阅读说明：本技术 个人雷达 (Personal radar ) 是由 丹尼尔·约瑟夫·李 于 2018-01-04 设计创作，主要内容包括：一种用于利用多个频率的空间定位天线元件获得发射机或接收机的方向的相控阵无线电系统。还提供了一些用于获得指向无线电来源的角度或方向的无线电系统及方法。(A phased array radio system for obtaining the direction of a transmitter or receiver using spatially positioned antenna elements of multiple frequencies. Radio systems and methods for obtaining an angle or direction to a radio source are also provided.)

1. A radio system, comprising:

a transmitter having two or more antennas configured to broadcast a first signal at a first frequency and subsequently broadcast a second signal at a different second frequency;

a receiver having an antenna configured for receiving the first and second signals broadcast by the two or more antennas of the transmitter; and

a processing unit configured to perform the following operations:

measuring the amplitude and phase of a first signal at the first frequency received at the receiver;

measuring the amplitude and phase of a second signal at the second frequency received at the receiver; and

the measured amplitude and phase of each signal is used to identify the angle or direction pointing to the transmitter.

2. The radio system of claim 1, wherein the receiver measures the phase and amplitude of each signal by switching between the first antenna and the second antenna.

3. The radio system of claim 1, wherein the transmitter comprises a third antenna configured to broadcast a third signal at a different third frequency after broadcasting the second signal.

4. The radio system of claim 3, wherein the processing unit measures the amplitude and phase of the third signal received at the receiver, broadcast at the third frequency.

5. The radio system of claim 4, wherein the processing unit utilizes the measured amplitudes and phases of the first, second, and third signals to confirm the angle or direction pointing to the transmitter.

6. The radio system of claim 5, wherein the processing unit is further configured to modify an error using the first frequency, the second frequency, and the third frequency.

7. The radio system of claim 1, wherein radio frequency bursts are transmitted to the receiver through at least one antenna of the transmitter.

8. The radio system of claim 7, wherein the radio frequency bursts are communicated to the receiver through a plurality of antennas of the transmitter, the transmitter being configured for switching antennas when it transmits the radio frequency bursts.

9. The radio system of claim 1, wherein the frequencies of the signals are switched to different frequencies based on measurements made of the first and second signals from the first and second antennas.

10. The radio system of claim 9, wherein the processing unit subsequently determines the angle or direction to the transmitter based on the changed different frequency.

11. A method for obtaining an angle or direction pointing to a radio source, comprising:

broadcasting two or more signals at different frequencies from two or more antennas of a transmitter;

receiving, at a receiver, the two or more signals broadcast at different frequencies;

measuring the amplitude and phase of each signal received at the receiver; and

the measured amplitude and phase of each signal is used to identify the angle or direction of pointing to the radio source.

12. The method of claim 11, wherein the two or more signals broadcast at different frequencies allow a shortest path to be determined from which to obtain the angle or direction to the radio source.

13. The method of claim 12, wherein the identified phase shifts of the two or more signals are used to determine a distance to the transmitter along each angular path.

14. The method of claim 11, further comprising:

obtaining a phase measurement for each signal;

normalizing each signal to obtain a phase and a gain; and

the normalized signal is added to a phased array data structure that includes one or more preceding and succeeding phase measurements.

15. The method of claim 11, wherein the range of the at least one antenna in the phased array is identified by the transmitter with a specified set of frequencies.

16. The method of claim 11, wherein the phase of at least one signal is mathematically adjusted to allow for fewer antennas to be used.

17. A radio system, comprising:

a transmitter antenna configured for broadcasting a first signal at a first frequency for a specified period of time, a second signal at a different second frequency for the specified period of time, and a third signal at a different third frequency for the specified period of time;

two or more receiver antennas configured for receiving the first, second, and third signals; and

a processor configured to obtain angles and distances of a plurality of radio wave paths directed to the antenna.

18. The radio system of claim 17, wherein the transmitter transmits radio frequency bursts via the antenna.

19. The radio system of claim 18, wherein the receiver measures the phase and amplitude by switching between the two or more antennas.

20. The radio system of claim 17, further comprising:

at least one third receiver antenna configured for receiving the third signal such that the first receiver antenna receives the first signal, the second receiver antenna receives the second signal, and the third receiver antenna receives the third signal.

Technical Field

Embodiments of the present invention relate to systems and methods for detecting an object and/or movement of the object. More particularly, embodiments of the invention relate to personal radar, detection of object presence, and object location.

Prior Art

There are a number of ways how someone can detect an object and/or the motion of the object. Most devices use echo travel time, chirp, frequency modulation or doppler radar to detect an object or movement of the object. Many people use steerable antennas or phased array antennas to detect those objects. Others also detect motion within an area by using simple measurements of received signal strength. Such systems are often costly, power hungry, expensive, and/or inaccurate or imprecise.

Brief description of the drawings

Embodiments described herein relate to radio systems and methods for obtaining an angle or direction pointing to a radio source. In one embodiment, a radio system includes a transmitter having two or more antennas configured to broadcast a first signal at a first frequency and to broadcast a second signal at a different second frequency at a subsequent time. The radio system comprises a receiver having an antenna configured for receiving a first signal and a second signal broadcast by two or more antennas of the transmitter, the radio system further comprising a processing unit. The processing unit is configured to measure the phase and amplitude of the first signal received at the receiver at a first frequency, measure the phase and amplitude of the second signal received at the receiver at a second frequency, and confirm the angle or direction pointing to the transmitter using the measured amplitude and phase of each signal.

In another embodiment, a method for obtaining an angle or direction to a radio source is provided. The method comprises the following steps: the method includes broadcasting two or more signals from two or more antennas of a transmitter at different frequencies, receiving at a receiver the two or more signals broadcast at the different frequencies, measuring an amplitude and a phase of each signal received at the receiver, and identifying an angle or direction to a radio source using the measured amplitude and phase of each signal.

This brief description is provided to introduce a selection of concepts in a simplified form that are further described below in the detailed description. This brief description is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used as an aid in determining the scope of the claimed subject matter.

Additional features and advantages will be set forth in the description which follows, and in part will be readily apparent to those skilled in the art from that description or recognized by practicing the teachings of the disclosure as described herein. The features and effects of the embodiments described herein may be realized and obtained by means of the instruments and combinations particularly pointed out in the appended claims. Features of embodiments described herein will be more fully apparent from the ensuing description and appended claims.

Brief description of the drawings

In order to describe the manner in which at least some of the effects and features of the invention can be obtained, a more particular description of embodiments of the invention briefly described above will be rendered by reference to specific embodiments thereof which are illustrated in the appended drawings. It is appreciated that these drawings depict only typical embodiments of the invention and are therefore not to be considered limiting of its scope. Embodiments of the invention are illustrated and explained with additional specificity and detail through the use of the accompanying drawings.

FIG. 1 shows an example of a measurement system including two radios, each radio including an antenna;

FIG. 2 shows an example of detecting different types of objects with the measuring system;

FIG. 3 shows the measurement results of three different objects of different materials traversing the path between two ranging nodes or radios;

FIG. 4A shows an example of a measurement system that includes two radios that each include a radio frequency switch with two antennas;

FIG. 4B shows an example of a measurement system comprising two radios, one radio comprising a radio frequency switch having multiple antennas, and a second radio comprising an antenna;

FIG. 5 shows a block diagram of a method for performing measurements;

fig. 6 shows an example of an antenna arrangement for a virtual steerable antenna;

FIG. 7 shows a virtual antenna pattern generated when the virtual antenna is pointed at an angle of 0 degrees;

FIG. 8 shows a virtual antenna pattern produced when the virtual antenna is pointed at a 45 degree angle;

FIGS. 9A and 9B illustrate one embodiment of a system for determining direction or angle of arrival using frequency hopping;

FIG. 10 illustrates an alternative embodiment of a system for determining direction or angle of arrival using frequency hopping;

FIG. 11 illustrates a receiver computing an angle of arrival in one embodiment;

FIG. 12 illustrates burst transmission of radio frequency signals on different antennas using different frequencies in one embodiment;

FIG. 13 illustrates the use of specified frequencies on a plurality of different antennas in one embodiment;

fig. 14 shows a flow chart of a method for obtaining an angle or direction to a radio source.

Detailed Description

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings, but the present invention is not limited to only the embodiments listed herein. Like reference symbols in the drawings indicate like elements.

In the following detailed description, reference is made to the accompanying drawings which form a part hereof. In the drawings, like reference numerals are generally used to distinguish between similar components, unless otherwise specified herein. The exemplary embodiments described in the detailed description, drawings, and claims are not limiting. Other embodiments may be utilized, and other modifications may be made, without departing from the spirit or scope of the subject matter described herein. It will be readily understood that the aspects of the present invention, as generally described and illustrated in the figures herein, could be arranged, substituted, combined, separated or designed in a wide variety of different configurations, all of which are explicitly described herein.

Embodiments of the present invention relate to systems and methods for detecting and/or measuring and/or tracking an object, the movement of an object, or the movement of an object within an area. These embodiments measure the object or the motion of the object by using a novel way of an object that performs some high precision measurement method. These high precision measurement methods detect changes in wave propagation, for example, using one or more angles of arrival, time differences, and/or phase differences. The position of the object and the movement of the object can be determined from the changes in the wave propagation. Advantageously, the position and movement of objects interfering with wave propagation can also be measured.

Without direct line of sight, it is often difficult to detect objects in crowded areas or locations, such as jungles or scenic spots. According to embodiments of the present invention, an object entering the path of two devices (e.g., radios) can be detected by measuring the increased distance at which the radio signal needs to reach a new object in the path, as long as the two devices are able to communicate and can measure the effective path distance between them. In other words, a change in effective path distance serves as an indication that some object has entered the path between the two radios.

Conventional methods employ signal strength or link quality indicators, but these methods are unreliable because the signal strength can be enhanced or made weaker by refraction depending on the path or position of the object. In addition, conventional devices use echo transit time, chirp, frequency modulation, or doppler radar to detect or detect motion of an object. Some conventional devices use steerable antennas or phased array antennas to detect objects. These conventional devices combine signals in the antenna feed electronics to record multiple radio paths simultaneously, or use multiple radios.

Some embodiments of the invention may use a device (e.g., a device capable of transmitting and/or receiving signals such as electromagnetic signals, such as radio signals) or a pair of devices and a low cost switch to select a single antenna from a plurality of antenna arrays at a time. These embodiments include a stable system clock and are able to measure the phase between the antennas at different times, unlike conventional units that use multiple radio paths or multiple radios. Advantageously, embodiments of the present invention can be implemented at significantly lower cost.

These embodiments of the present invention employ a novel method of detecting motion of an object or object using the high precision ranging method described above, as an example of which is U.S. patent application No. US8,274,426, which is incorporated herein by reference in its entirety. In one embodiment, ranging methods may be utilized to obtain the angle-of-arrival, time difference, and/or phase difference of the narrowband signals used to detect changes in wave propagation. The position and movement of an object interfering with the wave propagation can be determined. The use of high resolution propagation path length measurements overcomes the conventional problems and significantly improves accuracy.

One embodiment uses a single radio and low cost switches to select a single antenna from many antenna arrays at a time. This is possible because the system includes closely synchronized clocks within a few hertz of each other. Since the system clock is stable, the phase between the antennas can be measured at different times, thereby obtaining the same information as the conventional unit at lower cost. This stability allows extremely high resolution on the millimeter scale.

The following discussion sets forth embodiments of the invention that are representative of embodiments in different platform configurations. The system may exhibit different characteristics with respect to detection capability, cost and complexity. In contrast to conventional systems, the present embodiments provide high resolution path length measurements, which allows a new approach for detecting disturbances of electromagnetic wave propagation.

Fig. 1 shows an example of a ranging system comprising two radios. The ranging system 10 can be used not only for ranging applications, but also for radar systems that can detect the presence of objects and the movement of objects. Each radio includes a single antenna, however, in the present embodiment, it is contemplated that each radio in the ranging system includes other additional antennas. Fig. 1 also shows that the effective paths of signals at different frequencies are different between radios. Although fig. 1 shows two radios, embodiments of the present invention may be configured to include multiple radios. For example, each of a plurality of different pairs of radios in a ranging system including multiple radios may use a particular frequency. In addition, one radio may communicate with a different radio using a different frequency.

Fig. 1 shows a system that includes a radio 100 and a radio 102, the radio 100 and the radio 102 communicating via an active path 110 (e.g., a line of sight in one example). The radios 100 and 102 may perform high precision ranging as described in U.S. patent US8,274,426, the entire contents of which are incorporated herein by reference, and have phase measurement capability. One of the radios, for example, radio 102, includes a high precision, high stability controllable oscillator. In this example, the radio device 100 is a host, and the radio device 100 transmits a narrowband radio signal at a frequency higher than that of the local oscillator. In one example, this is achieved by using a phase locked loop and a voltage controlled oscillator included in radio 100 (radio 102 may be similarly configured). This higher frequency signal is sent to the second node or radio 102. The radio 102 tunes to the higher frequency signal using its phase locked loop and voltage controlled oscillator. The radio 102 may also tune a controllable high stability local oscillator to the input signal. In this way, a super-high synchronization system is realized.

This higher frequency helps to tune the local oscillator with greater accuracy. Advantageously, lower resolution phase measurements at higher frequencies may be employed, and may be associated with lower frequency clock oscillators due to the use of phase locked loops.

For example, assume that the low frequency is 16MHz and the high frequency is 2.4 GHz. A multiplier 150 is provided. If the second unit (e.g., radio 102) uses the 2.4GHz signal to tune its local 16MHz signal to achieve phase coherence of the local signal with the 16MHz signal of node 1 or radio 100, a low resolution phase measurement unit at the 2.4GHz signal is sufficient to achieve extremely high synchronization stability. For example, assume that a 10 degree phase error at a 2.4Ghz signal is corrected every 15 milliseconds, which corresponds to 1/15 degree correction every 15 milliseconds or absolute sync stability at 4.4 degree error per second (0.012222 Hz). Which corresponds to 764 parts per trillion of synchronization stability.

The second radio 102 transmits a narrowband signal back to the first node or radio 100. Due to the highly synchronous oscillator, the second radio 102 acts as an almost perfect active reflector, which looks like incoming radio waves are simply reflected back to the radio 100. The first node or radio 100 may then measure the difference between its local high frequency signal and the incoming high frequency signal. The difference in phase will correspond to the path length.

If the movement of an object (e.g., object 108) passes through path 110, path 110 changes. That is, the length of path 110 varies over distance because the radio waves or radio transmissions between radio 100 and radio 102 move around object 108. Because radios 100 and 102 are configured to detect an accurate range or distance, changes in distance may be detected. The change in distance may be interpreted as the presence of a new object, object 108.

Additionally, the size and/or velocity of the object 108 may be measured by looking at the peak change in distance and the time required to achieve the peak change. The peak will reflect the size of the interfering object and the time to peak is related to the velocity of the object.

Further, using two or more frequencies, the size of the object 108 may be quickly inferred due to the different propagation characteristics at the different frequencies. For example, a 900MHz signal will be transmitted differently around interfering object 108 as compared to a 2.4GHz signal. Due to the local oscillator with high stability and the almost perfect active reflector, the difference in path can be measured and hence the size of the object 108 can be determined. Thus, the radio 100 is capable of transmitting a signal 104 at a first frequency and a second signal 106 at a second frequency. As previously described, the radio 102 can effectively reflect these frequencies. The size of the object 108 and the speed of the object may then be determined.

As described above, when a change in distance of the transmission path 110 is detected, the presence of an object can be determined. The size and/or velocity of the object can also be detected.

Fig. 2 illustrates an example of the use of ranging system 10 to detect different types of objects, which may effectively be used as a radar system. The radar system may be configured for use in a particular area, and the radio may be disposed in the area (e.g., disposed around or within the area) in a manner that enables identification and tracking of objects and their movement. Fig. 2 shows a variety of objects, including a teflon body 202, a steel body 204, and a human arm 206, each of the object 202, the object 204, and the object 206 moving into the path of a node or radio 100 and 102.

Fig. 3 shows the measured phase, path distance and variation. Fig. 3 shows measurements 300 of three different materials (or objects of different materials) across the path of two ranging nodes (e.g., radio 100 and radio 102). The material is in the path for a period of time before being removed again. Different path variations for different objects are illustrated and correspond to different material properties, including dimensions.

One embodiment of the two-way radio system may be used for perimeter control, allowing protection of a certain area by placing multiple two-way radio systems around the area, where each link defines the perimeter of the area to be protected. If a foreign object passes any of the plurality of paths established by the plurality of two-way radio systems, an alarm may be raised identifying the location of the path that has been breached and the size of the object. The ability of the radio to use different frequencies can also enhance the ability to control the perimeter. Each link (which may contain a pair of radios and each radio may belong to more than one pair of radios) may use the same or different frequencies.

Fig. 4A shows an example of a multi-antenna system for detecting the presence or absence of an object, and the position of the object through the electromagnetic wave path. Fig. 4A shows an electromagnetic wave path 420 that may be established between two wireless devices (node 422 and node 432). Node 422 may include two or more antennas (shown as antennas 424 and 426). Node 432 may include two or more antennas (shown as antennas 428 and 430). The antennas may be spatially separated by any distance that will determine the angular resolution and detect the angular width. In one example, the distance is equal to the frequency wavelength divided by 2(λ/2) because this provides a detection angle of 180 degrees. In another example, the distance may be related to the size of the object being detected. For example, the distance may be half the size of the object to be detected.

As described above, nodes 422 and 432 may participate in high resolution ranging and may switch between antennas. Thus, some radio paths or some electromagnetic paths may be established and measured or monitored. Electromagnetic wave path 420 may include paths 438, 440, 442, and 444, with path 438 established between antenna 424 and antenna 430, path 442 established between antennas 426 and 428, and path 444 located between antennas 426 and 430.

The ability to track objects or the motion of objects is further enhanced by establishing multiple paths. For example, if object 434 or object 436 were to intersect between two nodes, then each path 420 between node 422 and node 432 would have a different change in distance over time. For example, if objects 434 and 436 move from below into path 420, they will affect the respective paths in different ways. For example, when detecting object 436 via path 438 prior to path 440, object 434 is detected by path 440 prior to path 438, since the distribution of nodes in any given system may be known, the location of the object across path 420 between nodes 422 and 432 may be inferred.

For example, when a change in the path 444 is detected, the presence of the object 436 may be detected. When a change in path 438 is next detected, rather than path 440, the position of object 436 relative to nodes 422 and 432 may be inferred. The position of the object can be inferred even when the antennas are spaced relatively close together due to the nature of the electromagnetic waves.

This meaning of one-dimensional positioning may be used, for example, in perimeter alarm systems, where it is useful to know not only that an object crosses a line or perimeter, but also where in the perimeter has been crossed. This is particularly important if the distance between nodes is large.

The extended scenario of the two node scenario shown in fig. 4A is a 2+ node scenario, where the nodes all participate in high resolution ranging with each other. Now, the cross-distance is able to locate objects within the observation area not only by looking at the changes in signal strength and attenuation, but also by the changes in radio path length.

In another example, the ranging system may include a single radio that includes multiple antennas and a single transmitter. The base station may include a receiver radio (or transceiver) with phase measurement capability and multiple antennas. For example, as an example, fig. 4B shows a base station 402 that includes one receiver radio (or transceiver 402) and multiple antennas 404. In this example, the antenna 404 is connected to one radio 402 using a network of antenna switches 406. In this example, in one embodiment, radio 402 may be connected to one of antennas 404 at a time, although the switch 406 may be configured to connect more than one antenna to the radio at a time. The second unit, referred to as the transmitter 408, includes a transmitter radio (or transceiver) and requires only one antenna 410. The second unit or transmitter 408 emits a narrow band signal that illuminates the environment 400.

Due to the high stability local clock described above, the base station 402 can switch between different antennas 404 and measure the difference between different received signals. The base station 402 may recombine the signals using a microcontroller unit (e.g., processing device) and create a virtual steerable antenna. The steerable antenna can be used to "map" the different paths 413, 414, the signal being transmitted from the transmitter 408 to the base station 402, essentially resulting in a mapping of signal strength versus angle. An object, such as object 411 or object 412, reflects the signal from transmitter 408 back to base station 402. The virtual steerable antenna will then provide a higher signal strength in the direction of the object 411 and another higher signal strength in the direction of the object 412. This increases the signal strength in those directions that are indicative of the object, and thus the angle of the object can be determined. In addition to detecting objects, the speed and/or direction of movement may be determined and tracked. In one example, historical data for the object may also be stored in memory.

The distance of the object can be obtained by measuring the path lengths of the paths 413 and 414. The path length may be determined using a steerable antenna and using high precision radio frequency ranging results. Knowing the location of the transmitter 408, the base station 402, and the angle of the detected object, the object can be triangulated by obtaining the location for a given path length. This location need not be unique as there may be a mirroring solution. Adding multiple base stations or limiting the detection area can resolve these secondary locations, resulting in unique object locations.

The system may further track the object by measuring the position of the object over time. Assume that there is only a scene of object 411 and that base station 402 locates the object using the method described previously. After a period of time, the object 411 moves to the position of the object 412. Since the signal strength has disappeared from the previous angle, the base station 402 will now find that the object 411 is no longer in its old position, but instead there is now a stronger signal from the angle of the path 414. Thus, it has been tracked that the object 411 has moved from the position 411 to the position 412. In one example, the object may be identified, for example, by measuring a dimension of the object.

Ranging or radar systems as shown in fig. 4A and/or 4B may also be used to obtain range (using phase, similar to the previously described examples) and direction (angle). In one example, two or more base stations 402 may be used. In this case, two or more base stations may also be used using direction (angle) measurements, and the position of the transmitting node can be triangulated using the direction (angle) measurements.

Furthermore, the radio may frequency hop to different frequencies in order to take advantage of differences in propagation characteristics. The radio 408 may frequency hop to different frequencies to take advantage of differences in propagation characteristics.

Conventional radar systems employ radio frequency chirp or conventional frequency modulated radar to detect passive radio frequency signal reflecting objects. Embodiments may use a frequency hopping high resolution ranging system to achieve similar results by observing phase changes over multiple frequencies. This provides a radar system using a high frequency hopping high resolution ranging system.

Detecting passive radio frequency reflecting components includes detection of multipath components in a ranging system. If the goal is to measure the distance between two systems, multipath is undesirable because multipath will affect the accurate measurement of distance. But the multipath comes from radio frequency signal reflecting objects located at different locations and therefore introduces new path lengths. If the locations of the transmitter and receiver are known (e.g., either by field survey or by using a radio frequency positioning system), then the change in multipath indicates movement of the radio frequency signal reflecting objects, and the system becomes an active personal radar system.

A personal radar system may include two or more transmit and receive pairs that participate in high-resolution ranging. The transmitter and receiver use the narrowband carrier frequency(s) to synchronize their clocks and then hop over one or more secondary non-contiguous frequency carriers in one example. The carriers of different frequencies have different wavelengths from each other and therefore the receiver will measure the phase change at different frequencies. In addition, multipath will affect different frequencies differently. The receiving node can now enter the time domain diagram from the phase domain by fast fourier transforming the measured phase. Different multipath components will now show up as different peaks in the result of the fast fourier transform. By keeping track of different multipath lengths, a system with only one transmitter and one receiver can map changes in the environment and detect whether a new object enters or leaves the environment.

Combining the results of some transmit/receive pairs and knowing the location of these transmit/receive pairs allows triangulation of the actual reflector location. Triangulation is performed better when there are more node pairs.

Fig. 5 illustrates a method for performing a ranging method. Some examples of ranging methods include, but are not limited to, determining a distance to an object, tracking a motion of an object, determining a size of an object, identifying a location of a transmitter in a system, establishing a perimeter, performing radar in an area, and the like, or any combination thereof.

The systems and methods discussed herein may use the propagation path between radio signals and these radios. By synchronizing one radio with another, high precision ranging is achieved, and changes in detected path distance may indicate the presence of an object.

The method 500 begins by transmitting a signal in block 502. The signal is typically transmitted from one radio to another (these radios may be similarly configured). This signal causes the two radios to become highly synchronized, with the radios synchronized in block 504. This may be a continuous process of continuing to synchronize signals transmitted from one radio and effectively reflected by another radio.

In block 506, a measurement is performed. Performing the measurement may comprise determining a distance to the object, determining the presence of the object, determining the size and/or the speed and/or the direction of the object. The capabilities of the system are expanded when additional radios are added to the system or when an antenna is added to a single radio. As previously discussed, the virtual steerable antenna may be used to determine the direction of a detected object.

The ranging system 10 may be connected to a server computer through a network. The data collected by the ranging system 10 may then simply be transmitted for remote analysis.

Fig. 6 shows an example of a multi-antenna setting for calculating a virtual steerable antenna. Multiple antennas may extend the capabilities of a personal radar system or examples disclosed herein. Combining the measured phases at each antenna allows to create a virtual steerable antenna that can be pointed in different directions.

Fig. 6 shows an example of such an antenna array, in which arrangement the antenna positions are as follows: antenna 1: 0/5.9, antenna 2: 5.2/3.0, antenna 3: 5.2/3.0, antenna 4: 0/-5.9. Knowing the antenna position may determine or determine the virtual antenna position. For example, the virtual antennas may be centered at center 0/0 to the right (0 degrees). Given the wavelength frequency of the desired signal, the expected phase shifts for the different antennas can be calculated. In fig. 6, assuming a frequency of 2.5GHz, the phase shift at antenna 1 is 0, the phase shift at antenna 2 is 2.7, the phase shift at antenna 3 is 2.7, and the phase shift at antenna 4 is 0 radians.

Knowing these values, they can be subtracted from the phase measured during the high resolution ranging operation. This effectively concentrates the antenna in the 0 degree direction. Fig. 7 depicts the resulting virtual antenna pattern.

The advantage of a virtual antenna to a physically tuned phased array is that all directions can be viewed simultaneously. For example, to observe the signal from a 45 degree direction (see fig. 6), the phase shift can be calculated as antenna 1: 2.2, antenna 2: 3.0, antenna 3: 0.8 and antenna 4: 2.2 rads. Again, an assumption is made about the signal direction and the virtual antenna pattern results in the pattern shown on fig. 8 are viewed.

Using virtual antennas on one carrier frequency will provide peak power and angle information for different multipath components. However, using high resolution ranging and hopping across multiple frequencies now allows the computation of the above-described fast fourier transform directed in the direction of each individual virtual antenna. This gives additional information on the multipath distance.

High resolution ranging systems with radio frequency switches to multiple antennas provide an improvement over conventional systems because the angle, power and distance of each multipath component can be determined.

The present innovations can now be combined with a number of different receive and transmit combinations with different antenna patterns (lines, circles, crosses, two-dimensional arrays, three-dimensional cubes, etc.). The antenna array may also be provided on a transmitter only, with a single antenna receiver, or on a receiver, with a single antenna transmitter. Coordination may be responsible for antenna switching so that both ends can calculate angle, distance, and power information for multipath components. Combining the information in these instantiations will allow for a robust radar system in which radio frequency reflecting objects can be located and tracked.

One general advantage of the present innovation is the friendliness to other users of the spectrum. Because frequency hopping does not have to be continuous and can occur in a random fashion, other users can use the spectrum simultaneously without being affected by the ranging process. Frequency hopping also has the following advantages: certain frequencies of significant interference may be blocked and frequency hopped back and forth across frequencies.