WO2021198759A1 - System, apparatus and device of doppler detection and ranging - Google Patents

Abstract

In many applications such as automobiles on busy highways, if a lot of vehicles on road are equipped with Doppler radars or LIDARs to help improve driving safety, no matter human-driven or autonomous-driven, if the radars use same frequency, or LIDARS are modulated by signals of same frequency, avoiding interference among them is a hard task. Assigning distinct frequencies is one of the solutions, however not only it wastes expensive spectrum resource, but also the task itself to dynamically assign frequency to vehicles randomly coming together becomes a hard one to do. The disclosed invention of Doppler group sensor (including radar, LIDAR and sonar) will allow sensor devices to inherently work together using shared frequency without interfering with one another, without sacrificing performance, and without much increase in costs. Furthermore, this feature is achievable without having to involve higher layer protocols.

Description

System, Apparatus and Device of Doppler Detection and Ranging

This invention relates generally to utility of Doppler effect, in particular, to Doppler effect based wave detection and ranging system, devices and apparatuses (also known as Doppler radar, Doppler sonars, Doppler LIDARs and Doppler sensors) that may work together in proximity with one another in groups.

Doppler effect has been used in RAdio Detection And Ranging (RADAR or radar), SOund Navigation And Ranging (SONAR or sonar), LIght Detection And Ranging (LIDAR or lidar) and generally, wave detection and ranging equipment to detect objects in many applications, including detecting relative speed thereof. Since they are all based on the same principle of Doppler effect, they are treated in general as Doppler sensors. When more than one such Doppler sensors work in proximity of each other at a same frequency, detecting errors may occur. For example, when automobiles equipped with Doppler radars drive on a road, a first radar on one vehicle receives reflected waves transmitted from a second radar on another vehicle, the frequency difference between the first and the second radar transmitters will erroneously be confused as Doppler shift and detecting wrong relative speed (refer to ). Although techniques such as frequency division, time division, code division, and/or beam division may be used to mitigate the coexistence problem of radar devices, the coordination of their frequency, time, code and/or beam orientation is a difficult task, as the individual automobiles (and their Doppler radar devices) come together on roads randomly. With limited frequency/time/code resources, it is impossible to pre-assign each Doppler sensor device in the world to a unique frequency, time or code. Therefore, there is a need in the art to allow a group of Doppler radars, Doppler sonars or Doppler LIDARs, i.e., Doppler sensors effectively work together using shared frequency.

When more than one Doppler sensors (including Doppler radars, sonars or LIDARs) work in proximity of each other at a same frequency, their signals may interfere with each other, causing detecting errors (e.g., misdetections and false detections, a.k.a. ghost targets). Assigning different frequencies, time slots, or codes to devices is a difficult task by itself since the individual sensor devices may come together randomly, and it also wastes resources (such as frequency spectrum). Therefore, there is a need in the art to allow a group of Doppler sensors effectively work together using shared frequency, yet still allowing multiple objects to be sensed by multiple senor devices simultaneously without compromise in performance.

In one aspect, the invention provides embodiments of a system of Doppler group sensors for sensing objects, comprising signal transmitter(s) and signal receiver(s); each of the signal transmitter(s) comprises: a radio receiver, for receiving a broadcasted signal and based on the broadcasted signal to generate a frequency reference signal and/or a timing signal; a signal generator for generating a first signal of continuous wave(s) (CW) and/or a second signal of frequency modulated continuous wave(s) (FMCW) based on the frequency reference signal and/or the timing signal; a transmitter frontend module for transmitting a transmitted signal as waves for object sensing based on the first and/or the second signal; each of the signal receiver(s) comprises: a radio receiver, for receiving the broadcasted signal and based on the broadcasted signal to generate a frequency reference signal and/or a timing signal; a signal generator for generating a (reproduced) first signal and/or a (reproduced) second signal base on the frequency reference signal and/or the timing signal; a receiver frontend module, for receiving signals associated with objects being sensed, and producing a frontend output signal; at least one mixer, for mixing the frontend output signal with a reproduced local replica signal based on the (reproduced) first signal and/or the (reproduced) second signal, and producing a mixing product signal for further processing; and any two of the signal generators in the system (no matter at same location or at distinct locations) generate their copies of the first signal substantially identical to each other in frequency at any time of operation, and generate their copies of the second signal substantially identical to each other in instantaneous frequency at any time of operation.

In another aspect, at least one embodiment of the invention provides a transmitter apparatus that functions as an active beacon or an illuminator in a system of Doppler group sensors, comprising: a radio receiver, for locking to a broadcasted signal, and deriving, from the broadcasted signal, a frequency reference signal and/or a timing signal; a signal generator, for generating a first signal and/or a second signal based on the frequency reference signal and/or the timing signal; a transmitter frontend module, for generating a transmitted signal based on the first signal and/or the second signal, and sending said transmitted signal as waves into propagation media; and whereby the transmitter apparatus is operable to generate and use, at any time of operation, said first signal and the second signal substantially identical in instantaneous frequency with a counterpart thereof generated elsewhere in other devices within the system of Doppler group sensors.

In yet another aspect, at least one embodiment of the invention provides a receiver apparatus, as a standalone device or a functional subsystem in a device of combined functions, for sensing objects in a system of Doppler group sensors, comprising: a radio receiver, for locking to a broadcasted signal from an antenna, and deriving, from the broadcasted signal, a frequency reference signal and/or a timing signal; a signal generator, for generating, based on the frequency reference signal and/or the timing signal, a first signal and/or a second signal; a receiver frontend module, for receiving signals associated with objects being sensed, and providing a frontend output signal; at least one mixer, for mixing the frontend output signal with a local replica signal based on the first signal and/or the second signal, and producing at least one mixing product signals for further processing; and whereby the receiver apparatus is operable to generate and use, at any time of operation, said first signal and second signals substantially identical in instantaneous frequency to a counterpart thereof generated elsewhere in other devices within the system of Doppler group sensors.

In further yet another aspect, the invention provides a method of determining relative speeds and ranges (distances) of beacon-attached objects using Doppler group sensor system, comprising steps, performed in a signal receiver, of: determining Doppler shifts of beacon-attached objects from CW component(s) in the signals; determining frequency shifts of the beacon-attached objects from FM swept signal component(s) in the signals; identifying, based on magnitude correlation, object association between the Doppler shifts and the frequency shifts; determining net frequency shifts caused by wave propagation delay by deducting the Doppler shift results from the frequency shift results; calculating the relative speeds of the beacon-attached objects based on the Doppler shifts; and calculating the ranges of the beacon-attached objects based on the net frequency shifts caused by wave propagation delay; wherein, the signal receiver and the beacons are substantially synchronized apparatuses in instantaneous frequency of the CW signal component(s) and the FM swept signal component(s) in the Doppler group sensor system.

Other aspects of the invention will become clear thereafter in the detailed description of the preferred embodiments and the claims.

A system of a plurality of Doppler sensors (Doppler radars, Doppler sonars, or Doppler LIDARs), including active beacons and illuminators that may be associated therewith, as long as they are built and function according to gist disclosed herein, will allow them to inherently coexist and work together in proximity of each other at same frequency or frequencies without negatively affecting each other, and therefore, not only making detection of massive objects by massive sensors possible, but also saving expensive spectrum resources without compromising performance of detection. And this is achievable inherently within the "physical layer" and does not have to involve higher layer protocols.

For a better understanding of the invention and to show more clearly how it may be carried into effect, reference will now be made, by way of example only, to the accompanying drawings which illustrate distinctive features of at least one exemplary embodiment of the invention, in which:

illustrates a block diagram of a typical Doppler radar (prior art);

illustrates a block diagram of a typical Doppler LIDAR (prior art);

illustrates an example that a plurality of Doppler sensors interfere with each other in an automobile application (prior art);

illustrates an example a plurality of Doppler sensors interfere with each other in an application of personal wearable protective device (prior art);

illustrates a block diagram of one embodiment of Doppler group sensor using radio waves, also known as radar;

illustrates a block diagram of one embodiment of Doppler group sensor using light carrier, also known as LIDAR;

is a block diagram of another embodiment of Doppler group sensor using radio waves, also known as radar;

is a block diagram of another embodiment of Doppler group sensor using light carrier, also known as LIDAR;

shows a block diagram of yet another preferred embodiment of Doppler group sensor using radio waves (also known as radar), a combined device of "active beacon" and radar receiver which plays both an "active beacon" function and a radar receiver function in a system;

shows a block diagram of yet another preferred embodiment of Doppler group sensor using light carrier (also known as LIDAR), a combined device of "active beacon" and LIDAR receiver which plays both an "active beacon" function and a LIDAR receiver function in a system;

illustrates an exemplary automobile application scenario of a Doppler group sensor system using the device embodiment of or ;

illustrates a block diagram of a radar illuminator device in another embodiment of Doppler group sensor system using radio waves (radar sensor system) that may be suitable for use in a highway automobile application;

illustrates a block diagram of a radar receiver device in another embodiment of Doppler group sensor system using radio waves (radar sensor system) that may be suitable for use in a highway automobile application;

illustrates a block diagram of a LIDAR illuminator device in another embodiment of Doppler group sensor system using light carrier (LIDAR sensor system) that may be suitable for use in a highway automobile application;

illustrates a block diagram of a LIDAR receiver device in another embodiment of Doppler group sensor system using light carrier (LIDAR sensor system) that may be suitable for use in a highway automobile application;

illustrates an exemplary use case of embodiment of and or and ;

shows modifications to the embodiment in and to make it an embodiment of FM modulated Doppler group sensor;

shows modifications to the embodiments in , , , , , , and to make them embodiments of FM modulated Doppler group sensor system or subsystems thereof;

illustrates a variant embodiment of and that separately detects the CW tone(s) and FM modulated tone(s);

illustrates a variant embodiment of and that separately detects the CW tone(s) and FM modulated tone(s);

shows exemplary spectrum results of FM modulated Doppler group radar using embodiment in modified according to and , in which Fig. 14A shows exemplary spectrum results from CW tone path, Fig. 14B shows exemplary spectrum results from sawtooth FM tone path, and Fig. 14C shows processed range detection resulting from Fig. 14A and Fig. 14B;

shows an exemplary frequency sweeping waveform that alternating between CW and frequency ramp;

is a flowchart showing the steps to determine both ranges (distances) and relative speeds of objects using Doppler group radar system with beacon and combined CW and FM wave signal.

It will be appreciated that in the description herein, numerous specific details are set forth in order to provide a thorough understanding of the invention. However, it will be understood by those of ordinary skill in the art that the invention may be practiced without these specific details. In other instances, well-known methods, procedures and components have not been described in detail so as not to obscure the invention. Furthermore, this description is not to be considered as limiting the scope of the invention, but rather as merely providing a particular preferred working embodiment thereof.

In the specification and claims, the terminologies "radar", "sonar" and "LIDAR" / "lidar" are used interchangeably, referring to a device that detects or senses objects using waves. The wave used may be electromagnetic wave such as microwave, light wave, or acoustic wave, such as ultrasound, sound wave, or other types of waves. Terminology "sensor" is also used in the specification and claims to refer to devices that detects or senses objects using waves, and it is used interchangeably with "radar", "sonar" and "LIDAR" / "lidar". Although embodiments are described using electromagnetic waves, they are also applicable to other types of waves, and it is understandable by the skilled in the art that, for example, an antenna needs to be replaced by a transducer if acoustic wave is used, and replaced by a light emitter or detector if light wave is used, and so on.

A Doppler "group radar" is a family of improved Doppler radar or radars that are suitable to work together in proximity of each other. To explain how Doppler group radars work and how Doppler group radars are built, we first review the prior art, a conventional Doppler radar. As illustrated in , a block diagram of typical embodiment of a conventional Doppler radar (prior art) is shown. This Doppler radar system includes a CW (continuous wave) signal generator 10, which may be implemented using a crystal oscillator, a frequency synthesizer that locks to a reference oscillator built-in the device (not shown in drawing), or other types of CW generator. For purpose of Doppler detection, the CW generator preferably creates low phase noise, which is a type of random (unpredictable) phase modulation in the CW signal. The CW signal is fed to a splitter 20 to create two branches of signals. One branch of the split signal is amplified through a power amplifier 30 and sent to a transmitting antenna 40. The electromagnetic wave of the CW signal is transmitted into space towards objects under detection (not shown in drawing) and bounces back to a receiving antenna 50, amplified by an amplifier 60, usually referred to in the art as a low noise amplifier (LNA) and preferably the amplifier also includes tuning circuit to suppress unwanted signals outside the signal band of the radar. The amplified signal is then mixed with the other branch of CW signal from the splitter 20 at a mixer 70 to be down converted to baseband, which is also referred to in the art as IF (intermediate frequency) or zero IF (zero intermediate frequency). Preferably the mixer is a quadrature mixer that produces both in-phase and quadrature baseband signals. The baseband signal(s) will next be filtered by a filter 80 to remove components in 2nd (and higher) harmonics, also remove noises and interferences above the maximum Doppler shifts of interests in the application. In some applications the filter 80 may also block DC (direct current) and close to DC components that represent signals bounced back from objects with zero speed relative to the antennas 50 and 40, i.e., the (relatively) "stationary" objects. An amplifier 90 bring the signal to desired level for further processing, usually including (not shown in drawing) analog to digital converter and DSP (digital signal processor).

People skilled in the art understand that, if an object is moving towards the antennas 40 and 50 at a speed v, the signal bounced back from the object and seen at the receiving antenna 50 would exhibit a higher frequency than that of the CW signal at the transmitting antenna 40, by an amount referred to as Doppler shift, which is | fd |= 2 f v / ( c – v) , where f is the frequency of the transmitted CW signal; c is the wave travelling speed; for electromagnetic wave, c is also referred to speed of light which is about 3x10 ⁸ m/s in free space (vacuum) and in air; if an object is moving away from the antennas 40 and 50 at a speed v, the signal bounced back from the object and seen at the receiving antenna 50 would exhibit a lower frequency than that of the CW signal at the transmitting antenna 40, by the amount of | fd | = 2 f v / ( c + v). If the Doppler sensor is a sonar device using acoustic waves, the block diagram would need to replace the antennas 40 and 50 by sound transducers, and the wave speed c needs to be replaced by speed of acoustic wave, about 343 m/s in air and 1481 m/s in water.

Similarly, a Doppler "group LIDAR" is a family of improved Doppler LIDAR or LIDARs that are suitable to work together in proximity of each other. To explain how Doppler group LIDARs work and how Doppler group LIDARs are built, we first review the prior art, a conventional Doppler LIDAR. As illustrated in , a block diagram of a Doppler LIDAR (prior art, as disclosed in US 6,697,148) is shown. In , blocks 10, 20, 70, 80, 90 are identical to the corresponding ones in with same numerals, as have been explained, and are not re-explained. Components 30, 40, 50 and 60 are replaced by 330, 340, 350 and 360 and they are explained one by one next. One branch of the split signal from splitter 20 is used to modulate an amplitude of an optical signal in a "light source and amplitude modulator" module 330. In some implementation the light source and amplitude modulator may be separately implemented, for example, the light source may be constant strength laser, and the amplitude modulator may be a Mach-Zehnder light modulator; in some other implementations, the light source and amplitude modulator may be a combined device, for example, implemented by a laser diode or an LED. The amplitude-modulated light output may be optionally amplified by a light power amplifier 340 before being transmitted, or be directly transmitted. Some additional optical components may also be used to facilitate the delivering of light signal into air, e.g., optical fiber, lenses and mirrors (not shown in drawing). The light wave carries the CW signal in its amplitude over space towards objects under detection (not shown in drawing) and bounces back to receiving optical components such as light filters, mirrors, lenses and optical fiber (not shown in drawing) and is fed into a low noise optical detector (also known as photodetector) 350 to detect the optical signal amplitude. The detector output is amplified and band-pass filtered to remove components outside the CW frequency band by BPF (band-pass filter) and receiver module 360. The amplified and filtered signal is then mixed with the other branch of CW signal from the splitter 20 at a mixer 70 to be down converted to baseband. The rest processing downstream is identical as explained with .

The Doppler shift +/- fd will cause the output signals of mixer 70 to be at frequency +/- fd. From this signal frequency fd, objects and moving speed thereof can be detected and derived. A positive fd means the object is approaching the radar, and a negative fd means the object is leaving the radar. The higher the | fd |, the higher the object speed is.

What happens if a plurality of such conventional Doppler radar devices work in a same frequency band and in proximity of each other? Referring to an exemplary scenario as shown in , assuming a Doppler radar device installed on vehicle 1 transmits at frequency f1, and another Doppler radar device installed on vehicle 11 transmits at frequency f2, and f2 - f1 = fe to be the frequency difference of the two radar transmitters. The radar signal 3 from the radar on vehicle 1 hits an object vehicle 111 and bounces back (signal 5 in drawing) to the radar receiver on vehicle 1 and exhibits a Doppler shift fd, which is dependent on relative speed between vehicle 1 and vehicle 111 as expected. Meanwhile radar signal 7 from a radar on vehicle 11 also hits the object vehicle 111 and bounces not only back to the radar on vehicle 11 as intended but also to the radar receiver on vehicle 1 (signal 9 in drawing). The frequency of received signal 9 at radar receiver on vehicle 1 depends not only on relative speed between vehicle 1 and vehicle 111, but also depends on relative speeds between vehicle 11 and vehicle 111, and further more, it also adds the frequency difference fe. Signals from a single object (vehicle 111) will be detected as two objects on the radar of vehicle 1, one is the true detection with relative speed as can be calculated from fd, another is a false detection with erroneously derived relative speed depending on fe, as well as speed of vehicle 11 which is irrelevant to the relative speed between the intended object vehicle 111 and the radar device (vehicle 1).

shows an exemplary application scenario of Doppler sensors on personal wearable protective device, such as that disclosed in US 10,154,695 B2, in which Doppler radars or sonars are utilized in wearable devices that are carried by older adults to detect falls prior to hitting floor or objects, and deploy protective air bags to prevent injuries. In some use cases as shown in the figure, people carrying such devices may gather together and the Doppler sensors must work in proximity of other identical or similar Doppler sensor devices. Assuming a first person wearing a Doppler sensor transmitting signal at frequency f ₁, if the person is not falling, this signal bounces back from the floor and many other stationary or slow moving objects will exhibit zero or very low Doppler shifts. If other surrounding sensor devices each transmits at their own free running frequencies slightly higher or lower than f ₁ by non-zero amounts ∆f ₁, ∆f ₂, ⋯, ∆f _n , ⋯ These signals either bouncing back from objects or directly coming to the sensor receiver of the first person, the sensor detected Doppler shifts of these signals will be added by these amounts ∆f ₁, ∆f ₂, ⋯, ∆f _n , ⋯ and they are likely to confuse the sensors and detect false falls. In other words, such Doppler sensor will work in detecting falls if deployed alone, but will have trouble if deployed in a group together.

Now we explain how a Doppler group sensor device or a Doppler group sensor system is built and how it will avoid the problem as described above, by way of example through embodiments.

In and , block diagrams of one embodiment family of Doppler group sensor are illustrated, wherein is a Doppler group sensor using radio waves, also known as radar; and is a Doppler group sensor using light carrier, also known as LIDAR. They are both suitable to coexist with other Doppler group sensor devices of same kind. In the figures, the functions of the elements 20, 70, 80 and 90 are identical to the corresponding ones in or that are marked with same numerals; the functions of the elements 30, 40, 50, and 60 are identical to the corresponding ones in that are marked with same numerals; and the functions of the elements 330, 340, 350, and 360 are identical to the corresponding ones in that are marked with same numerals. What are new in the and are the elements 110, 120, and 130, and are now explained. In both figures, the radio receiver 120 and the antenna 130 are used to receive, over the air, a signal or signals that will be explained in more detail in next a few paragraphs, and by successfully acquiring and phase locking or frequency locking to the signal(s), produces a reference frequency signal and output it to the frequency synthesizer 110. Deriving from the reference signal frequency, the frequency synthesizer 110 then generates a CW signal at a desired frequency for the Doppler sensor. All Doppler group radar devices ( ) of same frequency channel that may work together in an area are required to transmit at an exactly same frequency; all Doppler group LIDAR devices ( ) that may work together in an area are required to modulate the light carrier by an exactly same identical CW frequency. This can be achieved by 1) locking (in frequency or phase) to a same radio signal, 2) locking to signals that are locked with each other in their generation process, or 3) locked to high precision independent frequency standard sources, such as atomic clock. As shown in and , methods 1) or 2) is used. Method 3 may be too expensive to use today (but may be possible someday in future).

In one preferred embodiment, the radio receiver 120 acquires and locks to GNSS satellite signals, e.g., GPS, GLONASS, Beidou, Galileo, or the kind. As known in the art, all these GNSS signals come from precision frequency source of atomic clocks. Although movements of satellites causing signals received at antenna 130 to exhibit significant Doppler shifts, since the GNSS simultaneously broadcasts orbit data that can accurately derive and correct these shifts after a "position fix" is achieved, there has been matured technology to generate accurate reference clock based on GNSS, including correction of Doppler shifts caused by moving of radio receiver 120 itself, known in the art as GNSS disciplined oscillator.

In another embodiment, the radio receiver 120 may acquire and lock to ground station signal(s) of standard frequency and time signal service (SFTS) such as defined in Article 1.53 of the International Telecommunication Union's (ITU) Radio Regulations (RR), or space station signals of standard frequency and time signal-satellite service (SFTSS) such as defined in Article 1.54 of ITU RR.

In yet another embodiment, receiver 120 in all coexisting member devices of Doppler group sensors may acquire and lock to a commonly agreed radio signal. This radio signal may be originally for purpose of other services. This signal does not have to provide an absolute accuracy of frequency, but ensures frequency synchronization among all coexisting member devices of the group sensors. For example, the devices may all lock to the carrier of an AM radio station, a TV station, or a cellular base station, etc. A protocol needs to be in place to ensure member devices will correctly identify, among potentially many broadcasted signals, which one of them they all lock to. One simple example is a lookup table of signals ordered by priority. Such lookup table may also list only one signal to use.

In an alternative embodiment, in applications such as that shown in , in which devices of Doppler group sensors are stationary or quasi-stationary (or relatively stationary, relatively quasi-stationary, such as devices worn by passengers on a same moving train), an autonomous procedure may be performed to make all sensor devices in a cluster synchronized and make the group sensor work. The procedure may pick one of the member devices (referred to as leader) in a group sensor cluster to transmit a reference signal and all other member devices are synchronized with this reference signal (referred to hereinafter as leader reference signal). The leader reference signal may be transmitted using a separate dedicated antenna (not shown in drawing, e.g. an omnidirectional antenna) and/or in a separate dedicated channel (not shown in drawing). The leader reference signal must have a predetermined frequency relationship with the CW signals generated by the frequency synthesizers 110 of the sensor devices, and the frequency relationship is known to all member devices.

In another preferred embodiment, regional special purpose transmitter stations, referred to, in this application, as reference broadcast stations, are built to serve local Doppler group sensor users in the region. These special purpose stations will broadcast predefined frequency reference signals authorized by radio spectrum regulation authorities and follow commonly agreed standard. All member devices of Doppler group sensors are required to synchronize with at least one of the reference signals broadcasted by a reference station and follow a commonly agreed standard in deriving their CW signal frequency from the reference signal. Preferably the reference broadcast stations also broadcast time mark signal and station geographical position information, for example, in terms of latitude and longitude as well as altitude. The geographical position information of the station may be used for correcting Doppler shift of the frequency reference signal as seen at receiver radio 120, caused by movement of the radio receiver 120. More preferably, multiple such stations are deployed around serving region and each device of a Doppler group sensor system will receive 3 or more such signals from multiple directions. In such condition, even if the device is moving, based on timing mark and/or geographical location information broadcasted, the device is able to accurately correct Doppler shifts in received reference broadcast signals.

When Doppler sensor devices as in or are all synchronized and deployed in application scenario of , what will happen? Assuming a first person wearing a device transmitting signal at frequency f1, if the person is not falling, this signal bounces back from the floor and many other stationary or slow moving objects will exhibit zero or very low Doppler shifts, which will cause the mixer 70 to output a DC and very low frequency fluctuations, and they may, by design, be blocked by the filter 80. As other surrounding radar devices are all synchronized, each of them also transmits at the frequency equal to f1 with only very small phase noise (random frequency drifts). These signals, either bouncing back from stationary objects and slow-moving persons, or line of sight directly coming to the sensor receiver of the first person, if the sensor receiver of the first person has sufficient dynamic range to handle stronger signals coming through line of sight paths, the sensor detected Doppler shifts of these signals will also be zero or very low frequency and may be blocked as well, by design, by the filter 80. Only when the person falls and the associated fast moving will get high Doppler shits be detected. It is true, however, when a second person falls, who is close to the first person, the sensor device wearing on the first person may also detects a fall (in this application it is allowable). In other words, for the application scenario of , the quasi-synchronized sensors of or do work, in most cases except, by chances, the special cases as will be explained in the next paragraph.

Since all member devices in a cluster are (quasi-)synchronized, their transmitted signals are coherent with each other for radar. By chances, a wanted signal, from a member radar transmitter and bouncing back from an object under detection, may arrive at its receiving antenna 50 in destructive phase (about 180 degrees) and similar magnitude with another signal (line-of-sight directly or indirectly after being reflected) from a transmitter of another member radar device and they each other cancel out. Similarly for LIDAR, the CW modulating signals are coherent with each other. By chances, more than one beams of light signals, from light transmitter of self device as well as one (or more) other member LIDAR transmitter(s) and bouncing back from objects under detection or line-of-sight directly from a LIDAR transmitter, may happen to arrive at the optical detector 350 with overall amplitude in destructive way and cancel out. When such chances of cancellation happen, the detection may fail. Such chance is very low since an interfering signal happens to have nearly same Doppler shift and out of phase, as seen at given receiver antenna 50 or at a given photodetector 350, is very unlikely. To further reduce such failing chances, an improved embodiment will be described with and in next paragraph.

and is another preferred embodiment family of Doppler group sensors, suitable to coexist with other Doppler group sensors of same kind, wherein is a Doppler group radar and is a Doppler group LIDAR. In , the functions of the elements of 120, 130, 20, 30, 40, 50, 60, 70, 80 and 90 are identical to the corresponding ones in that are marked with same numerals; and in the functions of the elements of 120, 130, 20, 330, 340, 350, 360, 70, 80 and 90 are identical to the corresponding ones in that are marked with same numerals, and hence are not described again. The frequency synthesizer 210 in both figures is modified to produce more than one output signals, and the output signals are linearly combined in adder 220. The output signals of synthesizer 210 each has a distinct CW frequency and the frequency difference between any pair of them shall be more than twice of the maximum Doppler shift of concern in the application plus a guard band. This way, between them they will not interfere with each other. Furthermore, it is desirable that any of the frequency of synthesizer 210 output shall be away from n times of another frequency of synthesizer 210 output by at least amount of (n + 1) times "maximum Doppler of concern plus a guard band". It can be understood by skilled people in the art that, with good linearity of all elements in the signal chains, the radar in simultaneous transmit multiple tones and detection can be achieved through any frequency component of the tones, and the LIDAR in simultaneous modulates multiple tones onto light carrier and detection can be achieved through any frequency component of the modulated tones. As a member of Doppler group radar/LIDAR cluster, each radar/LIDAR device shall transmit at a number of frequencies that are pre-agreed among the members of the cluster. As such, all devices are synchronized in their transmitting frequencies without being confused as Doppler shift. It can also be understood by those skilled in the art that, the chance of multiple tones all happen to simultaneously cancel each other between users is very minimal. As cancelling tones must happen to have nearly same Doppler shift, in practice, duel tones would be sufficient in typical applications. As can be realized by the skilled in the art, the embodiment in is a degeneration special case of the embodiment in , and the embodiment in is a degeneration special case of the embodiment in .

shows a block diagram of another preferred embodiment of Doppler group sensor using radio waves (also known as radar), wherein the upper part 900 is the "active beacon" part of the radar device and the lower part 800 is the receiver part of the radar device, whereas the middle part 700 is the common part shared by the radio beacon function and receiver function. This embodiment may be used in an automotive application and fully-automated (unmanned) cargo terminal application, for example. The active beacon part, 900 together with 700, transmits a beacon signal for purpose of being seen. In an automotive application, this part is desirable to be installed on every vehicle on road that supports such feature. Like a lighthouse, the beacon signal is for purpose of letting others "see" it rather than illuminating objects sounding it. The radar receiver part, 800 together with 700, detects and measures signals coming from active beacons of other devices (installed on other vehicles, for example).

The active beacon part 700 and 900 actually is nearly identical to the transmitting path in , except that antenna 140 may be desirable to be replaced by an omnidirectional antenna. That is because the beacon, in many applications, is desired to be seen by (other) radars from any direction around. As in previous embodiments, the transmitting frequency will be frequency (or phase) locked so that all beacons in a cluster of beacon devices transmit at identical frequency or frequencies. Again, it is desirable to transmit at more than one frequency simultaneously to reduce the chance that signals from two (or more) radio beacons in cluster arrive at a radar receiver antenna to happen to cancel out one another and causing misdetection.

The receiver part 700 and 800 in fact is identical to the receiving path in previous embodiments ( ), however, in this embodiment, the receiver is intended to detects signal coming directly from (other) radio beacons rather than detecting the signals bounced from passive objects. For typical objects like cars, a reflected path usually is weaker than a line-of-sight direct path by 15 dB or more, gain of the receiver path in is desirably optimized for line-of-sight signal strengths for the detection range in design. Since every active beacon is synchronized and transmits at an identical frequency (or a sets of identical frequencies), a radar receiver will observe Doppler shifts from any of them only dependent on the relative speed between a beacon under detection and the receiver, not depending on factors such as frequency error and drifts and moving speed of any other objects around. Again, a misdetection may happen if signals from two or more beacons happen to cancel out when arriving at antenna 50. The method to reduce such chances of misdetection is again to simultaneously use more than one tone frequencies for detection as explained in previous embodiment of . People ordinarily skilled in the art will be able to derive Doppler and speed relations in such beacon and receiver use case base on principles of Doppler effects, and will not be detailed herein.

shows a block diagram of another preferred embodiment of Doppler group sensor using light carrier (also known as LIDAR), similar to the radar counterpart in , the upper part 910 is the "active beacon" part of the LIDAR device and the lower part 810 is the receiver part of the LIDAR device, whereas the middle part 700 is the common part shared by the beacon function and receiver function. The active beacon part, 910 together with 700, transmits an optical beacon signal for purpose of being seen. In an automotive application, for example, this part is desirable to be installed on every vehicle on road that supports such feature. The beacon signal is for purpose of letting others "see" it like a lighthouse, rather than illuminating objects sounding it. The LIDAR receiver part, 810 together with 700, detects and measures signals coming from active beacons of other devices (installed on other vehicles, for example).

The active beacon part 700 and 910 actually is nearly identical to the transmitting path in , except that the transmitted light signal may be desirable to be emitted to all directions, rather than forming a narrow beam, e.g., through optical components (not shown in drawing). And the light source and amplitude modulator module 30 may use a light source to facilitate this omnidirectional emitting task, e.g., using an LED as light source. That is because the beacon, in many applications, is desired to be seen by (other) LIDARs from any direction around. As in previous embodiments, the CW frequency will be quasi-synchronized so that individual beacons in a cluster of beacon devices all modulate their light signals by identical CW frequency or frequencies. Again, it is desirable to use more than one CW frequencies simultaneously to reduce the chance that signals from two or more light beacons in cluster arrive at a LIDAR receiver to happen to cancel each other in their amplitude waveforms and causing misdetection.

The receiver part 700 and 810 in fact is identical to the receiving path in previous embodiments ( ), however, in this embodiment, the receiver is intended to detects signal coming directly from (other) optical signal beacons rather than detecting the signals bounced from passive objects. Dynamic range of the receiver path in is desirably optimized for line-of-sight signal strengths for the detection range in design. Since every active beacon is quasi-synchronized and modulates at an identical CW frequency (or a sets of identical CW frequencies), a LIDAR receiver will observe Doppler shifts from any of them only dependent on the relative speed between a beacon under detection and the receiver, not depending on factors such as frequency error and drifts and moving speed of any other objects around. Other aspects are similar to the radar embodiment counterpart, and will not be repeated again.

illustrates an exemplary automobile application scenario of a Doppler group sensor system using the device embodiment of or . In the example, all vehicles on road (such as 1, 11, 111, and so on) are equipped with active beacons that transmit a radio beacon signal (2, 22 or 222 and so on) of a tone (or a set of tones) at precisely an identical frequency (or an identical set of frequencies), or transmit an modulated optical beacon signal (2, 22 or 222 and so on) modulated by a tone (or a set of tones) at precisely an identical frequency (or an identical set of frequencies), this is achieved by using their built-in receiver (not shown in drawing) to lock to navigation signals from GNSS 33 and disciplines their built-in local oscillators (not shown in drawing). Radar/LIDAR receivers, also equipped with by the vehicles (such as 1, 11, 111, and so on) then detect the beacon signals and measure the radio signal Doppler shifts or measure the Doppler shifts in modulated CW(s) of the light carriers. Since all beacons use a same (set of) tone frequency or frequencies, all sensor receivers only need to detect signals at the same (set of) transmitting or modulating CW frequency or frequencies, and no higher layer protocols are required to coordinate the use of CW frequencies in beacons and to tune receivers to these frequencies. In the radar case, since a radio beacon tone only requires spectrum band of plus/minus maximum Doppler shifts around a tone frequency plus a guard gap on each side, and all devices share a same frequency or share a couple of frequencies for multi-tones, required spectrum for the Doppler group radar is very minimal.

, , , and illustrate another family of Doppler group sensor system embodiment that may be suitable for use in a highway automobile application. In particular, shows a radar illuminator device and shows a radar receiver device; shows a LIDAR illuminator device and shows a LIDAR receiver device.

Referring now to , block diagram of illuminator device of the Doppler group radar system in the preferred embodiment. In the block diagram, elements of 120, 130, 210, 220, 30 and 40 are identical to the corresponding ones in with same numerals. Comparing it with transmitter path of , only splitter 20 is eliminated in and the rest are identical to the transmitter path in . The illuminator devices may be installed on stationary platforms to radiate CW tone (or tones) to objects under detection so that the signals bouncing back from these objects will be detected by radar receivers, which may be separately installed on board of moving platforms (such as cars and cargo vehicles). Again, all illuminator devices transmit one tone or a number of tones at precisely identical frequency or frequencies, so that frequency differences (of corresponding tone signals) between all illuminator devices are zero and will not be erroneously detected as a Doppler shift. Also again, as did in the embodiment of , more than one tones may be transmitted simultaneously to illuminate objects under detection, so as to reduce chances of misdetections caused by tone signals coming from two (or more) illuminators (bounced by objects or directly through line-of-sight path) happen to arrive at a receiver destructively and nearly cancel out.

Referring now to , block diagram of receiver device of the Doppler group radar system in the preferred embodiment. In the block diagram, elements of 120, 130, 210, 220, 50, 60, 70, 80, and 90 are identical to the corresponding ones in with same numerals. Comparing it with the portion of related to receiver chain, only splitter 20 is eliminated in and the rest are identical to the portion in . The radar receiver devices may be installed on board of moving platforms (such as cars and cargo vehicles) to detect reflected signals from objects under detection. These reflected signals originally come from illuminators which may be installed physically away from the receivers. Again the detection may be simultaneously performed at more than one CW tone frequencies to reduce chances of misdetection caused by multipath/multisource cancellation as explained also in previous embodiments. People ordinarily skilled in that art will be able to derive Doppler and speed relations in such stationary illuminator and moving receiver use case base on principles of Doppler effects, and will not be detailed herein.

Referring now to , block diagram of illuminator device of the Doppler group LIDAR system. In the block diagram, elements of 120, 130, 210, 220, 330 and 340 are identical to the corresponding ones in with same numerals. Comparing it with transmitter path of , only splitter 20 is eliminated in and the rest are identical to the transmitter path in . Other aspects of the group LIDAR illuminator device is similar to the group radar illuminator counterpart and are not repeated.

Referring now to , block diagram of receiver device of the Doppler group LIDAR system in the preferred embodiment. In the block diagram, elements of 120, 130, 210, 220, 350, 360, 70, 80, and 90 are identical to the corresponding ones in with same numerals. Comparing it with the portion of related to the receiver chain, only splitter 20 is eliminated in and the rest are identical to the portion in . The LIDAR receiver devices may be installed on board of moving platforms (such as cars and cargo vehicles) to detect reflected signals from objects under detection. These reflected signals originally come from illuminators which may be installed physically away from the receivers. Again the detection may be simultaneously performed at more than one CW tone frequencies to reduce chances of misdetection caused by multipath/multisource cancellation as explained also in previous embodiments.

illustrates an exemplary use case of embodiment of and , or and in highway automobile application. Illuminators (such as built by way of or ) are installed on roadside towers (e.g., 4 and 44 in drawing) or above road structures (not shown in drawing) along the highway, which may lock to signals from GNSS 33 and produce CW tone (or tones) identical in frequency (or frequencies) and transmit towards automobiles on road (e.g., signal paths 6 and 8 shown in drawing). The signals hit an automobile (e.g. vehicle 111) and are reflected to the air, such as signal paths shown in drawing 66 and 88, they are received by radar or LIDAR receivers installed on board of vehicles (e.g. that on vehicle 1), the radar or LIDAR receivers may be built by way of or and they may also be locked to GNSS signals from GNSS satellites 33. Receiving the reflected signals (e.g. 66 and 88), the receiver is able to detect the Doppler shift of the signals. On the road, there may be mixed type of vehicle objects, some of them (e.g. vehicle 11) may be equipped with an active beacon signal transmitter as described in or , sending in air a beacon signal 22, a radar/LIDAR receiver such as that on board of vehicle 1 should also be able to detect the beacon signal since they shall be at same CW frequency as what the illuminators transmit. For purpose of reliable detection of both reflected signals and actively transmitted active beacon signals, the beacon transmitted power is desirably regulated to similar levels as the reflected signal power to optimize radar receiver link budget. Alternatively, the active beacons may be assigned a frequency (or a set of frequencies) different from what the illuminators use, and a radar/LIDAR receiver is designed to receive signal frequencies of both type of signals. In the drawing although it illustrated only one radar/LIDAR receiver on vehicle 1 detecting signals, in fact every vehicle may be equipped with a radar/LIDAR receiver and they should work in the same way as that on vehicle 1. They form a group sensor cluster without interfering with each other although on same frequency or frequencies.

It is known in the art that using frequency modulated signal to replace CW would enable a Doppler radar/LIDAR to detect not only object speed but also object range (distance). The Doppler group sensor disclosed herein is also able to incorporate that technology, as will be described herein below.

Referring to , which shows modifications to the embodiment in or to make it an embodiment of FM modulated Doppler group radar. The subsystem shown in will replace corresponding subsystem of elements 110, 120, and 130 in or , and keep all the rest in or as they were. In , the antenna 130 is identical to that in or . Radio receiver 320 however not only outputs a frequency reference signal 301 as in or but also a precise timing indicating signal 303. The timing signal 303 may consists of a time marking pulse whose edge (e.g. rising edge) marks beginning of a predetermined time interval. The timing signal 303 may further consists of an n-bit time counter value (e.g., a time counter value associated with GPS time). The timing may be derived from GNSS signals as known in the art, or may be derived from ground station signal(s) of Standard frequency and time signal service (SFTS) as defined in Article 1.53 of the International Telecommunication Union's (ITU) Radio Regulations (RR), or space station signals of Standard frequency and time signal-satellite service (SFTSS) as defined in Article 1.54 of ITU RR, or derived from other suitable broadcasted signals, including reference signals from reference broadcast stations built specifically for this purpose, as described hereinbefore. Based on the precise reference frequency and timing signals 301 and 303, the frequency synthesizer 310 will produce a FM modulated output signal and makes sure every member device in the Doppler group sensor cluster reproduces this FM modulated signal exactly identical in their instantaneous frequency at any time. Such frequency synthesis technology is known in the art, e.g., those based on DDS (direct digital synthesis), and is not explained in further detail herein. In some applications, it may be desirable to alternate over time between sending FM signal and CW signal, and such arrangement may also be time-synchronized among all member devices in cluster precisely, by following a commonly agreed protocol. For example, when the timing signal 303 ticks, start sending signal configuration A if the time counter value of signal 303 or a system timing counter (not shown in drawing) is a odd number, and sending signal configuration B if the counter is an even number, and so on. As will be appreciated by people skilled in the art, the transmitting signal for a radar or the modulating signal for a LIDAR may be frequency modulated in sawtooth wave, triangle wave, sine wave or other types of waveforms, per application requirements.

Referring to , which shows modifications to the embodiments in , , , , , , and to make them embodiments of FM modulated Doppler group sensor systems. The subsystem shown in will replace corresponding subsystem of elements 120, 130, 210 and 220 in , , , , , , and , and keep all the rest in the figures as they were, no matter in a sensor transmitter, receiver, active beacon, or an illuminator. The subsystem in works in same way as the one in except that, frequency synthesizer 311 generates more than one signals, and at least one of the signals is FM modulated at least over some time intervals. Again, in all devices of the group sensor cluster, all (active) signals from any instances of the frequency synthesizers 311 in devices of the cluster are precisely time synchronized, i.e., at any time instant, the instantaneous frequency is identical between any two corresponding signals of any two devices in the cluster. Other feathers are same as described for and will not be elaborated herein.

In some embodiments, not all tones are FM modulated. In a sensor receiver, it may be desirable to separately detect the CW tone(s) and FM modulated tone(s). As examples, shows a variant embodiment of and that separately detects CW tone(s) and FM modulated tone(s); shows a variant embodiment of and that separately detects CW tone(s) and FM modulated tone(s).

In , the generated CW tones from frequency synthesizer 311 are fed to combiner 220 as did in (if only one tone is CW tone, combiner 220 is not required), but all rest FM modulated tones are fed to another combiner 420 (if only one tone is FM modulated tone, combiner 420 is not required). The combined signal of CW tones is fed to mixer 70 as did in , but the combined signal of FM modulated tones is fed to a separate mixer 470. Received signal from antenna 50 after amplified and filtered by tuning amplifier 60 is split into two branches by splitter 420 and the outputs are fed to the mixers 70 and 470. Functions of filter 480 and amplifier 490 are same as their counterparts 80 and 90, respectively. The output signal from amplifier 90 is baseband signal from CW tones and that from amplifier 490 is baseband signals from FM modulated tones, they may be passed to an analog to digital converter and DSP module (both not shown in drawing) for further processing.

Similarly in , the generated CW tones from frequency synthesizer 311 are fed to combiner 220 as did in (if only one tone is CW tone, combiner 220 is not required), but all rest FM modulated tones are fed to another combiner 420 (if only one tone is FM modulated tone, combiner 420 is not required). The combined signal of CW tones is fed to mixer 70 as did in , but the combined signal of FM modulated tones is fed to a separate mixer 470. Received signal from photodetector 350 after amplified and filtered by tuning amplifier 360 is split into two branches by splitter 420 and the outputs are fed to the mixers 70 and 470. Functions of filter 480 and amplifier 490 are same as their counterparts 80 and 90, respectively. The output signal from amplifier 90 is baseband signal from CW tones and that from amplifier 490 is baseband signals from FM modulated tones, they may be passed to an analog to digital converter and DSP module (both not shown in drawing) for further processing.

Similarly, people skilled in the art understand that other embodiments described hereinabove may also be implemented as described in or , to separately mixing CW tone(s) and FM tone(s), and will not be repeatedly described herein.

How does a FM Doppler group radar system detect both speed and range (distance)? This paragraph assumes using the embodiments of active beacon as shown in with modification shown in , and receiver 800 using separate mixing structure like in . Assuming all devices use multi-tones, and some of the tones is/are CW and some other of the tones is/are FM swept using sawtooth waveform at a constant sweeping rate of ∆f Hz/second increasing for T seconds then jumps back by amount (∆f • T) Hz. At any time instant, all beacons under detection in the cluster as well as all radar receivers are generating exactly same frequency in producing the transmitting signals as well as local oscillator signals fed into mixers (70, 470). Assume arbitrary number of objects are moving around a radar receiver in cluster, each carrying an active beacon as described. The CW tone(s) transmitted by a beacon seen at the radar receiver will exhibit a Doppler shift dependent on the beacon speed relative to the radar receiver. Multiple beacons will be detected as Doppler shift lines in spectrum analysis results, e.g., through FFT (Fast Fourier transform). Fig. 14A gives an example of Doppler shifts of four beacons. Each line represents a beacon and its associated object, the lines with positive frequency shifts represent objects moving closer to the radar receiver and negative frequency shifts represent objects moving farther from the radar receiver. The height of the lines represents received signal strength from a beacon. From the frequency shifts, object speeds relative to the receiver can be calculated. Next, we need to detect the range (distance) of the beacon installed objects. The FM swept tone(s) arriving at receiver antenna is delayed due to wave propagation. The FM swept tone(s) of a beacon with distance d away from the receiver will take d / c seconds to arrive at the receiver antenna, where c is the propagation speed of wave. In other words, locally generated LO (local oscillator) signal, although exactly identical to the beacon signal in frequency at any time, is actually mixing with beacon signal tone(s) generated d / c seconds ago. Due to sweeping, the instantaneous frequencies between them has shifted by ∆f • d / c Hz, furthermore, due to beacon installed objects and/or the receiver may be moving, in addition to the shifting amount caused by sweeping and propagation delay, they also added amount of Doppler shifts. Spectrum analysis of the radar receiver output may display a spectrum like Fig. 14B. This is an intermediate result that contains both range (distance) and speed information, for purpose of method illustration only. We need to deduct the amount of Doppler frequency shift to get the net shift caused by signal propagation delay and FM sweeping, i.e., to deduct the Doppler shift obtained from the CW signal detection (of corresponding beacon). Among the multiple lines in Fig. 14A and Fig. 14B, we need to correctly identify which line in Fig. 14A and in Fig. 14B corresponds to a given beacon. Various methods can accomplish this task, some examples will be discussed next. Assuming we correctly identified them one by one, then deducts the Doppler caused shifts, we can get range (distance) caused shifts shown, by way of example, in Fig. 14C, in which, the horizontal coordinates of lines represent the ranges (distances) of the beacons to the receiver. Combining the results from Fig. 14A and Fig. 14C, the FM modulated Doppler group radar is able to detect and report both relative speeds and distances of multiple beacon-installed objects. As known in the art, other algorithms are also available to determine both relative velocity and range of objects.

As discussed, we need to deduct Doppler amount of individual beacon signal, from spectrum analysis. How can we identify each spectrum lines in CW baseband and FM modulated baseband channels and associate them correctly for each of the detected objects (beacons)? One way is by strength. When not experiencing multipath effects, since CW tone(s) and FM modulated tone(s) from a given beacon are close in frequency, and coming from same transmitter, received by same antenna and amplifier, mixer and its downstream path components may also be designed with nearly same gain, spectrum lines from CW tone(s) and FM tone(s) from a same beacon should be detected at nearly equal strengths, but spectrum lines from different beacons would vary in their strengths, depending on factors such as distance, effective radiated transmitted power in receiver direction, receiver antenna beam pattern in beacon direction. Most cases they are easy to identify and distinguish. However, it is still possible that two beacons are detected at same strength and cannot uniquely detect their speeds and distances. One way to facilitate the identification is to let beacons add some dithering modulation, such as low frequency random amplitude modulation (random between beacons but identical to all CW and FM tones in same beacon). This way, the pair of spectrum lines respectively detected in CW baseband path and FM baseband path that always vary their strengths in a same way (i.e., statistically strong correlation) must come from a same beacon. Another way of dithering is to use a digital ID of beacons to be amplitude modulated on CW and FMCW tone(s), or phase/frequency modulated into the CW and FMCW tone(s). Other methods are also possible. The digital ID is a data sequence that may include a device serial number and may also include properties and status of the device and the object that the device is associated with. The digital ID may include static data and dynamic data.

Similar to what described in the paragraph above, not only active beacons, but also all embodiments of group sensor transmitter apparatus as described hereinabove may further add a time-variant artificial dithering or modulation to the amplitude of the transmitted signal, or phase/frequency modulated into the CW and FMCW tone(s), and the dithering may be based on a low frequency random waveform generated independently in an individual transmitter apparatus, or alternatively based on a digital ID of the individual transmitter apparatus. Other alternative contents are also possible.

If using single tone only in the beacon embodiment of (modified with ) or (modified with ), how can we use FM modulation to detect both speeds and range (distance) in a group radar cluster? One way to achieve this is to alternate over time CW and sawtooth frequency sweep, for example, to use tone frequency that varies as shown in . For an interval T1 the synthesizer generates CW signal, and then for an interval of T2 the frequency stats to ramp at a constant rate of ∆f Hz/second, then jumps back to the CW frequency for another interval T1, and ramp again for an interval of T2 and repeats on. All devices in a cluster are synchronized to repeat the frequency cycle. During a CW interval, Doppler shifts of target beacons are measured, which obtains relative moving speeds between the receiver and each of the target beacons in cluster; during the ramping intervals frequency shifts caused by propagation delay and frequency sweep plus their Doppler shifts are measured for the target beacons, then this measured frequency shifts are deducted by their Doppler shift value individually for each beacon, obtaining the net shifts caused by propagation delay and frequency sweep, their range (distance) can be calculated. Again, in the process, pairs of spectrum lines between the two intervals need to be correctly identified to detect correct amount of Doppler shift. In this process, lines maintaining same magnitude before and after a frequency jump are from a same beacon. If no two lines showing same strength at the moment of frequency jump, there is no ambiguity to find solutions. To reduce chances of ambiguous solutions, similar to the method described in previous paragraph, random (between beacons) low frequency amplitude modulation may be added to beacon transmitting signals (although random over time, maintaining constant for T1 + T2, across the jump points) and if at one frequency jump still there is ambiguity, wait for another cycle to identify again. Drawback of using single tone signal is, the Doppler deducted during ramp actually is from the other time period, if object speed changes quickly during this period, will introduce some error due to the misalignment.

is a flowchart summaries the steps to determine both ranges (distances) and relative speeds of objects using Doppler group sensor system with beacon and both CW and FM signals, as discussed in previous paragraphs. Beginning from step 602; first, from mixing product signals of local CW tone(s) and received/detected signals, at step 604, a group sensor receiver is able to determine a first array containing Doppler shifts for objects detected in the field of view; next, from mixing product signals of local FM swept tone(s) and received/detected signals, at step 606, the receiver is able to determine a second array of frequency shifts for the objects, note however, the array elements for the first array and the second array may not be indexed by corresponding objects; next at step 608, the association of elements in the two arrays need to be identified, for example, using methods described in previous paragraphs, or by other methods, and the array indexes are rearranged to make correct object association between first array and a rearranged second array; at step 610, the (rearranged) second array minus the first array element by element, obtain a third array that contains net frequency shifts caused by propagation delay of objects. From this third array, we can calculate ranges (distances) of objects (step 612), so the first and the third arrays provide both relative speed and distance of detected objects, the task ends at step 614.

With the above describe examples, people of ordinary skill in the art would be able to work out detection methods of objects for other embodiments of CW and/or FMCW Doppler group sensor systems, such as those in , , , , , , , , as well as and , as modified according to or , or , or , with or without beacon, with or without illuminator, with sensor devices being quasi-stationary or moving, mixed device types, etc. Since the use cases are application dependent and there exist a lot of combinations, elaborating all cases is not necessary. Furthermore, detection methods and processing algorithms are not unique, people of ordinary skill in the art would be able to work out variations and proprietary algorithms.

Certain terms are used to refer to particular components. As one skilled in the art will appreciate, people may refer to a component by different names. It is not intended to distinguish between components that differ in name but not in function.

The terms "including" and "comprising" are used in an open-ended fashion, and thus should be interpreted to mean "including, but not limited to". The terms "example" and "exemplary" are used simply to identify instances for illustrative purposes and should not be interpreted as limiting the scope of the invention to the stated instances.

Also, the term "couple" in any form is intended to mean either a direct or indirect connection through other devices and connections.

It should be understood that various modifications can be made to the embodiments described and illustrated herein, without departing from the invention, the scope of which is defined in the appended claims.

Claims (25)

1. A system of Doppler group sensor or sensors for sensing objects, comprising:
   at least one signal transmitter; and
   at least one signal receiver;
   wherein, each of the at least one signal transmitter comprises:
   a first radio receiver, for receiving at least one broadcasted signal and based on said broadcasted signal to generate at least one of a first frequency reference signal and a first timing signal;
   a first signal generator, coupled to the radio receiver, for generating at least one of a first signal and a second signal base on at least one of the first frequency reference signal and the first timing signal;
   a transmitter frontend module, coupled to the first signal generator, for producing a transmitted signal based on one of the first signal, the second signal, or a linear combination of the first and the second signals;
   and wherein, each of the at least one signal receiver comprises:
   a second radio receiver, for receiving the at least one broadcasted signal and based on said broadcasted signal to generate at least one of a second frequency reference signal and a second timing signal;
   a second signal generator, coupled to the second radio receiver, for generating at least one of a third signal and a forth signal base on at least one of the second frequency reference signal and the second timing signal;
   a receiver frontend module, for receiving signals from or associated with objects being sensed, and producing a frontend output signal;
   at least one mixer, each coupled to the second signal generator and the receiver frontend module, for mixing the frontend output signal with one of the third signal, the forth signal, or a linear combination of the third and the forth signals, and producing a mixing product signal for further processing; and
   whereby any two of the first or second signal generators in the system, if exist and active to operate, are operable to generate:
   copies of the first signal and the third signal, if active, substantially identical to each other in frequency at any time of operation; and
   copies of the second signal and the forth signal, if active, substantially identical to each other in instantaneous frequency at any time of operation.
2. The System of Doppler group sensor or sensors of Claim 1, wherein the broadcasted signal is at least one of:
   a Global Navigation Satellite System (GNSS) signal;
   a GPS signal;
   a GLONASS signal;
   a Beidou signal;
   a Galileo signal;
   a standard frequency and time signal service (SFTS) signal;
   a standard frequency and time signal-satellite service (SFTSS) signal;
   a wireless signal that is locked in frequency to a GNSS signal; and
   a wireless signal that is commonly available to all of the first and the second radio receivers in the system.
3. The system of Doppler group sensor or sensors of Claim 1, wherein
   at least one of the first and the second signal generators are shared as one module, and at least one of the first and the third signals, if active, are shared as one signal, and at least one of the second and the forth signals, if active, are shared as one signal; and
   at least one of the first and the second radio receivers are shared as one module, and at least one of the first frequency reference signal and the second frequency reference signal are shared as one signal, and at least one of the first timing signal and the second timing signal, if active, are shared as one signal.
4. The System of Doppler group sensor or sensors of Claim 1, wherein the first signal and the third signal each is at least one of:
   a continuous wave (CW) signal;
   a CW signal that is gated on and off over time; and
   a linear combination of a plurality of CW signals at distinct frequencies.
5. The System of Doppler group sensor or sensors of Claim 1, wherein the second signal and the forth signal each is at least one of:
   a frequency modulated signal;
   a frequency modulated signal that is gated on and off over time; and
   a linear combination of a plurality of frequency modulated signals at distinct frequencies.
6. The system of Doppler group sensor or sensors of Claim 1, wherein each of the at least one signal transmitters, if active, is further operable to produce the transmitted signal with magnitudes thereof based on at least one of :
   a digital ID data sequence of said signal transmitter; and
   a low frequency random waveform, generated independently in said signal transmitter.
7. The system of Doppler group sensor or sensors of Claim 1, wherein said linear combination of the first and the second signals includes linear combination coefficients that are time varying.
8. The system of Doppler group sensor or sensors of Claim 5, wherein the plurality of frequency modulated signals maintain one of the following quantities a constant or constants:
   a difference or differences of instantaneous frequencies between any pair thereof; or
   a ratio or ratios of instantaneous frequencies between any pair thereof.
9. The system of Doppler group sensor or sensors of Claim 1, wherein at least one of the at least one signal transmitter functions as an active beacon transmitter, and is attached to an object for being sensed by said at least one signal receiver physically located away from this instance of active beacon.
10. The system of Doppler group sensor or sensors of Claim 1, wherein at least one of the at least one signal transmitter functions as an illuminator transmitter, and is operable to transmit said transmitted signal towards objects being sensed.
11. The system of Doppler group sensor or sensors of Claim 10, wherein the illuminator transmitter is installed on at least one of:
    a stationary platform; and
    a movable platform.
12. The system of Doppler group sensor or sensors of Claim 1, wherein
    the transmitter frontend module further comprises a module of light source and amplitude modulator, coupled to the first signal generator, for generating a modulated optical signal by amplitude-modulating one of the first signal, the second signal, or a linear combination of the first and the second signals onto an optical carrier signal, and producing the modulated optical signal as the transmitted optical signal; and
    wherein the receiver frontend module further comprises an optical detector, coupled to the at least one mixer, for detecting an amplitude of optical signals received from or associated with objects being sensed, and producing the frontend output signal.
13. The system of Doppler group sensor or sensors of Claim 1, wherein the transmitter frontend module further comprises:
    an amplifier, coupled to the first signal generator, for amplifying the transmitted signal;
    a transmitting antenna, coupled to the amplifier, for transmitting the transmitted signal as radio waves;
    and wherein the receiver frontend module further comprises:
    a receiving antenna, for receiving signals from or associated with objects being sensed;
    a low noise amplifier, coupled to the receiving antenna, for amplifying the signals from the receiving antenna; and
    a filter, coupled with the low noise amplifier and the mixer, for attenuating frequency components outside concerned bandwidth and producing the frontend output signal.
14. The system of Doppler group sensor or sensors of Claim 1, wherein the transmitter frontend module further comprises:
    an amplifier, coupled to the first signal generator, for amplifying the transmitted signal; and
    a transmitting transducer, coupled to the amplifier, for transmitting the transmitted signal as acoustic waves;
    and wherein the receiver frontend module further comprises:
    a receiving transducer, for receiving signals from or associated with objects being sensed;
    a low noise amplifier, coupled to the receiving antenna, for amplifying the signals from the receiving antenna; and
    a filter, coupled with the low noise amplifier and the mixer, for attenuating frequency components outside concerned bandwidth and producing the frontend output signal.
15. A receiver apparatus in a system of Doppler group sensor(s) for sensing objects, comprising:
    a radio receiver, for locking to a broadcasted signal from an antenna, and deriving, from the broadcasted signal, at least one of a frequency reference signal and a timing signal;
    a signal generator, coupled with the radio receiver, for generating, based on the at least one of the frequency reference signal and the timing signal, at least one of a first signal and a second signal;
    a receiver frontend module, for receiving signals associated with objects being sensed, and providing a frontend output signal;
    a least one mixer, coupled with the receiver frontend module and the signal generator, for mixing the frontend output signal with at least one of the first signal, the second signal and a linear combination of the first and the second signals, and producing at least one mixing product signals for further processing; and
    whereby the receiver apparatus is operable to generate and use, at any time of operation, said at least one of the first signal and the second signal substantially identical in instantaneous frequency to a counterpart thereof generated elsewhere in other devices within the system of Doppler group sensor(s).
16. The receiver apparatus of Claim 15 is at least one of:
    a standalone device operable in said system; and
    a functional subsystem in a device of combined functions in said system.
17. The receiver frontend module of Claim 15 further includes a least one of:
    a receiving antenna, for receiving radio signals from, or associated with objects being sensed;
    a receiving transducer, for receiving acoustic signals from, or associated with objects being sensed;
    a photodetector, for detecting an amplitude of optical signals from, or associated with objects being sensed;
    an amplifier, coupled to one of the receiving antenna, receiving transducer, or the photodetector, for amplifying signals provided by one of the receiving antenna, receiving transducer, or the photodetector; and
    a filter, coupled to the amplifier, for attenuating unwanted frequency components in signals provided to said filter.
18. The receiver apparatus of Claim 15 further includes a least one of:
    at least one second filter, coupled with the at least one mixer, for selectively blocking frequency components outside bandwidth of application concerns;
    at least one second amplifier, coupled with the at least one mixer, for amplifying signals in baseband;
    at least one analog to digital converter, coupled with the at least one second amplifier and the at least one second filter, for digitizing signals in baseband channel; and
    a digital signal processer, coupled to the analog to digital converter, for processing the baseband signal and obtaining wanted sensing results.
19. A transmitter apparatus in a system of Doppler group sensor(s), comprising:
    a radio receiver, for locking to a broadcasted signal from an antenna, and deriving, from the broadcasted signal, at least one of a frequency reference signal and a timing signal;
    a signal generator, coupled with the radio receiver, for generating, based on the at least one of the frequency reference signal and the timing signal, at least one of a first signal and a second signal;
    a transmitter frontend module, coupled with the signal generator, for generating a transmitted signal based on at least one of the first signal and the second signal, and sending said transmitted signal as waves into propagation media;
    whereby the transmitter apparatus is operable to generate and use, at any time of operation, said at least one of the first signal and the second signal substantially identical in instantaneous frequency with a counterpart thereof generated elsewhere in other devices within the system of Doppler group sensor(s).
20. The transmitter apparatus of Claim 19 is at least one of:
    a standalone device operable in said system; and
    a functional subsystem in a device of combined functions in said system.
21. The transmitter apparatus of Claim 19 is at least one of
    an active beacon apparatus operable in said system and attached to an object being sensed by said system; and
    an illuminator apparatus operable in said system.
22. The illuminator apparatus of Claim 21 is installed on at least one of
    a stationary platform; and
    a movable platform.
23. The transmitter frontend module of Claim 19 further includes at least one of
    a signal power amplifier, coupled to the signal generator, for amplifying the transmitted signal and producing an amplified transmitted signal;
    a transmitting antenna, coupled to the signal power amplifier or the signal generator, for sending the transmitted signal or the amplified transmitted signal as radio waves to propagation media;
    a transmitting transducer, coupled to the signal power amplifier or the signal generator, for sending the transmitted signal or the amplified transmitted signal as acoustic waves to propagation media;
    a light source and amplitude modulator module, coupled with the signal generator, for modulating an amplitude of a light signal using a modulating signal based on at least one of said first signal and second signal, and producing an optical transmitted signal;
    an optical power amplifier, coupled with the light source and amplitude modulator module, for amplifying the optical transmitted signal and producing an amplified optical transmitted signal; and
    a module of optics, for facilitating transmitting the optical transmitted signal or the amplified optical transmitted signal into light wave propagation media.
24. The transmitter apparatus of Claim 19 is further operable to generate the transmitted signal, if active, with magnitudes thereof based on at least one of:
    a digital ID data sequence of said transmitter apparatus; and
    a low frequency random waveform generated independently in said transmitter apparatus.
25. A method of determining at least one of relative speeds and ranges (distances) of beacon-attached objects in a Doppler group sensor system, comprising steps, performed in a signal receiver, of:
    determining, from CW signal components in the signals from the beacons, Doppler shifts;
    determining, from FM swept signal components in the signals from the beacons, frequency shifts;
    identifying, based on magnitude correlation, object association between the Doppler shifts and the frequency shifts;
    determining, by deducting the Doppler shift results from the frequency shift results, net frequency shifts caused by wave propagation delay;
    calculating, based on the net frequency shifts caused by wave propagation delay, the ranges of the beacon-attached objects; and
    calculating, based on the Doppler shifts, the relative speeds of the beacon-attached objects;
    wherein, the signal receiver and the beacons are substantially synchronized apparatuses in instantaneous frequency of the CW signal component and the FM swept signal component in the Doppler group sensor system.

Images