MULTIMODAL RADAR SYSTEM

• US 20180031689A1
• Filed: 02/04/2016
• Published: 02/01/2018
• Est. Priority Date: 02/04/2015
• Status: Active Grant

• Current Assignee: ARTsys360, Ltd.
• Original Assignee: ARTsys360, Ltd.
• Inventors: BEN-ARI, Erez
• Granted Patent: US 10,809,366 B2
• Time in Patent Office: Days
• CPC Class Codes: G01S 13/4454 phase comparisons monopulse, i.e. comparing the echo signals received by an interferometric antenna arrangement
• CPC Class Codes: H01Q 13/04 Biconical horns biconical dipoles comprising two conical surfaces having collinear axes and adjacent apices and fed by a two-conductor transmission line H01Q9/28
• CPC Class Codes: H01Q 21/205 providing an omnidirectional coverage turnstile aerials H01Q21/26

Abstract

A radar system and method for determining location of targets, wherein the energy reflected from an object is received by the omnidirectional antenna elements and the received RF signal is downconverted to an intermediate frequency (IF) signal. The IF signals are digitized. The digitized IF signals received at the first omnidirectional antenna are digitally processed so as to form modal beams with opposite phase slope as output signals. The digitized IF signal received at the second omnidirectional antenna is digitally processed as to form a reference signal of phase reference. Phase differences between the signals and the reference signals are determined, such that each phase difference includes a first component proportional to the azimuth of the arriving signal and a second component corresponding to the elevation of the arriving signal, from which the azimuth and the elevation of the arriving signal can be extracted.

Claims

1. A radar system for inferring direction-of-arrival (DOA) of reflected signals covering 360°

azimuth within a predefined range of elevations below and above the horizon to detect, identify and track a target by incorporating multimodal and interferometer direction-finding (DF) techniques, the radar system comprising;

an antenna system for transmitting and receiving radio frequency (RF) signals, the antenna system comprising;

a plurality of antenna elements configured so as to transmit and receive radio frequency (RF) signals;

a plurality of receiving and/or transmitting (Rx/Tx) modules connected to respective ones of the plurality of antenna elements to transmit and receive the RF signals to and from the plurality of antenna elements;

a digital signal processing unit (DSPC) operably connected to the plurality of Rx/Tx modules and configured and operable to process received RF signals to infer the direction-of-arrival (DOA) of reflected signals covering 360°

azimuth within the predefined range of elevations below and above the horizon to detect, identify and track the target; and

an exciter module operably connected to the DSPC and configured and operable to generate and distribute timing signals to the DSPC, the Rx/Tx modules and the plurality of antenna elements.

2. The radar system according to claim 1, wherein each of the Rx/Tx modules is operatively and directly connected to the respective one of the plurality of antenna elements.

3. The radar system according to claim 1, wherein the Rx/Tx module allows excitation of microwave signals resulting in radiated energy at 0°

-360°

azimuthal direction.

4. The radar system according to claim 1, wherein the Rx/Tx modules further convert a received RF signal into an intermediate frequency (IF) signal, by mixing the received RF signal with a local oscillator (LO) signal.

5. The radar system according to claim 1, wherein the DSPC is configured and operable to process the intermediate frequency (IF) signal so as to infer the azimuth and elevation of an incoming RF signal.

6. The radar system according to claim 1, wherein the plurality of antenna elements comprises:

a first omnidirectional antenna; and

a second omnidirectional antenna, which is located coaxially about a predefined vertical axis in relation to the first omnidirectional antenna and separated therefrom at a predefined vertical distance.

7. The radar system according to claim 1, further comprising analog-to-digital converters located on the DSPC or on the Rx/Tx modules.

8. The radar system according to claim 1, wherein each of the Rx/Tx modules comprises:

an RF circulator connected to receive an RF signal from a corresponding one of the antenna elements and a Tx signal excited at a Tx input port of the Rx/Tx module and filtered by an RF Tx filter and output the received RF signal and the filtered Tx signal;

an RF amplifier connected to the first RF filter to amplify the received RF signal;

an RF-to-IF mixer connected to the RF amplifier to downconvert the received RF signal into an intermediate frequency (IF) signal by mixing the received RF signal with a local oscillator (LO) signal;

an IF filter connected to an output of the RF-to-IF mixer to filter the IF signal; and

an IF amplifier connected to the IF filter to receive the filtered IF signal and output an amplified IF signal.

9. The radar system according to claim 1, wherein the DSPC comprises:

a plurality of analog-to-digital converters (ADCs), each one connected to receive an IF signal from a corresponding one of the Rx/Tx modules to convert an analog RF signal received from a corresponding one of the antenna elements to a digital signal;

a programmable logic component field-programmable gate array (FPGA) connected to an output of the ADCs for receiving digital signals from the ADCs and multiply each digital signal received from the first omnidirectional antenna by an appropriate complex weight to digitally obtain model beams with a desired order and phase slope, wherein the digital signal received from the second omnidirectional antenna is time-delayed to compensate for time consumed by multiplication of the digitized IF signal received by the first omnidirectional antenna and transform the digitized IF signal received by the second omnidirectional antenna into a reference signal;

a digital-signal-processor (DSP) connected to the FPGA to receive the output signals of the desired modal order and phase slopes and the output reference signal for further processing; and

a microcontroller connected to the FPGA and the DSP to monitor voltages and temperature of the DSPC.

10. The radar system according to claim 1, wherein the exciter module is further configured and operable to generate and distribute local oscillator (LO) signals and/or transmission signals (Tx).

11. The radar system according to claim 10, wherein the exciter module comprises a distribution mechanism configured to distribute the LO signals to the Rx/Tx modules.

12. The radar system according to claim 1, wherein the exciter module comprises:

a master oscillator that generates clock signals;

an RF Tx filter;

a Tx chain synthesizer module having an output connected to the RF Tx filter to filter any unwanted signals that are present at the output of the Tx chain synthesizer module and output a filtered signal;

an LO chain synthesizer module;

a clock distributor module connected to the master oscillator and configured to distribute the clock signals to the antenna elements, the Rx/Tx modules, the DSPC, the Tx chain synthesizer module and the LO chain synthesizer module;

an RF Tx power divider having output ports each connected directly to a respective one of the Rx/Tx modules; and

an RF amplifier connected to an output of the RF Tx filter to amplify the filtered signal from the RF Tx filter to output an amplified signal, and direct the amplified signal toward an RF Tx power divider.

13. The radar system according to claim 1, wherein the one or more antenna elements comprises a first omnidirectional antenna configured to form a circular array.

14. The radar system according to claim 1, wherein the one or more antenna systems is configured for estimation of the direction-of-arrival (DOA) of a signal that arrives from the horizon within an azimuth of from 0°

to 360° and

a range of from −

45°

to 45°

elevation below and above the horizon, respectively.

15. The radar system according to claim 1, wherein the plurality of antenna elements comprises:

a first omnidirectional antenna; and

a second omnidirectional antenna, which is located coaxially about a predefined vertical axis in relation to the first omnidirectional antenna and separated therefrom at a predefined vertical distance;

wherein;

the first omnidirectional antenna is configured and operable to receive an arriving signal and transform the received signal into a plurality of output signals that are processed in the DSPC to generate at least two signals;

a first signal and a second signal with opposite phase slope wherein the phases of the first and second signals are proportional to an azimuth angle of the arriving signal;

the second omnidirectional antenna is configured and operable to receive an arriving signal and transform the received signal into a reference signal of a reference phase, the reference phase has a zero phase-slope and is independent of an azimuth angle of the arriving signal;

the phases of first and second signals are shifted from the reference phase by a phase shift that depends upon an elevation direction of the arriving signal, corresponding to the distance between the first and second omnidirectional antennas;

the antenna system is configured and operable to calculate at least two phase differences;

a first phase difference Δ

₁ between the phase of the first signal and the reference phase, and a second phase difference Δ

₂ between the phase of the second signal and the reference phase,

each one of the phase difference includes a first phase component proportional to the azimuth angle of the arriving signal and a second phase component corresponding to the elevation angle of the arriving signal, and

the DSPC is further configured and operable to determine the azimuth and the elevation angles of the arriving signal from the phase differences.

16. The radar system according to claim 15, wherein the first omnidirectional antenna element is connected to a circular waveguide (CWG).

17. The radar system according to claim 16, wherein the circular waveguide (CWG) is configured to guide a TE₁₁ and TE₂₁ or higher-order circular-waveguide-modes received from the first omnidirectional antenna element, and is of a diameter sufficient to allow propagation of the higher order circular-waveguide-modes.

18. The radar system according to claim 16, wherein the CWG comprises a plurality of output feeds.

19. The radar system according to claim 15, wherein the first omnidirectional antenna element is a multimodal omnidirectional antenna element comprising a biconical horn antenna.

The

20. The radar system according to claim 6,

wherein the second omnidirectional antenna element is a biconical dipole antenna element.

21. The radar system according to claim 6, wherein the second omnidirectional antenna element is coaxially located above the first omnidirectional antenna, and a feed line is coaxially inserted through a waveguide portion of the first omnidirectional antenna.

22. The radar system according to claim 1, wherein the antenna system is configured to output a plurality of output signals, digitally processed so as to generate a plurality of phase modes.

23. The radar system according to claim 1, wherein the antenna system is configured to estimate the DOA of a wireless RF signal.

24. The radar system according to claim 1, wherein each of the Rx/Tx modules allows excitation of microwave signals in each respective antenna element, alone or simultaneously with any other Rx/Tx modules thereby excite several antenna elements so as to steer the radiated energy into one or several predefined directions.

25. A method for special detection, identification and tracking of one or more objects or targets comprising operating the radar system as defined in claim 1.

26. A method for detection, identification and tracking of one or more objects or targets comprising:

transmitting a radio frequency (RF) signal through a feed of a first omnidirectional antenna or a second omnidirectional antenna;

receiving, at a first omnidirectional antenna arriving RF signal reflected off an object;

converting the received signal into a digital intermediate frequency (IF) signal;

multiplying, in a digital signal processing card (DSPC), the digitized IF signal from the first omnidirectional antenna with complex weights and sum together to generate a first signal and a second signal with opposite phase slope wherein the phases of the first and second signals are proportional to an azimuth angle of the arriving signal;

receiving the arriving signal at the second omnidirectional antenna;

converting the arriving signal into a digital reference signal of a reference phase, the reference phase having a zero phase-slope and being independent of the azimuth angle of the arriving signal;

shifting the phases of first and second signals from the reference phase by a phase shift that depends upon an elevation direction of the arriving signal, corresponding to the distance between the first and second omnidirectional antennas;

calculating at least two phase differences comprising a first phase difference Δ

₁ between the phase of the first signal and the reference phase, and a second phase difference Δ

₂ between the phase of the second signal and the reference phase, wherein each one of the phase difference includes a first phase component proportional to the azimuth angle of the arriving signal and a second phase component corresponding to the elevation angle of the arriving signal, and

calculating the azimuth and the elevation angles of the arriving signal from the phase differences.

27. The method according to claim 26, wherein the step of multiplying further comprises summing the complex weighted signals to form a third signal with a +2 phase slope;

wherein the step of calculating at least two phase differences further comprises extracting a third phase difference between the third signal and the reference phase, and

wherein the first, second and third phase difference are used to calculate first-order and second-order elevation contributions.