Millimeter wave detector suitable for short-distance moving target

Abstract

The invention discloses a millimeter wave detector suitable for a short-distance moving target. The millimeter wave detector comprises a millimeter wave front end and an intermediate frequency signal processing unit, wherein the intermediate frequency signal processing unit comprises a low-pass filtering and amplifying circuit which is used for realizing low-pass filtering of a first preset frequency; comprising a detection circuit which is used for outputting an envelope signal of a second preset frequency and filtering a triangular wave signal of a third preset frequency; the band-pass filtering and amplifying circuit is used for realizing band-pass filtering between a fourth preset frequency and a fifth preset frequency; and the signal peak threshold judgment circuit is used for judging whether a detection target appears in a distance range needing to be detected or not according to the signal output by the band-pass filtering and amplifying circuit. The millimeter wave detector suitable for the short-distance moving target has the beneficial effect that the short-distance target detection sensitivity can be effectively improved.

Description

Technical Field

[0001] The present application relates to the technical field of millimeter-wave detection, and more specifically, to a millimeter-wave detector applicable to short-range moving targets. Background Art

[0002] In the related art, when detecting moving targets within a relatively short range (0.1 m to 10 m), the following two solutions are often adopted:

[0003] Single-frequency continuous wave system: For detecting moving targets at short ranges, a millimeter-wave detector can adopt the method of transmitting a single-frequency continuous wave, and the receiver receives the target echo and detects the intermediate-frequency Doppler echo signal to determine whether there is a moving target at short range.

[0004] Frequency-modulated continuous wave system: For detecting moving targets at short ranges, the millimeter-wave detector transmits a triangular-wave frequency-modulated continuous wave, the receiver receives the target echo, and after mixing, an intermediate-frequency signal is obtained. The intermediate-frequency signal is generally composed of a fixed leakage triangular-wave signal and a weak echo signal. The frequency of the echo signal is proportional to the target distance, and the upper limit distance of the detected target is less than the lower limit distance of the background. Therefore, the amplification of the weak detected target signal and the suppression of the large background signal can be achieved through intermediate-frequency filtering.

[0005] However, both of the above two solutions have their respective drawbacks:

[0006] For a millimeter-wave detector with a single-frequency continuous wave system, the intermediate-frequency Doppler signal only contains the velocity information of the target and does not contain the distance information of the target. In addition, the upper limit of the detection distance and the lower limit of the background distance generally only differ by 2 to 5 m. The radar cross-sectional areas of the detected target and the background target in motion differ greatly. Therefore, generally, the amplitude of the intermediate-frequency Doppler signal of the background target is similar to or even larger than that of the detected target. Therefore, it is impossible to detect the detected target and suppress the background target through the amplitude of the finally output intermediate-frequency Doppler signal.

[0007] For a millimeter-wave detector with a frequency-modulated continuous wave system, the intermediate-frequency signal output by mixing has a fixed leakage triangular-wave signal. However, the frequency of the leakage triangular-wave signal is generally greater than the frequency of the echo signal corresponding to a distance of 0.1 m, that is, the leakage triangular-wave frequency is generally within the intermediate-frequency signal frequency range corresponding to the detected target. Therefore, if the lower limit frequency of the intermediate-frequency filter is higher than the leakage triangular-wave frequency, the target signals at very short ranges such as 0.1 m will be filtered out, and the detection of short-range targets cannot be achieved. If the lower limit frequency of the intermediate-frequency filter is lower than the leakage triangular-wave frequency, the leakage triangular-wave signal cannot be suppressed, and thus the amplification of the intermediate-frequency echo signal of the detected target cannot be achieved.

[0008] In view of the deficiencies in the related art, no effective solution has been proposed yet. Summary of the Invention

[0009] The content of this application is partially used to introduce concepts in a brief form, which will be described in detail in the following detailed implementation section. The content of this application is not intended to identify the key features or essential features of the claimed technical solution, nor is it intended to limit the scope of the claimed technical solution.

[0010] Some embodiments of this application propose a millimeter-wave detector applicable to short-range moving targets to solve the technical problems mentioned in the above background section.

[0011] As a first aspect of this application, some embodiments of this application provide a millimeter-wave detector applicable to short-range moving targets, including:

[0012] A millimeter-wave front end for generating, transmitting, and receiving millimeter-wave signals;

[0013] An intermediate-frequency signal processing unit for processing and filtering the pre-filter intermediate-frequency signal output by the millimeter-wave front end to output a post-filter intermediate-frequency signal;

[0014] Wherein, the millimeter-wave front end and the intermediate-frequency signal processing unit are electrically connected;

[0015] Wherein, the intermediate-frequency signal processing unit includes:

[0016] A low-pass filter amplification circuit for implementing low-pass filtering of a first preset frequency;

[0017] Including a detection circuit for outputting an envelope signal of a second preset frequency and filtering out a triangular wave signal of a third preset frequency;

[0018] A band-pass filter amplification circuit for implementing band-pass filtering between a fourth preset frequency and a fifth preset frequency;

[0019] A signal peak threshold judgment circuit for judging whether a detection target appears within the distance range to be detected according to the signal output by the band-pass filter amplification circuit;

[0020] Wherein, the low-pass filter amplification circuit, the detection circuit included, the band-pass filter amplification circuit, and the signal peak threshold judgment circuit are electrically connected in sequence.

[0021] Furthermore, the millimeter-wave front end includes: a triangular wave generation circuit, a millimeter-wave oscillator, a power divider, a power amplifier, a transmitting antenna, a receiving antenna, a low-noise amplifier, and a mixer;

[0022] Among them, the triangular wave generating circuit is electrically connected to the millimeter wave oscillator; the millimeter wave oscillator is electrically connected to the power divider; the power divider is respectively electrically connected to the power amplifier and the mixer; the power amplifier is electrically connected to the transmitting antenna; the low noise amplifier is electrically connected to the receiving antenna.

[0023] Further, the mixer is electrically connected to the intermediate frequency signal processing unit to send the intermediate frequency signal to the low-pass filtering and amplifying circuit of the intermediate frequency signal processing unit.

[0024] Further, the frequency f of the triangular wave generated by the triangular wave generating circuit 1 m needs to satisfy the following conditions:

[0025]

[0026] Among them, λ is the wavelength corresponding to the center frequency of the millimeter wave signal output by the millimeter wave oscillator 2, and v h is the upper limit of the speed in the direction of the connection line between the detected target and the millimeter wave detector.

[0027] Further, the first preset frequency of the low-pass filtering and amplifying circuit is

[0028] Further, among them, Δf is the frequency modulation bandwidth of the triangular wave frequency modulated continuous wave millimeter wave detector, R1 is the upper limit of the distance of the target detection range, and f m is the frequency of the triangular wave signal output by the triangular wave generating circuit, and c is the speed of light.

[0029] Further, the detection circuit includes: a detection diode, a resistor and a capacitor;

[0030] Among them, the positive electrode of the detection diode is connected to the output end of the low-pass filtering and amplifying circuit; the resistor and the capacitor are respectively connected between the negative electrode of the detection diode and the ground.

[0031] Further, the detection circuit outputs an envelope signal with a frequency of f1 and filters out a triangular wave signal with a frequency of fm, where fm is set to be at least greater than 10×f1.

[0032] Further, f1 is the Doppler frequency corresponding to the relative speed of the detected moving target.

[0033] Further, the fourth preset frequency and the fifth preset frequency of the band-pass filtering and amplifying circuit are respectively the upper limit f of the filtering bandwidth H and the lower limit f l ,

[0034] Among them,

[0035] Among them, v h is the upper limit of the speed in the direction of the connection line between the detected target and the millimeter-wave detector, and v L is the lower limit of the speed in the direction of the connection line between the detected target and the millimeter-wave detector.

[0036] The beneficial effect of this application is that it provides a millimeter-wave detector applicable to short-range moving targets that can effectively improve the detection sensitivity of short-range targets. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] The drawings constituting a part of this application are used to provide a further understanding of this application, making other features, purposes, and advantages of this application more obvious. The schematic drawings and descriptions of the exemplary embodiments of this application are used to explain this application and do not constitute an improper limitation of this application.

[0038] In addition, throughout the drawings, the same or similar reference numerals represent the same or similar elements. It should be understood that the drawings are schematic, and the elements and components are not necessarily drawn to scale.

[0039] In the drawings:

[0040] Figure 1 is a schematic diagram of the architecture of a millimeter-wave detector according to an embodiment of this application;

[0041] Figure 2 is a schematic diagram of the architecture of a millimeter-wave front end according to an embodiment of this application;

[0042] Figure 3 is a schematic diagram of the architecture of an intermediate-frequency signal processing unit according to an embodiment of this application;

[0043] Figure 4 is a schematic diagram of the architecture including a detection circuit according to an embodiment of this application;

[0044] Figure 5 is a schematic diagram of an intermediate-frequency signal with triangular-wave leakage and Doppler modulation according to an embodiment of this application, where the horizontal axis is time and the vertical axis is voltage. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0045] Hereinafter, embodiments of the present disclosure will be described in more detail with reference to the drawings. Although some embodiments of the present disclosure are shown in the drawings, it should be understood that the present disclosure can be implemented in various forms and should not be construed as limited to the embodiments set forth herein. On the contrary, these embodiments are provided to more thoroughly and completely understand the present disclosure. It should be understood that the drawings and embodiments of the present disclosure are only for exemplary purposes and are not used to limit the protection scope of the present disclosure.

[0046] In addition, it should be noted that, for the convenience of description, only the parts related to the relevant invention are shown in the drawings. Without conflict, the embodiments in the present disclosure and the features in the embodiments can be combined with each other.

[0047] It should be noted that the concepts such as "first" and "second" mentioned in the present disclosure are only used to distinguish different devices, modules or units, and are not used to limit the order of functions executed by these devices, modules or units or their interdependent relationships.

[0048] It should be noted that the modifications of "one" and "multiple" mentioned in the present disclosure are illustrative rather than restrictive. Those skilled in the art should understand that, unless otherwise clearly specified in the context, it should be understood as "one or more".

[0049] The names of the messages or information exchanged between multiple devices in the embodiments of the present disclosure are only for illustrative purposes and are not used to limit the scope of these messages or information.

[0050] The present disclosure will be described in detail below with reference to the drawings and in combination with embodiments.

[0051] Referring to Figures 1 to 5 As shown, the millimeter-wave detector applicable to short-range moving targets of the present application includes: a millimeter-wave front end and an intermediate-frequency signal processing unit.

[0052] Specifically, the millimeter-wave front end is used to generate, transmit and receive millimeter-wave signals; the intermediate-frequency signal processing unit is used to perform processing and filtering on the pre-filter intermediate-frequency signal output by the millimeter-wave front end to output a post-filter intermediate-frequency signal. Among them, the millimeter-wave front end and the intermediate-frequency signal processing unit are electrically connected;

[0053] Specifically, the intermediate-frequency signal processing unit includes: a low-pass filter amplification circuit, a detection circuit, a band-pass filter amplification circuit, and a signal peak threshold judgment circuit.

[0054] Among them, the low-pass filter amplification circuit is used to implement low-pass filtering of a first preset frequency; the detection circuit is used to output an envelope signal of a second preset frequency and filter out a triangular wave signal of a third preset frequency; the band-pass filter amplification circuit is used to implement band-pass filtering between a fourth preset frequency and a fifth preset frequency; the signal peak threshold judgment circuit is used to judge whether a detection target appears within the detection distance range according to the signal output by the band-pass filter amplification circuit; among them, the low-pass filter amplification circuit, the detection circuit, the band-pass filter amplification circuit, and the signal peak threshold judgment circuit are electrically connected in sequence.

[0055] Furthermore, the millimeter-wave front end includes: a triangular wave generation circuit, a millimeter-wave oscillator, a power divider, a power amplifier, a transmitting antenna, a receiving antenna, a low-noise amplifier, and a mixer;

[0056] Among them, the triangular wave generation circuit is electrically connected to the millimeter-wave oscillator; the millimeter-wave oscillator is electrically connected to the power divider; the power divider is respectively electrically connected to the power amplifier and the mixer; the power amplifier is electrically connected to the transmitting antenna; the low-noise amplifier is electrically connected to the receiving antenna.

[0057] Further, the mixer is electrically connected to the intermediate-frequency signal processing unit to send the intermediate-frequency signal to the low-pass filter amplification circuit of the intermediate-frequency signal processing unit.

[0058] Further, the triangular wave frequency f generated by the triangular wave generation circuit 1 m needs to satisfy the following conditions:

[0059]

[0060] Among them, λ is the wavelength corresponding to the center frequency of the millimeter-wave signal output by the millimeter-wave oscillator 2, and v h is the upper limit of the speed in the direction of the connection line between the detected target and the millimeter-wave detector.

[0061] Further, the first preset frequency of the low-pass filter amplification circuit is

[0062] Further, among them, Δf is the frequency modulation bandwidth of the triangular wave frequency-modulated continuous-wave millimeter-wave detector, R1 is the upper limit of the distance of the target detection range, and f m is the frequency of the triangular wave signal output by the triangular wave generation circuit, and c is the speed of light.

[0063] Further, the detection circuit includes: a detection diode, a resistor, and a capacitor;

[0064] Among them, the positive electrode of the detection diode is connected to the output end of the low-pass filter amplification circuit; the resistor and the capacitor are respectively connected between the negative electrode of the detection diode and the ground.

[0065] Further, the detection circuit outputs an envelope signal with a frequency of f1 and filters out the triangular wave signal with a frequency of fm, where fm is set to be at least greater than 10×f1.

[0066] Further, f1 is the Doppler frequency corresponding to the relative speed of the detected moving target.

[0067] Further, the fourth preset frequency and the fifth preset frequency of the band-pass filter amplification circuit are respectively the upper limit f of the filter bandwidth H and the lower limit f L ,

[0068] Among them,

[0069] Among them, v h is the upper limit of the speed in the direction of the connection line between the detected target and the millimeter-wave detector, and v L is the lower limit of the speed in the direction of the connection line between the detected target and the millimeter-wave detector.

[0070] The following is a more detailed introduction to the technical solution of this application:

[0071] This application proposes a millimeter-wave detector, which can achieve high-sensitivity detection (output a high peak-to-peak intermediate-frequency signal) for moving targets with low RCS (RCS is the radar cross-section area movement, and the RCS of the detected target is defined as RCS1) that suddenly appear within the range of 0.1 m to R1, but suppress moving targets beyond a distance of R1 and interference signals from high-RCS backgrounds (the RCS of the background is RCS2) beyond a distance of R2.

[0072] R1, R2, RCS1, and RCS2 are generally:

[0073] R1 = 5 m to 7 m, R2 > 10 m;

[0074] RCS1 = 0.1 m 2 , and RCS2 > RCS1 × 100.

[0075] The above solution can process the intermediate-frequency echo signal to achieve high-sensitivity detection of low-RCS moving targets at close range and suppression of interference signals from high-RCS backgrounds.

[0076] The overall structure of the new millimeter-wave detector proposed in this application is as Figure 1 shown, and the intermediate-frequency signal processing circuit structure is as Figure 1 shown, which consists of a millimeter-wave front-end 1 and an intermediate-frequency signal processing unit 2. The millimeter-wave front-end 1 generates and transmits millimeter-wave signals and mixes and converts the received millimeter-wave signals to output intermediate-frequency signals. The intermediate-frequency signal processing unit 2 performs intermediate-frequency processing on the intermediate-frequency signals output by the millimeter-wave front-end 1 and outputs intermediate-frequency signals that can be recognized by the backend.

[0077] The composition of the millimeter-wave front-end is as Figure 2 shown, which is a classic traditional triangular-wave frequency-modulated continuous-wave millimeter-wave transceiver front-end circuit, consisting of a triangular-wave generation circuit 1, a millimeter-wave oscillator 2, a power divider 3, a power amplifier 4, a transmitting antenna 5, a receiving antenna 6, a low-noise amplifier 7, and a mixer 8.

[0078] In the millimeter-wave front-end of this application, the triangular-wave frequency f m generated by the triangular-wave generation circuit 1 needs to meet the following conditions:

[0079]

[0080] where λ is the wavelength corresponding to the center frequency of the millimeter-wave signal output by the millimeter-wave oscillator 2, and v h is the upper limit of the velocity in the direction of the line connecting the detected target and the millimeter-wave detector.

[0081] The intermediate-frequency signal processing unit is composed of Figure 3 as shown, and is composed of a first-stage low-pass filter amplification circuit, a second-stage envelope detection circuit, a third-stage band-pass filter amplification circuit, and a final-stage peak detection and judgment circuit.

[0082] The first-stage low-pass filter circuit 1 can be implemented by various forms of filter circuits. The key lies in that the cut-off frequency of the first-stage low-pass filter circuit is

[0083]

[0084] where Δf is the frequency modulation bandwidth of the triangular-wave frequency-modulated continuous-wave millimeter-wave detector, R1 is the upper limit of the distance for the target detection range, and f m is Figure 2 the frequency of the triangular-wave signal output by the triangular-wave generation circuit 1 in, and c is the speed of light.

[0085] The second-stage envelope detection circuit 2 is composed of Figure 4 the diode envelope detection circuit shown, and is composed of a detection diode D1, a resistor R1, and a capacitor C1. This envelope detection circuit can output an envelope signal with a frequency of f1 and filter out the triangular-wave signal with a frequency of fm. f1 is generally the Doppler frequency corresponding to the relative velocity of the detected moving target. In this application, fm needs to be set to be at least greater than 10×f1.

[0086] The third-stage band-pass filter amplification circuit 3 can be implemented by various forms of filter circuits. The key lies in that the upper limit f H and the lower limit f L of the filter bandwidth are determined by the velocity range of the detected target.

[0087]

[0088] where v h is the upper limit of the velocity in the direction of the line connecting the detected target and the millimeter-wave detector, and v L is the lower limit of the velocity in the direction of the line connecting the detected target and the millimeter-wave detector.

[0089] Working process:

[0090] Figure 2The triangular wave generation circuit 1 of the millimeter-wave front end generates a triangular wave signal, which is input into the millimeter-wave oscillator 2. The millimeter-wave oscillator 2 outputs a millimeter-wave local oscillator signal frequency-modulated by the triangular wave. The millimeter-wave local oscillator signal is split into two paths by the power divider 3. One path is transmitted to the target area through the power amplifier 4 and the transmitting antenna 5, and the other path is input into the local oscillator port of the mixer 8. The echo signal in the target area enters the millimeter-wave detector through the receiving antenna 6 and the low-noise amplifier 7, and is converted into an intermediate-frequency signal after passing through the mixer 8.

[0091] The intermediate-frequency signal enters Figure 3 the intermediate-frequency signal processing unit.

[0092] If the high RCS background target or the detected target is at a distance greater than R2, the intermediate-frequency of the resulting interference signal is greater than the cut-off frequency f of the low-pass filter 1 1_low , so the interference signal can be eliminated to prevent false triggering.

[0093] If the detected moving target with low RCS appears within the required detection range of 0.1 m to R1, at this time the intermediate-frequency echo signal frequency is as Figure 5 shown, and it is composed of the leaked triangular wave signal and the intermediate-frequency echo signal of the frequency-modulated continuous wave of the detected target superimposed on the leaked triangular wave, and this intermediate-frequency echo signal is modulated by the Doppler signal of the detected target. Therefore, the intermediate-frequency signal can be retained and amplified after passing through the low-pass filter and amplifier circuit 1. After passing through the envelope detection circuit 2, the Doppler signal of the detected target is detected as the envelope, while the leaked triangular wave signal and the intermediate-frequency echo signal of the frequency-modulated continuous wave of the detected target superimposed on the leaked triangular wave are filtered out by the envelope detection circuit. The Doppler signal of the detected target passes through the third-stage band-pass filter and amplifier circuit, and the remaining interference signals can be further filtered out to improve the signal-to-noise ratio. Finally, it only needs to pass through the signal peak threshold to determine whether the detected target appears within the required detection distance range.

[0094] The technical solution of this application designs the intermediate-frequency signal processing unit of the traditional triangular wave frequency-modulated continuous wave millimeter-wave detector, which can perform high-sensitivity detection on moving targets with low RCS within the detection range of 0.1 m to R1, while suppressing the background interference signal with high RCS at a distance of R2, and can filter out the leaked triangular wave of the traditional triangular wave frequency-modulated continuous wave. Finally, it only needs to pass a simple signal peak threshold judgment to determine whether a target appears within the range of 0.1 m to R1.

[0095] The above description is only some preferred embodiments of the present disclosure and an explanation of the applied technical principles. Those skilled in the art should understand that the scope of the invention involved in the embodiments of the present disclosure is not limited to the technical solutions formed by the specific combination of the above technical features, but should also cover other technical solutions formed by any combination of the above technical features or their equivalent features without departing from the above inventive concept. For example, the technical solutions formed by mutually replacing the above features with the technical features (but not limited to) disclosed in the embodiments of the present disclosure that have similar functions.

Claims

1. A millimeter-wave detector applicable to short-range moving targets, comprising: A millimeter-wave front end for generating, transmitting, and receiving millimeter-wave signals; Characterized in that: The millimeter-wave detector applicable to short-range moving targets further comprises: An intermediate-frequency signal processing unit for performing processing and filtering on the pre-filter intermediate-frequency signal output by the millimeter-wave front end to output a post-filter intermediate-frequency signal; Wherein, the millimeter-wave front end and the intermediate-frequency signal processing unit are electrically connected; Wherein, the intermediate-frequency signal processing unit comprises: A low-pass filter amplification circuit for implementing low-pass filtering at a first preset frequency; Including a detection circuit for outputting an envelope signal at a second preset frequency and filtering out a triangular-wave signal at a third preset frequency; A band-pass filter amplification circuit for implementing band-pass filtering between a fourth preset frequency and a fifth preset frequency; A signal peak threshold judgment circuit for judging whether a detection target appears within the distance range to be detected according to the signal output by the band-pass filter amplification circuit; Wherein, the low-pass filter amplification circuit, the detection circuit including, the band-pass filter amplification circuit, and the signal peak threshold judgment circuit are electrically connected in sequence.

2. The millimeter-wave detector applicable to short-range moving targets according to claim 1, characterized in that: The millimeter-wave front end includes: a triangular-wave generation circuit, a millimeter-wave oscillator, a power divider, a power amplifier, a transmitting antenna, a receiving antenna, a low-noise amplifier, and a mixer; Wherein, the triangular-wave generation circuit is electrically connected to the millimeter-wave oscillator; the millimeter-wave oscillator is electrically connected to the power divider; the power divider is electrically connected to the power amplifier and the mixer respectively; the power amplifier is electrically connected to the transmitting antenna; the low-noise amplifier is electrically connected to the receiving antenna.

3. The millimeter-wave detector applicable to short-range moving targets according to claim 2, characterized in that: The mixer is electrically connected to the intermediate-frequency signal processing unit to send the intermediate-frequency signal to the low-pass filter amplification circuit of the intermediate-frequency signal processing unit.

4. The millimeter-wave detector applicable to short-range moving targets according to claim 3, characterized in that: The triangular wave frequency f generated by the triangular wave generating circuit 1 m needs to satisfy the following conditions: where λ is the wavelength corresponding to the center frequency of the millimeter-wave signal output by the millimeter-wave oscillator 2, and v h is the upper limit of the velocity in the direction of the line connecting the detected target and the millimeter-wave detector.

5. The millimeter-wave detector applicable to short-range moving targets according to claim 4, characterized in that: The first preset frequency of the low-pass filter amplifier circuit is 6. The millimeter-wave detector applicable to short-range moving targets according to claim 5, characterized in that: Among them, Δf is the frequency modulation bandwidth of the triangular wave frequency modulated continuous wave millimeter wave detector, R1 is the upper limit of the distance for the target detection range, f m is the frequency of the triangular wave signal output by the triangular wave generation circuit, and c is the speed of light.

7. The millimeter-wave detector applicable to short-range moving targets according to claim 6, characterized in that: The detection circuit including comprises: a detection diode, a resistor, and a capacitor; Wherein, the positive electrode of the detection diode is connected to the output end of the low-pass filter amplification circuit; the resistor and the capacitor are respectively connected between the negative electrode of the detection diode and the ground.

8. The millimeter-wave detector applicable to short-range moving targets according to claim 7, characterized in that: The detection circuit including outputs an envelope signal with a frequency of f1 and filters out a triangular-wave signal with a frequency of fm, wherein fm is set to be at least greater than 10×f1.

9. The millimeter-wave detector applicable to a short-distance moving target according to claim 8, wherein: The f1 is the Doppler frequency corresponding to the relative speed of the detected moving target.

10. The millimeter-wave detector applicable to a short-distance moving target according to claim 9, wherein: The fourth preset frequency and the fifth preset frequency of the band-pass filter amplification circuit are the upper limit f H and the lower limit f L , Among them, Among them, v h is the upper speed limit in the direction of the line connecting the detected target and the millimeter-wave detector, and v L is the lower speed limit in the direction of the line connecting the detected target and the millimeter-wave detector.

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