Friend transponder for aided navigation

Abstract

The invention relates to a friend transponder for aided navigation. An apparatus includes a receive antenna configured to receive a radar signal. The apparatus includes a return signal generator configured to generate a return signal based on the received radar signal. The return signal includes at least a first component at a first frequency offset from a carrier frequency of the received radar signal and a second component at a second frequency offset from the carrier frequency. The apparatus also includes a transmit antenna configured to transmit the return signal.

Description

Technical Field

[0001] This disclosure generally relates to the transmission and reception of radar signals. Background Technology

[0002] In flight applications such as urban air mobility, the need for precise navigation to vertical takeoff and landing (VTOL) stations is increasing, particularly in areas with unreliable or compromised satellite navigation system signals, such as GPS signals. Air-rental platforms, such as autonomous electric vertical takeoff and landing (eVTOL) aircraft, are typically compact, lightweight structures with limited sensor capacity due to potential interference and space constraints, and lack a metallic ground plane for interference mitigation. These challenges underscore the need for universal sensor solutions. Summary of the Invention

[0003] One aspect of the subject matter disclosed below is an apparatus comprising a receiving antenna configured to receive radar signals. The apparatus includes a return signal generator configured to generate a return signal based on the received radar signals. The return signal includes at least a first component at a first frequency offset from the carrier frequency of the received radar signals, and a second component at a second frequency offset from the carrier frequency. The apparatus also includes a transmitting antenna configured to transmit the return signal.

[0004] Another aspect of the subject matter disclosed below is a method comprising receiving a radar signal at a device. The method includes generating a return signal at the device based on the received radar signal. The return signal includes at least a first component at a first frequency offset from the carrier frequency of the received radar signal, and a second component at a second frequency offset from the carrier frequency. The method also includes transmitting the return signal at the device.

[0005] Another aspect of the subject matter disclosed below is an aircraft including a radar system. The radar system includes a transmitting antenna configured to transmit radar signals. The radar system also includes a receiving antenna configured to receive a return signal corresponding to the radar signal and including a first component at a first frequency offset from the carrier frequency of the radar signal and a second component at a second frequency offset from the carrier frequency. The radar system further includes a radar return analyzer configured to identify a landing position based at least on the detection of the first and second components. The aircraft also includes a navigation system coupled to the radar system and configured to generate navigation commands based on the identified landing position.

[0006] The features, functions, and advantages described herein can be implemented independently in various embodiments or in combination in other embodiments, further details of which can be found in the following description and figures. Attached Figure Description

[0007] Figure 1 This is a diagram illustrating a system including an ally transponder according to some examples of this disclosure.

[0008] Figure 2 Examples based on this disclosure include Figure 1 A diagram of the vertical take-off and landing platform of the friendly transponder.

[0009] Figure 3 Based on some examples of this disclosure, it is possible to Figure 1 A diagram of the components and operations implemented in the system.

[0010] Figure 4 Based on some examples of this disclosure Figure 1 An example of radar tracking diagrams for a radar source and a friendly transponder.

[0011] Figure 5 Some examples based on this disclosure may be included in Figure 1 A diagram of an aircraft in a system.

[0012] Figure 6 This shows the operation. Figure 1 A flowchart illustrating an example of the methods for a friendly responder in a system.

[0013] Figure 7 It is a block diagram of a computing environment including a computing device configured to support aspects of computer-implemented methods and computer-executable program instructions (or code) according to the present disclosure. Detailed Implementation

[0014] This paper discloses systems and methods for assisted navigation using friendly transponders. The need for precise navigation to vertical takeoff and landing (VTOL) platforms is increasing in flight applications, such as urban air mobility, especially in areas where GPS signals are unreliable or compromised. Air-leasable vehicle platforms such as eVTOLs are typically compact, lightweight structures with limited sensor capacity due to potential interference and space constraints, and lack a metallic ground plane for interference mitigation. These challenges highlight the need for universal sensor solutions.

[0015] As Detection and Avoidance (DAA) technology evolves into a commercially important and / or necessary sensor solution, and transitions to Design Assurance Level A and / or Level B (DAL A / B) solutions, leveraging its advantages and simplified certification process, expanding its capabilities to include tasks such as precision landing becomes more feasible. According to one aspect, this technology extends the use of DAA airborne radar over difficult-to-resolve ground clutter for landing purposes.

[0016] According to one aspect of the disclosed technology, the friendly transponder introduces a unique approach by replicating the received waveform from the airborne radar while incorporating two distinct bi-peak Doppler frequency shifts (one positive and one negative). In a particular implementation, this technique simulates the simultaneous presence of incoming and outgoing flight objects at the same location, with matched radar cross-section (RCS) values ​​and predefined velocities. In some implementations, the friendly transponder further introduces a predetermined delay in the returned signal, which replicates the relative distance offset between the position of the friendly transponder and the apparent positions of the incoming and outgoing flight objects, enabling the friendly transponder to be detected even when it is within the radar blind zone of the aircraft (such as during the final phase of landing).

[0017] In one respect, this technology enhances landing accuracy in challenging environments, surpassing conventional systems. Furthermore, the adjustable RCS generated through signal amplification allows for a compact form factor. In another respect, the relative simplicity of the converter's circuitry facilitates verifiability, usability analysis, and integrity using relatively few hardware components.

[0018] According to one aspect, the disclosed technology expands the use of frequency modulated continuous wave (FMCW) DAA airborne radar for landing purposes. While airborne radar is not specifically designed to handle ground clutter, this approach involves using a specialized transponder that provides a unique signature corresponding to a specific landing site. The advantage of this design is its simplicity, which allows for easier authentication, cost-effective implementation, and low setup and maintenance costs. The transponder can transmit the same waveform as the airborne radar, but with two predefined Doppler frequency shifts (one positive and one negative). By utilizing this transponder technology, air-rental vehicle platforms can achieve accurate and reliable landing capabilities even in challenging GPS-denied or compromised environments.

[0019] According to one aspect, the disclosed technology provides precise relative navigation, which can be implemented in various airframes, including those with limited available space and formed from composite materials. The disclosed transponder solution, due to its simple design, offers a more cost-effective alternative to conventional technologies. It can be implemented at a lower cost and with a simpler certification cycle, thereby reducing setup costs and maintenance requirements. The solution also allows for more reliable and accurate landing capabilities, even in challenging environments where conventional landing systems might be inadequate.

[0020] According to one approach, a friendly transponder located at a fixed position near the vertical takeoff and landing platform can generate a predefined Doppler frequency shift of the received signal from the airborne radar, exceeding the operational flight envelope and falling below the radar ambiguity Doppler range, and then transmit the signal back to the airborne radar.

[0021] According to one aspect, the disclosed technology includes a dedicated transponder that transmits a unique signature corresponding to a specific landing site and is designed to work in conjunction with an FMCW (Frequency Modulated Continuous Wave) airborne radar. This differs from existing solutions, which may rely on different transponder technologies or may not specifically address the need for landing site signatures. Therefore, the use of FMCW (Frequency Modulated Continuous Wave) detection and avoidance (DAA) can be extended to airborne radar for landing purposes in the context of urban air mobility.

[0022] According to one aspect, the disclosed technology can be applied to pulse radar, allowing the simulation of predefined Doppler and altitude values ​​beyond operational flight conditions. These predefined values ​​can be dynamically adjusted based on factors such as time and geographical location. For example, different values ​​can be provided at different times of the day. This feature not only aids in VTOL identification but also helps reduce unintentional interference. To enhance system effectiveness, the rate of Doppler injection can be adjusted within a certain margin. This allows for further differentiation between friendly transponders and background clutter. The rate of Doppler injection can be ramped up or ramped down, providing a means of distinguishing desired signals from unwanted interference. By combining these capabilities, this method provides pulse radar with improved versatility and adaptability. It enables the system to simulate predefined Doppler and altitude values ​​beyond operational flight conditions while also providing the flexibility to adjust the injection rate to optimize performance and minimize interference.

[0023] Specific examples are shown in the accompanying drawings and the following description. This solution encompasses all the drawings, which share common features. The drawings include numerous examples of different types of systems, devices, and operations that may be combined with this solution. It should be understood that those skilled in the art will be able to devise various arrangements that, while not expressly described or shown herein, embody the principles described herein and are included within the scope of the claims that follow this specification. Furthermore, any examples described herein are intended to aid in understanding the principles of this disclosure and should be construed as non-limiting. Therefore, this disclosure is not limited to the specific embodiments or examples described below, but is limited by the claims and their equivalents.

[0024] Specific examples are described herein with reference to the accompanying drawings. Throughout the description, common features are indicated by common reference numerals.

[0025] As used herein, various terms are used for the purpose of describing specific examples and are not restrictive. For example, the singular forms “a,” “one,” and “the” are also intended to include the plural forms unless the context clearly indicates otherwise. Furthermore, some features described herein can be singular or plural. For illustration, Figure 7 It describes a configuration including one or more processors ( Figure 7 The term "processor" (720) in the designation indicates that the device may include a single processor 720 or may include multiple processors 720. For ease of reference, these features are generally introduced as "one or more" features and are subsequently referred to in the singular unless an aspect relating to multiple features is described.

[0026] The term “comprising” is used interchangeably with “including”. Additionally, the term “wherein” is used interchangeably with the term “its”. As used herein, “exemplary” indicates an example, implementation, and / or aspect, and should not be construed as limiting or indicating a preference or preferred implementation. As used herein, ordinal terms used to modify elements (e.g., “first,” “second,” “third,” etc.) do not themselves indicate any priority or order of the element relative to another element, but merely distinguish the element from another element with the same name (but using ordinal terms). As used herein, the term “set” refers to a grouping of one or more elements, and the term “multiple” refers to multiple elements.

[0027] As used herein, unless the context otherwise requires, “get,” “generate,” “calculate,” “use,” “select,” “access,” and “determine” are interchangeable. For example, “get,” “generate,” “calculate,” or “determine” a parameter (or signal) can refer to actively generating, calculating, or determining a parameter (or signal), or it can refer to using, selecting, or accessing a parameter (or signal) that has already been generated, for example, by another component or device. As used herein, a device “configured to” perform an operation includes dedicated circuitry, hardware, or other components that enable the operation to be performed by the device. As an example, programming a general-purpose processor with instructions that, when executed by the processor, cause the processor to perform a specific operation results in a dedicated processor being configured to perform that specific operation. A device can be configured to perform multiple operations. A device configured to perform an operation does not necessarily exclude the device from being configured to perform other operations.

[0028] As used herein, “connection” can include “communication connection,” “electrical connection,” or “physical connection,” and may (or alternatively) include any combination thereof. Two devices (or components) may be directly or indirectly connected (e.g., a communication connection, electrical connection, or physical connection) via one or more other devices, components, wires, buses, networks (e.g., wired networks, wireless networks, or combinations thereof). As an illustrative, non-limiting example, two devices (or components) in an electrical connection may be in the same device or different devices and may be connected via electronics, one or more connectors, or inductive connections. In some embodiments, two devices (or components) in a communication connection (e.g., electrical communication) may directly or indirectly send and receive electrical signals (digital or analog signals), for example, via one or more wires, buses, networks, etc. As used herein, “direct connection” is used to describe two devices connected (e.g., a communication connection, electrical connection, or physical connection) without intermediate components.

[0029] refer to Figure 1 The diagram illustrates a system 100, which includes components associated with aircraft navigation in applications such as urban air mobility. System 100 includes a device illustrated as a friendly transponder 102, which includes a receiving antenna 110, a return signal generator 112, and a transmitting antenna 114. System 100 also includes an aircraft 150, which includes a radar system 152 coupled to a navigation system 156.

[0030] Receiving antenna 110 is configured to receive radar signal 120 from radar system 152 of aircraft 150. Return signal generator 112 is configured to generate return signal 113 based on the received radar signal 111 (e.g., a filtered and / or amplified version of radar signal 120). Return signal 113 includes at least a first component at a first frequency offset from the carrier frequency of the received radar signal 111 and a second component at a second frequency offset from the carrier frequency. Transmitting antenna 144 is configured to transmit return signal 113, which is illustrated as transmitted return signal 122.

[0031] According to one aspect, the first frequency offset and the second frequency offset have matching magnitudes and opposite signs, such as reference... Figure 3 Further detailed description. According to one aspect, the first frequency offset and the second frequency offset are within a threshold range from the carrier frequency. In some aspects, the first component simulates a first Doppler signature of a first object traveling toward the source of the radar signal 120 at a first velocity, and the second component simulates a second Doppler signature of a second object traveling away from the source of the radar signal 120 at a second velocity substantially matching the first velocity. According to one aspect, the return signal generator 112 includes a mixer configured to mix the received radar signal 111 with a mixed signal to generate a return signal 113, wherein the mixed signal includes components having frequencies substantially matching the first frequency offset and the second frequency offset, such as reference... Figure 3 Further description.

[0032] According to one aspect, the friendly transponder 102 is configured to indicate the landing location of the autonomous aircraft, such as in Figure 2 As shown in the diagram. The combination of the first and second components included in the return signal 113 can be used as a unique identifier corresponding to the landing location. In some implementations, the return signal 113 includes a pattern that uniquely identifies the friendly transponder 102 (e.g., based on frequency allocation, time allocation, or another characteristic in the frequency and / or time domains).

[0033] According to one aspect, the radar system 152 of the aircraft 150 includes a radar return analyzer 154, which is configured to identify a landing position transponder (e.g., landing transponder 102) based on the detection of a first component and a second component in the transmitted return signal 122. A navigation system 156 is coupled to the radar system 152 and configured to generate navigation instructions 158 based on the identified landing position. For example, the navigation instructions 158 may be generated by a flight computer and presented to one or more operators or pilots of the aircraft 150, or may be provided to an autopilot system or autonomous aircraft operating system to control the operation of the aircraft 150, or both.

[0034] Figure 2A specific example 200 of a landing location including a friendly transponder 102 is depicted, which is shown as a vertical takeoff and landing platform 210. The vertical takeoff and landing platform 210 includes a landing and takeoff (TLOF) area 212, a final approach and takeoff (FATO) area 214, and a safety area (SA) 216.

[0035] Friendly transponder 102 is located in FATO 214 and is configured to receive radar signal 120 from aircraft 150 and transmit a return signal 122 based on the received radar signal (e.g., based on a filtered and / or amplified version of radar signal 120). The transmitted return signal 122 includes at least a first component that is at a first frequency offset from the carrier frequency of the received radar signal 120 and a second component that is at a second frequency offset from the carrier frequency, as referenced. Figure 3 Further description.

[0036] Aircraft 150 is configured to transmit radar signals 120 and, in conjunction with a DAA system, receive and analyze return signals 122. In a particular embodiment, the radar system 152 of aircraft 150 is configured to provide elevation coverage (graphically depicted as circular segment 240) to receive return signals within an elevation range spanning from above to below the longitudinal axis of aircraft 150. In a non-limiting example, coverage may be determined based on one or more applicable standards or guidelines, such as those similar to the Radio Technical Committee on Aeronautics (RTCA) specifications for DAA systems (e.g., DO-366). Reference Figure 5 An illustrative example of elevation and azimuth coverage of a DAA system that can be used in conjunction with friendly transponder 102 is described in more detail.

[0037] The friendly transponder 102 enables the aircraft 150 to pinpoint its landing location with a certain precision, such as TLOF 212. In particular, the transmitted return signal 122 (received at the aircraft 150) provides a unique signature that distinguishes the friendly transponder 102 from any other object that may be around the vertical takeoff and landing platform 210.

[0038] In some implementations, the friendly transponder 102 is oriented such that the propagation direction of the transmitted return signal 122 is elevated to reduce reflections from nearby objects. As shown, the height 224 above the vertical takeoff and landing platform elevation 220 indicates the minimum height clearance around SA216 at a distance 222 from FATO 214, which may correspond to the minimum slope 230 of the approach path. In an illustrative, non-limiting example, for a 1:8 slope as the minimum slope 230, the height 224 at a distance of approximately 25 feet 222 may correspond to approximately 3.125 feet. Therefore, in some examples, the friendly transponder 102 is tilted above the minimum slope 230 to reduce or eliminate ringing caused by reflections of the return signal 122 received at the friendly transponder 102 from objects around SA216.

[0039] Figure 3 Depicting what can be done Figure 1 Examples of components and operations implemented in the system are shown in Block Figure 302. The components of the friendly transponder 102 include a low-noise amplifier (LNA) 314 coupled to a receiving antenna 110, an optional delay device 328, a mixer 318 coupled to the LNA 314 and a signal generator 320, and a bandpass filter (BPF) 326 configured to filter the output of the mixer 318 to generate a return signal 113 transmitted by the transmitting antenna 114. In certain aspects, the mixer 318 and the signal generator 320, and optionally the LNA 314, BPF 326, or both, correspond to... Figure 1 The return signal generator 112 or is included Figure 1 The return signal generator 112.

[0040] LNA314 is configured to amplify the received radar signal 111 from receiving antenna 110 to generate an amplified received radar signal 316. The carrier frequencies of the received radar signal 111 and the amplified received radar signal 316 are shown as F. C +F DO , of which F C The carrier frequency (e.g., frequency ramp) transmitted by the radar system 152 of the aircraft 150 is indicated, and F DO The Doppler shift is indicated by the speed of the aircraft 150 toward the friendly transponder 102.

[0041] Optional delay device 328 is configured to receive a signal (e.g., amplified received radar signal 316) as input and generate a delayed version of the signal as output. The delayed version of the signal has a waveform substantially the same as the input signal, but is offset in time by a predetermined time delay. For example, delay device 328 may include a delay line (e.g., a coaxial cable) whose length is selected such that the propagation delay of the signal substantially matches the predetermined time delay. As an illustrative, non-limiting example, other components that may be included in delay device 328 may include a surface acoustic wave (SAW) delay line, a magnetostrictive delay line, a fiber optic RF delay line, or an LC network.

[0042] Signal generator 320 is configured to generate a Doppler frequency shift signal 322. In a particular embodiment, the Doppler frequency shift signal 322 has a frequency F. DS The sinusoidal signal, corresponding to the Doppler shift, is interpreted by the radar system 152 as a frequency shift caused by a moving object when the Doppler shift is included in the transmitted return signal 122, as further described below. According to some aspects, the signal generator 320 includes a crystal-based oscillator (e.g., a surface acoustic wave (SAW) or quartz resonator), a counter (e.g., a 32 MHz clock and a down-counter to the tone frequency), one or more other types of oscillators, or combinations thereof.

[0043] Mixer 318 is configured to mix and amplify the received radar signal 316 and the Doppler frequency shift signal 322 to generate a signal with frequency F. C +F DO ±F DS The mixed signal 324 includes a first component (F) that mimics the positive Doppler frequency shift of a first object moving toward the aircraft 150. C +F DO +F DS ), and the second component (F) of the negative Doppler frequency shift of a second object mimicking the movement of a second object 150 away from the aircraft. C +F DO -F DS ).

[0044] BPF 326 is configured to limit the bandwidth of the returned signal 113. In one aspect, BPF 326 operates in a manner similar to a roofing filter. In the example, BPF 326 transmits a frequency range (e.g., passband) comprising the first and second components of the mixed signal 324, and attenuates frequencies outside the passband.

[0045] The resulting return signal 113 output by BPF 326 is transmitted by transmit antenna 114 to generate a transmit return signal 122 as a double-peak Doppler, which includes at least a carrier frequency (e.g., F) relative to the received radar signal 111. C +F DO The first frequency offset (e.g., F) DS The first component at ) and the second frequency offset (e.g., -F) at a distance from the carrier frequency of the received radar signal 111. DS The second component at (). Therefore, the first frequency offset and the second frequency offset have matching amplitudes and opposite signs.

[0046] Graph 304 depicts an example of frequency as a function of time and includes a center track 360, an upper track 362, and a lower track 364. The center track 360 corresponds to the carrier frequency of the received radar signal 111 (e.g., F). C +F DO The upper trace 362 corresponds to the first component in the return signal 113 and is shown as a triangular wave that varies linearly between a lower frequency F1 and a higher frequency F2 (e.g., in a frequency modulated continuous wave (FMCW) implementation). The upper trace 362 corresponds to the first component in the return signal 113 and is shown as a high-frequency component above the carrier (e.g., F1). C +F DO +F DS The lower trace 364 corresponds to the second component in the return signal 113 and is shown as a low-frequency component below the carrier (e.g., F). C +F DO -F DS ), which simulates an object traveling away from the aircraft 150 or has the signature of an object traveling away from the aircraft 150. The magnitude of the peak frequency difference between the center trace 360 ​​and the upper trace 362 (e.g., |F DS |) and the magnitude of the peak frequency difference between the center trace 360 ​​and the lower trace 364 (e.g., |-F) DS The delay between the center trace 360 ​​and the upper trace 362 is substantially the same and is denoted as ΔF. The delay between the center trace 360 ​​and the lower trace 364 is substantially matched with the delay between the center trace 360 ​​and the lower trace 364, and is indicated as the difference between the first time 370 (e.g., the lower peak of the center trace 360) and the second time 372 (e.g., the lower peak of the upper trace 362 and the lower trace 364).

[0047] In an illustrative, non-limiting example, radar signal 120 has a carrier frequency F in the Ku band. CThis frequency ramp is in the range of 15.4 GHz to 16.7 GHz, and the friendly transponder 102 is configured to simulate a pair of objects, including a first object moving towards the aircraft 150 at 150 knots (77.17 m / s) and a second object moving away from the aircraft 150 at 150 knots. The frequency F of the Doppler shift signal 322 is... DS According to equation F DS =2(v*cos(α)) / λ, where v is the velocity of the object, α is the angle between the direction of motion and the line between the source and the observer, and λ is the wavelength of the transmitted signal. At 16.1 GHz (e.g., at the center of the frequency ramp from 15.4 GHz to 16.7 GHz), λ = 0.0187 m. For a speed of 150 knots towards / away from the aircraft, v = 77.17 m / s, and α = 0. As a result, F DS The selection of approximately 8.3 kHz causes the Doppler double peaks in the transmitted return signal 122 to mimic the radar signature of a pair of objects moving in opposite directions at 150 knots.

[0048] In embodiments where the friendly transponder 102 includes an optional delay device 328, the predetermined time delay introduced in the output of the delay device 328 propagates through the remaining signal processing (e.g., mixing at mixer 318 and filtering at filter 326) and is included in the transmitted return signal 122. One effect of introducing the predetermined time delay is that the friendly transponder 102 can remain detectable even within the radar blind range of the radar system 152. For example, the radar blind range corresponds to a minimum distance from the radar at which an object is too close to be reliably detected by the radar. To illustrate, when an object is within the blind range, the echo from the object returns before the radar receiver can detect it (e.g., as an illustrative, non-limiting example, due to transmitter leakage at the radar system 152 or windowing used during signal processing). By introducing a predetermined time delay in the transmitted return signal 122, the friendly transponder 102 artificially prolongs the echo return time (e.g., increases the distance between the first time 370 and the second time 372) and simulates the object being outside the blind zone, even when the aircraft 150 is in the final stage of landing. The predetermined time delay introduced by the delay device 328 corresponds to a known offset that the radar system 152 can take into account.

[0049] Block diagram 308 illustrates examples of components of aircraft 150, including a transmitting antenna 340, a receiving antenna 342, and a radar system 152 including a radar return analyzer 154. The transmitting antenna 340 is configured to transmit radar signal 120, and the receiving antenna 342 is configured to receive transmitted return signals 122 (in addition to return signals from other objects near aircraft 150). The radar return analyzer 154 is configured to process the received return signals and interpret the transmitted return signals 122 as a pair of objects substantially co-located at the position of the friendly transponder 102, traveling at substantially the same speed and in opposite directions (towards and away from aircraft 150), and having substantially the same RCS.

[0050] To illustrate, the radar return analyzer 154 can analyze the frequency and phase difference between each of the first and second components in the transmitted radar signal 120 and the received return signal 122. Because the transmitted frequency varies linearly with time, the propagation delay between the aircraft 150 and the friendly transponder 102 introduces a beat frequency (e.g., a consistent frequency offset) proportional to the distance between the aircraft 150 and the friendly transponder 102. Therefore, the radar return analyzer 154 estimates that the positions of the first object simulated by the upper track 362 and the second object simulated by the lower track 364 are both at the position of the friendly transponder 102. In an implementation where the friendly transponder 102 includes a delay device 328, the radar return analyzer 154 adjusts the calculation to remove the effects of a predetermined time delay from the position estimation. The Doppler frequency shift observed across the sequential ramps of the transmitted radar waveform indicates a frequency offset F of the first object based on the upper track 362. DS Moving toward aircraft 150 at a first speed (e.g., 150 knots), and instructing the second object to deflect at a frequency based on the lower trace 364 -F DS The object moves away from the aircraft 150 at a first speed (e.g., 150 knots). Because each of the first and second components has substantially the same signal strength, the radar return analyzer 154 estimates that the first and second objects have the same RCS.

[0051] According to one aspect, radar system 152 is configured to use various criteria, individually or in combination, to detect friendly transponder 102. As an illustrative and non-limiting example, one criterion that radar system 152 can use to detect and / or identify friendly transponder 102 is the detection of a dual Doppler signature. For example, in an illustrative and non-limiting example, radar system 152 detects friendly transponder 102 in response to detecting a Doppler signature with opposite signs at a speed within a first threshold of a predetermined speed (such as a predetermined speed of 150 knots and a first threshold of 3 knots), and manifests as two objects moving in opposite directions, each with a speed of 77.17 ± 1.53 m / s.

[0052] The radar system 152 can be used to detect and / or identify friendly transponder 102 or maintain tracking of a detected friendly transponder 102 based on a second criterion of detection of Doppler biphasics having substantially the same amplitude. In the example, if the amplitude of the Doppler biphasics indicates that the two objects have velocities within a second threshold (e.g., 2 m / s) of each other, then a trajectory for the friendly transponder 102 is maintained.

[0053] The radar system 152 can be used to detect and / or identify friendly transponders 102 or maintain tracking of detected friendly transponders 102 based on a third criterion of detection of Doppler bimodals having substantially the same RCS. In the example, tracking of the friendly transponder 102 is maintained if the RCS of the Doppler bimodals indicates that the two objects have radar cross-sections (in decibels per square meter (dBsm)) within each other's third threshold.

[0054] Radar system 152 can be used to detect and / or identify friendly transponder 102 or maintain tracking of detected friendly transponder 102 based on a fourth criterion of detection of Doppler bimodalities with substantially similar positions. In the example, if the trajectories of the bimodalities are within a fourth threshold distance from each other in meters, such as within a sphere with a diameter equal to the fourth threshold distance, then the trajectory for friendly transponder 102 is maintained.

[0055] Illustrative depiction 306 of the friendly transponder 102 illustrates the difference in antenna flare length, which can be used to reduce or minimize leakage between the receiver (RX) and transmitter (TX). In illustrative depiction 306, the receiver's antenna flare 310 is longer than the transmitter's antenna flare 330. Combined with the compact form factor of the friendly transponder 102, the use of a smaller antenna inherently provides a wider beam, which is beneficial for size reduction and also enhances the usefulness of navigation assistance. Amplification can be used with the compact antenna to compensate for size.

[0056] Although an FMCW implementation is shown, in other implementations, the radar can be another type of radar, such as a pulse radar. Although a single mixed frequency F is shown... DS However, in other examples, two or more mixed frequencies can be used in a single transponder (e.g., more than two components can be inserted into the return signal).

[0057] Although a single optional delay device 328 is shown at the input of mixer 318, in other implementations, one or more such delay devices may alternatively or additionally be included at the input of LNA 314, the input of filter 326, the input of transmit antenna 114, or a combination thereof. While delay device 328 is described as introducing a predetermined time delay, in some implementations the time delay may be adjustable or selectable, such as to operate in one or more preset configurations known to radar analyzer 154.

[0058] although Figure 3 A cost-effective implementation primarily using passive components is described; however, in other implementations, the friendly responder 102 may include one or more processors (e.g., digital signal processors (DSPs)) configured to generate a return signal 113, such as Figure 7 As shown. For example, in the digital implementation of the friendly transponder 102, the received radar return signal (e.g., radar signal 111) or an amplified received radar return signal (e.g., radar signal 316) can be digitized and processed in the digital domain, which allows mixing, filtering, amplification, delay, etc., to be implemented with increased adjustability compared to using analog components. The output (e.g., a digital version of the return signal 113) can then be converted to analog for transmission. Therefore, the components included in the return signal 113 can be adjustable and / or time-varying, for example, by using different frequencies for different times of day.

[0059] According to some implementations, different mixed frequencies can be selected for various vertical takeoff and landing (VTOL) stations. In some examples, the landing zone may include multiple friendly transponders that can operate using the same or different frequencies. Additionally or alternatively, time-based signaling can be used with specific patterns to further aid in VTOL station identification, enhance landing zone uniqueness, or both. Multiple transponders can be configured in unique configurations, enhancing robustness to potential multipath interference through template matching. In some examples, frequency sequences and / or patterns of frequency variation over time can be used to provide additional unique information for identifying each friendly transponder / landing zone. Other aspects that can be implemented include specific polarization (e.g., horizontal, vertical), specific signal coding, or both.

[0060] Figure 4 An illustrative, non-limiting example of a radar tracking diagram 400 for radar source 402 and friendly transponder 102 is depicted. Figure 4In the diagram, each arrow represents a corresponding object, wherein the direction of the arrow indicates the object's direction of travel, the width of the arrow corresponds to the object's radar cross-section (RCS), and the length of the arrow is proportional to the object's velocity. The use of arrows to represent objects is depicted as an illustrative example; in other embodiments, one or more other graphical conventions may be employed to represent clutter and moving objects at different azimuths or altitudes relative to a selected reference frame.

[0061] A detailed view 404 of the signature of the friendly transponder 102 shows a first track and a second track. The first track is the arrival (downward arrow) of the radar source 402 and corresponds to a first object 410 moving toward the radar source 402. The second track is the departure (upward arrow) of the radar source 402 and corresponds to a second object 412 moving away from the radar source 402. The first object 410 may correspond to the first component of the return signal 113 (e.g., Figure 3 The upper trace 362), and the second object 412 may correspond to the second component of the return signal 113 (e.g., Figure 3 The lower trace 364). In this example, the first object 410 and the second object 412 are in substantially the same position and have substantially the same velocity (arrow length) and radar cross-section (arrow width), thus providing a radar cross-section that can be obtained by... Figure 1 The radar return analyzer 154 easily detects and distinguishes friendly transponder signatures from ground clutter.

[0062] The friendly transponder 102 includes an analog or digital delay line (e.g., Figure 3 In the implementation of the delay device 328, the positions of the first object 410 and the second object 412 are along the same orientation as the friendly transponder 102, but offset from the actual range of the friendly transponder 102 by a known relative distance, which corresponds to a predetermined time delay introduced by the delay line. Therefore, the friendly transponder 102 may be physically within the blind range of the radar 402, such as during the final phase of landing, but remains detectable because the pair of objects 410 and 412 appear to be at the indicated distance from the friendly transponder 102. Upon detecting that the first object 410 and the second object 412 are signatures of the friendly transponder, the radar system compensates for the relative distance offset to determine the physical location of the friendly transponder 102.

[0063] Figure 5 Examples of the aircraft 150 and its corresponding DAA field of view are depicted in side view 500 and top view 502, which can be derived from... Figure 1 The friendly transponder 102 in system 100 is accommodated.

[0064] Side view 500 shows the elevation coverage, which includes a first portion 510 spanning from the longitudinal axis of the aircraft 150 to above the longitudinal axis at a first angle α, and a second portion 512 spanning from the longitudinal axis of the aircraft 150 to below the longitudinal axis at a second angle β. Top view 502 shows the azimuth coverage, which includes a first portion 520A and a second portion 520B overlapping in an overlapping portion 522 in front of the aircraft 150. According to some aspects, the first portion 510 and the second portion 512 of the elevation coverage, as well as the first portion 520A, the second portion 520B, and the overlapping portion 522 of the azimuth coverage, may be adapted based on applicable standards or guidelines, such as RTCA specifications similar to those used for DAA systems (e.g., RTCADO-366), as illustrative and non-limiting examples.

[0065] In certain implementations, the elevation coverage extends further below the longitudinal axis, for example in the third portion 514 of the third angle γ spanning from the longitudinal axis to below it, to provide enhanced coverage and accuracy for assisted navigation (e.g., landing) using the friendly transponder 102. Thus, the extended elevation coverage illustrates a further increase in the capabilities of the DAA airborne radar in providing landing assistance.

[0066] Figure 6 This is a flowchart illustrating an example of a method 600 for operating a friendly transponder. At block 602, method 600 includes receiving a radar signal at a device. For example, the device may include or correspond to a friendly transponder 102 that receives radar signal 120 via receiving antenna 110.

[0067] At block 604, method 600 includes generating a return signal at a device based on a received radar signal, wherein the return signal includes at least a first component at a first frequency offset from the carrier frequency of the received radar signal and a second component at a second frequency offset from the carrier frequency. For example, the return signal generator 112 of the friendly transponder 102 generates a return signal 113 based on a received radar signal 111.

[0068] According to one aspect, generating the return signal includes mixing the received radar signal with a mixed signal, and the mixed signal includes components having frequencies substantially matching the first frequency offset and the second frequency offset. For example, refer to Figure 3 Mixer 318 mixes the amplified received radar signal 316 with a frequency F DS The Doppler frequency shift signal 322 is mixed to generate a mixed signal 324, and the mixed signal 324 is filtered by BPF 326 to generate a return signal 113. The return signal 113 has a first component (e.g., F). C +F DO +F DS(corresponding to the upper trace 362), the first component is derived from the carrier frequency (e.g., F) of the received radar signal 111. C +F DO ) offset of the first frequency offset (e.g., F DS The return signal 113 also has a second component (e.g., F). C +F DO -F DS (corresponding to the lower trace 364), the second component is derived from the carrier frequency (e.g., F) of the received radar signal 111. C +F DO ) offset of the second frequency offset (e.g., -F) DS ).

[0069] In the illustrative example, the first component simulates a first object traveling toward the radar signal source at a first velocity (e.g., Figure 4 The first Doppler signature of the first object 410 is simulated, and the second component simulates the second Doppler signature of the second object (e.g., the second object 412) traveling away from the radar signal source at a second velocity substantially matching the first velocity. In a particular implementation, the first frequency offset and the second frequency offset have matching magnitudes and opposite signs. According to one aspect, the first frequency offset and the second frequency offset are within a threshold range from the carrier frequency. In some embodiments, generating the return signal further includes introducing a predetermined time delay that simulates the distance offset between the first object and the second object and the location of the device. For example, delay device 328 introduces a predetermined time delay such that the transmitted return signal 122 simulates a location outside the radar blind range.

[0070] At block 606, method 600 includes transmitting a return signal at the device. For example, friendly transponder 102 transmits a return signal 113 via transmit antenna 114 to generate a transmitted return signal 122.

[0071] According to one approach, a return signal is generated and transmitted to indicate the landing location of the autonomous aircraft. According to some implementations, a combination of the first and second components serves as a unique identifier corresponding to the landing site. In one example, the device corresponds to a transponder, such as a friendly transponder 102, and the return signal includes a pattern that uniquely identifies the transponder.

[0072] Figure 7 This is a block diagram of a computing environment 700 including a computing device 710 configured to support aspects of computer-implemented methods and computer-executable program instructions (or code) according to the present disclosure. For example, the computing device 710 or portions thereof is configured to execute instructions to initiate, execute, or control references. Figures 1 to 6One or more operations are described. In some implementations, computing device 710 corresponds to friendly transponder 102, radar system 152, navigation system 156, or a combination thereof.

[0073] Computing device 710 includes one or more processors 720. The one or more processors 720 are configured to communicate with system memory 730, one or more storage devices 750, one or more input / output interfaces 740, one or more communication interfaces 760, or any combination thereof. System memory 730 includes volatile memory devices (e.g., random access memory (RAM) devices), non-volatile memory devices (e.g., read-only memory (ROM) devices, programmable read-only memory, and flash memory) or both. System memory 730 stores operating system 732, which may include a basic input / output system for booting computing device 710 and a complete operating system enabling computing device 710 to interact with users, other programs, and other devices. System memory 730 stores system (program) data 738, such as data corresponding to aspects associated with generating return signals, or identifying the location of friendly converters based on received return signals.

[0074] System memory 730 includes one or more applications 734 (e.g., instruction set 736) executable by one or more processors 720. As an example, one or more applications 734 include those executable by one or more processors 720 to initiate, control, or execute references. Figures 1 to 6 Instructions for one or more operations described. For illustration, one or more applications 734 include instructions executable by one or more processors 720 to initiate, control, or perform one or more operations described for the reference return signal generator 112, radar system 152, navigation system 156, or combinations thereof.

[0075] System memory 730 includes a non-transitory computer-readable medium storing instructions that, when executed by one or more processors 720, cause one or more processors 720 to perform the operations described above.

[0076] One or more storage devices 750 include non-volatile storage devices, such as disks, optical disks, or flash memory devices. In a particular example, storage device 750 includes both removable and non-removable memory devices. Storage device 750 is configured to store an operating system, an image of the operating system, applications (e.g., one or more of applications 734), and program data (e.g., program data 738). In a particular aspect, system memory 730, storage device 750, or both include tangible computer-readable media. In a particular aspect, one or more of storage devices 750 are external to computing device 710.

[0077] One or more input / output interfaces 740 enable computing device 710 to communicate with one or more input / output devices 770 to facilitate user interaction. For example, one or more input / output interfaces 740 may include display interfaces, input interfaces, or both. For example, input / output interface 740 is adapted to receive input from a user, input from another computing device, or a combination thereof. Input / output interface 740 may conform to one or more standard interface protocols, including serial interfaces (e.g., Universal Serial Bus (USB) interfaces or Institute of Electrical and Electronics Engineers (IEEE) interface standards), parallel interfaces, display adapters, audio adapters, or custom interfaces (“IEEE” is a registered trademark of the Institute of Electrical and Electronics Engineers of Piscataway, New Jersey). Input / output devices 770 may include one or more user interface devices and displays, including some combination of buttons, keyboards, indicating devices, displays, speakers, microphones, touchscreens, and other devices.

[0078] One or more processors 720 are configured to communicate with one or more devices (or controllers) 780 via one or more communication interfaces 760. For example, one or more communication interfaces 760 may include network interfaces.

[0079] Non-transitory computer-readable media may store instructions that, when executed by one or more processors, cause one or more processors to initiate, execute, or control operations to perform some or all of the functions described above. For example, the instructions may be executable to implement Figures 1 to 7 One or more of the operations or methods. Figures 1 to 7 One or more of the operations or methods may be implemented, in whole or in part, by one or more processors (e.g., one or more central processing units (CPUs), one or more graphics processing units (GPUs), one or more neural processing units (NPUs), one or more digital signal processors (DSPs)) executing instructions, by dedicated hardware circuitry, or by any combination thereof.

[0080] The following examples from the first set of interconnected examples describe specific aspects of this disclosure:

[0081] According to Example 1, an apparatus includes: a receiving antenna configured to receive a radar signal; a return signal generator configured to generate a return signal based on the received radar signal, wherein the return signal includes at least: a first component at a first frequency offset from the carrier frequency of the received radar signal; and a second component at a second frequency offset relative to the carrier frequency; and a transmitting antenna configured to transmit the return signal.

[0082] Example 2 includes the device according to Example 1, wherein the first frequency offset and the second frequency offset have matching magnitudes and opposite signs.

[0083] Example 3 includes the device according to Example 1 or Example 2, wherein a receiving antenna, a return signal generator, and a transmitting antenna are included in a transponder to indicate the landing location of the autonomous aircraft.

[0084] Example 4 includes the device according to Example 3, wherein the received radar signal corresponds to a Detect and Avoid (DAA) airborne radar, and wherein the return signal simulates a first object moving toward the DAA airborne radar at a first speed, and a second object in the same position as the first object moving away from the DAA airborne radar at a second speed substantially matching the first speed.

[0085] Example 5 includes the device according to Example 4, wherein simulating the return signals of the first and second objects enables the DAA airborne radar to distinguish the transponder from ground clutter.

[0086] Example 6 includes a device according to any one of Examples 3 to 5, wherein a combination of the first component and the second component is used as a unique identifier corresponding to the landing site.

[0087] Example 7 includes the device according to any one of Examples 3 to 6, wherein the return signal includes a pattern that uniquely identifies the transponder.

[0088] Example 8 includes a device according to any one of Examples 1 to 7, wherein the first frequency offset and the second frequency offset are within a threshold range from the carrier frequency.

[0089] Example 9 includes a device according to any one of Examples 1 to 8, wherein a first component simulates a first Doppler signature of a first object traveling toward a source of a radar signal at a first velocity, and wherein a second component simulates a second Doppler signature of a second object traveling away from a source of a radar signal at a second velocity substantially matching the first velocity.

[0090] Example 10 includes a device according to any one of Examples 1 to 9, wherein the return signal generator includes a mixer configured to mix a received radar signal with a mixed signal to generate a return signal, the mixed signal including a component having a frequency substantially matching a first frequency offset and a second frequency offset.

[0091] Example 11 includes the device according to Example 10, wherein the return signal generator further includes: an amplifier coupled to a mixer and configured to amplify the return signal; a signal generator configured to generate a mixed signal; and a filter configured to filter the return signal.

[0092] According to Example 12, a system includes: a device according to any one of claims 1 to 11; and an aircraft configured to transmit radar signals, the aircraft further including a radar return analyzer configured to identify a landing position transponder based on the detection of a first component and a second component in the returned signal.

[0093] According to Example 13, a method includes: receiving a radar signal at a device; generating a return signal at the device based on the received radar signal, wherein the return signal includes at least: a first component at a first frequency offset from the carrier frequency of the received radar signal; and a second component at a second frequency offset relative to the carrier frequency; and transmitting the return signal at the device.

[0094] Example 14 includes the method according to Example 13, wherein the first frequency offset and the second frequency offset have matching magnitudes and opposite signs.

[0095] Example 15 includes the method according to Example 13 or Example 14, wherein a return signal is generated and transmitted to indicate the landing location of the autonomous aircraft.

[0096] Example 16 includes the method according to Example 15, wherein a combination of the first component and the second component is used as a unique identifier corresponding to the landing location.

[0097] Example 17 includes the method of Example 15 or Example 16, wherein the device corresponds to a transponder, and wherein the return signal includes a pattern that uniquely identifies the transponder.

[0098] Example 18 includes the method according to any one of Examples 13 to 17, wherein the first frequency offset and the second frequency offset are within a threshold range from the carrier frequency.

[0099] Example 19 includes the method according to any one of Examples 13 to 18, wherein a first component simulates a first Doppler signature of a first object traveling toward a source of a radar signal at a first velocity, and wherein a second component simulates a second Doppler signature of a second object traveling away from a source of a radar signal at a second velocity substantially matching the first velocity.

[0100] Example 20 includes the method according to Example 19, wherein generating the return signal includes introducing a predetermined time delay that simulates the distance offset between the positions of the first object and the second object and the device.

[0101] Example 21 includes the method according to any one of Examples 13 to 20, wherein generating the return signal includes mixing the received radar signal with a mixed signal, the mixed signal including components having frequencies substantially matching the first frequency offset and the second frequency offset.

[0102] According to Example 22, an apparatus includes: a memory configured to store instructions; and a processor configured to execute instructions to perform a method according to any one of Examples 13 to 21.

[0103] According to Example 23, a non-transitory computer-readable medium stores instructions that, when executed by one or more processors, cause the one or more processors to perform the method according to any one of Examples 13 to 21.

[0104] According to Example 24, an apparatus includes means for performing the method according to any one of Examples 13 to 21.

[0105] According to Example 25, a non-transitory computer-readable medium includes instructions that, when executed by one or more processors, cause the one or more processors to perform operations, the operations including: receiving a radar signal; generating a return signal based on the received radar signal, wherein the return signal includes at least a first component at a first frequency offset from a carrier frequency of the received radar signal and a second component at a second frequency offset from the carrier frequency; and transmitting the return signal.

[0106] According to Example 26, a radar system includes: a transmitting antenna configured to transmit a radar signal; a receiving antenna configured to receive a return signal corresponding to the radar signal and including a first component at a first frequency offset from a carrier frequency of the radar signal and a second component at a second frequency offset from the carrier frequency; and a radar return analyzer configured to identify a landing location based at least on the detection of the first and second components.

[0107] According to Example 27, an aircraft includes a radar system comprising a transmitting antenna configured to transmit radar signals; a receiving antenna configured to receive a return signal corresponding to the radar signals and including a first component at a first frequency offset from a carrier frequency of the radar signals and a second component at a second frequency offset from the carrier frequency; and a radar return analyzer configured to identify a landing position based at least on the detection of the first and second components; and the aircraft further includes a navigation system coupled to the radar system and configured to generate navigation instructions based on the identified landing position.

[0108] Example 28 includes an aircraft according to Example 27, wherein the radar system corresponds to a detection and avoidance (DAA) radar, wherein a return signal is received from a transponder and simulates a first object traveling toward the aircraft at a first speed and a second object located at the same position as the first object and traveling away from the aircraft at a second speed substantially matching the first speed, and wherein the return signal enables a radar return analyzer to distinguish the transponder from ground clutter.

[0109] This application involves the following provisions:

[0110] 1. A device (102) for assisting navigation, said device comprising:

[0111] A receiving antenna (110) configured to receive radar signals (120);

[0112] A return signal generator (112) is configured to generate a return signal (113) based on the received radar signal, wherein the return signal includes at least:

[0113] The first component (362) is located at a first frequency offset from the carrier frequency of the received radar signal; and

[0114] The second component (364), the second component is at a second frequency offset from the carrier frequency; and

[0115] A transmitting antenna (114) is configured to transmit the return signal.

[0116] 2. The device according to Clause 1, wherein the first frequency offset and the second frequency offset have matching magnitudes and opposite signs.

[0117] 3. The device according to Clause 1, wherein the receiving antenna, the return signal generator and the transmitting antenna are included in a transponder to indicate the landing position (212) for the autonomous aircraft (150).

[0118] 4. The device according to Clause 3, wherein the received radar signal corresponds to detecting and avoiding DAA airborne radar, and wherein the return signal simulates a first object (410) and a second object (412), the first object moving toward the DAA airborne radar at a first speed, and the second object moving away from the DAA airborne radar at the same position as the first object and at a second speed matching the first speed.

[0119] 5. The device according to Clause 4, wherein simulating the return signals of the first and second objects enables the DAA airborne radar to distinguish the transponder from ground clutter.

[0120] 6. The device according to Clause 3, wherein the combination of the first component and the second component is used as a unique identifier corresponding to the landing location.

[0121] 7. The device according to Clause 3, wherein the return signal includes a pattern that uniquely identifies the transponder.

[0122] 8. The device according to Clause 1, wherein the first frequency offset and the second frequency offset are within a threshold range from the carrier frequency.

[0123] 9. The device according to Clause 1, wherein the first component simulates a first Doppler signature of a first object traveling toward the source of the radar signal at a first velocity, and wherein the second component simulates a second Doppler signature of a second object traveling away from the source of the radar signal at a second velocity matching the first velocity.

[0124] 10. The apparatus according to Clause 1, wherein the return signal generator includes a mixer (328) configured to mix a received radar signal with a mixed signal (322) to generate the return signal, the mixed signal including a frequency F having a frequency F matching the first frequency offset and the second frequency offset. DS The amount.

[0125] 11. The device according to Clause 10, wherein the return signal generator further comprises: an amplifier (314) coupled to the mixer and configured to amplify the return signal; a signal generator (320) configured to generate the mixed signal; and a filter (326) configured to filter the return signal.

[0126] 12. A method (600) for assisted navigation, the method comprising:

[0127] Receive (602) radar signal (120) at device (102);

[0128] A return signal (113) is generated (604) at the device based on the received radar signal, wherein the return signal includes at least:

[0129] The first component (362) is located at a first frequency offset from the carrier frequency of the received radar signal; and

[0130] The second component (364), the second component is at a second frequency offset from the carrier frequency; and

[0131] The return signal (606) is sent at the device.

[0132] 13. The method according to Clause 12, wherein the first frequency offset and the second frequency offset have matching magnitudes and opposite signs.

[0133] 14. The method according to Clause 12, wherein the return signal is generated and transmitted to indicate the landing position (212) for the autonomous aircraft (150).

[0134] 15. The method according to Clause 14, wherein the combination of the first component and the second component is used as a unique identifier corresponding to the landing location.

[0135] 16. The method according to Clause 12, wherein the first component simulates a first Doppler signature of a first object (410) traveling toward the source of the radar signal at a first velocity, and wherein the second component simulates a second Doppler signature (412) of a second object traveling away from the source of the radar signal at a second velocity matching the first velocity.

[0136] 17. The method according to Clause 16, wherein generating the return signal comprises: introducing a predetermined time delay that simulates the distance offset between the positions of the first object and the second object and the device.

[0137] 18. The method according to Clause 12, wherein generating the return signal comprises: mixing the received radar signal with a mixed signal (322), the mixed signal comprising a frequency F having a frequency matching the first frequency offset and the second frequency offset. DS The amount.

[0138] 19. An aircraft (150), said aircraft comprising:

[0139] Radar system (152), the radar system comprising:

[0140] A transmitting antenna (340) configured to transmit radar signals (120);

[0141] A receiving antenna (342) configured to receive a return signal (122) corresponding to the radar signal and including a first component (362) at a first frequency offset from the carrier frequency of the radar signal and a second component (364) at a second frequency offset from the carrier frequency; and

[0142] A radar return analyzer (154), configured to identify the landing location based at least on the detection of the first component and the second component; and

[0143] A navigation system (156) is connected to the radar system and is configured to generate navigation instructions (158) based on the identified landing location.

[0144] 20. The aircraft described in Clause 19, wherein:

[0145] The radar system corresponds to the detection and avoidance of DAA radar.

[0146] The return signal is received from the transponder and simulates a first object (410) and a second object (412), the first object moving toward the aircraft at a first speed, and the second object being at the same position as the first object and moving away from the aircraft at a second speed matching the first speed.

[0147] The return signal enables the radar return analyzer to distinguish the transponder from ground clutter.

[0148] The illustrations described herein are intended to provide a general understanding of the structure of various embodiments. The illustrations are not intended as a complete description of all elements and features of apparatuses and systems utilizing the structures or methods described herein. Many other embodiments may become apparent to those skilled in the art upon review of this disclosure. Other embodiments may be utilized and derived from this disclosure, allowing structural and logical substitutions and changes to be made without departing from the scope of this disclosure. For example, method operations may be performed in a different order than those shown in the figures, or one or more method operations may be omitted. Therefore, this disclosure and the accompanying drawings should be considered illustrative rather than restrictive.

[0149] Furthermore, although specific examples have been illustrated and described herein, it should be understood that any subsequent arrangements designed to achieve the same or similar results may replace the specific embodiments shown. This disclosure is intended to cover any and all subsequent adaptations or variations of the various embodiments. Combinations of the above embodiments, as well as other embodiments not specifically described herein, will be apparent to those skilled in the art upon reading this specification.

[0150] The abstract of this disclosure is intended not to be construed as limiting the scope or meaning of the claims. Furthermore, in the foregoing detailed description, various features may be combined together or described in a single implementation for the purpose of simplifying this disclosure. The foregoing examples are illustrative but not limiting of this disclosure. It should also be understood that many modifications and variations are possible based on the principles of this disclosure. The claimed subject matter, as reflected in the appended claims, may apply to all features of fewer than any of the disclosed examples. Therefore, the scope of this disclosure is defined by the appended claims and their equivalents.

[0151] This application claims the benefit of U.S. Provisional Patent Application No. 63 / 701,444, filed September 30, 2024, entitled “ALLYTRANSPONDER FOR ASSISTEDNAVIGATION,” the contents of which are incorporated herein by reference in their entirety.

Claims

1. A device (102) for assisting navigation, the device comprising: a receive antenna (110) configured to receive a radar signal (120); a return signal generator (112) configured to generate a return signal (113) based on the received radar signal, wherein the return signal comprises at least: a first component (362) at a first frequency offset from a carrier frequency of the received radar signal; and a second component (364) at a second frequency offset from the carrier frequency; and a transmit antenna (114) configured to transmit the return signal.

2. The apparatus of claim 1, wherein, The first and second frequency offsets have matching magnitudes and opposite signs.

3. The apparatus of claim 1, wherein, The receive antenna, the return signal generator, and the transmit antenna are comprised in a transponder to indicate a landing location (212) for an autonomous aircraft (150).

4. The apparatus of claim 3, wherein, The received radar signal corresponds to a detect and avoid (DAA) on-board radar, and wherein the return signal emulates a first object (410) and a second object (412), the first object traveling toward the DAA on-board radar at a first speed, the second object traveling away from the DAA on-board radar at a second speed that matches the first speed at the same location as the first object.

5. The apparatus of claim 4, wherein, The return signal emulating the first and second objects enables the DAA on-board radar to distinguish the transponder from ground clutter.

6. The apparatus of claim 3, wherein, A combination of the first and second components serves as a unique identifier corresponding to the landing location.

7. The apparatus of claim 3, wherein, The return signal comprises a pattern that uniquely identifies the transponder.

8. The apparatus of claim 1, wherein, The first and second frequency offsets are within a threshold range from the carrier frequency.

9. A method (600) for assisting navigation, the method comprising: receiving (602), at a device (102), a radar signal (120); generating (604), at the device, a return signal (113) based on the received radar signal, wherein the return signal comprises at least: a first component (362) at a first frequency offset from a carrier frequency of the received radar signal; and a second component (364) at a second frequency offset from the carrier frequency; and transmitting (606), at the device, the return signal.

10. An aircraft (150), the aircraft comprising: a radar system (152) comprising: a transmit antenna (340) configured to transmit a radar signal (120); a receive antenna (342) configured to receive a return signal (122), the return signal (122) corresponding to the radar signal and comprising a first component (362) at a first frequency offset from a carrier frequency of the radar signal and a second component (364) at a second frequency offset from the carrier frequency; and a radar return analyzer (154) configured to identify a landing location based at least on the detection of the first component and the second component; and a navigation system (156) coupled to the radar system and configured to generate navigation instructions (158) based on the identified landing location.

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