GB2608640A - Radar apparatus - Google Patents

Radar apparatus Download PDF

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Publication number
GB2608640A
GB2608640A GB2109907.2A GB202109907A GB2608640A GB 2608640 A GB2608640 A GB 2608640A GB 202109907 A GB202109907 A GB 202109907A GB 2608640 A GB2608640 A GB 2608640A
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GB
United Kingdom
Prior art keywords
signal
signals
radar apparatus
modulated
waveform
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Pending
Application number
GB2109907.2A
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GB202109907D0 (en
Inventor
Harris Andrew
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
AGD Systems Ltd
Original Assignee
AGD Systems Ltd
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by AGD Systems Ltd filed Critical AGD Systems Ltd
Priority to GB2109907.2A priority Critical patent/GB2608640A/en
Publication of GB202109907D0 publication Critical patent/GB202109907D0/en
Publication of GB2608640A publication Critical patent/GB2608640A/en
Pending legal-status Critical Current

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Classifications

    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S7/00—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00
    • G01S7/02—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S13/00
    • G01S7/40—Means for monitoring or calibrating
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S13/00—Systems using the reflection or reradiation of radio waves, e.g. radar systems; Analogous systems using reflection or reradiation of waves whose nature or wavelength is irrelevant or unspecified
    • G01S13/02—Systems using reflection of radio waves, e.g. primary radar systems; Analogous systems
    • G01S13/06—Systems determining position data of a target
    • G01S13/08—Systems for measuring distance only
    • G01S13/32—Systems for measuring distance only using transmission of continuous waves, whether amplitude-, frequency-, or phase-modulated, or unmodulated
    • G01S13/34—Systems for measuring distance only using transmission of continuous waves, whether amplitude-, frequency-, or phase-modulated, or unmodulated using transmission of continuous, frequency-modulated waves while heterodyning the received signal, or a signal derived therefrom, with a locally-generated signal related to the contemporaneously transmitted signal
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S13/00—Systems using the reflection or reradiation of radio waves, e.g. radar systems; Analogous systems using reflection or reradiation of waves whose nature or wavelength is irrelevant or unspecified
    • G01S13/02—Systems using reflection of radio waves, e.g. primary radar systems; Analogous systems
    • G01S13/06—Systems determining position data of a target
    • G01S13/08—Systems for measuring distance only
    • G01S13/32—Systems for measuring distance only using transmission of continuous waves, whether amplitude-, frequency-, or phase-modulated, or unmodulated
    • G01S13/34—Systems for measuring distance only using transmission of continuous waves, whether amplitude-, frequency-, or phase-modulated, or unmodulated using transmission of continuous, frequency-modulated waves while heterodyning the received signal, or a signal derived therefrom, with a locally-generated signal related to the contemporaneously transmitted signal
    • G01S13/343—Systems for measuring distance only using transmission of continuous waves, whether amplitude-, frequency-, or phase-modulated, or unmodulated using transmission of continuous, frequency-modulated waves while heterodyning the received signal, or a signal derived therefrom, with a locally-generated signal related to the contemporaneously transmitted signal using sawtooth modulation
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S13/00—Systems using the reflection or reradiation of radio waves, e.g. radar systems; Analogous systems using reflection or reradiation of waves whose nature or wavelength is irrelevant or unspecified
    • G01S13/02—Systems using reflection of radio waves, e.g. primary radar systems; Analogous systems
    • G01S13/50—Systems of measurement based on relative movement of target
    • G01S13/58—Velocity or trajectory determination systems; Sense-of-movement determination systems
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S13/00—Systems using the reflection or reradiation of radio waves, e.g. radar systems; Analogous systems using reflection or reradiation of waves whose nature or wavelength is irrelevant or unspecified
    • G01S13/02—Systems using reflection of radio waves, e.g. primary radar systems; Analogous systems
    • G01S13/50—Systems of measurement based on relative movement of target
    • G01S13/58—Velocity or trajectory determination systems; Sense-of-movement determination systems
    • G01S13/583—Velocity or trajectory determination systems; Sense-of-movement determination systems using transmission of continuous unmodulated waves, amplitude-, frequency-, or phase-modulated waves and based upon the Doppler effect resulting from movement of targets
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S13/00—Systems using the reflection or reradiation of radio waves, e.g. radar systems; Analogous systems using reflection or reradiation of waves whose nature or wavelength is irrelevant or unspecified
    • G01S13/88—Radar or analogous systems specially adapted for specific applications
    • G01S13/91—Radar or analogous systems specially adapted for specific applications for traffic control

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  • Engineering & Computer Science (AREA)
  • Radar, Positioning & Navigation (AREA)
  • Remote Sensing (AREA)
  • Physics & Mathematics (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • General Physics & Mathematics (AREA)
  • Electromagnetism (AREA)
  • Radar Systems Or Details Thereof (AREA)

Abstract

A frequency modulated continuous wave (FM-CW) radar apparatus, the FM-CW radar apparatus comprising: a signal generator 105 that is configured to generate a waveform signal as an output, the frequency of the waveform being modulated using an asymmetric triangular waveform; a transmitter 101 which is operable to transmit the modulated waveform signal; a receiver which is operable to receive a receive signals corresponding to at least a portion of the transmitted modulated signal that has been reflected from an object; and a processing circuit configured to sample received I and Q signals using an analogue to digital converter and then process the digitised I 112 and Q 114 signals by a cross-correlation function to determine the presence of the modulated signal. The signal generator preferably comprises an asymmetric triangular waveform generator circuit. The arrangement preferably generates a fault signal when the absence of the modulated signal in both the I and Q signals is detected.

Description

RADAR APPARATUS
This invention relates to radar apparatus and in particular to fault detection within radar apparatus.
In many traffic applications it is known to use a traffic monitoring radar. Such applications include speed warning signs, traffic data collection and temporary traffic lights. Traffic applications may include the detection of road going vehicles, trains and or pedestrians, for example.
A basic radar apparatus comprises a transmitter for emitting radio frequency (RF) waves, and a receiver for receiving a reflected portion of the emitted waves. The transmitter comprises an electronic circuit known as a modulator that creates the voltage waveforms, and an antenna. The receiver comprises an antenna -which could I5 be shared with the transmitter -and a demodulator.
There arc many different types of radar apparatus, and in a simple form a value such as the distance to the reflective target, known as the range, can be calculated by the demodulator from the elapsed time between emitting the RF wave and receiving the reflected portion of the RF wave. If the object is moving relative to the radar apparatus there will be a difference in frequency between the emitted wave and the received wave due to the well-known Doppler Effect which may also be calculated by the receiver of the apparatus. This data can then be used to determine the operation of a device such as a speed warning sign or traffic lights.
The emitted RF wave generated by the modulator may comprise a short pulse or may be a continuous wave (CW). A type of CW radar apparatus is the frequency modulated continuous wave (FM-CW) radar apparatus in which the frequency of the emitted RF waveform is modulated, typically using a repeating asymmetric triangular waveform.
An example of a typical waveform is shown in Figure 1 of the drawings. The signal comprises a linear ramp portion 10 that varies from a minimum frequency to a maximum frequency, with a rapid flyback 20 at the end before the ramp is repeated.
In traffic detector applications it is important to know that the monitoring apparatus has not developed a fault and that it maintains the ability to detect traffic at all times.
US9910135B2 describes a technique of performing a radar self-test function by injecting a 'known target' into the transmission periodically. As such, there may be substantial time periods where a fault is present but unknown.
Whilst it is relatively straight forward to monitor the transmitter stage, because it is under the control of the radar, it is more of a challenge to know that the receiver stage is working correctly. Many existing traffic detectors simply monitor the time since the last detection of a target, where the target may be a train, vehicle or pedestrian for example, and indicate a fault if a period of time has elapsed without detecting a target.
There are problems associated with this approach in that it relies on knowledge of expected traffic levels. More significantly, in the event of a receiver fault occurring before the timcout has expired then there is a period of time when the radar is not able to detect traffic or determine that a fault exists. I5
It would therefore be beneficial to provide a radar apparatus that is operable to overcome or at least mitigate the disadvantages disclosed herein above According to a first aspect there is provided a frequency modulated continuous wave (FM-CW) radar apparatus, the FM-CW radar apparatus comprising: a signal generator that is configured to generate a waveform signal as an output, the frequency of the waveform being modulated using an asymmetric triangular waveform; a transmitter which is operable to transmit the modulated waveform signal; a receiver which is operable to receive a receive signals corresponding to at least a portion of the transmitted modulated signal that has been reflected from an object; and a processing circuit configured to sample received I and Q signals using an analogue to digital converter and then process the digitised I and Q signals by a cross-correlation function to determine the presence of the modulated signal.
The FM-CW radar apparatus of the first aspect advantageously provides an apparatus operable to continually monitor the health of the radar and its ability to detect traffic at all times.
The signal generator may comprise an asymmetric triangular waveform generator circuit. The frequency of the waveform may be modulated by a modulator comprising the asymmetric triangular waveform generator circuit configured to produce a modulated signal.
The received I and Q signals may be monitored substantially continually for the presence of the modulated signal. The modulated signal may be present in the down-converted I and Q signals, even in the absence of a target, as a result of a number of factors including mixer breakthrough, transmit/receive antenna coupling and close to radar stationary objects reflecting the transmitted signal back to the radar. The absence of the modulated signal in both the I and Q signals may indicate a fault.
In this way, the FM-CW radar apparatus may advantageously provide a means for continuously monitoring the health of the radar receiver, even in the absence of a target. As such, faults within the receiver stage may be detected immediately without requiring monitoring the time since the last detection of a target and indicating a fault only if a period of time has elapsed without detecting a target.
The FM-CW radar apparatus may be configured to generate a fault signal indicating a fault when the absence of the modulated signal in both the I and Q signals is detected.
The FM-CW radar apparatus may be configured to generate a fault signal indicating a fault when the absence of the modulated signal in both the I and Q signals is detected on at least two occasions.
The FM-CW radar apparatus may therefore be operable to indicate a fault to the rest of the system as soon as a fault occurs. The radar apparatus may be configured to output a fault signal suitable for feeding to an input of a graphical user interface or other device. In this way, a user may be alerted to the presence of a fault.
The cross-correlation function may compare separately the received digital I and Q signals with an asymmetric triangular waveform that is biased to have an average value of zero. If the received I and Q data comprises a perfectly flat signal, then when this is cross correlated with the asymmetric triangular waveform that is biased to have an average value of zero the output cross correlation product will be zero. As such, a DC level would give a ramp factor tending towards zero.
The cross correlation product value may be used to determine the presence of the modulated signal and hence the health of the receiver stage of the radar. An output cross correlation product of zero resulting from the comparison of the received digital I and Q signals may indicate the absence of the modulated signal. This may indicate a fault in the receiver stage and the processing circuit may then generate a fault signal.
Each of the transmitter and receiver may be associated with a respective antenna.
Alternatively the transmitter and receiver may share a common antenna with signals being routed by a circulator.
The processing circuit may also be configured to calculate the speed and/or range of a target object using reflected transmitted signals. In some embodiments, the FM-CW radar apparatus may comprise an additional processing circuit configured to calculate the speed and/or range of a target object using reflected transmitted signals. The FMCW radar apparatus may be configured to calculate the direction of movement of the target object. The target object may comprise a train, a vehicle or a pedestrian, for
example.
The processing circuit may detect the speed and/or direction of movement of the target using Doppler processing on the received signals. The return signals reflected from a moving target object will be frequency shifted in proportion to their speed and the direction of travel can be determined by the frequency shift. The processing circuit may operate warning signs or traffic lights dependent on the detected speed and/or direction of movement of the target object. The radar apparatus may use a frequency modulated continuous wave technique to measure the speed and range of a target.
The radar apparatus may be portable and may include a battery power source. The battery may comprise a rechargeable battery and may be recharged from a portable wind turbine or a portable solar panel or solar array.
The apparatus may include a user operable input. The apparatus may include a screen and the input may comprise a graphical user interface, GUI.
There will now be described by way of example only one embodiment of the present invention with reference to and as illustrated in the accompanying drawings of which: Figure 1 is a plot of a typical repeating asymmetric triangular waveform against time; Figure 2 is a block diagram of an embodiment of a FM-CW radar apparatus in accordance with the present invention; Figure 3 is an example asymmetric triangular waveform that is biased to have an average value of zero; Figure 4a is an example of data captured for an I-clutter; Figure 4b is a calculated cross correlation product resulting from the data of Figure 4a: Figure 5a is an example of data captured for an 1-clutter without a modulated signal; and Figure 5b is a calculated cross correlation product resulting from the data of Figure 5a.
Figure 2 is a block diagram of an embodiment of a FM-CW radar apparatus 100 in accordance with the present invention.
A transmit antenna 101 is driven by a voltage controlled oscillator, VCO, 105 whose modulating input is connected to the output of an asymmetric waveform generator (not shown). The asymmetric waveform generator generates an asymmetric triangular waveform in order that the VCO 105 produces a frequency ramped waveform as used in many frequency modulated continuous wave, FMCW, radars. The asymmetric waveform generator generates an asymmetric triangular waveform that is biased to have an average value of zero. The VCO 105 also has an enable line that is used to enable or disable the oscillator. The VCO 105 also feeds a signal to a mixer 110 that is replica of the signal fed to the transmit antenna 101. This signal is used to down convert the received radar return signals from the receive antenna 102 to 1 and Q baseband signals using the mixer 110. These baseband signals are typically filtered and then amplified by amplifiers and then converted to the digital domain using analogue to digital converters, ADC. The digitized 1 112 and Q 114 signals are then suitable for further digital signal processing by the processing circuit 108. The ADC may form part of the processing circuit 108.
The processing circuit 108 is configured to sample the received 1 112 and Q 114 signals using an ADC and then process the digitised I 112 and Q 114 signals by a cross-correlation function to determine the presence of the modulated signal in the received 1 112 and Q 114 signals. The cross-correlation function is described in more details in Figures 3 to 5.
The received 1 112 and Q 114 signals are monitored substantially continually by the processing circuit 108 for the presence of the modulated signal. The modulated signal may be present substantially continuously in the down-converted I 112 and Q 114 signals, even in the absence of a target, as a result of a number of factors including mixer breakthrough, transmit/receive antenna coupling and close to radar stationary objects reflecting the transmitted signal back to the radar.
The absence of the modulated signal in both the 1112 and Q 114 signals may indicate a fault. The FM-CW radar apparatus 100 is configured to generate a fault signal indicating a fault when the absence of the modulated signal in both the 1 112 and Q 114 signals is detected. The FM-CW radar apparatus 100 is therefore operable to indicate a fault to the rest of the system as soon as a fault occurs.
Figure 3 shows an example modulation waveform that is biased to have an average value of zero where the modulation waveform is an asymmetric triangular waveform 200. The processing circuit 108 uses the cross-correlation function by comparing separately the received digital 1 112 and Q 114 signals with the asymmetric triangular waveform 200 that is biased to have an average value of zero. The cross correlation product value can then be used to determine the presence of the modulated signal and hence the health of the receiver stage of the radar apparatus 100.
Figure 4a is an example of data captured for an 1-clutter 300 and Figure 4b is a calculated cross correlation product 400 resulting from the data of Figure 4a. Figures 4a and 4b show an example in a case whore the receiver stage is not experiencing a fault. The samples are taken from the middle of the ramp in order to avoid any flyback voltage at either end.
Figure 5a is an example of data captured for an I-clutter 500 without a modulated signal and Figure 5b is a calculated cross correlation product 600 resulting from the data of Figure 5a. Figures 5a and 5b show an example in a case where the receiver stage is experiencing a fault. The samples are taken from the middle of the ramp in order to avoid any flyback voltage at either end. A fault condition exits if the modulated signal is not present in both the I and Q clutter signal. The FM-CW radar apparatus 100 is configured to generate a fault signal indicating a fault when the absence of the modulated signal in both the I and Q signals is detected.

Claims (7)

  1. CLAIMS1. A frequency modulated continuous wave (FM-CW) radar apparatus, the FM-CW radar apparatus comprising: a signal generator that is configured to generate a waveform signal as an output, the frequency of the waveform being modulated using an asymmetric triangular waveform; a transmitter which is operable to transmit the modulated waveform signal; a receiver which is operable to receive a receive signals corresponding to at least a portion of the transmitted modulated signal that has been reflected from an object; and a processing circuit configured to sample received I and Q signals using an analogue to digital converter and then process the digitised 1 and Q signals by a cross-correlation function to determine the presence of the modulated signal.
  2. 2. A FM-CW radar apparatus as claimed in claim 1 wherein the signal generator comprises an asymmetric triangular waveform generator circuit.
  3. 3. A FM-CW radar apparatus as claimed in claim 1 or claim 2 wherein the received 1 and Q signals are monitored substantially continually for the presence of the modulated signal.
  4. 4. The FM-CW radar apparatus as claimed in any preceding claim configured to generate a fault signal indicating a fault when the absence of the modulated signal in both the i and Q signals is detected.
  5. 5. The FM-CW radar apparatus as claimed in any preceding claim configured to generate a fault signal indicating a fault when the absence of the modulated signal in both the 1 and Q signals is detected on at least two occasions.
  6. 6. The FM-CW radar apparatus as claimed in any preceding claim configured to output a fault signal suitable for feeding to an input of a graphical user interface or other device.
  7. 7. The FM-CW radar apparatus as claimed in any preceding claim wherein the cross-correlation function may compare separately the received digital I and Q signals with an asymmetric triangular waveform that is biased to have an average value of zero.
GB2109907.2A 2021-07-09 2021-07-09 Radar apparatus Pending GB2608640A (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
GB2109907.2A GB2608640A (en) 2021-07-09 2021-07-09 Radar apparatus

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
GB2109907.2A GB2608640A (en) 2021-07-09 2021-07-09 Radar apparatus

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GB202109907D0 GB202109907D0 (en) 2021-08-25
GB2608640A true GB2608640A (en) 2023-01-11

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Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20180038943A1 (en) * 2016-08-05 2018-02-08 Texas Instruments Incorporated Failure Detection in a Radar System
US9910135B2 (en) 2013-01-15 2018-03-06 Autoliv Development Ab FMCW radar self-test
WO2020016879A1 (en) * 2018-07-19 2020-01-23 Arbe Robotics Ltd. Apparatus and method of rf built in self-test (rfbist) in a radar system

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US9910135B2 (en) 2013-01-15 2018-03-06 Autoliv Development Ab FMCW radar self-test
US20180038943A1 (en) * 2016-08-05 2018-02-08 Texas Instruments Incorporated Failure Detection in a Radar System
WO2020016879A1 (en) * 2018-07-19 2020-01-23 Arbe Robotics Ltd. Apparatus and method of rf built in self-test (rfbist) in a radar system

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