Discriminate multipath using differential travel times of location signals in different frequency bands

Abstract

A system and method to discriminate multipath using differential travel times of location signals in different frequency bands and, more particularly, but not exclusively, to discriminate multipath using two frequencies time of arrival.

Description

[0001] DISCRIMINATE MULTIPATH USING DIFFERENTIAL TRAVEL TIMES

[0002] OF LOCATION SIGNALS IN DIFFERENT FREQUENCY BANDS

[0003] RELATED APPLICATIONS

[0004] This application claims the benefit of priority under 35 USC §119(e) of U.S. Provisional Patent Application No. 63 / 715,660 filed on 4 November, 2024, the contents of which are incorporated herein by reference in their entirety.

[0005] FIELD AND BACKGROUND OF THE INVENTION

[0006] The invention, in some embodiments thereof, relates to system and method to discriminate multipath using differential travel times of location signals in different frequency bands and, more particularly, but not exclusively, to discriminate multipath using two frequencies time of arrival.

[0007] Even with high directivity antenna, it is possible for a direction-finding system to receive a signal reflection or multipath and / or have an antenna pointing to a reflection or multipath. Such signals can be very misleading when it is important to locate the source of the signal. Additionally, even highly focused signals can be reflected by large metal surfaces and / or can be hidden by various objects.

[0008] United States Patent No. 9,383,441 appears to disclose, “A mobile device determines its location accurately by measuring the range to a position reflector as well as azimuth and elevation angles of arrival (AO A) at the reflector. The mobile can transmit a coded radar signal and process reflections to determine its location. The reflectors may include internal delays that can identify the reflector and provide transmit / receive separation for the mobile. The reflection can include a primary and further delayed secondary reflection. The mobile can determine the internal delay of the reflector based on the delay between primary and secondary reflections. The range and AOA information can be combined with information about the position, orientation, and characteristics of the reflectors to determine location. In some systems, the mobile device can determine its location in a three-dimensional space using reflections from only one reflector. The reflectors, which can be economically produced, can be unpowered and low profile for easy installation.”

[0009] United States Patent No. 9,277,525 appears to disclose, “A wireless location system is disclosed including one or more location centers for outputting locations of mobile stations (MS) for both local and global MS location requests via Internet communication between a distributed network of location centers. The system uses a plurality of MS locating technologies including those based on: two-way TOA and TDOA; pattern recognition; distributed antenna provisioning; GPS signals. Difficulties, such as multipath, poor location accuracy and poor coverage are alleviated via such technologies in combination with: (a) adapting and calibrating system performance according to environmental and geographical changes; (b) capturing location signal data for continual enhancement of an historical database; (c) evaluating MS locations via heuristics and constraints related to terrain, MS velocity and MS path extrapolation, and (d) adjusting likely MS locations. The system is useful for 911 emergency calls, tracking, routing, people and animal location including applications for confinement to and exclusion from certain areas.”

[0010] Additional art includes United States Patent No. 10,874,314, United States Patent No. 9,454,683, United States Patent No. 11,12,144, and United States Patent Publication No. 2019 / 0102582.

[0011] DESCRIPTION OF THE DRAWINGS

[0012] Some embodiments of the invention are herein described, by way of example only, with reference to the accompanying drawings. With specific reference now to the drawings in detail, it is stressed that the particulars shown are by way of example and for purposes of illustrative discussion of embodiments of the invention. In this regard, the description taken with the drawings makes apparent to those skilled in the art how embodiments of the invention may be practiced.

[0013] In the drawings:

[0014] Fig. 1 : Schematic diagram illustrating a direct path and multipath signal, in accordance with an embodiment of the current invention.

[0015] Fig. 2: Schematic diagram illustrating a LF signal, HF direct path and HF multipath signal, in accordance with an embodiment of the current invention.

[0016] Fig. 3: A block diagram describing a multi-band interrogation signal system, in accordance with an embodiment of the current invention.

[0017] Fig. 4: A chart describing a message-sequence timing system, in accordance with an embodiment of the current invention. FIG. 5: A unit-level block diagram of a radar transceiver, in accordance with an embodiment of the current invention.

[0018] Fig. 6: A flow chart describing a message-sequence timing method, in accordance with an embodiment of the current invention.

[0019] SUMMARY OF THE INVENTION

[0020] A system of one or more computers can be configured to perform particular operations or actions by virtue of having software, firmware, hardware, or a combination of them installed on the system that in operation causes or cause the system to perform the actions. One or more computer programs can be configured to perform particular operations or actions by virtue of including instructions that, when executed by data processing apparatus, cause the apparatus to perform the actions.

[0021] In one general aspect, the method may include transmitting an interrogation signal. The method may also include receiving response signals on a penetrating band and a non-penetrating band. The method may furthermore include determining a time of arrival for each response signal. The method may in addition include classifying a non-penetrating signal as multipath when a time of arrival of the non-penetrating signal is significantly greater than a time of arrival of a penetrating signal. Other embodiments of this aspect include corresponding computer systems, apparatus, and computer programs recorded on one or more computer storage devices, each configured to perform the actions of the methods.

[0022] Implementations may include one or more of the following features. The method may include calculating a differential travel time (AT) for each signal exchange. The method may include classifying the non-penetrating signal as multipath when the differential travel time exceeds a threshold value ((th). The method or claim 4, where the threshold value ((th) is derived, at least in part, from channel conditions. The method may include classifying the non-penetrating signal as direct when the differential travel time does not exceed a threshold value ((th). The method where said interrogation signal includes a signal on a penetrating band. The method where said interrogation signal further includes a signal on a non-penetrating band. The method where said penetrating band is a low band. The method where said low band has a sub-GHz frequency. The method where said non-penetrating band is a high band. The method where said high band has a frequency ranging between 60 GHz to 100 GHz. 12 where the response signals on the penetrating band and the response signal on the non-penetrating band are transmitted simultaneously. The method may include determining the time of arrival of each signal directly from their receipt times. The method where the response signals on the penetrating band and the response signal on the non-penetrating band are not transmitted simultaneous. The method may include determining the time of arrival of each signal from a transmission or reception timestamps for each signal. The method where each signal further may include a timestamp. The method may include ignoring non-penetrating signals classified as multipath when computing line-of-fire or range. Implementations of the described techniques may include hardware, a method or process, or a computer tangible medium.

[0023] In one general aspect, system may include a first unit and a second unit, where each unit includes a penetrating band transceiver and a non-penetrating band transceiver. System may also include control circuitry, where the control circuitry is configured for: transmitting an interrogation signal; receiving response signals on a penetrating band and a non-penetrating band; determining a time of arrival for each response signal; and classifying a non-penetrating signal as multipath when a time of arrival of the non-penetrating signal is significantly greater than a time of arrival of a penetrating signal. Other embodiments of this aspect include corresponding computer systems, apparatus, and computer programs recorded on one or more computer storage devices, each configured to perform the actions of the methods.

[0024] In one general aspect, discriminate multipath system may include a first unit and a second unit, where each unit includes a high-frequency (HF) transceiver and a low-frequency (LF) transceiver. Discriminate multipath system may also include control circuitry, where the control circuitry is configured to:. System may furthermore include transmit an interrogation signal from the first unit on at least one of a high band and a low band. System may in addition include receive on the first unit response signals on a high band and a low band from the second unit. System may moreover include compute a time-of-arrival (ToA) for each of the response signals. System may also include compute a differential travel time from the times of arrival of the response signals. System may furthermore include classify a high frequency signal as multipath if the differential travel time exceeds a threshold value (rth), and as direct if the differential travel time does not exceed the threshold value (rth). Other embodiments of this aspect include corresponding computer systems, apparatus, and computer programs recorded on one or more computer storage devices, each configured to perform the actions of the methods. DESCRIPTION OF THE INVENTION

[0025] The invention, in some embodiments thereof, relates to system and method to discriminate multipath using differential travel times of location signals in different frequency bands and, more particularly, but not exclusively, to discriminate multipath using two frequencies time of arrival.

[0026] OVERVIEW

[0027] An aspect of some embodiments of the current invention relates to a system and method to discriminate multipath using differential travel times of location signals in different frequency bands is disclosed and described. Optionally, the system may include at least two transceivers. Optionally, the transceivers may include electromagnetic wave transceivers, for example, a radiofrequency device, and / or a millimeter wave device (e.g., radar), and / or an optical device (e.g., lidar). Optionally, at least one antenna may be dedicated to transmitting and / or receiving a signal unidirectionally. Optionally, at least one antenna may be dedicated to transmitting and / or receiving a signal omnidirectionally. Optionally the electromagnetic signals may include Doppler radar and / or lidar.

[0028] As used herein, the term “Frequency -Modulated Continuous Wave radar” or “FMCW” may relate to a type of radar system that transmits a continuous signal whose frequency changes over time. FMCW radar continuously transmits a signal whose frequency is constantly changing. When this signal encounters a target, it is reflected back to the radar. By comparing the reflected signal to the original transmitted signal, the radar can determine the target's distance and speed. FMCW radar offers high range resolution and accurate Doppler velocity measurement, making it suitable for applications requiring precise distance and speed information. The FMCW system can scan a wide range of frequencies for Doppler effect echoes. The frequency range can be adjusted. The FMCW system can also transmit a spread spectrum "chirp" signal that covers a significant frequency band, The form and bandwidth of the FMCW signal can be adjusted. This means that each device occupies a large band in the frequency spectrum.

[0029] As used herein, the term “Doppler radar” may relate to a type of that detects a return signal at a frequency that has been changed from the outgoing signal. The radar measures the Doppler shift of a reflected signal to determine a target's relative velocity. This shift in frequency is caused by the relative motion between the radar and the target and / or intentionally induced by the transmitter.

[0030] As used herein, the term “moving search window” may relate to a receiver procedure that sweeps frequency and / or offset to acquire a peer’s narrowband despite unknown clock and / or offset.

[0031] As used herein, the term “offset search window” may relate to a sweep of receiver mixing conditions configured to accept a peer chirp with a frequency / time offset within a selected range of frequencies, ±Af.

[0032] As used herein, the terms “wideband” and “narrowband” may refer to the communication band before and after acquisition, respectively.

[0033] As used herein, the terms “Time-of-arrival” and “ToA” are used interchangeably, and may relate to a transmit-to-receive interval for a given signal.

[0034] As used herein, the term “differential travel time” (AT) may relate to is the difference in arrival time between two or more signals that originated from the same source or event. This time difference is a direct measurement of dispersion, where a signal's propagation speed through a medium (like space, fiber optic cable, or the atmosphere) depends on its frequency. The difference in travel time (AT) at the receiver between two signals may be calculated. Optionally, the two signals may include a high frequency (HF) signal and a low frequency (LF) signal, e.g., AT = ToA(HF) - ToA(LF).

[0035] As used herein, the term “high-band” may relate to high frequency (HF) wave or optical carrier frequencies of used for radar and / or lidar ranging between 60 GHz to 100 GHz. For example, wave radar or optical FMCW lidar carriers used for a directional path (such as., -76-81 GHz radar frequencies; 400-1550 nm optical frequencies)

[0036] As used herein, the term “medium-band” may relate to medium frequency (MF) wave radar / lidar carrier frequencies ranging between 1 GHz to 60 GHz.

[0037] As used herein, the term “low-band” may relate to low frequency (LF) wave radar and / or lidar carrier frequencies which are sub-GHz (e.g., 300 kHz to 2 GHz). Optionally, the low-band may be an auxiliary band used for omnidirectional reach and / or lower attenuation.

[0038] As used herein, the term “wake-up interval” may relate to a specific, pre-determined period of time during which a device, often a low-power device and / or battery-operated device, "wakes up" from a sleep state or standby mode to perform a specific task. This process may be a key part of a power-saving strategy.

[0039] As used herein, the term “beat” or “beat frequency” (fb), often referred to as the Intermediate Frequency (IF) signal, is the output frequency generated when a received signal is mixed with a reference signal. In conventional FMCW radar the reference signal may be a transmitted signal and the received signal may be an echo from a target of the transmitted signal and the beat may be used as a direct, linear measure of the target's range.

[0040] As used herein, the term “IF passband” is the specific range of frequencies (a band) that the Intermediate Frequency (IF) electronic filter is designed to allow to pass within an acceptable attenuation. It defines the usable frequency spectrum after the mixing process.

[0041] As used herein, the term “IF bandwidth” (BIF) is the width of the IF passband. Optionally BIF measured in Hertz. BIF is a design parameter chosen to be wide enough to capture the beat frequencies of expected targets.

[0042] The terms “IF bandwidth” and “IF passband” and / or “beat” relate to a specific range of intermediate frequencies (IF) that a receiver's bandpass filter is designed to pass while blocking others, allowing the desired signal to be separated, amplified, and processed with reduced interference from adjacent channels or noise, that is the passband of the receiver’s IF chain, e.g., in some embodiments BIF is 3 dB width of the passband of the receiver’s IF chain.

[0043] As used herein, the terms the “intermediate frequency chain” and “IF chain” may relate to a series of electronic components in a receiver (e.g., superheterodyne receiver, etc.) which processes a radio frequency (RF) signal, such as, after it has been down-converted to a fixed, lower frequency. The IF chain may be a core part of the receiver's architecture, and / or may provide signal amplification and / or filtering.

[0044] As used herein, the term “sweep signal” refers to a signal that changes frequency over time within a specific bandwidth. A “chirp signal” is a type of sweep signal in which the frequency increases or decreases with time. In some sources, the term “chirp” is used interchangeably with “sweep signal”, and is a standard in spread-spectrum communications, sonar, radar, and laser systems.

[0045] As used here, a penetrating signal refers an electromagnetic wave that can pass through obstacles such as walls, buildings, or other materials with low attenuation. For example, a penetrating signal may include a signal on a penetrating band. For example, penetrating bands typically have lower frequencies than non-penetrating bands. Lower frequency signals tend to travel through various mediums with less loss of strength than higher frequency signals. Penetrating signals and / or bands are often used in applications where it is necessary to detect or communicate through barriers, such as in underground communication, medical imaging, or through-wall radar systems.

[0046] As used here, a non-penetrating signal is an electromagnetic wave that is significantly attenuated or blocked by obstacles such as walls, buildings, or other materials. These signals often user non-penetrating bands. Non-penetrating band generally have higher frequencies, which are more likely to be absorbed or reflected by the materials they encounter. Non-penetrating signals are used in applications where line-of-sight communication is desired, such as in high-frequency radar systems, satellite communications, and certain wireless networking technologies.

[0047] As used here, low attenuation refers to the minimal reduction in signal strength as an electromagnetic wave travels through a medium. Signals with low attenuation maintain their power and integrity over longer distances and / or through various materials. Low attenuation may be a desirable characteristic in communication systems, as it facilitates reliable signal transmission and reception.

[0048] As used here, diffraction is the bending of electromagnetic waves around obstacles and the spreading of waves as they pass through narrow openings. This phenomenon may occur when the wavelength of the signal is comparable to the size of the obstacle or opening. Diffraction allows signals to propagate beyond line-of-sight and can be utilized to enhance signal coverage in complex environments.

[0049] As used here, reflection is the phenomenon where an electromagnetic wave bounces off a surface or obstacle, changing its direction of propagation. Reflective surfaces can cause signals to travel along multiple paths, leading to multipath propagation. Reflection is a critical consideration in radar and communication systems, as it can affect signal quality and accuracy.

[0050] As used here, multipath refers to the propagation of electromagnetic waves along multiple paths due to reflection, diffraction, and scattering. Multipath signals can interfere with each other, causing signal fading, distortion, and reduced accuracy in measurements. Understanding and mitigating multipath effects may improve functioning of radar, wireless communication, and / or navigation systems. Diffraction plays a significant role in the propagation of penetrating signals, allowing them to bend around obstacles and spread through narrow openings. This phenomenon enhances the coverage and reliability of LF signals in complex environments. Conversely, HF signals are less affected by diffraction due to their shorter wavelengths, making them more susceptible to blockage by obstacles. Omnidirectional signals, which radiate equally in all directions, are often associated with penetrating signals to ensure wide-area coverage. Unidirectional signals, focused in a specific direction, are typically used with non-penetrating signals to achieve targeted communication and higher signal strength.

[0051] Reflection and multipath propagation are critical considerations for both penetrating and non-penetrating signals. Reflective surfaces can cause signals to travel along multiple paths, leading to multipath effects. For penetrating signals, multipath propagation can enhance coverage by allowing signals to reach areas beyond line-of-sight. However, for non-penetrating signals, multipath can cause interference and reduce measurement accuracy. Path loss affects both types of signals, with LF signals generally experiencing lower path loss over longer distances compared to HF signals.

[0052] As used here, an omnidirectional signal is an electromagnetic wave that radiates with similar power over a wide range of directions from its source. This type of signal is used to facilitate coverage over a wide area and is commonly employed in applications such as broadcasting, wireless networking, and certain radar systems.

[0053] As used here, a unidirectional signal is an electromagnetic wave that is focused in a specific direction, providing targeted coverage and higher signal strength in that direction. Unidirectional signals are used in applications where precise targeting and reduced interference are required, such as in directional antennas, radar systems, and point-to-point communication links.

[0054] As used here, path loss is the reduction in signal strength as an electromagnetic wave travels through space or a medium. Path loss is influenced by factors such as distance, frequency, and the presence of obstacles.

[0055] In some embodiments, a system may utilize LF band as a penetrating band and a HF band as a non-penetrating band. For example, an FMCW radar system may transmit a low- frequency (LF) signal in the range of 300 kHz to 2 GHz and a high-frequency (HF) signal in the range of 60 GHz to 100 GHz. The LF signal, due to its lower frequency, may exhibit low attenuation and penetrate obstacles such as walls and buildings. Conversely, the HF signal, with its higher frequency, may experience significant attenuation when encountering obstacles, resulting in nonpenetrating behavior.

[0056] Attenuation of HF signals can be exemplified by their interaction with materials such as concrete and metal. For instance, an HF signal passing through a concrete wall may experience substantial attenuation, reducing its strength by several decibels (dB). Similarly, metal surfaces can reflect HF signals, causing them to travel along multiple paths and leading to multipath propagation. In contrast, LF signals passing through the same concrete wall may experience reduced or negligible attenuation, maintaining their strength and integrity. For example, loss may be quantified as a high number of decibels per meter dB / m of material thickness. For example, a 5 GHz signal might lose 10 dB to 20dB when passing through a single concrete wall. For example, a 900 MHz signal might only lose 2 dB to 5 dB through the same concrete wall, making the loss insignificant for reliable communication.

[0057] In some embodiments, the system may differentiate between direct and multipath signals based on their differential travel times. For example, if the HF signal takes a longer path due to reflection off obstacles, it may arrive later than the LF signal, which travels directly through the obstacles. By comparing the time of arrival of the HF and LF signals, the system can classify the HF signal as a multipath signal if its differential travel time exceeds a threshold value. This classification facilitates range and line-of-fire decisions.

[0058] According to some embodiments, the system may be a multi-band interrogation signal system. Optionally, the system may be configured to transmit and / or receive two or more signals at different frequencies. Optionally, the system may be configured to transmit and / or receive a higher frequency signal and a lower frequency signal. Optionally, the higher frequency signal may be higher than the lower frequency signal. Optionally, the bands of the frequencies may be far apart. Optionally, the system may include separate antennas for each band.

[0059] Some embodiments may relate to a method for multi-band interrogation signaling. Optionally, the method may include a system with at least two radiofrequency transceivers. Optionally, the transceivers may be configured to transmit, and / or detect, and / or receive radiofrequency signals from similar transceivers. According to some embodiments, the system may be configured to measure the time of arrival of two or more signals of different frequencies transmitted simultaneously. Optionally, the frequency of one signal one may be higher than the other frequency. In some embodiments, HF and LF signals may be transmitted at different times. For example, either the interrogation signal and / or the response signal may include timing information on the transmission and / or reception of the signal such that a differential travel time (the difference between the transmission time and reception time) of the HF signal and LF signal may be calculated. For example, the differential travel time of the HF signal being greater than the differential travel time of the LF signal may be a signal that the HF signal traveled a multipath path.

[0060] According to some embodiments, a first unit (e.g., firing unit, etc.) may transmit multiple interrogation signals. Optionally, each of the signals transmitted may have a different frequency (e.g., a higher frequency and a lower frequency). Optionally, a second unit (e.g., receiving unit, etc.) may receive the transmitted signals and transmit multiple response signals. Optionally, each of the response signals transmitted may have a different frequency (e.g., a higher frequency and a lower frequency). Optionally, the first unit may receive the response signals transmitted by the second unit.

[0061] In some embodiments, a set of signals and / or responses may be used to determine whether the received higher frequency response signals are from a direct path and / or multipath. Optionally, this may be used to compute whether a first unit is in the line of fire (LoF) and / or exposed and / or in range to a second unit.

[0062] According to some embodiments, the system may transmit a higher frequency signal and a lower frequency signal to a directional seeker. Optionally, the seeker may receive the higher frequency signal and the lower frequency signal simultaneously from one or more transceivers in the line of sight of the seeker which may not be hidden by obstacles. Optionally, the seeker may receive the higher frequency signal (which may take a multipath route) after the low frequency signal from transceivers that in the line of sight of the seeker and may be hidden by obstacles. Optionally, the seeker may compute the location and / or obstruction information about the transceivers.

[0063] In some embodiments, the HF response signal and response LF response signals may be transmitted simultaneously and / or the difference in time of arrival of the two signals corresponds to the difference in time and length of travel. Alternatively, or additionally, the second (responding) unit transmits HF and LF signals but not necessarily simultaneously and transmits timing information (the time interval between the sending of the HF and LF signal). Optionally, the first unit receives the timing information and from the difference between the time of arrival of the signals and the elapsed time of transmission, the first unit computes the difference in time of travel and / or distance traveled. Alternatively, or additionally, the second unit transmits timing information about the elapsed time between reception of the HF and LF interrogation and / or wake up signals to the first unit. The first unit knows when the HF and LF interrogation and / or wake up signals were transmitted and backs out the time of travel to the second unit. Alternatively, or additionally, the first unit transmits information about the elapsed time between sending the HF and LF interrogation / wake up signals to the second unit who computes the travel times based on the time of receipt of the HF and LF interrogation and / or wake up signals.

[0064] According to some embodiments, the high frequency “wake-up” may be directional and / or may not penetrate obstacles, therefore any unit receiving the high frequency “wake-up” signal has received a direct high frequency signal because it is 1) on the direct line of transmission; and / or 2) in the open; 3) the range to the second unit may be computed based on the time of travel of the high frequency signal; and / or 4) certain obstacles (e.g., large metal objects) may reflect and / or refract the high frequency signal (a multipath signal). For example, a receiving unit not on the direct line of transmission and / or behind an obstacle may receive a reflected (non-penetrating) and / or refracted high frequency signal. Similarly, the response signal may reach the first unit along a multipath. Optionally, direct signals and multipath signals may be differentiated.

[0065] According to some embodiments, the system may differentiate between direct signals and multipath signals. Optionally, a low frequency signal and a high frequency signal may be transmitted by the first unit sequentially and / or simultaneously. Optionally, a low frequency signal and a high frequency signal may be transmitted by the second unit sequentially and / or simultaneously. Optionally, since the low frequency signal does pass through obstacles (penetrating) and / or is omnidirectional, every unit may receive a direct low frequency signal. Optionally, the direct low frequency signal may be the dominant signal. Optionally, the low frequency signal may be filtered to ensure that multipath echoes are eliminated. Optionally, the low frequency response signal may be a direct signal responding to a direct signal. According to some embodiments, if the high frequency signal may be a multipath signal, it may have a longer path than the direct low frequency signal. Optionally, the timing of the high frequency response signal and the low frequency response signal may be measured. Optionally, the timing of the high frequency response signal and the low frequency response signal may be compared. Optionally, based on differences between the high frequency response signal and the low frequency response signal in phase and / or time of travel multipath high frequency signals may be differentiated from direct path high frequency signals. Time of travel may be determined by reception time (e.g., when HF and LF signals are transmitted simultaneously) and / or comparative differential travel times (for example, when the HF and LF signals are not transmitted simultaneously but timing information is communicated [e.g., from the transmitter to the receiver]).

[0066] According to some embodiments, if the high frequency response signal arrives later and / or has a greater differential travel time than the low frequency response signal it may be assumed to be a multipath signal.

[0067] According to some embodiments, other factors may affect the response signal’s travel time. Optionally, the second unit may report timing and / or phase information (e.g., when and what phase it received the higher frequency signal and / or lower frequency “wake up” signals, and when and in what phase it transmitted the higher frequency response signal and / or lower frequency response signal, etc.). Optionally, from this and / or from the known time of transmission of the higher frequency and / or lower frequency “wake up” signals a precise time of travel and / or phase shift for the higher frequency signal and / or lower frequency may be calculated. Optionally, the higher frequency signal and / or lower frequency signal may be calculated even if the response times are not equal. Optionally, calculation may not require synchronization between the first unit and the second unit.

[0068] According to some embodiments, if the higher frequency signal is multipath, the system may assume that the second unit may either not on the direct line of communication and / or may be behind an obstacle.

[0069] According to some embodiments, if the higher frequency signal is a direct signal, the system may assume that the receiving unit is on the direct line of communication and in the open. According to some embodiments, a first unit (e.g., a firing unit, etc.) may transmit a high frequency signal. Optionally, one or more second units (e.g., a receiving unit) may search for the high frequency signal over a range of frequencies (e.g., the exact clock rate of the transmission is not known). Optionally, the search may include use of a Doppler function of a radar and / or lidar to search over a window of frequencies. Optionally, the system may use a moving Doppler window (e.g., the Doppler window may be moved up and / or down to increase the range of searched frequencies). Optionally, when the receiving radar unit receives a high frequency signal, the clock of the receiver unit may be synchronized to that of the incoming unit (e.g., the clock is set to equal the frequency of signal from the first unit). Optionally, the second unit may send a response signal back to the first unit. Optionally, along with the response signal the second unit may send the time and phase on which the signal was received. Optionally, the first unit may receive the response signal and timing information from the second unit. Optionally, the two units may then communicate. For example, synchronization of interrogator and transponder chirp signals whereby the transponder clock may be drifted until it has synchronized with the interrogator clock within the Doppler frequency search window. Optionally, the system may facilitate computation of a distance between two units without requiring an echo of the signal (e.g., synchronizing the clocks and then computing a time of travel of the signal transmitted between two units).

[0070] According to some embodiments, the signals may be narrow band chirps. Optionally, the chirp may be a linear up-chirp, linear down-chirp, exponential up-chirp, exponential down-chirp, etc. Optionally, the duration of the chirp may range between 1 ms to 20 ms, and / or 20 ms to 50 ms, and / or between 50 ms to 100 ms, and / or between 100 ms to 150 ms, and / or between 150 ms to 200 ms.

[0071] According to some embodiments, a low frequency signal and a high frequency signal may be transmitted by the firing unit sequentially and / or simultaneously. Optionally, a low frequency signal and a high frequency signal may be transmitted by the receiving unit sequentially and / or simultaneously. Optionally, since the low frequency signal does pass through obstacles (penetrating) and / or is omnidirectional. Optionally, every receiving unit may receive a direct low frequency signal. Optionally, the direct low frequency signal may be the dominant signal. Optionally, the low frequency signal may be filtered to ensure that multipath echoes are eliminated. Optionally, the low frequency response signal may be a direct signal responding to a direct signal. For example, a receiving unit not on the direct line of transmission and / or behind an obstacle may receive a reflected and / or refracted high frequency signal (non-penetrating). Similarly, the response signal may reach the firing unit along a multipath. Optionally, direct signals and multipath signals may be differentiated.

[0072] According to some embodiments, if the high frequency signal may be a multipath signal, it may have a longer path than the direct low frequency signal. Optionally, the timing of the high frequency response signal and the low frequency response signal may be measured. Optionally, the timing of the high frequency response signal and the low frequency response signal may be compared. Optionally, based on differences between the high frequency response signal and the low frequency response signal in phase and / or time of travel multipath high frequency signals may be differentiated from direct path high frequency signals.

[0073] According to some embodiments, if the high frequency response signal arrives later than the low frequency response signal it may be assumed to be a multipath signal.

[0074] According to some embodiments, multipath geometries may include direct line of sight path with a single reflection and / or multiple reflections (e.g., non-penetrating signal). Optionally, reflections may be off a smooth surface, such as a large building, the ground, or a body of water, mountain, etc. Multipath geometries may include one or more non-line-of-sight paths, e.g., with multiple reflections, such as from urban canyons where a signal may bounce off multiple buildings before reaching a receiver, inside buildings where signals encounter multiple surfaces like walls, floors, ceilings, and furniture to create a dense, complex multipath environment where signals scatter in all directions, etc. Multipath geometries may include diffraction which may bend a signal around a sharp edge and / or an obstacle.

[0075] According to some embodiments, the high frequency “wake-up” signal may be directional and may not penetrate obstacles, therefore any unit receiving the high frequency “wake-up” signal has received a direct high frequency signal because it is 1) on the direct line of transmission; and / or 2) in the open; 3) the range to the second unit may be computed based on the time of travel of the high frequency signal; and / or 4) certain obstacles (e.g., large metal objects) may reflect and / or refract the high frequency signal (a multipath signal). For example, a receiving unit not on the direct line of transmission and / or behind an obstacle may receive a reflected and / or refracted high frequency signal. Similarly, the response signal may reach the first unit along a multipath. According to some embodiments, if the higher frequency signal is multipath, the system may assume that the receiving unit may either not in the line of fire and / or may be behind an obstacle. According to some embodiments, if the higher frequency signal is a direct signal, the system may assume that the receiving unit is on the direct line of communication and in the open.

[0076] According to some embodiments, the clocks of the transceivers may be synchronized or unsynchronized. Optionally, signals transmitted by the transceivers may include a timestamp. Optionally, the transmitted signals may include time field information. Optionally, the transceivers may timestamp the transmission and / or reception events, e.g., timestamp transmission of a HF signal, timestamp receipt of a LF signal, etc. Optionally, each interrogation / response exchange may include one or more timestamps, e.g. for an interrogation / response exchange, the first unit records transmission / reception timestamps etc. Optionally, when transmission of a HF signal and a LF signal are simultaneous, the time of arrival of each signal (e.g., ToA(HF) and ToA(LF)) may be determined directly from receipt times. Optionally, when transmission of a HF signal and a LF signal are not simultaneous, the transceiver may include a transmission and / or reception timestamps for each HF signal and / or each LF signal. Optionally, for a non-simultaneous HF signal and FL signal pair, the times of arrival may be computed from known transmission / reception pairs.

[0077] According to some embodiments, from the time of arrival timestamps of the signals, the differential travel time (AT) may be calculated, e.g., AT = ToA(HF) - ToA(LF). The differential travel time may be used to classify the signal as a direct path signal or a multipath signal when compared to a threshold value (Tth). The system may classify the HF signal path as a multipath signal when the differential travel time exceeds a threshold value, e.g., if AT > Tth, the HF measurement is a multipath signal and may be ignored for range or line of fire decisions. The system may classify the HF signal path as a direct signal when the differential travel time does not exceed a threshold value, e.g., if AT < Tth, the HF measurement is a direct signal and should be included in range or line of fire decisions. The system may classify the HF path as a multipath signal when the differential travel time is significant.

[0078] If the high frequency signal is a multipath signal, it may have a longer path than the direct low frequency signal. Optionally, based on differences in phase and / or time of travel multipath high frequency signals may be differentiated from direct path high frequency signals. Optionally, a high frequency multipath signal may have a longer travel time than a low frequency direct path signal, enabling travel time differential (AT) based discrimination. If a high frequency signal is received by a second transceiver after a low frequency signal is received by a second transceiver when both signals were transmitted simultaneously by the first transceiver, then the high frequency signal may be classified as a multipath signal. Optionally, a high frequency multipath signal may have a longer travel time than a high frequency direct path signal, enabling travel time differential (AT) based discrimination. If a first high frequency signal is received by a second transceiver after a second high frequency signal is received by a second transceiver when both signals were transmitted simultaneously by the first transceiver, then the first high frequency signal may be classified as a multipath signal.

[0079] According to some embodiments, the threshold may be derived from channel conditions. Optionally, channel conditions may include path loss (e.g., due to distance), fading (e.g., due to multipath propagation), interference (e.g., due to crowding), noise (e.g., generated by electronic devices or natural sources), etc. The threshold value may range between 1 ps to 1 ns, and / or 1 ns to 100 ns, and / or 100 ns to 1 ps. Optionally, the threshold value may depend, at least in part, on multipath geometry and / or bandwidth of the signal. Optionally, LF timing may be used to provide clock-offset compensation. Optionally, HF acquisition may require prior Doppler and / or offset lock before time of arrival is calculated. Optional phase tags facilitate additional consistency checks.

[0080] According to some embodiments, prior to time of arrival determination, the HF receiver may acquire and / or lock onto a signal using a moving Doppler window. Optionally, the tuning may continue until the frequency error is equal to and / or smaller than the smallest increment the receiver uses to tune the search. This may indicate that the correct frequency band has been found and / or is very close to the true frequency of the signal. Optionally, this process may be performed continuously for a set number of chirps. The frequency and phase stability criteria may be met for a consecutive series of measurement cycles (e.g., chirps). Optionally, the system's ability to distinguish between two closely spaced objects may be limited by its frequency resolution. Optionally, the number of consecutive chirps transmitted by the radar may set this minimum detectable frequency difference. Optionally, the bandwidth of the radar's chirp may be increased such that the signal sweeps over a wider range of frequencies. Optionally, the number of consecutive chirps transmitted may be increased. SPECIFIC EMBODIMENTS

[0081] Before explaining at least one embodiment of the invention in detail, it is to be understood that the invention is not necessarily limited in its application to the details of construction and the arrangement of the components and / or methods set forth in the following description and / or illustrated in the drawings and / or the Examples. The invention is capable of other embodiments or of being practiced or carried out in various ways. The following numeric values and configurations are illustrative and non-limiting; other parameter ranges may be used without departing from the scope of the invention.

[0082] Reference is now made to the exemplary figures.

[0083] Fig. 1 is a schematic diagram illustrating a direct path signal 11 and multipath signal 13, in accordance with an embodiment of the current invention. For example, the system may differentiate between direct signals 11 and multipath signals 13. Optionally, the direct signals 11 may be penetrating. Optionally, multipath signals 13 may be non-penetrating. The system may include two or more transceivers. In a given exchange, a first transceiver 14 may send a signal to a second transceiver 12. The signal may follow a direct path and / or a multipath. Optionally, the multipath may include reflection off (non-penetrating) one or more obstacles 10 between the first transceiver 14 and the second transceiver 12.

[0084] If the high frequency signal is a multipath signal 13, it may have a longer path than the direct low frequency signal 11. Optionally, based on differences in phase and / or time of travel multipath high frequency signals 13 may be differentiated from direct path high frequency signals 11. Optionally, a high frequency multipath signal 13 may have a longer travel time than a low frequency direct path signal 11, enabling travel time differential (AT) based discrimination. Optionally, a high frequency multipath signal 13 may have a longer travel time than a high frequency direct path signal 11, enabling travel time differential (AT) based discrimination.

[0085] Multipath geometries may include direct line of sight path with a single reflection and / or multiple reflections (e.g., non-penetrating signal). Optionally, reflections may be off a smooth surface, such as a large building, the ground, or a body of water, mountain, etc. Multipath geometries may include one or more non-line-of-sight paths, e.g., with multiple reflections, such as from urban canyons where a signal may bounce off multiple buildings before reaching a receiver, inside buildings where signals encounter multiple surfaces like walls, floors, ceilings, and furniture to create a dense, complex multipath environment where signals scatter in all directions, etc. Multipath geometries may include diffraction which may bend a signal around a sharp edge and / or an obstacle.

[0086] Fig. 2 is a schematic diagram illustrating a low frequency signal 19, high frequency direct path 21 and high frequency multipath signal 23, in accordance with an embodiment of the current invention. For example, the system may differentiate between direct signals 21, 19 and multipath signals 23. Optionally, the direct signals 19 may be penetrating. Optionally, multipath signals 23 may be non-penetrating. The system may include two or more transceivers. In a given exchange, a first transceiver 24 may send a signal to a second transceiver 22. The signal may follow a direct path (e.g., HF direct path signal 21, LF signal 19) and / or a multipath (e.g., HF multipath signal 23). Optionally, the multipath may include reflection off one or more obstacles 20 between the first transceiver 24 and the second transceiver 22.

[0087] A low frequency signal 19 and a high frequency signal 21, 23 may be transmitted by the first transceiver 24 sequentially and / or simultaneously. Optionally, a low frequency signal 19 and a high frequency signal 21, 23 may be transmitted by the second transceiver 22 sequentially and / or simultaneously. Optionally, since the low frequency signal 19 does pass through obstacles (penetrating) and / or is omnidirectional, every unit may receive a direct low frequency signal 19. Optionally, the direct low frequency signal 19 may be the dominant signal. Optionally, the low frequency signal 19 may be filtered to ensure that multipath echoes are eliminated. Optionally, the low frequency response signal 19 may be a direct signal 19 responding to a received direct signal.

[0088] The timing may be the time from transmission of a signal by a first transceiver 24 to receipt of the signal by a second transceiver 22. Optionally, the signal may include a timestamp.

[0089] If the high frequency signal may be a multipath signal 23, it may have a longer path than the direct low frequency signal 19 and / or direct high frequency path. Optionally, the timing of the high frequency response signal 21, 23 and the low frequency response signal 19 may be measured. Optionally, the timing of the high frequency response signal 21 , 23 and the low frequency response signal 19 may be compared. Optionally, based on differences between the high frequency response signal 21, 23 and the low frequency response signal 19 in phase and / or time of travel multipath high frequency signals 23 may be differentiated from direct path high frequency signals 21.

[0090] If the high frequency signal 23 is a multipath signal, it may have a longer path than the direct low frequency signal 19. Optionally, based on differences in phase and / or time of travel multipath high frequency signals 23 may be differentiated from direct path high frequency signals 21. Optionally, a high frequency multipath signal 21 may have a longer travel time than a low frequency direct path signal 19, enabling travel time differential (AT) based discrimination. If a high frequency signal 23 is received by a second transceiver 22 after a low frequency signal 19 is received by a second transceiver 22 when both signals 19, 23 were transmitted simultaneously by the first transceiver 24, then the high frequency signal 23 may be classified as a multipath signal. Optionally, a high frequency multipath signal 23 may have a longer travel time than a high frequency direct path signal 21, enabling travel time differential (AT) based discrimination. If a first high frequency signal 23 is received by a second transceiver 22 after a second high frequency signal 21 is received by a second transceiver 22 when both signals were transmitted simultaneously by the first transceiver 24, then the first high frequency signal 23 may be classified as a multipath signal.

[0091] Fig. 3 is a block diagram describing a multi-band interrogation signaling system, in accordance with an embodiment of the current invention. For example, system 300 includes a first unit 316 and a second unit 326. Each unit includes control circuitry 310, 320. Each unit includes a low-band transceiver 312, 322 configured for omnidirectional transmission and reception. Each unit includes a high-band transceiver 314, 324 configured for unidirectional transmission and reception. Optionally, the lower frequency transceivers 312, 322 may communicate with each other. Optionally, the higher frequency transceivers 314, 324 may communicate with each other. Optionally, the clocks of the transceivers may be synchronized. Optionally, signals transmitted by the transceivers may include a timestamp. Optionally, Optionally, the system may include a directional device, e.g., compass, GPS, etc.

[0092] The system (e.g., the high frequency transceivers 32 and 33) may include two or more radar and / or lidar transceivers. Optionally, the system may be configured to receive one or more signals. Optionally, the radar and / or lidar transceivers may transmit and / or receive signals. Optionally, two or more radar and / or lidar transceivers may transmit and / or receive signals from each other. Optionally, the frequency and / or phase and / or timing of the signals of the two or more radar and / or lidar transceivers may be synchronized.

[0093] For example, in a two-unit, two-band system 300. A first unit 316 includes a low-frequency (LF) transceiver 312 and a high-frequency (HF) transceiver 314. A second unit 326 includes LF transceiver 322 and HF transceiver 324. In operation, unit 316 may transmit a LF interrogation signal and / or a HF interrogation signal. Unit 326 may receive the signal / s and return a LF response signal and / or a HF response signal. Each unit may time-stamp its own transmission and / or reception events for both LF signals and HF signals. The response signal / s from unit 326 may carry the timestamps needed for unit 316 to determine a differential travel time for the exchange (e.g., the difference in travel time between transmission by unit 316 and receipt by unit 326 and transmission by unit 326 and receipt by unit 316; the difference in travel time between transmission of the high frequency and low frequency transmissions by unit 326 and receipt by unit 316; the difference in travel time between transmission of two high frequency transmissions and / or low frequency transmissions by unit 326 and receipt by unit 316; etc.).

[0094] The control circuitry of unit 316 may compute the differential travel time. The differential travel time (AT) may be calculated based on the time of arrival (ToA) of the signals for the same exchange, e.g., AT = ToA(HF) - ToA(LF). The control circuitry may classify the HF signal path as a multipath signal when the differential travel time exceeds a threshold and / or when the differential travel time (AT) is significant. The control circuitry may classify the HF signal path as a direct signal when the differential travel time does not exceed a threshold. Optionally, the threshold may be derived from channel conditions.

[0095] Channel conditions may include path loss (e.g., due to distance), fading (e.g., due to multipath propagation), interference (e.g., due to crowding), noise (e.g., generated by electronic devices or natural sources), etc.

[0096] Fig. 4 is a chart describing a message-sequence timing method, in accordance with an embodiment of the current invention. For example, in method 400, each of a first unit 402 (e.g., a firing unit and / or an interrogating transceiver) and / or a second unit 422 (e.g., a receiver unit and / or a responding unit) may include a HF transceiver 406, 426 with one or more antennas 408, 410, 428, 430 and / or a LF transceiver 404, 424 with an antenna. For example, the HF transceiver may transmit and / or receive over a unidirectional antenna 410, 430 and / or an omni-directional antenna 408 / 428. Optionally, one of the HF transceivers (e.g., the second unit) or both of the units may not include a directional antenna. For example, the first unit may send a directed HF signal in the direction of the second unit using an omni-directional antenna. The second unit optionally receives the HF signal on an omni-directional antenna and responds with an omnidirectional signal transmitted over an omnidirectional antenna. Alternatively, or additionally, the second unit may send a receive the HF signal or send response using a directional antenna (optionally, scanning over various directions). In some embodiments, the first unit receives the HF response with an omni directional signal. Alternatively, or additionally, the HF signal may be transmitted with an omnidirectional antenna and / or the response may be received using a directed antenna.

[0097] In some embodiments, each of the first and second unit includes a LF -transceiver 404, 424. Optionally, the LF transceiver includes an omni-directional antenna. For example, the first unit 402 may send a LF interrogation signal in all directions and / or the second unit (LF transceiver 424) may receive the signal. Optionally the second unit transmits a LF response to the HF interrogation signal and / or the LF interrogation signal in the LF band on omnidirectional antenna. Optionally the second unit transmits a HF response to the HF interrogation signal and / or the LF interrogation signal in the HF band on omnidirectional and / or unidirectional antenna. Optionally, the response may include information about the received LF and / or HF interrogation signals. For example, the response may include information about the timing of reception the HF and / or LF interrogation signals. Optionally, the response may include information about the transmission of the LF and / or HF response signals. For example, the response may include information about the timing of transmission of the HF and / or LF response signals. For example, when the interrogating unit receiver the response, it may compare the differential travel time of reception of the HF interrogation signal with the time of transmission of the HF interrogation signal to the differential travel time of reception of the LF interrogation signal with respect to the time of transmission of the LF interrogation signal. For example, when the interrogating unit receiver the response, it may compare the differential travel time of reception of the HF response signal with the time of transmission of the HF response signal to the differential travel time of reception of the LF response signal with respect to the time of transmission of the LF response signal. For example, if the differential travel time of the HF signal were greater than the differential travel time of reception of the LF signal this may be a sign that the HF signal was transmitted along a multi-path path. Fig. 5 is a unit-level block diagram of a radar transceiver illustrating an HF radar (or lidar) transceiver and an LF transceiver, in accordance with an embodiment of the current invention. For example, system 500, includes a HF chain and a LF chain. Each transceiver may include a transmission antenna and a receiver antenna. A transmitter may be configured for generating and emitting a signal.

[0098] In the HF chain, the HF transceiver 524 includes a wave generator 502. For example, the wave generator 502 may use a voltage-controlled oscillator (VCO), synthesizer, and / or a frequency synthesizer to create a continuous wave (CW) and / or pulsed signal and / or laser. The HF transceiver 524 may include a duplexer 504. Optionally, a power amplifier 506 (e.g., low- noise amplifier (LNA)), such as a solid-state amplifier and / or a traveling-wave tube amplifier, is used to amplify the signal. This amplified signal is optionally transmitted through a directional antenna, which focuses the RF energy toward the target and / or determines the beam shape and range. Optionally, the system includes a receiver. In some embodiments, the same antenna is used for both transmitting and receiving signals. Alternatively, or additionally, the system may use separate antennas for receiving and transmitting. The received signal may be amplified by amplifier 514. For example, a low-noise amplifier (LNA) is employed to amplify the weak signal without introducing significant noise, preserving signal integrity. The amplified signal is optionally fed into a mixer 510, which combines the incoming signal with a reference signal (e.g., mixer with a local reference). For example, the reference signal may be produced by the wave generator. Optionally, the system may include amplifiers 506, 514 and / or filters 512 (e.g., IF filter / gain stage having an IF acceptance bandwidth). For example, the amplifiers and / or filters may prepare the received signal and / or the mixed signal for further analysis. The signal is optionally converted from analog to digital (e.g., using an analog-to-digital converter (A / D) 516). In some embodiments, the digitized signal may be analyzed by a processor (control circuitry) 518 using digital signal processing, for example using a Fast Fourier Transform (FFT), which transforms the radar signal from the time domain to the frequency domain. Control circuitry 518 may be configured to time-stamp transmission and / or reception events on both bands. Control circuitry 518 may be configured to compute time of arrival of each signal, e.g., ToA(HF) and ToA(LF). Control circuitry 518 may be configured to determine differential time of travel (AT) for an exchange. Control circuitry 518 may be configured to run a multipath / direct path classifier. Control circuitry 518 may be configured to provide classification results to an application logic (e. g. , ignore HF samples flagged multipath when making line of fire or range decisions).

[0099] The system includes a display and control unit 518. For example, a graphical and / or numerical interface may show information such as range and / or direction. Optionally, the interface may be used to configure radar settings, including frequency, sensitivity, and pulse repetition frequency (PRF). In some embodiments, a duplexer, (e.g., switch or circulator) may facilitate the radar to use the same antenna for transmitting and receiving signals. The duplexer may reduce interference or damage to sensitive components. Optionally, the system incorporates clutter filters, for example, to reduce the effects of multipath signals. In some embodiments, the system includes a power supply to function. Optionally, the power supply may be AC or DC.

[0100] In some embodiments, the LF chain includes an omnidirectional transceiver and antenna, a LF transceiver 520 may include a separate antenna 522 from the HF transceiver.

[0101] Prior to time measurement, the HF receiver may perform acquisition by sweeping an offset (Doppler) window and only accepting a response signal with low frequency errors to ensure valid time of arrival. Tuning may continue until the frequency error is equal to and / or smaller than the smallest increment the receiver uses to tune the search. This may indicate that the correct frequency band has been found and / or is very close to the true frequency of the signal. Optionally, this process may be performed continuously for a set number of chirps. The frequency and phase stability criteria may be met for a consecutive series of measurement cycles (e.g., chirps). Optionally, the system's ability to distinguish between two closely spaced objects may be limited by its frequency resolution. Optionally, the number of consecutive chirps transmitted by the radar may set this minimum detectable frequency difference. Optionally, the bandwidth of the radar's chirp may be increased such that the signal sweeps over a wider range of frequencies. Optionally, the number of consecutive chirps transmitted may be increased.

[0102] Fig. 6 is a flow chart describing a message-sequence timing method, in accordance with an embodiment of the current invention. For example, message-sequence timing method 400 may include a single signal exchange including sending and receiving one or more low frequency (LF) signals and / or one or more high frequency (HF) signals. Optionally, the signals may include timestamps. Method 400 may illustrate the message flow and timing used to derive time of arrival (ToA) values of the signals and / or calculation of differential travel time (AT) to classify the path of a signal. In interrogation step 602, a first unit transmits LF and HF interrogations simultaneously or sequentially. The signals may include a transmission timestamp. The signals are received 604 by a second unit. The signals may receive a reception timestamp. Optionally, each signal may an individual timestamp. The second unit may send a response 606 signal. Optionally, the response signal may be a HF signal. Optionally, the response signal may be a HF signal and a LF signal. Optionally, the HF signal and LF signal may not be simultaneous. The response signal may include a timestamp. The response signal may include timing fields. The response signal may be a dual band response that includes the relevant timestamps for both bands. The first unit may receive the response signal / s. Using the provided timestamps, the first unit may compute 608 the time of arrival of the signals e.g., ToA(LF) and ToA(HF) for the same exchange. From the time of arrival timestamps of the response signals, the differential travel time (AT) may be calculated, e.g., AT = ToA(HF) - ToA(LF). The differential travel time may be used to classify 610 the signal as a direct path signal or a multipath signal when compared to a threshold value (T^), e.g., if AT > Tth, the HF measurement is a multipath signal and may be ignored for range or line of fire decisions. If AT < Tth, the HF measurement is a direct signal and should be included in range or line of fire decisions. Optionally, LF timing may provide clock-offset compensation. Optionally, HF acquisition may require prior Doppler and / or offset lock before time of arrival is calculated. Optional phase tags allow additional consistency checks

[0103] These embodiments are provided by way of example and are in no means intended to limit the scope of the invention.

[0104] While the invention has been described in its preferred form or embodiment with some degree of particularity, it is understood that this description has been given only by way of example and that numerous changes in the details of construction, fabrication, and use, including the combination and arrangement of parts, may be made without departing from the spirit and scope of the invention.

[0105] ADVANTAGES

[0106] Compared to single-band ToA or phase-based localization, some embodiments of the current invention system robustly reject multipath reflections. For example, a system may exploit band-dependent propagation. In some embodiments, the disclosed method improves detection reliability, reduces false range estimates, and / or facilitates accurate localization in complex environments such as urban canyons or inside structures.

[0107] GENERAL

[0108] It is expected that during the life of a patent maturing from this application many relevant building technologies, artificial intelligence methodologies, computer user interfaces, image capture devices will be developed and the scope of the terms for design elements, analysis routines, user devices is intended to include all such new technologies a priori.

[0109] Unless otherwise defined, all technical and / or scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the invention pertains. Although methods and materials similar or equivalent to those described herein can be used in the practice or testing of embodiments of the invention, exemplary methods and / or materials are described below. In case of conflict, the patent specification, including definitions, will control. In addition, the materials, methods, and examples are illustrative only and are not intended to be necessarily limiting.

[0110] As will be appreciated by one skilled in the art, some embodiments of the pretransmitted invention may be embodied as a system, method or computer program product. Accordingly, some embodiments of the pretransmitted invention may take the form of an entirely hardware embodiment, an entirely software embodiment (including firmware, resident software, micro-code, etc.) or an embodiment combining software and hardware aspects that may all generally be referred to herein as a “circuit,” “module” or “system.” Furthermore, some embodiments of the pretransmitted invention may take the form of a computer program product embodied in one or more computer readable medium(s) having computer readable program code embodied thereon. Implementation of the method and / or system of some embodiments of the invention can involve performing and / or completing selected tasks manually, automatically, or a combination thereof. Moreover, according to actual instrumentation and equipment of some embodiments of the method and / or system of the invention, several selected tasks could be implemented by hardware, by software or by firmware and / or by a combination thereof, e.g., using an operating system. For example, hardware for performing selected tasks according to some embodiments of the invention could be implemented as a chip or a circuit. As software, selected tasks according to some embodiments of the invention could be implemented as a plurality of software instructions being executed by a computer using any suitable operating system. In an exemplary embodiment of the invention, one or more tasks according to some exemplary embodiments of method and / or system as described herein are performed by a data processor, such as a computing platform for executing a plurality of instructions. Optionally, the data processor includes a volatile memory for storing instructions and / or data and / or a non-volatile storage, for example, a magnetic hard-disk and / or removable media, for storing instructions and / or data. Optionally, a network connection is provided as well. A display and / or a user input device such as a keyboard or mouse are Optionally, provided as well.

[0111] Any combination of one or more computer readable medium(s) may be utilized for some embodiments of the invention. The computer readable medium may be a computer readable signal medium or a computer readable storage medium. A computer readable storage medium may be, for example, but not limited to, an electronic, magnetic, optical, electromagnetic, infrared, or semiconductor system, apparatus, or device, or any suitable combination of the foregoing. More specific examples (a non-exhaustive list) of the computer readable storage medium would include the following: an electrical connection having one or more wires, a portable computer diskette, a hard disk, a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or Flash memory), an optical fiber, a portable compact disc read-only memory (CD-ROM), an optical storage device, a magnetic storage device, or any suitable combination of the foregoing. In the context of this document, a computer readable storage medium may be any tangible medium that can contain, or store a program for use by or in connection with an instruction execution system, apparatus, or device.

[0112] A computer readable signal medium may include a propagated data signal with computer readable program code embodied therein, for example, in baseband / or as part of a carrier wave. Such a propagated signal may take any of a variety of forms including, but not limited to, electro-magnetic, optical, or any suitable combination thereof. A computer readable signal medium may be any computer readable medium that is not a computer readable storage medium and that can communicate, propagate, or transport a program for use by or in connection with an instruction execution system, apparatus, or device.

[0113] Program code embodied on a computer readable medium and / or data used thereby may be transmitted using any appropriate medium, including but not limited to wireless, wireline, optical fiber cable, RF, etc., or any suitable combination of the foregoing.

[0114] Computer program code for carrying out operations for some embodiments of the pretransmitted invention may be written in any combination of one or more programming languages, including an object-oriented programming language such as Java, Smalltalk, C++ or the like and conventional procedural programming languages, such as the "C" programming language or similar programming languages. The program code may execute entirely on the user's computer, partly on the user's computer, as a stand-alone software package, partly on the user's computer and partly on a remote computer or entirely on the remote computer or server. In the latter scenario, the remote computer may be connected to the user's computer through any type of network, including a local area network (LAN) or a wide area network (WAN), or the connection may be made to an external computer (for example, through the Internet using an Internet Service Provider).

[0115] Some embodiments of the pretransmitted invention may be described below with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems) and computer program products according to embodiments of the invention.

[0116] It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions may be provided to a processor of a general-purpose computer, special purpose computer, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, create means for implementing the functions / acts specified in the flowchart and / or block diagram block or blocks.

[0117] These computer program instructions may also be stored in a computer readable medium that can direct a computer, other programmable data processing apparatus, or other devices to function in a particular manner, such that the instructions stored in the computer readable medium produce an article of manufacture including instructions which implement the function / act specified in the flowchart and / or block diagram block or blocks.

[0118] The computer program instructions may also be loaded onto a computer, other programmable data processing apparatus, or other devices to cause a series of operational steps to be performed on the computer, other programmable apparatus or other devices to produce a computer implemented process such that the instructions which execute on the computer or other programmable apparatus provide processes for implementing the functions / acts specified in the flowchart and / or block diagram block or blocks.

[0119] Data and / or program code may be accessed and / or shared over a network, for example the Internet. For example, data may be shared and / or accessed using a social network. A processor may include remote processing capabilities for example available over a network (e.g., the Internet). For example, resources may be accessed via cloud computing. The term “cloud computing” refers to the use of computational resources that are available remotely over a public network, such as the internet, and that may be provided for example at a low cost and / or on an hourly basis. Any virtual or physical computer that is in electronic communication with such a public network could potentially be available as a computational resource. To provide computational resources via the cloud network on a secure basis, computers that access the cloud network may employ standard security encryption protocols such as SSL and PGP, which are well known in the industry.

[0120] Some of the methods described herein are generally designed only for use by a computer, and may not be feasible or practical for performing purely manually, by a human expert. A human expert who wanted to manually perform similar tasks might be expected to use completely different methods, e.g., making use of expert knowledge and / or the pattern recognition capabilities of the human brain, which would be vastly more efficient than manually going through the steps of the methods described herein.

[0121] Throughout this application, various embodiments of this invention may be pretransmitted in a range format. It should be understood that the description in range format is merely for convenience and brevity and should not be construed as an inflexible limitation on the scope of the invention. Accordingly, the description of a range should be considered to have specifically disclosed all the possible subranges as well as individual numerical values within that range. For example, description of a range such as from 1 to 6 should be considered to have specifically disclosed subranges such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6 etc., as well as individual numbers within that range, for example, 1, 2, 3, 4, 5, and 6. This applies regardless of the breadth of the range.

[0122] Whenever a numerical range is indicated herein, it is meant to include any cited numeral (fractional or integral) within the indicated range. The phrases “ranging / ranges between” a first indicate number and a second indicate number and “ranging / ranges from” a first indicate number “to” a second indicate number are used herein interchangeably and are meant to include the first and second indicated numbers and all the fractional and integral numerals therebetween.

[0123] As used herein the term “about” refers to ± 10%

[0124] The terms "comprises", "comprising", "includes", "including", “having” and their conjugates mean "including but not limited to".

[0125] The term “consisting of’ means “including and limited to”.

[0126] The term "consisting of' means that the composition, method or structure may include additional ingredients, steps and / or parts, but only if the additional ingredients, steps and / or parts do not materially alter the basic and novel characteristics of the claimed composition, method or structure.

[0127] As used herein, the singular form "a", "an" and "the" include plural references unless the context clearly dictates otherwise.

[0128] As used herein, the terms “multiple”, “multi” and “plurality” are used interchangeably, and may relate to one or more, e.g., 1, 2, 3, 4, 5, 10, 20, 100, 1,000, etc.

[0129] It is appreciated that certain features of the invention, which are, for clarity, described in the context of separate embodiments, may also be provided in combination in a single embodiment. Conversely, various features of the invention, which are, for brevity, described in the context of a single embodiment, may also be provided separately or in any suitable subcombination or as suitable in any other described embodiment of the invention. Certain features described in the context of various embodiments are not to be considered essential features of those embodiments, unless the embodiment is inoperative without those elements. Although the invention has been described in conjunction with specific embodiments thereof, it is evident that many alternatives, modifications and variations will be apparent to those skilled in the art. Accordingly, it is intended to embrace all such alternatives, modifications and variations that fall within the spirit and broad scope of the appended claims.

[0130] All publications, patents and patent applications mentioned in this specification are herein incorporated in their entirety by reference into the specification, to the same extent as if each individual publication, patent or patent application was specifically and individually indicated to be incorporated herein by reference. In addition, citation or identification of any reference in this application shall not be construed as an admission that such reference is available as prior art to the pretransmitted invention. To the extent that section headings are used, they should not be construed as necessarily limiting.

Claims

CLAIMSWhat is claimed is:

1. A method for identifying multipath interference, the method comprising: transmitting an interrogation signal; receiving response signals on a penetrating band and a non-penetrating band; determining a time of arrival for each response signal; and classifying a non-penetrating signal as multipath when a time of arrival of the nonpenetrating signal is significantly greater than a time of arrival of a penetrating signal.

2. The method of claim 1, further comprising calculating a differential travel time (AT) for each signal exchange.

3. The method of claim 2, further comprising classifying the non-penetrating signal as multipath when the differential travel time exceeds a threshold value (Tth).

4. The method of claim 2, further comprising classifying the non-penetrating signal as direct when the differential travel time does not exceed a threshold value (Tth).

5. The method of claim 3 or claim 4, wherein the threshold value (Tth) is derived, at least in part, from channel conditions.

6. The method of claim 1, wherein said interrogation signal includes a signal on a penetrating band.

7. The method of claim 6, where said interrogation signal further includes a signal on a nonpenetrating band.

8. The method of claim 1, wherein said penetrating band is a low band.

9. The method of claim 8, wherein said low band has a sub-GHz frequency.

10. The method of claim 1, wherein said non-penetrating band is a high band.

11. The method of claim 10, wherein said high band has a frequency ranging between 60 GHz to 100 GHz.

12. The method of claim 1, wherein the response signals on the penetrating band and the response signal on the non-penetrating band are transmitted simultaneously.

13. The method of claim 12, further comprising determining the time of arrival of each signal directly from their receipt times.

14. The method of claim 1, wherein the response signals on the penetrating band and the response signal on the non-penetrating band are not transmitted simultaneous.

15. The method of claim 14, further comprising determining the time of arrival of each signal from a transmission or reception timestamps for each signal.

16. The method of claim 1, wherein each signal further comprises a timestamp.

17. The method of claim 1, further comprising ignoring non-penetrating signals classified as multipath when computing line-of-fire or range.

18. A non-transitory computer-readable medium storing instructions that, when executed, cause performance of the method of claim 1.

19. A system for identifying multipath interference, comprising: a first unit and a second unit, wherein each unit includes a penetrating band transceiver and a non-penetrating band transceiver; and control circuitry, wherein the control circuitry is configured for: transmitting an interrogation signal; receiving response signals on a penetrating band and a non-penetrating band; determining a time of arrival for each response signal; and classifying a non-penetrating signal as multipath when a time of arrival of the nonpenetrating signal is significantly greater than a time of arrival of a penetrating signal.

20. The system of claim 19, wherein the control circuitry is further configured for calculating a differential travel time (AT) for each signal exchange.

21. The system of claim 20, wherein the control circuitry is further configured for classifying the non-penetrating signal as multipath when the differential travel time exceeds a threshold value (Tth).

22. The system of claim 20, wherein the control circuitry is further configured for classifying the non-penetrating signal as direct when the differential travel time does not exceed a threshold value (rth).

23. The system of claim 21 or claim 22, wherein the threshold value (rth) value is derived, at least in part, from channel conditions.

24. The system of claim 19, wherein said interrogation signal includes a signal on a penetrating band.

25. The system of claim 24, where said interrogation signal further includes a signal on a nonpenetrating band.

26. The system of claim 19, wherein said penetrating band is a low band.

27. The system of claim 26, wherein said low band has a sub-GHz frequency.

28. The system of claim 19, wherein said non-penetrating band is a high band.

29. The system of claim 28, wherein said high band has a frequency ranging between 60 GHz to 100 GHz.

30. The system of claim 19, wherein the response signals on the penetrating band and the response signal on the non-penetrating band are transmitted simultaneous.

31. The system of claim 30, wherein the control circuitry is further configured for determining the time of arrival of each signal directly from their receipt times.

32. The system of claim 19, wherein the response signals on the penetrating band and the response signal on the non-penetrating band are not transmitted simultaneous.

33. The system of claim 32, wherein the control circuitry is further configured for determining the time of arrival of each signal from a transmission or reception timestamps for each signal.

34. The system of claim 19, wherein each signal further comprises a timestamp.

35. The system of claim 19, wherein the control circuitry is further configured for ignoring nonpenetrating signals classified as multipath when computing line-of-fire or range.

36. A discriminate multipath system comprising: a first unit and a second unit, wherein each unit includes a high-frequency (HF) transceiver and a low-frequency (LF) transceiver; and control circuitry, wherein the control circuitry is configured to: transmit an interrogation signal from the first unit on at least one of a high band and a low band; receive on the first unit response signals on a high band and a low band from the second unit; compute a time-of-arrival (ToA) for each of the response signals; compute a differential travel time from the times of arrival of the response signals; and classify a high frequency signal as multipath if the differential travel time exceeds a threshold value (rth), and as direct if the differential travel time does not exceed the threshold value (zth).

37. The system of claim 36, wherein the high band and the low band are a radar or lidar band.

38. The system of claim 36, wherein the high band ranges between 60 GHz to 100 GHz.

39. The system of claim 36, wherein the low band has a sub-GHz frequency.

40. The system of claim 36, wherein the interrogation signals are transmitted simultaneously on the high band and the low band.

41. The system of claim 36, wherein the response signals are transmitted simultaneously on the high band and the low band.

42. The system of claim 36, wherein the time of arrival of each response signal is determined from response reception time.

43. The system of claim 42, wherein the time of arrival of each response signal is computed from transmit / receive timestamps included in each response signal.

44. The system of claim 36, wherein the response signals are not transmitted simultaneously on the high band and the low band.

45. The system of claim 36, further comprising clock-offset compensation derived from the low frequency exchange.

46. The system of claim 36, wherein classification further comprises phase information reported by the second unit.

47. The system of claim 36, wherein the first unit and the second unit employ an omnidirectional antenna for low frequency signals and a unidirectional antenna for high frequency signals.

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