cell sensors. The vapor cell sensor system may be implemented as the vapor cell sensor system 300 shown in FIG. 3 or in another manner. In some instances, an RSNR system may include more than two lasers. In some instances, the RSNR system may be part of a navigation system that includes more than four satellites located at different orbits and multiple RSNR systems. In some instances, the example process 600 is a specific implementation of the process 500.

[0119] The example process 600 can be configured to measure signals spread across the electromagnetic spectrum for navigation signals. The example process 600 can be configured to solve the problem of GPS denial, due to jamming, spoofing and effects such as weather and interference. The RSNR system may be carried by a platform, e.g., the vehicle. It is assumed that there are more than two satellite constellations used for navigation and that at least one satellite constellation with at least 4 satellites resides in LEO 102 and at least one satellite constellation with at least four satellites resides in MEO 104. The example is not exhaustive and many other ways to implement it exist as variants. In some instances, the RSNR system may be configured to detect signals that are not meant intentionally for navigation purposes. For example, the RSNR system may use signals that are out of the GNSS frequency bands to augment the example process 600. In some instances, the example process 600 may include operations to monitor other quantities,lying outside position and timing, such as the angle-of-arrival in order to separate true navigation signals from others in the local environment.

[0120] At 602, PRN codes are scanned until a signal is acquired for each satellite constellation. In some implementations, the RSNR system performs an acquisition search by correlating locally generated PRN replicas with the incoming RF / IF samples while sweeping code phase and Doppler frequency to find correlation peaks. Once a peak exceeds a detection threshold, the receiver declares acquisition and initializes tracking loops (e.g., DLL / PLL / FLL) for that satellite signal.

[0121] At 604, data from the satellite and positions of the other satellites are obtained. After acquisition, the RSNR system demodulates and decodes the satellite’s broadcast navigation message (or equivalent constellation message) to obtain timing and orbital parameters needed for positioning. The navigation message also provides satellite health / status flags and clock-related terms; the RSNR system checks these indicators to determine whether the satellite should be used in the solution. If the satellite is not healthy (or fails validity checks), the RSNR system relies on almanac-based visibility predictions to select alternate satellites expected to be trackable and usable.

[0122] At 606, the PRN codes of the other necessary satellites are selected using the almanac data. The almanac provides coarse orbit and status information that allows the RSNR system to predict which satellites should be above the horizon and approximately where they are, reducing acquisition time. Using these predictions, the receiver prioritizes PRNs with higher expected elevation angles and better expected geometry (e.g., improving dilution of precision), and it narrows the Doppler / code search windows accordingly.

[0123] At 608, the data from all four satellites is downloaded once the satellite signals are locked. In some instances, the data can be downloaded from the broadcast navigation messages carried on each locked satellite signal. In some instances, the data may include ephemeris (precise satellite orbit parameters), satellite clock corrections, health / status, and other navigation parameters (e.g., UTC and ionospheric model coefficients, depending on constellation). Once this information is decoded and time-tagged, the RSNR system cancompute each satellite’s position at transmit time and form measurement equations for positioning.

[0124] At 610, the atmospheric data is used in combination with the different frequencies from the different satellite constellations. In some instances, atmospheric data may include ionospheric delay and tropospheric delay affecting signal propagation. In certain examples, the atmospheric data may include other information. With multifrequency reception (e.g., L1 / L2 / L5 or analogous bands), the RSNR system can estimate and correct ionospheric delay using frequency-dependent combinations for example, and the corrected measurements are then used to improve the accuracy of the computed ranges.

[0125] At 612, a position of the vapor cell sensor, where the satellite signals are received, is calculated based on the data. The RSNR system computes pseudo-ranges (and optionally carrier-phase observables) to at least four satellites, while also computing each satellite’s Earth-Centered, Earth-Fixed (ECEF) position from the decoded ephemeris and applying clock / atmospheric corrections. In some instances, the position may be solved in ECEF coordinates (x, y, z) together with a receiver clock bias term, using an iterative leastsquares or Kalman-filter approach that minimizes residuals between predicted and measured ranges. The ECEF solution can then be converted to geodetic coordinates (latitude, longitude, altitude) for reporting and downstream use. In certain examples, the position may include the coordinates or may be solved in another manner.

[0126] At 614, the calculated position is refined using phase shifts. If several vapor cells are positioned at different points on the platform and the positions are known that data can also be used to estimate the accuracy of the position or refine the position using the multiple measurements. A phase shift is a phase difference between a received carrier relative to a local oscillator. In some examples, the position determined can be refined by incorporating carrier-phase residuals into the estimator (e.g., a Kalman filter), updating the position and clock states to reduce measurement innovations while enforcing consistency across satellites and frequencies. If multiple vapor cells are mounted on the platform with known baselines, the RSNR system can compare simultaneous solutions to quantifyinternal consistency, detect outliers, and optionally fuse measurements to further tighten the position estimate and compute an accuracy metric (e.g., via residual statistics or RAIM-style integrity checks).

[0127] Operations 602, 604, 606, 608, 610, 612, 614 in the example process 600 may be repeated for each satellite constellation operating at different frequencies (in parallel) or located in different orbits. In some instances, operations 602-614 may be performed using known GNSS / GPS receiver techniques, including signal acquisition and tracking, navigation-message decoding, ephemeris and clock correction processing, atmospheric delay compensation, pseudo-range-based position estimation, and carrier-phase-based refinement. Operations 602, 604, 606, in the example process 600 may be repeated for each frequency until hand-off is necessary. When hand-off is necessary the system can change the satellite PRN code to detect the new satellite that can be used.

[0128] At 616, positions determined using the different satellite constellations are compared. For example, position solutions derived independently from different constellations (and, where available, different frequencies) can be cross-compared to detect inconsistencies indicative of spoofing, interference, or multipath bounce. A configurable tolerance (e.g., a maximum allowable separation between constellationspecific position fixes and / or residual thresholds) can be applied to flag outliers, downweight suspect measurements, or exclude a constellation from the fused solution. In some instances, the RSNR system can compare estimated angles of arrival (AoA) — and their stability over time — against expected satellite sky geometry (from ephemeris) and / or across sensors on the platform, where anomalous clustering or rapid AoA changes can indicate a non-spaceborne source or strong reflective paths. In some instances, the RSNR system can detect and identify unanticipated AoA so as to detect outliers, fault or jamming signals. In some instances, other criterium can be used to detect outliers or other inconsistencies or improve positioning.

[0129] In some instances, transient phase can be detected, and the Doppler shifts of the signals (satellites relative to the vehicle) can be determined, which can be used to augment the data of GNSS for processing. For example, the Doppler shifts can be used to identifyspoofing and jamming signals. For another example, angle of arrival from a vehicle mounted sensor array can be used to help identify interfering and spoofing signals, directing the system to discard the affected navigation signals as necessary.

[0130] The redundancy of the multiple signals can be used to identify which signals are 'good' (e.g., navigation signals) and which are 'bad' (e.g., spoofing signals) by comparing the position, velocity and accelerations and timing information determined from the navigation signals to identify outlier readings and points where the signals were dropped. The information derived from these readings can be fed to a computer system of a user or an artificial intelligence (Al) system to make decisions about which values are true. The comparison of these signals can enable higher accuracy positioning too. For example, atmospheric corrections are better when navigation signals at different carrier frequencies are compared. A multi-frequency receiver can correct for local atmospheric conditions itself, without having to use the corrections supplied by the GNSS ground stations.

[0131] An example of the resiliency of such a system is to first imagine an adversary spoofing traditional GPS at 1.5 GHz. If the GNSS system includes navigation signals in Ku and X bands in addition to GPS, both in LEO orbits, the spoofing signal could be detected by referencing the Ku and X bands and detecting an anomaly between those positioning signals and traditional GPS. What is more is that at higher frequencies and in LEO the directionality of the incoming signals changes faster, therefore the AoA of the signals tells the inertial navigation system that the Ku and X band signals are coming from LEO and not a ground spoofing station, resulting in added evidence that the GPS is being spoofed. It would be difficult to spoof all the additional signals from LEO as it is extremely expensive, limiting the ability to countries, and the satellite positions can be tracked.

[0132] At 618, a final position is determined. The final position can be determined based on some or all of the satellite data from multiple satellite constellations, which may include the result of comparing the positions determined from different satellite constellations (at 616). Accordingly, the final position may represent a final output based on fusing, filtering or otherwise processing satellite data from multiple distinct constellations. In some implementations, the RSNR system is configured to generaterespective position solutions (and / or intermediate observables such as corrected pseudoranges, carrier phases, and residuals) from two or more satellite constellations (e.g., GPS, Galileo, GLONASS, BeiDou), and to determine a final position solution based on the comparison and fusion of the constellation-specific data. In some instances, the satellite data from different constellations can be averaged to obtain better spatial resolution in the position information and time resolution in the timing information. For example, the RSNR system may compute a consistency metric between constellation-specific position fixes, such as a position-separation value, innovation / residual statistics from a least-squares or Kalman estimator, or a geometry-weighted dilution metric, and may accept, weight, or reject measurements based on whether the metric satisfies a predetermined criterion. When discrepancies exceed a tolerance, the RSNR system may execute one or more mitigation actions, such as excluding one or more satellites or an entire constellation from the navigation solution, down-weighting measurements exhibiting elevated residuals, reacquiring or re-tracking suspected signals, switching to frequencies less impacted by interference, applying multipath screening based on carrier-to-noise ratio, lock indicators, or AoA checks, and / or reporting an integrity flag indicating a suspected spoofing, interference, or multipath condition. In some instances, the final position can then be output as a fused estimate (e.g., in ECEF or geodetic coordinates) together with an associated uncertainty value derived from the remaining measurements and the applied weighting / exclusion decisions. In some implementations, the final position is determined based on a comparison of position data obtained from different satellite constellations according to a predetermined criterion (e.g., a tolerance threshold, residual metric, a discrepancy in AOA; or integrity check) that governs weighting, acceptance, or exclusion of constellation-specific solutions. In some instances, a Kalman filter can be used to anticipate the next position based on prior satellite data to better eliminate uncertainty in the present data. At 620, Doppler shift data is collected to determine velocities. At 622, necessary handoff times are calculated based on almanac and satellite velocities. The Doppler-based velocity determination and hand-off management operations may be implemented as the operations in conventional GPS / GNSS receiver processing.

[0133] In some instances, operations of the process 600 can be repeated in whole or in parts depending on knowledge of the satellite orbits and the status of whether or not the system is locked onto the satellite navigation signals.

[0134] Some of the subject matter and operations described in this specification can be implemented in digital electronic circuitry, or in computer software, firmware, or hardware, including the structures disclosed in this specification and their structural equivalents, or in combinations of one or more of them. Some of the subject matter described in this specification can be implemented as one or more computer programs, i.e., one or more modules of computer program instructions, encoded on a computer storage medium for execution by, or to control the operation of, data-processing apparatus. A computer storage medium can be, or can be included in, a computer-readable storage device, a computer-readable storage substrate, a random or serial access memory array or device, or a combination of one or more of them. Moreover, while a computer storage medium is not a propagated signal, a computer storage medium can be a source or destination of computer program instructions encoded in an artificially generated propagated signal. The computer storage medium can also be, or be included in, one or more separate physical components or media.

[0135] Some of the operations described in this specification can be implemented as operations performed by a data processing apparatus on data stored on one or more computer-readable storage devices or received from other sources.

[0136] The term "data-processing apparatus" encompasses all kinds of apparatus, devices, and machines for processing data, including by way of example a programmable processor, a computer, a system on a chip, or multiple ones, or combinations, of the foregoing. The apparatus can include special purpose logic circuitry, e.g., an FPGA (field programmable gate array) or an ASIC (application specific integrated circuit). The apparatus can also include, in addition to hardware, code that creates an execution environment for the computer program in question, e.g., code that constitutes processor firmware, a protocol stack, a database management system, an operating system, a cross-platform runtime environment, a virtual machine, or a combination of one or more of them.

[0137] A computer program (also known as a program, software, software application, script, or code) can be written in any form of programming language, including compiled or interpreted languages, declarative or procedural languages, and it can be deployed in any form, including as a stand-alone program or as a module, component, subroutine, object, or other unit suitable for use in a computing environment. A computer program may, but need not, correspond to a file in a file system. A program can be stored in a portion of a file that holds other programs or data (e.g., one or more scripts stored in a markup language document), in a single file dedicated to the program, or in multiple coordinated files (e.g., files that store one or more modules, sub programs, or portions of code). A computer program can be deployed to be executed on one computer or on multiple computers that are located at one site or distributed across multiple sites and interconnected by a communication network.

[0138] Some of the processes and logic flows described in this specification can be performed by one or more programmable processors executing one or more computer programs to perform actions by operating on input data and generating output. The processes and logic flows can also be performed by, and apparatus can also be implemented as, special purpose logic circuitry, e.g., an FPGA (field programmable gate array) or an ASIC (application specific integrated circuit).

[0139] In a general aspect, a Rydberg sensing based navigation receiver (RSNR) system is presented.

[0140] In a first example, a method includes by operation of a vapor cell sensor system, sensing navigation signals from satellites of two or more distinct satellite constellations; obtaining sensor data generated by the vapor cell sensor system based on sensing the navigation signals from the vapor cell sensor system; and by operation of one or more processors, generating navigation data based on the navigation signals by processing the sensor data from the vapor cell sensor system. The navigation data includes position and timing information.

[0141] Implementations of the first example may include one or more of the following features. The two or more distinct satellite constellations include a first satelliteconstellation that operates in a LEO, and a second, distinct satellite constellation that operates in a MEO. The vapor cell sensor system includes a first vapor cell sensor that senses a first subset of the navigation signals from a first satellite constellation of the two or more distinct satellite constellations, and a second vapor cell sensor that senses a second subset of the navigation signals from a second, distinct satellite constellation of the two or more distinct satellite constellations. The vapor cell sensor system includes a first plurality of vapor cell sensors operating at a first frequency, and generating navigation data includes determining an AoA of the navigation signals sensed by the first plurality of vapor cell sensors operating at the first frequency.

[0142] Implementations of the first example may include one or more of the following features. Generating the navigation data includes obtaining a plurality of PRN codes from a plurality of satellites in each satellite constellation; obtaining a plurality of navigation messages associated with at least a subset of satellites in the plurality of satellites in each satellite constellation using the plurality of PRN codes; and selecting, based on satellite information in the plurality of navigation messages, at least four satellites from the subset in each satellite constellation. Obtaining the plurality of PRN codes and the plurality of navigation messages includes obtaining in-phase and quadrature signals of the plurality of satellites based on coherent sensing by the vapor cell sensor system. The navigation signals are encoded using distinct phase encodings, and the plurality of PRN codes and the plurality of navigation messages are obtained based on incoherent sensing by the vapor cell sensor system.

[0143] Implementations of the first example may include one or more of the following features. The method further includes determining respective Doppler shifts of navigation signals from the selected at least four satellites in each satellite constellation; augmenting the navigation messages from the selected at least four satellites according to the Doppler shifts; and calculating the position and timing information based on the respective augmented navigation messages from the selected at least four satellites in each satellite constellation. The vapor cell sensor system includes a probe laser and two coupling lasers, and obtaining the plurality of PRN codes and the plurality of navigation messages includes operating the vapor cell sensor system to perform incoherent sensing based on the probelaser and the two coupling lasers. The vapor cell sensor system includes a probe laser and three coupling lasers, and obtaining the plurality of PRN codes and the plurality of navigation messages include operating the vapor cell sensor system to perform coherent sensing using the probe laser and the three coupling lasers. The method includes detecting presence of navigation interference by comparing the navigation data derived from the two or more distinct satellite constellations. Generating the navigation data includes determining a final position of the vapor cell sensor system by comparing the navigation data derived from the two or more distinct satellite constellations.

[0144] In a second example, a system includes a vapor cell sensor system and one or more processors configured to perform operations in the first example.

[0145] While this specification contains many details, these should not be understood as limitations on the scope of what may be claimed, but rather as descriptions of features specific to particular examples. Certain features that are described in this specification or shown in the drawings in the context of separate implementations can also be combined. Conversely, various features that are described or shown in the context of a single implementation can also be implemented in multiple implementations separately or in any suitable sub-combination.

[0146] Similarly, while operations are depicted in the drawings in a particular order, this should not be understood as requiring that such operations be performed in the particular order shown or in sequential order, or that all illustrated operations be performed, to achieve desirable results. In certain circumstances, multitasking and parallel processing may be advantageous. Moreover, the separation of various system components in the implementations described above should not be understood as requiring such separation in all implementations, and it should be understood that the described program components and systems can generally be integrated together in a single product or packaged into multiple products.

[0147] A number of embodiments have been described. Nevertheless, it will be understood that various modifications can be made. Accordingly, other embodiments are within the scope of the following claims.

Claims

CLAIMSWhat is claimed is:

1. A method comprising:by operation of a vapor cell sensor system, sensing navigation signals from satellites of two or more distinct satellite constellations;obtaining sensor data from the vapor cell sensor system, the sensor data being generated by the vapor cell sensor system based on sensing the navigation signals; and by operation of one or more processors, generating navigation data based on the navigation signals by processing the sensor data from the vapor cell sensor system, wherein the navigation data comprises position and timing information.

2. The method of claim 1, wherein generating the navigation data comprises:obtaining a plurality of pseudo-random noise (PRN) codes from a plurality of satellites in each satellite constellation;obtaining a plurality of navigation messages associated with at least a subset of satellites in the plurality of satellites in each satellite constellation using the plurality of PRN codes; andselecting, based on satellite information in the plurality of navigation messages, at least four satellites from the subset in each satellite constellation.

3. The method of claim 2, wherein obtaining the plurality of PRN codes and the plurality of navigation messages comprises obtaining in-phase and quadrature signals of the plurality of satellites based on coherent sensing by the vapor cell sensor system.

4. The method of claim 2, wherein the navigation signals are encoded using distinct phase encodings, and the plurality of PRN codes and the plurality of navigation messages are obtained based on incoherent sensing by the vapor cell sensor system.

5. The method of claim 2, comprising:determining respective Doppler shifts of navigation signals from the selected at least four satellites in each satellite constellation;augmenting the navigation messages from the selected at least four satellites in each satellite constellation according to the Doppler shifts; andcalculating the position and timing information based on the respective augmented navigation messages from the selected at least four satellites in each satellite constellation.

6. The method of claim 2, wherein the vapor cell sensor system comprises a probe laser and two coupling lasers, and obtaining the plurality of PRN codes and the plurality of navigation messages comprises operating the vapor cell sensor system to perform incoherent sensing based on the probe laser and the two coupling lasers.

7. The method of claim 2, wherein the vapor cell sensor system comprises a probe laser and three coupling lasers, and obtaining the plurality of PRN codes and the plurality of navigation messages comprises operating the vapor cell sensor system to perform coherent sensing using the probe laser and the three coupling lasers.

8. The method of any one of claims 1 through 7, wherein the two or more distinct satellite constellations comprise:a first satellite constellation that operates in a low earth orbit, anda second, distinct satellite constellation that operates in a medium earth orbit.

9. The method of any one of claims 1 through 7, wherein the vapor cell sensor system comprises:a first vapor cell sensor that senses a first subset of the navigation signals from a first satellite constellation of the two or more distinct satellite constellations, anda second vapor cell sensor that senses a second subset of the navigation signals from a second, distinct satellite constellation of the two or more distinct satellite constellations.

10. The method of any one of claims 1 through 7, wherein the vapor cell sensor system comprises a first plurality of vapor cell sensors operating at a first frequency, and generating navigation data comprises determining an angle of arrival of the navigation signals sensed by the first plurality of vapor cell sensors operating at the first frequency.

11. The method of any one of claims 1 through 7, comprising:detecting presence of navigation interference by comparing the navigation data derived from the two or more distinct satellite constellations.

12. The method of any one of claims 1 through 7, wherein generating the navigation data comprises:comparing positions determined from the two or more distinct satellite constellations; anddetermining a final position based on the comparison.

13. A system comprising:a vapor cell sensor system configured to:sense navigation signals from satellites of two or more distinct satellite constellations; andgenerate sensor data based on sensing the navigation signals; andone or more processors configured to:receive the sensor data from the vapor cell sensor system; and generate navigation data based on the navigation signals by processing the sensor data from the vapor cell sensor system, wherein the navigation data comprises position and timing information.

14. The system of claim 13, wherein the one or more processors are configured to: obtain a plurality of pseudo-random noise (PRN) codes from a plurality of satellites in each satellite constellation;obtain a plurality of navigation messages associated with at least a subset of satellites in the plurality of satellites in each satellite constellation using the plurality of PRN codes; andselect, based on satellite information in the plurality of navigation messages, at least four satellites from the subset in each satellite constellation.

15. The system of claim 14, wherein obtaining the plurality of PRN codes and the plurality of navigation messages comprises obtaining in-phase and quadrature signals of the plurality of satellites based on coherent sensing by the vapor cell sensor system.

16. The system of claim 14, wherein the navigation signals are encoded using distinct phase encodings, and the plurality of PRN codes and the plurality of navigation messages are obtained based on incoherent sensing by the vapor cell sensor system.

17. The system of claim 14, wherein the one or more processors are configured to: determine respective Doppler shifts of navigation signals from the selected at least four satellites in each satellite constellation;augment the navigation messages from the selected at least four satellites according to the Doppler shifts; andcalculate the position and timing information based on the respective augmented navigation messages from the selected at least four satellites in each satellite constellation.

18. The system of any one of claims 13 through 17, wherein the two or more distinct satellite constellations comprise:a first satellite constellation that operates in a low earth orbit, anda second, distinct satellite constellation that operates in a medium earth orbit.

19. The system of any one of claims 13 through 17, wherein the vapor cell sensor system comprises:a first vapor cell sensor that senses a first subset of the navigation signals from a first satellite constellation of the two or more distinct satellite constellations, anda second vapor cell sensor that senses a second subset of the navigation signals from a second, distinct satellite constellation of the two or more distinct satellite constellations.

20. The system of any one of claims 13 through 17, wherein the vapor cell sensor system comprises a first plurality of vapor cell sensors operating at a first frequency, and the one or more processors are configured to determine an angle of arrival of the navigation signals sensed by the first plurality of vapor cell sensors operating at the first frequency.

Images