TWI586987B - Signal processing device for continuous wave radar sensing system - Google Patents

Description

Signal processing device for continuous wave radar sensing system

The present invention relates to a signal processing device for a continuous wave radar sensing system, and more particularly to a signal processing device using an interlaced continuous wave radar sensing system.

Today's radar systems are widely used, typically for tracking or searching for targets. In order to improve the accuracy of the radar tracking target and reduce the error to improve the accuracy of the radar device, both the academic community and the industry continue to improve the accuracy of the radar device. The radar device is generally divided into "Pulsed Radar". And "Continuous-Wave Radar". Continuous wave radar can be further classified into "FMCW Radar" and "Doppler Radar".

The scanning waveform of the conventional FMCW radar is usually a low-frequency scanning wave type. The FMCW radar uses low power and has low emission peak power, which can avoid the danger of personnel suffering from microwave radiation, but the FMCW only processes the radar echo of one scan, although the signal processing It is relatively simple. The detection distance for small targets has the following disadvantages: the FMCW transmission scan time (Ts) must be lengthened to improve the received signal-to-noise ratio, and the moving target indication (Moving Target Indication, MTI) is added in the presence of clutter. The filter filters out stationary clutter and improves the detection of moving targets. However, if the scan time is too long, that is, the Pulse Repetition Frequency (PRF), then The clear region of the MTI band-pass filter becomes very narrow, so that when the target speed is slightly larger, the situation of the Buhler folding becomes very serious, and the target is easily MTI together with the clutter. Filtered out. Therefore, low PRF (~200Hz or less) is suitable for slow target detection, but it is not suitable for detection of higher speed targets. For higher speed target detection, a higher PRF (~2 kHz) must be used. However, high PRF also has its limitations. When the PRF is high, the Ts is short, which makes the signal-to-noise ratio of the single scan insufficient. In order to improve the signal-to-noise ratio, multiple scans must be used, and the Fast Fourier Transform (FFT) integral is added to increase Coherent gain, this method is called FMCW Doppler processing, which can simultaneously achieve the target distance and speed. Although high-frequency scanning waveforms can be used for fast target detection, low-speed targets are easily filtered by MTI, and cannot be considered at the same time for different targets with a wide range of speeds.

In the face of the environment from traditional and asymmetric threats, the detection of small targets has become the overall strategy of the search radar. Small target detection performance is still required in extreme environments and harsh climates. On land radar, Sub Clutter Visibility is an important parameter in ground clutter. In the case of radar at sea, motion compensation for mobile radar platforms must be increased. For the above reasons, the challenge of the security radar is that it usually operates in a strong and complex clutter environment to detect slow small targets. Therefore, in addition to having superior receiving sensitivity, the safety radar needs to have good targets and clutter identification capabilities.

The detection of slow small targets by low-power FMCW radars often faces the following challenges. The Radar Cross-Section (RCS) of small targets is usually less than 1 m ² , even 0.1 m ² , and the need for detection distance is a major challenge for low-power radars. The environment in which radar works, whether on land or at sea, the intensity of background clutter often far exceeds the RCS of small targets. It is especially difficult to detect low-speed small targets, so how to improve the target visibility of radar under clutter ( Sub Clutter Visibility) is another challenge.

This invention proposes a signal processing device for a continuous wave radar sensing system, which can improve the distance resolution, improve the signal-to-noise ratio, increase the detection distance, directly obtain the target speed, and improve the detection when the target speed range is very wide. Rate to improve the shortcomings of conventional techniques.

This paper proposes a signal processing device for a continuous wave radar sensing system. In the beam dwell time, the low PRF and high PRF mode cross scanning modes are used to obtain the best small target detection.

The present invention provides a signal processing device for a continuous wave radar sensing system, comprising: a transmitting unit comprising: a frequency sweep controller and a local oscillator, wherein the frequency sweep controller controls the local oscillator to generate a first frequency conversion signal and a a second frequency conversion signal; and a transmitting antenna electrically connected to the local oscillator, and sequentially interleaving and transmitting the first frequency conversion signal and the second frequency conversion signal; and a receiving device comprising: a receiving antenna, a a mixing and low-pass filter module, a analog-to-digital converter and a digital signal processing module, the receiving antenna receiving an echo signal of the first frequency conversion signal and the second frequency conversion signal, the mixing and low pass The filter module mixes the echo signal with the first frequency conversion signal and the second frequency conversion signal generated by the local oscillator to obtain a beat signal between the two, and the analog to digital converter After the beat signal is sampled and converted into a digital signal, the distance and movement of the target object relative to the signal processing device of the continuous wave radar sensing system are calculated by the digital signal processing module. Degree information.

In an embodiment of the signal processing device of the continuous wave radar sensing system of the present invention, the first frequency conversion signal is a high pulse repetition frequency signal, and the second frequency conversion signal is a low pulse repetition frequency signal.

In an embodiment of the signal processing device of the continuous wave radar sensing system of the present invention, a plurality of first frequency conversion signals and a plurality of second frequency conversion signals are generated during an antenna residence time.

In an embodiment of the signal processing device of the continuous wave radar sensing system of the present invention, the first frequency conversion signal and the second frequency conversion signal together account for 80% of the standing wave residence time.

In an embodiment of the signal processing device of the continuous wave radar sensing system of the present invention, the first frequency conversion signal and the second frequency conversion signal respectively occupy an equal time.

In an embodiment of the signal processing apparatus of the continuous wave radar sensing system of the present invention, the frequency of the high pulse repetition frequency signal is between 2 kHz and 4 kHz.

In an embodiment of the signal processing apparatus of the continuous wave radar sensing system of the present invention, the frequency of the low pulse repetition frequency signal is less than 200 Hz.

An embodiment of the signal processing apparatus of the continuous wave radar sensing system of the present invention further includes a moving target indicating filter, a Doppler signal processing module, and a target determining unit, wherein the moving target indicating filter includes a first A transposed memory can be temporarily stored through the digital signal processing module to obtain distance information through a fast Fourier transform operation, and after accumulating to a predetermined amount of information, the processing module via the Doppler signal will be The distance information in the first transposed memory is taken out and then subjected to a fast Fourier transform operation, and the two-dimensional information is rotated to the target judging unit, and the target judging unit uses the target detection logic to perform target detection and tracking.

In an embodiment of the signal processing device of the continuous wave radar sensing system of the present invention, the method further includes a second transposed memory, and the first transposed memory is accumulated to a predetermined amount of resources. After the data is processed, the data processing is started. At the same time as the data processing, the distance information can be temporarily stored in the second transposed memory through the fast Fourier transform operation through the digital signal processing module, and the first transposed memory is transmitted through the first transposed memory. The interactive use of the body and the second transposed memory can save the waiting time of data processing.

In an embodiment of the signal processing device of the continuous wave radar sensing system of the present invention, the first frequency conversion signal and the second frequency conversion signal are sawtooth waves.

10‧‧‧Signal processing device for continuous wave radar sensing system

11‧‧‧ Launch unit

111‧‧‧transmitting antenna

113‧‧‧Local oscillator

115‧‧‧Sweep frequency controller

13‧‧‧ Receiving unit

131‧‧‧Receiving antenna

133‧‧‧ Mixing and low-pass filter modules

135‧‧‧ analog to digital converter

137‧‧‧Digital Signal Processing Module

141‧‧‧First transposed memory

142‧‧‧Second transposed memory

143‧‧‧Doppler Signal Processing Module

145‧‧‧Target Judgment Unit

1 is a schematic diagram of a signal processing apparatus of a continuous wave radar sensing system according to an embodiment of the present invention; and FIG. 2 is a schematic diagram of a signal processing apparatus of a continuous wave radar sensing system according to an embodiment of the present invention; FIG. 3 is a schematic diagram showing a signal processing apparatus of a continuous wave radar sensing system according to another embodiment of the present invention having a second transposed memory.

The present invention mainly provides a signal processing device for a continuous wave radar sensing system, which utilizes a continuous wave that produces an interleaved output to solve the problem of a wide range of changes in the speed of the sensed target. The embodiments of the present invention will be described in detail below with reference to the accompanying drawings. In addition to the detailed description, the present invention can be widely practiced in other embodiments, and any alternatives, modifications, and equivalent changes of any of the embodiments are included in the scope of the present invention, and the scope of the following patents is quasi. In the description of the specification, a number of specific details are provided for the reader to have a more complete understanding of the present invention; however, the present invention may be implemented without omitting some or all of these specific details. In addition, well-known steps or elements are not described in detail to avoid unnecessarily limiting the present invention. The same or similar elements in the drawings will be denoted by the same or similar symbols. It is specifically noted that the drawings are for illustrative purposes only and are not representative of actual size or number of elements, and that irrelevant details are not fully depicted in order to facilitate the drawing.

This creation mainly provides a signal processing device for continuous wave radar sensing system. It uses low PRF and high PRF dual mode method, interleaving FMCW traditional mode and Doppler processing mode, and adopts FMCW Doppler processing. The effect of eliminating clutter is improved, and the target speed can be directly obtained. The speed range of the moving target is wide, and the more FFT points are processed by the Buhler, the wider the speed range is, and the range is large when the target moving speed range is large. The problem at the time.

For situations where the range of target moving speed varies greatly, such as dealing with fast air targets (such as drones) and slow targets (such as ground pedestrians). The FMCW traditional mode alone or the Doppler processing mode is insufficient and cannot be considered. The dual mode approach is a good solution to the aforementioned problems. In the FMCW legacy mode, the FMCW radar uses a very low sweep frequency that can cover low speed targets so that it is not filtered by the MTI filter. In the Doppler processing mode, the scanning frequency is up to 2 kHz and can handle the Doppler frequency up to 2 kHz without the speed confusion.

As shown in FIG. 1 , a schematic diagram of a signal processing device 10 for a continuous wave radar sensing system according to the present invention can be divided into a transmitting unit 11 and a receiving unit 13 according to the operation thereof; the transmitting unit 11 includes a transmitting antenna 111 and a local device. Local Oscillator 113 and a sweep The Sweep Controller 115 includes a receiving antenna 131, a mixing and low-pass filtering module 133, an analog-to-digital converter 135, and a digital signal processing module 137. The detection operation of the signal processing device 10 of the continuous wave radar sensing system is as follows. The frequency sweep controller 115 controls the local oscillator 113 to generate a frequency modulated continuous wave signal or other extended type of frequency modulated continuous wave signals, which are outwardly transmitted via the transmitting antenna 111. Radiation; correspondingly, after the receiving antenna 131 receives the echo signal reflected by the target, the mixing and low-pass filtering module 133 performs mixing and low-pass processing on the echo signal and the sine wave signal generated by the local oscillator 113. The beat frequency signal between the two can be obtained, and the analog to digital converter 135 can sample and convert the beat signal into a digital signal, and then the digital signal processing module 137 calculates the target relative to the continuous Information such as the distance and moving speed of the signal processing device 10 of the wave radar sensing system.

In order to calculate the distance, movement speed and the like of the target, the digital signal processing module 137 needs to convert the beat frequency signal of the time domain to the frequency domain. The common method is to use Fast Fourier Transtorm (FFT), but Not limited to this. However, in order to reduce the spectrum leakage, the digital signal processing module 137 can multiply the sampled beat signal in the time domain by a window function before the fast Fourier transform to avoid the target. The echoes interfere with each other in the spectrum, causing the signal to noise ratio to drop, affecting the performance of the signal processing device 10 of the continuous wave radar sensing system. After the window function and the fast Fourier transform, the digital signal processing module 137 detects the beat frequency of the target with a fixed or dynamic threshold (Threshold), for example, according to the difference of the modulation pattern (Pattern), Information such as the beat frequency of the chirp time or a beat frequency and its phase information can obtain the distance and relative speed of the target.

As can be seen from the above, using window function, fast Fourier transform and beat frequency detection, The digital signal processing module 137 can obtain information such as the distance and relative speed of the target. However, the digital signal processing module 137 performs spectrum analysis for a limited time, and the object resolution capability is limited by the bandwidth of the beat frequency fb in the frequency domain. The range resolution of the signal processing device 10 of the continuous wave radar sensing system is determined by the bandwidth of the frequency sweep controller 115. The Velocity Resolution of the signal processing device 10 of the continuous wave radar sensing system is determined by the starting frequency f0 and the modulation time Tm of the frequency sweep controller 115.

The signal processing device 10 of the present continuous wave radar sensing system is configured to achieve the best detection performance of the mobile small target, and further includes a Moving Target Indication Filter (MTIF) and a moving target indication filter 14 The first transposed memory 141 (CTM) can be temporarily stored in the digital signal processing module 137 through the fast Fourier transform operation to obtain the distance information, and after accumulating to a preset amount of information, The distance information in the first transposition memory 141 is taken out by the Doppler signal processing module 143 and subjected to a fast Fourier transform operation, and the two-dimensional information is rotated to the target judging unit 145, and the target judging unit 141 uses the target Detector. Measure logic for target detection and tracking.

Radars that detect slow small targets (RCS about 0.1~1m ² , speed 0.3~30m/sec) must have superior sensitivity. Under the condition that the peak transmit power is fixed, the target on target (or dwell time) is elongated, which helps the signal-to-noise ratio to be increased, and the detection distance is thus increased. The traditional FMCW radar adopts one-dimensional FFT processing to perform distance compression to obtain distance information, but the speed of the target cannot be obtained. When the scan time Ts is longer, the Pulse Repetition Intervals (PRI) is also larger. The more sampling points, the more the FFT points are, and the greater the gain, the higher the signal-to-noise ratio. Detect distance. If Ts and PRI are shortened, multiple scan waveforms can be accumulated under the constant Tot, and a two-dimensional Doppler process can be performed to obtain the velocity data of the target, and since the two-dimensional The processing has a coherent integration gain, and the detection distance can be maintained constant or even improved. Since the radar operates in a strong and complicated clutter environment, the clutter intensity is usually 100 times to 10,000 times (100~10000 m ² ) of the target. Therefore, by increasing the transmission bandwidth distance, the resolution is improved, and the distance element becomes smaller. The ratio of the power of the intra-band clutter becomes smaller, so as to improve the signal clutter ratio (S/C) and improve the subclutter visibility (SCV), thereby improving the detection rate of the slow small target.

The signal processing device 10 of the present continuous wave radar sensing system continuously sweeps and emits several FMCW sawtooth waves within an antenna dwell time. In the first sawtooth wave, after the output of the beat frequency of the receiving unit 13 is converted into a digit, an FFT processing operation is performed, and the output is stored in the memory as the distance data. In the above manner, as shown in FIG. 2, the FFT outputs of the second, third, and fourth sawtooth waves are sequentially arranged and stored in the first transposed memory 141, wherein the direction in which the data is stored is from bottom to top. The data of the same distance gate is taken out laterally for FFT operation. Therefore, this memory is called a turn-turn memory (Corner turn memory), and the data of each distance gate is subjected to the same FFT operation, and the output is 2D. Range-Doppler map.

The signal processing device 10 of the continuous wave radar sensing system of the present invention controls the local oscillator 113 to generate a plurality of frequency conversion signals during an antenna residence time by using a frequency sweep controller 115. The plurality of frequency conversion signals include a first frequency conversion signal and a second frequency conversion signal, wherein the first frequency conversion signal is a high pulse repetition frequency signal and the second frequency conversion signal is a low pulse repetition frequency signal. In this embodiment, the plurality of first frequency conversion signals and the plurality of second frequency conversion signals are included. Signal. In this embodiment, the first variable frequency signal and the second variable frequency signal are sawtooth waves. In order to reserve data calculation time, The first frequency conversion signal and the second frequency conversion signal always occupy an antenna residence time of 60% to 80%, preferably 80%. The first variable frequency signal and the second variable frequency signal respectively occupy an equal time in the occupied antenna staying time. In this embodiment, the frequency of the high pulse repetition frequency signal is between 2 kHz and 4 kHz, and the frequency of the low pulse repetition frequency signal is less than 200 Hz. As shown in FIG. 2, a plurality of high pulse repetition frequency signals may be generated to generate a plurality of low pulse repetition frequency signals, but a plurality of low pulse repetition frequency signals may be generated to generate a plurality of high pulse repetition frequency signals.

FMCW anti-collision radar usually uses low-speed scanning (PRF number 10Hz, <100Hz). Because of its Ts length (~10ms), filter BW is narrow and the distance resolution is high. With the up sweep and down sweep, the exact target distance and speed can be calculated. When the target RCS is smaller than the clutter of the same distance gate, the target will be obscured by the clutter, so the MTI is designed to filter out the clutter, but the moving target with too low speed may also be filtered by the MTI. To avoid moving targets at low speeds, it is common to use low PRF. Moving targets with speeds below 0.1 PRF are filtered out.

As described above, the receiving unit 13 includes: a receiving antenna 131, a mixing and low-pass filtering module 133, an analog-to-digital converter 135, and a digital signal processing module 137. The receiving antenna 131 receives the first variable frequency signal and the second frequency conversion. An echo signal of the signal, the mixing and low-pass filter module 133 performs mixing and low-pass processing on the echo signal and the first frequency conversion signal and the second frequency conversion signal generated by the local oscillator 113. The beat signal, and the analog to digital converter 135 samples and converts the beat signal into a digital signal, and the digital signal processing module 137 calculates the signal processing device of the target relative to the continuous wave radar sensing system. 10 distance, movement speed and other information, and then through the Doppler signal processing module 143 for 2D distance information operation, the most The target detection unit 145 performs target detection and tracking.

In another embodiment, as shown in FIG. 3, the moving target indication filter 14 further includes a second transposition memory 142. When the first transposition memory 141 accumulates to a preset amount of information, it will start. Data processing is performed, and at the same time as the data processing, the distance information can be temporarily stored in the second transposition memory 142 via the digital signal processing module 137 through the fast Fourier transform operation, and the first transposition memory 141 and the second transposition are transmitted. The interactive use of the memory 142 can save the waiting time of data processing.

The traditional FMCW radar adopts one-dimensional FFT processing to perform distance compression to obtain distance information, but the speed of the target cannot be obtained. When the scanning time Ts is longer (PRI is also larger), the more sampling points, the greater the FFT points, the greater the gain, and the higher the signal-to-noise ratio, thus increasing the detection distance. If Ts (and PRI) is shortened, multiple scan waveforms can be accumulated under the constant Tot, and the two-dimensional Doppler process can be used to obtain the target velocity data, and The Doppler process has a coherent integration gain, and the detection distance can be maintained constant or even improved.

This creation retains the advantages of the traditional FMCW radar, which has low peak power and good range resolution. Low peak power and low energy consumption reduce the risk of electromagnetic radiation from operators. The FMCW Doppler processing method improves the effect of eliminating clutter and can directly achieve the target speed. The range of speeds at which a moving target can be processed is wide, and the more the number of FFT points processed by the Doppler, the wider the speed range. Hybrid FMCW and Doppler processing are used to eliminate ground clutter, so you can detect very low moving speed targets. Doppler processing can increase the signal-to-noise ratio (SNR) to increase the detection distance while achieving the target speed.

The signal processing device of the continuous wave radar sensing system of the present invention uses a dual mode method, and the FMCW traditional mode and the Doppler processing mode are interleaved to solve the problem when the self-standard speed range is very wide. Interleaving can be interleaved during antenna dwell time or interleaved between scan by scan. For situations where the target speed varies widely, such as dealing with fast air targets (such as drones) and slow targets (such as ground pedestrians). Insufficient use of the FMCW legacy mode or the Doppler processing mode alone. In the FMCW legacy mode, the FMCW radar uses a very low sweep frequency that can cover low speed targets so that it is not filtered by the MTI filter. In the Doppler processing mode, the scanning frequency is up to 2 kHz and can handle the Doppler frequency up to 2 kHz without the speed confusion. Increasing the FMCW transmit mode bandwidth can improve the range resolution, improve the signal-to-clutter ratio (S/C), and improve the target detection capability of the radar under clutter.

10‧‧‧Signal processing device for continuous wave radar sensing system

11‧‧‧ Launch unit

111‧‧‧transmitting antenna

113‧‧‧Local oscillator

115‧‧‧Sweep frequency controller

13‧‧‧ Receiving unit

131‧‧‧Receiving antenna

133‧‧‧ Mixing and low-pass filter modules

135‧‧‧ analog to digital converter

137‧‧‧Digital Signal Processing Module

141‧‧‧First transposed memory

142‧‧‧Second transposed memory

143‧‧‧Doppler Signal Processing Module

145‧‧‧Target Judgment Unit

Claims (10)

A signal processing device for a continuous wave radar sensing system, comprising: a transmitting unit having a frequency sweep controller and a local oscillator, wherein the frequency sweep controller controls the local oscillator to generate a first frequency conversion signal and a second frequency conversion signal a transmitting antenna electrically connected to the local oscillator, and sequentially interleaving and transmitting the first variable frequency signal and the second variable frequency signal; and a receiving device having a receiving antenna, a mixing frequency and a low pass filtering mode a group, a analog-to-digital converter and a digital signal processing module, the receiving antenna receiving an echo signal of the first frequency conversion signal and the second frequency conversion signal, the mixing and low-pass filter module will be an echo signal Mixing and low-pass processing the first variable frequency signal and the second variable frequency signal generated by the local oscillator to obtain a beat signal between the two, and the analog to digital converter samples and converts the beat signal After the digital signal, the digital signal processing module calculates the distance and moving speed of the target relative to the signal processing device of the continuous wave radar sensing system. The signal processing device of the continuous wave radar sensing system according to claim 1, wherein the first frequency conversion signal is a high pulse repetition frequency signal, and the second frequency conversion signal is a low pulse repetition frequency signal. The signal processing device of the continuous wave radar sensing system according to claim 1, wherein the plurality of first frequency conversion signals and the plurality of second frequency conversion signals are generated during an antenna residence time. The signal processing device of the continuous wave radar sensing system of claim 3, wherein the first frequency conversion signal and the second frequency conversion signal together account for 80% of the standing wave residence time. The signal processing device of the continuous wave radar sensing system of claim 3, wherein the first frequency conversion signal and the second frequency conversion signal respectively occupy an equal time. Signal processing equipment for a continuous wave radar sensing system as described in claim 2 The high pulse repetition frequency signal has a frequency between 2 kHz and 4 kHz. The signal processing device of the continuous wave radar sensing system according to claim 2, wherein the frequency of the low pulse repetition frequency signal is less than 200 Hz. The signal processing device of the continuous wave radar sensing system according to claim 1, further comprising a moving target indicating filter, a Doppler signal processing module and a target determining unit, the moving target indicating filtering The device includes a first transposition memory, which can be temporarily stored through the digital signal processing module to obtain distance information through a fast Fourier transform operation, and after being accumulated to a preset amount of information, the device is processed by the Doppler signal. The module takes out the distance information in the first transposed memory and performs a fast Fourier transform operation, and rotates the two-dimensional information to the target judging unit. The target judging unit uses the target detection logic to perform target detection and track. The signal processing device of the continuous wave radar sensing system according to claim 8 , further comprising a second transposition memory, when the first transposed memory is accumulated to a preset amount of information, Data processing is started, and at the same time as the data processing, the distance information can be temporarily stored in the second transposed memory through the digital signal processing module through the fast Fourier transform operation, through the first transposed memory and the second trans The interactive use of memory can save the waiting time of data processing. The signal processing device of the continuous wave radar sensing system of claim 1, wherein the first frequency conversion signal and the second frequency conversion signal are sawtooth waves.