WO2022101739A1

WO2022101739A1 - Systems and methods for ascertaining spatial information of target objects

Info

Publication number: WO2022101739A1
Application number: PCT/IB2021/060158
Authority: WO
Inventors: Vitali KOZLOV; Yuval HADAD; Anna SLIOZBERG; Hagai ORTNER
Original assignee: I Comb Ltd.
Priority date: 2020-11-11
Filing date: 2021-11-03
Publication date: 2022-05-19

Abstract

Systems and methods derive spatial information associated with an object that is deployed in association with at least one beacon or at least one interrogation unit. The at least one beacon has a reflector antenna that has an adjustable internal impedance, and an impedance modulation unit that varies the internal impedance of the reflector antenna such that the reflector antenna produces impedance-modulated reflected signals in response to impinging interrogation signals. The at least one interrogation unit transmits an interrogation signal to impinge upon the reflector antenna, and receives reflected signals from the reflector antenna. A processing unit is associated with the at least one interrogation unit and processes the reflected signals received by the at least one interrogation unit to derive the spatial information.

Description

APPLICATION FOR PATENT

TITLE

Systems and Methods for Ascertaining Spatial Information of Target Objects CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority from US Provisional Patent Application No. 63/112,160, filed November 11, 2020, whose disclosure is incorporated by reference in its entirety herein. TECHNICAL FIELD

The present invention relates to distance measuring and object localization systems and methods.

BACKGROUND OF THE INVENTION

Accurate measurements of distance to a target object are crucial in many modem applications. One example of a distance measurement that utilizes remote measuring technique is a laser distance meter. However, laser distance meters require accurate positioning of a laser beam on a target. In addition, the measurement cannot be performed through optically opaque obstacles. A complimentary approach is based on radar technologies, where centimeter or millimeter carrier waves are used instead of optical beams. This type of measurement suffers from two major drawbacks. First, such radar systems have a significant degradation in angular resolution of measurement, and as a result, are highly sensitivity to clutter (radio frequency (RF) echoes retuned from other objects, which can be in the general vicinity of the target object, that are uninteresting). In other words, the radar beam captures echoes from such other objects, effectively introducing additional undesired targets that interfere with the distance measurement. The second major drawback of such radar systems is range accuracy, which is tightly coupled to operational bandwidth. In conventional radar systems used for distance measurement, the smallest typical resolution is limited to the centimeter range.

Another technology similar to distance measurement is RFID localization. This technology is based on localization of RFID tags with the help of a tag reader and signal post processing software. The technique is based on time of flight (ToF) technology but, cannot provide accuracies better than several centimeters. This inherent limitation is related to the limitations of present circuit technologies, which has a GHz-range internal clock. 1GHz, for example, gives about 1 nanosecond uncertainty in detection, which results in approximately 30 cm range accuracy. Faster clocks can improve this resolution, but still cannot reach millimeter (mm) accuracy. SUMMARY OF THE INVENTION

Embodiments of the present disclosure are directed to systems and methods for obtaining spatial information of a remote target object. The system employs an interrogation unit (or units) and a beacon (or beacons) having a reflector antenna with adjustable internal impedance and an impedance modulation unit that varies the internal impedance of the reflector antenna. In certain deployment configurations, the beacon is deployed in association with the target object, for example via removable attachment to the target object, such that the beacon and the target object are co-located and are remote from the interrogation unit. In other deployment configurations, the interrogation unit is deployed in association with target object such that the interrogation unit and the target object are co-located and are remote from the beacon. The interrogation unit is operative to transmit interrogation signals (in the form of waves of electromagnetic radiation) to the beacon over a wireless signaling channel (medium). The transmitted interrogation signals impinge upon the reflector antenna. In response to an impinging interrogation signal, the reflector antenna produces a reflected signal (also in the form of waves of electromagnetic radiation) that is an impedance modulated signal, due to the impedance variation applied by the impedance modulation unit. Hence, one or more of the parameters of the reflected signal varies as a function of the internal impedance of the reflector antenna. The interrogation unit is further operative to receive the reflected signal, and a processing unit linked to the interrogation unit processes the reflected signal to derive/determine spatial information of the target object that is descriptive of properties of the target object. Such properties (i.e., such spatial information) can include distance information and localization (location/position and orientation) information, as well as target object velocity. By employing impedance modulation at the reflector antenna in combination with signal processing algorithms employed by the signal processing unit, the embodiments of the present disclosure achieve accuracy of the distance and localization measurements on a millimeter (mm)- scale, for example accuracy to within 3 mm or better, and more preferably to within 1 mm or better, and most preferably to within 0.5 mm or better. In certain embodiments, the interrogation unit is configured as an ultra- wideband (UWB) radar unit that operates in the GHz frequency range, which makes the system according to embodiments of the present disclosure more robust against clutter (RF echoes from obstacles that are in vicinity of the target object), and further increases mm-scale accuracy. Localization accuracy on a mm- scale is further enabled by deployment configurations in which multiple beacons and/or multiple reflector antennas and/or multiple interrogation units are deployed in association with elements or subcomponents of the target object. According to the teachings of an embodiment of the present invention, there is provided a system that comprises: at least one beacon including: a reflector antenna, having an adjustable internal impedance, for reflecting impinging signals, and an impedance modulation unit in communication with the reflector antenna configured to vary the internal impedance of the reflector antenna such that the reflector antenna produces a reflected signal, that is an impedance modulated signal, in response to an impinging interrogation signal; at least one interrogation unit configured to transmit an interrogation signal that impinges upon the reflector antenna and to receive the reflected signal from the reflector antenna, one of the at least one beacon or the at least one interrogation unit is deployed in association with an object; and a processing unit electrically associated with the at least one interrogation unit configured to process the reflected signal received by the at least one interrogation unit to derive spatial information associated with the object.

Optionally, the at least one beacon is deployed in association with the object, and the spatial information includes a distance between the at least one interrogation unit and the object.

Optionally, the at least one interrogation unit is deployed in association with the object, and the spatial information includes a measurement of a distance between the at least one beacon and the object.

Optionally, the distance is less than 20 meters.

Optionally, the measurement of the distance is accurate to within 3 millimeters or better.

Optionally, the measurement of the distance is accurate to within 1 millimeter or better.

Optionally, the measurement of the distance is accurate to within 0.5 millimeters or better.

Optionally, the object is a rigid body comprising a plurality of object elements, and the at least one beacon includes a plurality of beacons, each beacon being deployed in association with a corresponding one of the object elements.

Optionally, the spatial information includes a measurement of a localization of the object in three-dimensional space, and the localization includes a centroid position of the object and an angular position of the object.

Optionally, the measurement of the centroid position of the localization is accurate to within 3 millimeters or better.

Optionally, the measurement of the centroid position of the localization is accurate to within 1 millimeter or better.

Optionally, the measurement of the centroid position of the localization is accurate to within 0.5 millimeters or better. Optionally, the measurement of the angular position of the localization includes three angles and is accurate to within 3 degrees or better for each of the three angles.

Optionally, the measurement of the angular position of the localization includes three angles and is accurate to within 1 degree or better for each of the three angles.

Optionally, the measurement of the angular position of the localization includes three angles and is accurate to within 0.5 degrees or better for each of the three angles.

Optionally, the impedance modulation unit is configured to vary the internal impedance of the reflector antenna in a continuous manner between a plurality of impedance states.

Optionally, the impedance modulation unit is configured to vary the internal impedance of the reflector antenna in a sinusoidal manner between a plurality of impedance states.

Optionally, the impedance modulation unit is configured to vary the internal impedance of the reflector antenna in discrete manner between a plurality of impedance states.

Optionally, the impedance modulation unit is configured to vary the internal impedance of the reflector antenna by employing a coded modulation technique.

Optionally, the impedance modulation unit is configured to vary the internal impedance of the reflector antenna at a modulation frequency of at least 10 Hz.

Optionally, the impedance modulation unit is configured to vary the internal impedance of the reflector antenna at a modulation frequency of at least 100 Hz.

Optionally, processing the reflected signal by the processing unit includes isolating the at least one beacon on a Doppler map.

Optionally, the reflector antenna includes a plurality of spatially distributed antenna elements, each antenna element being deployed in association with a different corresponding portion of the object.

Optionally, the beacon further includes a signal amplification unit in signal communication with the reflector antenna and the impedance modulation unit.

Optionally, the at least one interrogation unit is operative to transmit the interrogation signal at a carrier frequency of at least 1 GHz.

Optionally, the carrier frequency is in a range from 3 GHz to 10 GHz.

Optionally, the carrier frequency is in a range from 21 GHz to 26 GHz.

Optionally, the carrier frequency is in a range from 76 - 81 GHz.

Optionally, the at least one interrogation unit is configured as an ultra-wideband radar unit.

Optionally, the at least one interrogation unit is integrated as part of a comb.

Optionally, the at least one beacon is integrated as part of a comb. There is also provided according to the teachings of an embodiment of the present invention, a method that comprises: deploying one of at least one interrogation unit or at least one beacon or in association with an object, the at least one beacon including a reflector antenna having an adjustable internal impedance and an impedance modulation unit in communication with the reflector antenna; transmitting, by the at least one interrogation unit, an interrogation signal that impinges upon the reflector antenna; varying, by the impedance modulation unit, the internal impedance of the reflector antenna such that the reflector antenna produces a reflected signal, that is an impedance modulated signal, in response to the impinging interrogation signal; receiving, by the at least one interrogation unit, the reflected signal; and processing, by at least one processor electrically associated with the at least one interrogation unit, the reflected signal received by the at least one interrogation unit to derive spatial information associated with the object.

Optionally, varying the internal impedance of the reflector antenna is performed in a continuous manner between a plurality of impedance states.

Optionally, varying the internal impedance of the reflector antenna is performed in a sinusoidal manner between a plurality of impedance states.

Optionally, varying the internal impedance of the reflector antenna is performed in a discrete manner between a plurality of impedance states.

Optionally, varying the internal impedance of the reflector antenna is performed by employing a coded modulation technique.

Optionally, processing the impedance modulated signal includes isolating the at least one beacon on a Doppler map.

There is also provided according to the teachings of an embodiment of the present invention, a system that comprises: at least one beacon deployed in association with an object and including: a reflector antenna, having an adjustable internal impedance, for reflecting impinging signals, and an impedance modulation unit in communication with the reflector antenna configured to vary the internal impedance of the reflector antenna such that the reflector antenna produces a reflected signal, that is an impedance modulated signal, in response to an impinging interrogation signal; and a processing unit electrically associated with an interrogation unit that receives the reflected signal from the reflector antenna in response to transmitting an interrogation signal that impinges upon the reflector antenna, the processing unit configured to process the received reflected signal to derive spatial information associated with the object.

Unless otherwise defined herein, 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 may 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.

BRIEF DESCRIPTION OF THE DRAWINGS

Some embodiments of the present invention are herein described, by way of example only, with reference to the accompanying drawings. With specific reference 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.

Attention is now directed to the drawings, where like reference numerals or characters indicate corresponding or like components. In the drawings:

FIG. 1 is a schematic representation of a system, according to an embodiment of the present disclosure, having an interrogation unit for interrogating a beacon deployed in association with a target object and receiving a reflected signal in response to the interrogation, and a processing unit for processing the reflected signal to derive spatial information of the target object;

FIG. 2 is a schematic representation of a system according to another embodiment of the present disclosure, in which multiple of beacons are spatially distributed and deployed in association with different corresponding elements of the target object;

FIG. 3 is a schematic block diagram of an exemplary interrogation unit according to embodiments of the present disclosure;

FIG. 4 is a schematic block diagram of an exemplary beacon, according to embodiments of the present disclosure; having a reflector antenna with adjustable internal impedance and an impedance modulation unit for varying the impedance of the reflector antenna;

FIG. 5 is a schematic block diagram of an exemplary processing unit according to embodiments of the present disclosure; and

FIG. 6 is a schematic representation of a system according to another embodiment of the present disclosure, in which multiple of interrogation units are spatially distributed and deployed in association with different corresponding elements of the target object. DESCRIPTION OF THE PREFERRED EMBODIMENTS

Embodiments of the present disclosure include systems and methods for obtaining spatial information of a target object.

The principles and operation of the systems and methods according to embodiments of the present disclosure may be better understood with reference to the drawings accompanying the description.

Embodiments of the present disclosure are applicable to various situations in which probing and/or detecting targets objects at relatively short distances (typically within 20 meters) is desired. Such target objects, can be, but are not limited to, tools (e.g., hammers, screwdrivers, drills, etc.), tableware or dishware including glassware and flatware (e.g., plates, bowls, cups, forks, knives, spoons, etc.), hair grooming equipment such as combs and hairbrushes, or any other smaller-scale and hand-held objects for which distance measurement and/or localization may be desired.

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.

Referring now to the drawings, FIG. 1 schematically illustrates a system, generally designated 10, according to certain embodiments of the present disclosure, for determining/deriving spatial information associated with a remote target object 18 (referred to interchangeably hereinafter as “object” or “target”). Generally speaking, the system 10 preferably includes one or more (i.e., at least one) interrogation unit 12, one or more (i.e., at least one) beacon 14 having a reflector antenna with adjustable (i.e., tunable) internal impedance that defines the internal impedance of the beacon 14, and a signal processing unit 16 electrically associated with the interrogation unit 12 for determining/deriving spatial information associated with the object 18.

Various deployment configurations of the system 10 according to embodiments of the present disclosure are contemplated herein, whereby either the beacon 14 or the interrogation unit 12 can be deployed in association with the object 18 such that either the beacon 14 and the object 18 are co-located and are remotely located from the interrogation unit 12, or the interrogation unit 12 and the object 18 are co-located and are remotely located from the beacon 14. In the example embodiment illustrated in FIG. 1, the beacon 14 is deployed in association with the object 18 so as to tag the object 18. The deployment of the beacon 14 (or interrogation unit 12) may be effectuated by removable attachment of the beacon 14 to the object 18. In other words, the beacon 14 and the interrogation unit 12 may be attached, either directly or indirectly, and preferably removably, to the object 18.

Preferably, the interrogation unit 12 and the beacon 14 are deployed such that the linear distance between the interrogation unit 12 and the beacon 14 is no more than 20 meters.

As also will be discussed further, the spatial information determined/derived by the signal processing unit 16 is descriptive of properties of the object 18, and can include a measured distance between the object 18 and the beacon 14 or interrogation unit 12, and may further include localization of the object 18 in 3D space.

With continued reference to FIG. 1, refer now also to FIG. 2, which illustrates deployment of the system according to certain embodiments of the present disclosure. By way of introduction, in certain preferred but non-limiting applications, the object 18 is a rigid body that includes multiple object elements (represented schematically in FIG. 2 as 19a, 19b, and 19c). The rigid body has a spatial position (localization) in three-dimensional (3D) space that is represented and defined by (i.e., includes) linear position (for example represented as a point, for example in an XYZ coordinate system, that typically coincides with the center of mass or centroid of the rigid body), and angular position (i.e., orientation or attitude, which is represented by three Euler angles, typically roll, pitch and yaw). In the example embodiment illustrated in FIG. 2, the at least one beacon 14 includes a plurality of beacons 14a, 14b, and 14c, where each of the beacons 14a, 14b, 14c is deployed in association with a corresponding one of the object elements 19a, 19b, 19c. Although only three beacons 14a, 14b, 14c are illustrated in FIG. 2 for simplicity of presentation, embodiments of the present disclosure can be implemented with any number of beacons. In practice, the larger the number of beacons, the greater the accuracy of distance measurement and/or localization.

The interrogation unit 12 is configured to transmit interrogation signals (represented schematically in FIG. 1 as 131) to impinge upon the reflector antenna of the beacon 14 so as to interrogate the beacon 14 (or each of the beacons), and to receive reflected signals (represented schematically in FIG. 1 as 13R) from the beacon 14 (or beacons) in response to the interrogation signals. In certain non-limiting embodiments, the interrogation unit 12 is a conventional off-the- shelf radar unit, while in other embodiments the interrogation unit 12 is implemented as a customized radar integrated circuit (chip). In certain preferred but non-limiting embodiments, the interrogation unit 12 is implemented as an ultra-wideband (UWB) radar unit, such as a radar unit from the AWR series of mmWave radar sensors available from Texas Instruments of Dallas, TX, USA, and the Novelda XeThru X4 UWB impulse radar chip available from SensorLogic of Bozeman, MT, USA. It is noted that the embodiments of the present disclosure do not typically rely on any built-in signal processors of the interrogation unit 12 for performing the signal processing algorithms of the embodiments disclosed herein, but rather rely on the signal processing unit 16 which is a separate unit from the interrogation unit 12.

With continued reference to FIGS. 1 and 2, refer now also to FIG. 3, which illustrates a schematic block diagram of an exemplary interrogation unit 12. Here, the interrogation unit 12 includes a transmitter (Tx) module 122 for transmitting the interrogation signals 131, and a receiver (Rx) module 124 for receiving the reflected signals 13R. In certain preferred embodiments, the Tx module 122 is configured to transmit the interrogation signal as a sequence of low energy pulses (i.e., a pulse train). In such embodiments, the reflected signal is a corresponding reflected pulse train, and the Rx module 124 is configured to receive such aforesaid pulse trains.

Although not illustrated in the drawings, the Tx module 122 preferably includes one or more transmit antennas and transmitter hardware/software components or circuitry including, for example, one or more attenuators, one or more amplifiers, one or more low pass filters, one or more local oscillators, one or more power dividers, one or more frequency mixers, and any other components typically employed in radar transmitter architectures. In certain embodiments, the Tx module 122 is also operative to generate the interrogation signals and includes one or more tone/pulse/signal/wav eform generators. In other embodiments, the processing unit 16 may include such a tone/pulse/signal/waveform generator so as to provide interrogation signal generation capability.

Similarly, although not illustrated in the drawings, the Rx module 124 preferably includes one or more receive antennas and receiver hardware/software components or circuitry including, for example, one or more low noise amplifiers, one or more low pass filters, one or more amplifiers, one or more local oscillators, one or more power dividers, one or more frequency mixers, one or more power splitters, and any other components typically employed in radar receiver architectures.

As should be apparent, the Tx and Rx modules may be implemented in a single transceiver module that performs both transmit and receive functionality. Moreover, a single Tx/Rx antenna may be used to both transmit the interrogation signal 131 and to receive the reflected signal 13R, with the interrogation unit 12 including a processor/controller for controlling the transmit/receive timing and switching of the Tx/Rx antenna.

In certain preferred embodiments, the interrogation unit 12 operates in the GHz frequency range, whereby the interrogation unit 12 is operative to transmit the interrogation signals at a carrier frequency of at least 1 GHz, and in certain non-limiting implementations at a carrier frequency in the range of 3 - 10 GHz, which can include various sub-ranges such as 3.5 - 6.5 GHz, 6 - 8 GHz, and 6 - 8.5 GHz. Other carrier frequency ranges that have been found to be particularly suitable include 24 - 24.5 GHz (and more preferably 24 - 24.25 GHz), 21 - 26 GHz, 76 - 77 GHz, and 77 - 81 GHz. The use of GHz range interrogation signals enables the interrogation signals to penetrate and/or diffract around obstacles or other “undesired” objects in the vicinity of the target object 18, making the system 10 according to certain embodiments of the present disclosure robust to clutter. Furthermore, the relatively broad bandwidth of the interrogation signals (in particular when utilizing an interrogation unit implemented as a UWB radar unit) enables efficient interrogation of beacons 14 by the interrogation unit 12 without requiring tight alignment of the transmit antenna(s) of the Tx module 122 to the antenna of the beacon 14. As a result, the system 10 according to embodiments of the present disclosure provides location and/or position measurement/detection and tracking of the object 18 in a significant angular range (portion/sector of 3D space) without requiring line-of-sight to the target object and thereby without necessitating use of scanning/steering mechanisms associated with the transmit antenna at the interrogation unit 12 to steer the transmit antenna beam toward beacon 14, and thereby reducing the complexity of the interrogation unit architecture and providing a compact system that can be suitably integrated with an appropriate target object.

With continued reference to FIGS. 1 - 3, refer now also to FIG. 4, which illustrates a schematic block diagram of an exemplary beacon 14 according to embodiments of the present disclosure. The beacon 14 includes a reflector antenna 142 that has an adjustable internal impedance and operates in a frequency range that at least partially covers the operational frequency band of the interrogation unit 12. The reflector antenna 142 is operative to reflect impinging signals (i.e., signals that impinge upon the reflector antenna), which includes the interrogation signals 131 transmitted by the interrogation unit 12. The reflector antenna 142 produces (and transmits) reflected signals in response to such impinging signals. When an interrogation signal 131 impinges upon the reflector antenna 142, the reflector antenna 142 in response produces a reflected signal 13R that propagates back toward the interrogation unit 12. The reflected signal 13R may also be referred to as a backscattered signal.

In embodiments in which the interrogation unit 12 operates as a UWB unit, the reflector antenna 142 is preferably implemented as a broadband reflector antenna. The reflector antenna can be implemented in various ways, including as a corner reflector, a curved reflector having a curved reflecting surface, or any other suitable type of reflector. The beacon 14 further includes an impedance modulation unit 144 linked or connected to (in electronic or signal communication with) the reflector antenna 142, and that is operative to vary (i.e., modulate) the internal impedance of the reflector antenna 142 (i.e., the internal impedance of the beacon 14) between a plurality of impedance states or impedance values. Thus, the impedance modulation unit 144 varies the internal impedance of the reflector antenna 144 such that the reflector antenna 142 produces reflected signal 13R as an impedance modulated signal in response to interrogation signal 131 impinging on the reflector antenna 142. The impedance modulation unit 144 generally performs direct impedance modulation which results in a time-modulated reflected signal 13R that represents the change over time of the reflection coefficient associated with the impedance of the beacon 14 (i.e., the internal impedance of the reflector antenna 142). The impedance modulation unit 144 can be configured to vary the internal impedance of the reflector antenna 142 according to any suitable modulation technique at any suitable modulation frequency, as will be further discussed below, which in certain cases may result in a periodic modulated signal. The impedance modulation unit 144 can perform the modulation using any suitable combination of power source and tunable capacitor or switch or other similar modulation inducing circuitry. In a preferred embodiment, the beacon 14 includes a power source 146 which is implemented as a battery which assists in performing the modulation. In certain embodiments, the power source 146 and modulation circuitry (e.g., tunable capacitor/switch) are implemented together in a singular small-scale circuit integrated in the beacon 14. In certain preferred but non-limiting embodiments, the beacon 14 also includes a signal amplifier unit (or simply “amplifier unit” for short) 148 having one or more signal amplifiers in signal communication with the reflector antenna 142 and the impedance modulation unit 142. The amplifier unit 148 is operative to amplify the interrogation signal that impinges upon (i.e., that is received/collected by) the reflector antenna 142, and/or is operative to amplify the reflected signal that is transmitted/propagated by the reflector antenna 142 back toward the interrogation unit 12.

Although not illustrated in the drawings, the beacon 14 may include additional electronic components including couplers, transmission lines, circular connectors, and the like. In certain embodiments, the impedance values across which the impedance modulation unit 144 varies the internal impedance of the reflector antenna 142 may be programmed into circuitry of the impedance modulation unit 144.

Parenthetically, in certain embodiments the reflector antenna 142 can include a plurality of reflector antennas or a plurality of antenna elements (represented schematically in FIG. 4 as 143a, 143b, and 143c) that each can operate as a reflector antenna with adjustable internal impedance. The antenna elements may be spatially distributed and deployed, for example, such that each reflector antenna is in association with a different corresponding portion of the object 18. For example, the antenna element 143a may be deployed in association with object element 19a, the antenna element 143b may be deployed in association with object element 19b, and the antenna element 143c may be deployed in association with object element 19c. In such embodiments, each reflector antenna may have a dedicated corresponding impedance modulation unit, or a single impedance modulation unit may be employed to separately vary the internal impedance of each of the reflector antennas.

The reflector antenna 142 is preferably designed so as to: a) provide maximal (or nearly maximal) back reflection (i.e., backscattering) over the entire bandwidth of the interrogation signal 131, b) provide maximal (or nearly maximal) back reflection for the polarization direction of the incident field of the electromagnetic wave of the signal 131, and c) provide small angular sensitivity of the reflection coefficient (mainly the phase) of the reflected signal 13R. Designing the reflector antenna 142 in such a way so as to meet the three above-mentioned provisions enables maximization of signal to noise ratio (SNR) and, as a result, provides better performance in terms of determining range (distance) and range accuracy.

Parenthetically, the transmitted interrogation signal may have any suitable polarization direction (e.g., vertical (V), horizontal (H), circular, etc.). Typically, any polarization on either the transmitted or received signal (by the interrogation unit 12) can be synthesized using H and V components. In general, there can be the following four combinations of transmit and receive polarizations with typical radars: H transmit and H receive, V transmit and V receive, H transmit and V receive, and V transmit and H receive. Usually, radar systems can have one, two, or all four of the aforesaid polarization combinations. In certain embodiments, the interrogation unit 12 can employ polarization coding (radar polarimetry) whereby all four of the polarization combinations are used during interrogation and response.

In certain non-limiting implementations, the impedance modulation unit 144 varies (i.e., modulates) the internal impedance of the reflector antenna 142 between the plurality of impedance states/values in a substantially continuous manner, for example in a sinusoidal manner according to a sinusoidal modulation. Other continuous functions, such as saw-tooth variation, may also be used. In other sometimes preferred embodiments, the impedance modulation unit 144 modulates the internal impedance of the reflector antenna 142 between the plurality of impedance states/values in a discrete manner, for example according to a rectangular impulse signal so as to modulate the internal impedance in a stepped or on-off manner. It is noted that other modulation waveforms and schemes for varying the internal impedance of the reflector antenna 142 are also contemplated herein, including more complex coded modulations techniques, such as phase encoding modulation, or any other modulation waveforms and schemes which could improve the SNR of the signal 13R received at the interrogation unit 12.

The signal processing unit (referred to interchangeably as “processing unit”) 16 is configured to detect the reflected signals 13R (i.e., the impedance modulated signal) received by the interrogation unit 12, and to process the detected/received impedance modulated signals in order to determine/derive spatial information associated with the object 18. In a simple case in which only a single interrogation unit 12 and a single beacon 14 with a singular reflector antenna are employed, the “spatial information” includes and can be limited to distance information, whereby the processing unit 16 processes the received impedance modulated signals to determine/derive/measure the distance between the object 18 and the interrogation unit 12 or between the object 18 and the beacon 14. In embodiments in which the beacon 14 is deployed in association with the object 18 (e.g., removably attached (directly or indirectly) to the object), the processing unit 16 processes the impedance modulated signals to determine the distance between the interrogation unit 12 and the object 18. In embodiments in which the interrogation unit 12 is deployed in association with the object 18, the processing unit 16 processes the impedance modulated signals to determine the distance between the beacon 14 and the object 18. In certain preferred embodiments in which a plurality of beacons (e.g., 14a, 14, 14c) is deployed or in which a single beacon with a plurality of reflector antennas is deployed (or in which a plurality of interrogation units are deployed), the “spatial information” further includes location/localization information, whereby the processing unit 16 processes the received impedance modulated signals to determine/derive the localization of the object 18 in 3D space, in which the localization of the object 18 typically includes (is typically defined by) position of center of mass (or centroid) of the object and angular position of the object (as discussed above).

By way of introduction, the processing unit 16 may process the received reflected signals to isolate/extract desired information in the received impedance modulated signal, for example, by employing Doppler analysis techniques or variations thereof. As is known to those of ordinary skill in the art of radar and radar signal processing, Doppler analysis enables determination/measurement of object distance, object linear position/location, and object angular position. By employing such Doppler-type analysis, the processing unit 16 measures/determines the distance between the interrogation unit and the beacon, thereby determining the distance to the target object from the interrogation unit(s) or the beacon(s). In certain embodiments, in particular when employing multiple interrogation units and/or multiple beacons and/or multiple reflector antennas, this information isolation/extraction employed by the processing unit 16 may further include measuring/determining the centroid position of the object and the angular position (e.g., Euler angles) of the object.

Bearing the above in mind, the principle of operation of the processing unit 16 for processing the detected/received impedance modulated signals is based on periodic (or any other suitable) time-modulation of the reflection coefficient associated with the impedance associated with the beacon 14 (i.e., due to the variation of the internal impedance of the reflector antenna 142 applied by the impedance modulation unit 144). The rapid time-modulation enables the processing unit 16 to identify changes in the reflection coefficient and to isolate the beacon 14 (reflector antenna 142) on a Doppler map, since in effect any slow-moving time-modulated signal (induced by a scatterer) is interpreted as a fast-moving target with velocities that generally are not attributable to any reasonable amount of motion in the environment surrounding the target object.

In operation, the processing unit 16 may process only a single frequency segment in time (e.g., a single tone), and the repeatability of this segment in time enables the processing unit 16 to filter the received impedance modulated signal, which is the echo (backscattered, reflected) signal which has been impedance modulated by the impedance modulation unit 144 so as to effectively color the signal with a modulation frequency. The reflected signal produced by the beacon 14 may have the general form of S_T(t) cos(m_Dt), where S_T(t) represents the transmitted interrogation signal, and

represents the Doppler frequency. Preferably, the aforementioned modulation frequency is at least 10 Hz, and is more preferably at least 100 Hz. In practice, the modulation frequency should be higher than the Doppler frequency and does not have a strict upper bound, but it is generally preferable that this frequency not exceed 10% above the carrier frequency.

The processing unit 16 may employ any suitable frequency-domain (spectral) analysis or time-domain analysis technique to isolate/extract desired information in the received impedance modulated signal. In certain embodiments, the processing unit 16 employs Fourier analysis, more preferably Fast Fourier Transform (FFT), to isolate the desired information. The desired information can be the presence (or absence) of the beacon 14 at a certain mm-scale range. In other embodiments, the processing unit 16 employs correlation processing in the time-domain. Since the reflected signal produced by the beacon 14 has the general form of S_T(t) cos(m_Dt), a correlation between the transmitted interrogation signal and the received reflected signal can be formed at the at the processing unit 16. It is noted that the signal processing techniques employed by the processing unit 16 offer certain advantages over conventional approaches. First, the processing unit 16 filters the received impedance modulated signal so as to concentrate on a single tone (or any other matching signal). As is known in the art, the amount of noise detected at the receiver grows proportionally to the signal bandwidth. Therefore, operating the processing unit 16 to concentrate on a single baseband frequency tone effectively suppresses the noise, thereby increasing SNR. Secondly, the processing unit 16 enables high-efficiency operation in cluttered environments in which multiple “undesired” objects are in the general vicinity of the object 18. Typically, such undesired objects can generate reflected signals when impinged upon by interrogation signals. In certain situations, backscattered signals generated by undesired objects can suppress desired reflected signals from the reflector antenna associated with the target object, especially when such undesired objects are larger (since larger objects are characterized with large radar cross-sections). However, frequency- shifted reflected signals are only produced by moving objects, which generate corresponding Doppler shifts. The rapid modulation employed by the embodiments of the present disclosure mimic fast-moving objects which are unlikely to appear in the surrounding environment that is in the vicinity of the target object. As a result, the rapidly modulated signals (13R), produced by the beacon 14 in response to interrogation signal 131, are easily separated from clutter (i.e., are easily separated from RF echoes from other “undesired” objects).

The processing unit 16 may be implemented using any suitable type of processing hardware and/or software, as is known in the art, including but not limited to any combination of various dedicated computerized processors operating under any suitable operating system and implementing suitable software or firmware modules. The computerized processors are preferably coupled to a storage medium, which can be one or more computerized memory devices, such as volatile data storage. The computerized processors may be implemented as any number of computerized processors including, but not limited to, microprocessors, microcontrollers, application- specific integrated circuits (ASICs), digital signal processors (DSPs), field-programmable gate arrays (FPGAs), field-programmable logic arrays (FPLAs), and the like. Such computerized processors include, or may be in electronic communication with non-transitory computer readable media, which stores program code or instruction sets that, when executed by the computerized processor, cause the computerized processor to perform actions. Types of non-transitory computer readable media include, but are not limited to, electronic, optical, magnetic, or other storage or transmission devices capable of providing a computerized processor with computer readable instructions. FIG. 5 illustrates a schematic block diagram of an exemplary processing unit 16 that includes at least one of such computerized processors 162 coupled to one such at least one of such storage medium 164 (i.e., computer memory). It is noted that although only a single processing unit 16 is illustrated in the drawings, the system 10 may employ multiple such processing units 16. The electrical association between the processing unit 16 and the interrogation unit 12 can be effectuated by any suitable data or signal coupling/interface, including, for example, a data bus, wired interface connection, and the like. In certain embodiments, the electrical association can include a wireless connection in which the interrogation unit 12 and the processing unit 16 each include a wireless transceiver configured to exchange signals and/or data.

The embodiments described thus far have pertained to deployment configurations in which the beacon 14 is deployed in association with the object 18. In such configurations, the interrogation unit 12 can be deployed as a static “home” unit that is accessible and/or controllable by a user of the system 10. However, as mentioned above, other deployment configurations of the system 10 are possible in which the interrogation unit 12 is deployed in association with the object 18. In such deployment configurations, the beacon 14 (or beacons) can be deployed as a static home unit. FIG. 6 schematically illustrates such a deployment configuration in which three interrogation units (labeled as “radar units” 12a, 12b, 12c in the figure) are spatially distributed and deployed such that each interrogation unit is deployed in association with a different corresponding portion of the object 18. For example, the interrogation unit 12a may be deployed in association with object element 19a, the interrogation unit 12a may be deployed in association with object element 19b, and the interrogation unit 12a may be deployed in association with object element 19c. Note that in FIG. 6, the interrogation signal transmitted by radar unit 12a is represented as 131a, and the responding reflected signal is represented as 13Ra. Similarly, the interrogation signal transmitted by radar unit 12b is represented as 131b, and the responding reflected signal is represented as 13Rb. Similarly, the interrogation signal transmitted by radar unit 12c is represented as 131c, and the responding reflected signal is represented as 13Rc.

Although only three interrogation units 12a, 12b, 12c are illustrated in FIG. 6 for simplicity of presentation, embodiments of the present disclosure can be implemented with any number of interrogation units. In practice, the larger the number of interrogation units, the greater the accuracy of distance measurement and/or localization. In certain embodiments, such as the example illustrated in FIG. 6, a single processing unit 16 is deployed in electrical association with the interrogation units. In other embodiments, each interrogation unit can have a corresponding processing unit electrically associated therewith, and a hub or home processing unit, which can be a standalone processing unit operable or controllable by an end user of the system, can receive (via a wired or wireless connection), aggregate, and process the data derived by the individual processing units, and/or receive, aggregate, and process the impedance modulated signals detected/received by each of the individual processing units.

In yet further embodiments, a plurality of interrogation units and a plurality of beacons (or a plurality of reflector antennas with adjustable internal impedance) can be employed. In one configuration, the beacons (or reflector antennas) are spatially distributed and are deployed in association with the object (similar to as described with reference to FIG. 2). In another configuration, the interrogation units are spatially distributed and deployed in association with the object (similar to as described with reference to FIG. 6).

In certain embodiments, the processing unit 16 may derive/calculate the localization of the object 18 using triangulation techniques, whereby the processing unit 16 co-processes the received impedance-modulated signals from multiple beacons (or the impedance-modulated signals received at multiple interrogation units) to triangulate the position of the object 18.

As discussed, utilization of multiple beacons or reflector antennas (or multiple interrogation units), enables accurate mm-scale distance measurement and localization of the target object 18 in 3D space. In order increase the accuracy of the distance measurement and localization, the antenna devices of the interrogation unit 12 and the beacon 14 should preferably have a stable phase center. In other words, each frequency component at the antennas should acquire the phase upon the wireless channel (the signal communication medium between the interrogation unit and the beacon), and should be insensitive to the angle of arrival to/from the receive/transmit antenna. Less than ideal performance of such radio frequency (RF) components of the interrogation unit and/or the beacon can be compensated using RF calibration in combination with post-processing algorithms (executed by the processing unit 16), and may be further improved using machine learning (ML) algorithms executed by the processing unit 16. For example, the processing unit 16 may implemented an ML algorithm which uses geometric triangulation (based on impedance modulation signals received from multiple beacons or reflector antennas) as an initial estimate for the localization, and then refines the localization estimate based upon additional received impedance modulation signals. By applying such preferred hardware characteristics, in combination with the processing techniques described above, the embodiments of the present disclosure can achieve accuracy of the distance measurement and/or the position of the localization measurement to within 3 mm or better, and in certain cases to within 1 mm or better, and in particularly preferred cases to within 0.5 mm or better. Furthermore, application of such preferred hardware characteristics, in combination with the processing techniques described above, enable the embodiments of the present disclosure to achieve accuracy of the angular position (represented by three angles) of the localization measurement, to within 3° or better (for each of the three angles), and in certain cases to within 1° or better (for each of the three angles), and in particularly preferred cases to within 0.5° or better (for each of the three angles).

As discussed above, the system according to embodiments of the present disclosure can achieve target object distance measurement and localization without necessitating use of scanning/steering mechanisms, thereby providing a compact system that can be suitably integrated with an appropriate target object. In certain exemplary but non-limiting implementations, the system according to the embodiments of the present disclosure is integrated as part of a smartcomb application. In one example implementation, the interrogation unit is integrated into a smartcomb, and a plurality of static beacons are deployed in spaced relation around the smartcomb. In another example implementation, a plurality of beacons are integrated into a smartcomb, and one or interrogation units are deployed in spaced relation around the smartcomb. As mentioned, the embodiments of the present disclosure are applicable for use with any suitable target object, preferably smaller-scale and hand-held objects such as, for example, tools and tableware or dishware.

Implementation of the systems and/or methods of embodiments of the disclosure can involve performing or completing selected tasks implemented by hardware, by software or by firmware or by a combination thereof. For example, hardware for performing selected tasks according to embodiments of the disclosure could be implemented as a chip or a circuit. As software, selected tasks according to embodiments of the disclosure could be implemented as a plurality of software instructions being executed by a computer using any suitable operating system. In certain embodiments of the disclosure, one or more tasks according to exemplary embodiments of systems and/or methods as described herein are performed by a computerized data processor that can execute 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, non-transitory storage media such as a magnetic hard-disk and/or removable media, for storing instructions and/or data.

For example, any combination of one or more non-transitory computer readable (storage) medium(s) may be utilized in accordance with the above-listed embodiments of the present disclosure. The non-transitory computer readable (storage) 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-exhau stive 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.

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.

As will be understood with reference to the paragraphs and the referenced drawings, provided above, various embodiments of machine-implemented methods are provided herein, some of which can be performed by various embodiments of systems described herein and some of which can be performed according to instructions stored in non-transitory computer-readable storage media described herein. Still, some embodiments of machine-implemented methods provided herein can be performed by other systems and can be performed according to instructions stored in computer-readable storage media other than that described herein, as will become apparent to those having skill in the art with reference to the embodiments described herein. Any reference to systems and computer-readable storage media with respect to machine- implemented methods is provided for explanatory purposes, and is not intended to limit any of such systems and any of such non-transitory computer-readable storage media with regard to embodiments of computer-implemented methods described above. Likewise, any reference to machine-implemented methods with respect to systems and computer-readable storage media is provided for explanatory purposes, and is not intended to limit any of such computer- implemented methods disclosed herein.

The block diagrams and flowcharts in the drawings illustrate the architecture, functionality, and operation of possible implementations of systems and/or methods according to various embodiments of the present disclosure. In this regard, each block in the block diagrams or flowcharts may represent a module, segment, or portion of code, which comprises one or more executable instructions for implementing the specified logical function(s). It should also be noted that, in some alternative implementations, the functions noted in the block may occur out of the order noted in the figures. For example, two blocks shown in succession may, in fact, be executed substantially concurrently, or the blocks may sometimes be executed in the reverse order, depending upon the functionality involved. It will also be noted that each block of the block diagrams and/or flowchart illustration, and combinations of blocks in the block diagrams and/or flowchart illustration, can be implemented by special purpose hardware-based systems that perform the specified functions or acts, or combinations of special purpose hardware and computer instructions.

The descriptions of the various embodiments of the present disclosure have been presented for purposes of illustration, but are not intended to be exhaustive or limited to the embodiments disclosed. Many modifications and variations will be apparent to those of ordinary skill in the art without departing from the scope and spirit of the described embodiments. The terminology used herein was chosen to best explain the principles of the embodiments, the practical application or technical improvement over technologies found in the marketplace, or to enable others of ordinary skill in the art to understand the embodiments disclosed herein.

As used herein, the singular form, “a”, “an” and “the” include plural references unless the context clearly dictates otherwise.

The word “exemplary” is used herein to mean “serving as an example, instance or illustration”. Any embodiment described as “exemplary” is not necessarily to be construed as preferred or advantageous over other embodiments and/or to exclude the incorporation of features from other embodiments.

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.

To the extent that the appended claims have been drafted without multiple dependencies, this has been done only to accommodate formal requirements in jurisdictions which do not allow such multiple dependencies. It should be noted that all possible combinations of features which would be implied by rendering the claims multiply dependent are explicitly envisaged and should be considered part of the invention.

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.

Claims

WHAT IS CLAIMED IS:

1. A system comprising: at least one beacon including: a reflector antenna, having an adjustable internal impedance, for reflecting impinging signals, and an impedance modulation unit in communication with the reflector antenna configured to vary the internal impedance of the reflector antenna such that the reflector antenna produces a reflected signal, that is an impedance modulated signal, in response to an impinging interrogation signal; at least one interrogation unit configured to transmit an interrogation signal that impinges upon the reflector antenna and to receive the reflected signal from the reflector antenna, wherein one of the at least one beacon or the at least one interrogation unit is deployed in association with an object; and a processing unit electrically associated with the at least one interrogation unit configured to process the reflected signal received by the at least one interrogation unit to derive spatial information associated with the object.

2. The system of claim 1, wherein the at least one beacon is deployed in association with the object, and wherein the spatial information includes a distance between the at least one interrogation unit and the object.

3. The system of claim 1, wherein the at least one interrogation unit is deployed in association with the object, and wherein the spatial information includes a measurement of a distance between the at least one beacon and the object.

4. The system of claim 2 or claim 3, wherein the distance is less than 20 meters.

5. The system of claim 4, wherein the measurement of the distance is accurate to within 3 millimeters or better.

6. The system of claim 4, wherein the measurement of the distance is accurate to within 1 millimeter or better.

7. The system of claim 4, wherein the measurement of the distance is accurate to within 0.5 millimeters or better.

8. The system of claim 1, wherein the object is a rigid body comprising a plurality of object elements, and wherein the at least one beacon includes a plurality of beacons, each beacon being deployed in association with a corresponding one of the object elements.

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9. The system of claim 1, wherein the spatial information includes a measurement of a localization of the object in three-dimensional space, the localization including a centroid position of the object and an angular position of the object.

10. The system of claim 9, wherein the measurement of the centroid position of the localization is accurate to within 3 millimeters or better.

11. The system of claim 9, wherein the measurement of the centroid position of the localization is accurate to within 1 millimeter or better.

12. The system of claim 9, wherein the measurement of the centroid position of the localization is accurate to within 0.5 millimeters or better.

13. The system of claim 9, wherein the measurement of the angular position of the localization includes three angles and is accurate to within 3 degrees or better for each of the three angles.

14. The system of claim 9, wherein the measurement of the angular position of the localization includes three angles and is accurate to within 1 degree or better for each of the three angles.

15. The system of claim 9, wherein the measurement of the angular position of the localization includes three angles and is accurate to within 0.5 degrees or better for each of the three angles.

16. The system of claim 1, wherein the impedance modulation unit is configured to vary the internal impedance of the reflector antenna in a continuous manner between a plurality of impedance states.

17. The system of claim 1, wherein the impedance modulation unit is configured to vary the internal impedance of the reflector antenna in a sinusoidal manner between a plurality of impedance states.

18. The system of claim 1, wherein the impedance modulation unit is configured to vary the internal impedance of the reflector antenna in discrete manner between a plurality of impedance states.

19. The system of claim 1, wherein the impedance modulation unit is configured to vary the internal impedance of the reflector antenna by employing a coded modulation technique.

20. The system of claim 1, wherein the impedance modulation unit is configured to vary the internal impedance of the reflector antenna at a modulation frequency of at least 10 Hz.

21. The system of claim 1, wherein the impedance modulation unit is configured to vary the internal impedance of the reflector antenna at a modulation frequency of at least 100 Hz.

22. The system of claim 1, wherein processing the reflected signal by the processing unit includes isolating the at least one beacon on a Doppler map.

23. The system of claim 1, wherein the reflector antenna includes a plurality of spatially distributed antenna elements, each antenna element being deployed in association with a different corresponding portion of the object.

24. The system of claim 1, wherein the beacon further includes a signal amplification unit in signal communication with the reflector antenna and the impedance modulation unit.

25. The system of claim 1, wherein the at least one interrogation unit is operative to transmit the interrogation signal at a carrier frequency of at least 1 GHz.

26. The system of claim 25, wherein the carrier frequency is in a range from 3 GHz to 10 GHz.

27. The system of claim 25, wherein the carrier frequency is in a range from 21 GHz to 26 GHz.

28. The system of claim 25, wherein the carrier frequency is in a range from 76 - 81 GHz.

29. The system of claim 1, wherein the at least one interrogation unit is configured as an ultra- wideband radar unit.

30. The system of claim 1, wherein the at least one interrogation unit is integrated as part of a comb.

31. The system of claim 1, wherein the at least one beacon is integrated as part of a comb.

32. A method comprising: deploying one of at least one interrogation unit or at least one beacon or in association with an object, the at least one beacon including a reflector antenna having an adjustable internal impedance and an impedance modulation unit in communication with the reflector antenna; transmitting, by the at least one interrogation unit, an interrogation signal that impinges upon the reflector antenna; varying, by the impedance modulation unit, the internal impedance of the reflector antenna such that the reflector antenna produces a reflected signal, that is an impedance modulated signal, in response to the impinging interrogation signal; receiving, by the at least one interrogation unit, the reflected signal; and processing, by at least one processor electrically associated with the at least one interrogation unit, the reflected signal received by the at least one interrogation unit to derive spatial information associated with the object.

33. The method of claim 32, wherein varying the internal impedance of the reflector antenna is performed in a continuous manner between a plurality of impedance states.

34. The method of claim 32, wherein varying the internal impedance of the reflector antenna is performed in a sinusoidal manner between a plurality of impedance states.

35. The method of claim 32, wherein varying the internal impedance of the reflector antenna is performed in a discrete manner between a plurality of impedance states.

36. The method of claim 32, wherein varying the internal impedance of the reflector antenna is performed by employing a coded modulation technique.

37. The method of claim 32, wherein processing the impedance modulated signal includes isolating the at least one beacon on a Doppler map.

38. A system comprising: at least one beacon deployed in association with an object and including: a reflector antenna, having an adjustable internal impedance, for reflecting impinging signals, and an impedance modulation unit in communication with the reflector antenna configured to vary the internal impedance of the reflector antenna such that the reflector antenna produces a reflected signal, that is an impedance modulated signal, in response to an impinging interrogation signal; and a processing unit electrically associated with an interrogation unit that receives the reflected signal from the reflector antenna in response to transmitting an interrogation signal that impinges upon the reflector antenna, the processing unit configured to process the received reflected signal to derive spatial information associated with the object.

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