Doppler radar system and signal processing method

Abstract

The invention discloses a Doppler radar system and a signal processing method, and belongs to the technical field of microelectronics. The system comprises a dual-frequency oscillator, a frequency chopper, a power amplifier, a low-noise amplifier, a frequency mixer, a differential chopper, an intermediate-frequency low-pass filter, an intermediate-frequency amplifier, an analog-to-digital converter and a chopping clock. The dual-frequency oscillator generates a dual-frequency radio frequency radar carrier signal; the frequency chopper is used for alternately gating carrier signals of a first frequency and a second frequency under the control of a chopping clock, and the frequency mixer outputs a mixed intermediate frequency signal to the differential chopper; the differential chopper outputs echo differential intermediate-frequency signals to the intermediate-frequency low-pass filter alternately in the forward and reverse directions under the control of high and low levels of the chopping clock, and a capacitance integrating circuit in the intermediate-frequency low-pass filter performs integral subtraction on the echo differential intermediate-frequency signals which are alternately input in the forward and reverse directions. Therefore, the direct-current voltage component of the filtered echo differential intermediate-frequency signal is reduced. The integration level of the Doppler radar system can be improved.

Description

Technical Field

[0001] The present invention relates to the field of microelectronic technology, and in particular to a Doppler radar system and a signal processing method. Background Art

[0002] Doppler radar systems are used to identify moving targets within the detection range and are often used in smart lighting systems, smart door locks, and security. In traditional Doppler radar systems, the reflected echo of a stationary target and the signal feedthrough form a strong intermediate frequency DC signal after mixing in the receiver. This DC signal needs to be filtered out before the signal generated by the Doppler frequency shift can be amplified, otherwise the receiver will be saturated and distorted.

[0003] In the related art, in order to filter out DC signals and retain low-frequency Doppler signals, large-capacitance capacitors are required, such as nanofarad (nF) or even microfarad (uF) capacitors. However, large-capacitance capacitors cannot be integrated inside the chip and need to be connected outside the chip, which limits the system integration. Summary of the invention

[0004] The present invention provides a Doppler radar system and a signal processing method. The technical solution is as follows:

[0005] On the one hand, a Doppler radar system is provided, comprising a power amplifier, a low noise amplifier, a mixer, an intermediate frequency low pass filter, an intermediate frequency amplifier, and an analog-to-digital converter; the system further comprises a dual frequency oscillator, a chopping clock, a frequency chopper, and a differential chopper; wherein the chopping clock is a high and low level periodic clock signal with a preset duty cycle;

[0006] The dual-frequency oscillator is used to input the generated dual-frequency radio frequency radar carrier signal into the frequency chopper; the dual frequency includes a first frequency and a second frequency;

[0007] The frequency chopper alternately selects the radar carrier signals of the first frequency and the second frequency according to the high and low levels of the received chopping clock, and outputs them to the power amplifier and the mixer, and the mixer mixes the echo signal amplified by the low noise amplifier with the radar carrier signal to obtain an echo differential intermediate frequency signal corresponding to the radar carrier signals of the first frequency and the second frequency, and the mixer outputs the echo differential intermediate frequency signal to the differential chopper;

[0008] The differential chopper is used to output the echo differential intermediate frequency signal alternately in positive and negative directions to the intermediate frequency low-pass filter under the control of the high and low levels of the chopping clock. The intermediate frequency low-pass filter integrates and averages the echo differential intermediate frequency signal alternately input in positive and negative directions using its internal capacitor integration circuit, thereby realizing the subtraction of the echo differential intermediate frequency signals corresponding to the two frequencies. After filtering, the echo differential intermediate frequency signal is amplified by the intermediate frequency amplifier and converted into a digital signal by the analog-to-digital converter.

[0009] On the other hand, a signal processing method based on any of the above-mentioned Doppler radar systems is provided, the method comprising:

[0010] The dual-frequency oscillator is used to generate a dual-frequency radio frequency radar carrier signal to a frequency chopper; the dual frequency includes a first frequency and a second frequency;

[0011] Controlling the frequency chopper and the differential chopper using the high and low levels of the chopping clock;

[0012] The frequency chopper is used to alternately select the radar carrier signals of the first frequency and the second frequency to be output to the power amplifier and the mixer under the control of the high and low levels of the chopping clock, and the mixer mixes the echo signal amplified by the low noise amplifier with the radar carrier signal to obtain an echo differential intermediate frequency signal corresponding to the radar carrier signals of the first frequency and the second frequency, and outputs the echo differential intermediate frequency signal to the differential chopper; the echo signal is a signal received by the system after the target reflects the radar carrier signal;

[0013] The differential chopper is used to output the echo differential intermediate frequency signal in positive and negative directions alternately to the intermediate frequency low-pass filter under the control of the high and low levels of the chopping clock, and the intermediate frequency low-pass filter uses its internal capacitor integration circuit to integrate and average the echo differential intermediate frequency signal input in positive and negative directions alternately, so as to achieve a subtraction operation of the echo differential intermediate frequency signals corresponding to the two frequencies;

[0014] The echo differential intermediate frequency signal after filtering is amplified by the intermediate frequency amplifier and converted into a digital signal by the analog-to-digital converter.

[0015] The technical solution provided by the present invention can at least bring the following beneficial effects:

[0016] A dual-frequency oscillator, a frequency chopper, a differential chopper and a chopper clock are arranged in a Doppler radar system, so that the frequency chopper alternately selects radar carrier signals of the first frequency and the second frequency under the control of the high and low levels of the chopper clock, and the mixer obtains echo differential intermediate frequency signals corresponding to the radar carrier signals of the first frequency and the second frequency after mixing the echo signal and the radar carrier signal. Under the control of the high and low levels of the chopper clock, the differential chopper outputs the echo differential intermediate frequency signals alternately in positive and negative directions to an intermediate frequency low-pass filter, so that the intermediate frequency low-pass filter integrates and averages the echo differential intermediate frequency signals alternately input in positive and negative directions by using its internal capacitor integration circuit, thereby realizing the subtraction of the echo differential intermediate frequency signals corresponding to the two frequencies and completing the signal filtering; and by subtracting the echo intermediate frequency signals corresponding to the two frequencies, the DC voltage component in the filtered echo differential intermediate frequency signal can be made close to 0. It can be seen that even if a DC blocking filter is not used in the Doppler radar system, the intermediate frequency DC signal can be filtered out. After eliminating the DC blocking filter with a large capacitance value, the integration of the Doppler radar system can be improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0018] Figure 1 It is a schematic diagram of the structure of a traditional Doppler radar system;

[0019] Figure 2 is a schematic diagram of the structure of a Doppler radar system provided by an embodiment of the present invention;

[0020] Figure 3 It is a schematic diagram of the control of a switch by a chopping clock and the frequency of gating under the control of the chopping clock provided by an embodiment of the present invention;

[0021] Figure 4 The present invention is a signal processing flow chart of a Doppler radar system provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0022] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments in the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0023] As mentioned above, a conventional Doppler radar system includes an RF oscillator, a power amplifier and a low noise amplifier, a mixer, a DC blocking filter, a low pass filter, an IF amplifier, an analog-to-digital converter, and a processor; please refer to Figure 1 , which is a schematic diagram of the structure of a traditional Doppler radar system, and its working mode includes:

[0024] The frequency oscillator transmits the generated radar carrier signal to the power amplifier and mixer at the same time. The power amplifier amplifies the radar carrier signal and transmits it to the radiation antenna TX to radiate electromagnetic waves to the detection space outside the chip. The electromagnetic wave signal encounters a reflective target and is reflected back to the receiving antenna RX, received by the receiving antenna RX and sent to the low-noise amplifier. The low-noise amplifier amplifies the received echo signal and mixes it with the radar carrier signal in the mixer. The echo signal of the stationary target has the same frequency as the carrier signal in the chip, and the phase difference is related to the radial distance between the reflective target and the radar and the wavelength of the radar wave. After mixing, DC signals with different voltage values ​​are formed. The echo signal of the moving target is mixed with the carrier signal in the chip to form a Doppler signal after the mixer. The DC isolation filter filters out the DC signal, and the Doppler signal is transmitted to the low-pass filter, which filters out the out-of-band noise and enters the intermediate frequency amplifier for signal amplification. The analog-to-digital converter converts the amplified Doppler signal into a digital signal, and the processor performs data processing.

[0025] for Figure 1 The expression of the radar carrier signal TX of the Doppler radar system shown is:

[0026] TX=cos(2πf0t+∮0)

[0027] Among them, f0 is the frequency of the carrier signal emitted by the radar, and ∮0 is the initial phase of the signal.

[0028] After the radar carrier signal is sent out, it hits the target and reflects to get the echo signal to the system receiver. The expression of the echo signal RX is:

[0029]

[0030] Where v is the moving speed of the target, R is the radial distance between the radar and the reflecting target, C is the speed of light, and B is the echo amplitude in the radar formula. The standard radar power formula shows that the amplitude B is related to R. 2 Inversely proportional.

[0031] The echo signal is multiplied and mixed with the radar carrier signal to obtain the intermediate frequency signal as follows:

[0032]

[0033] After the 2*f0 frequency term is filtered out by the low-pass filter, the low-frequency intermediate frequency signal is selected:

[0034]

[0035] in, is the Doppler frequency shift term, the target radial motion speed v, is a fixed phase shift.

[0036] For a stationary target, the velocity v of its echo signal is equal to 0, so the echo signal of the stationary target is a fixed DC voltage:

[0037]

[0038] The voltage value of this DC voltage is related to the echo signal amplitude, radial distance R and radar carrier signal wavelength C / f0. For close-range reflective targets, the radar transmits and receives signals, which are fed through and superimposed to produce a high voltage IF DC signal.

[0039] The DC blocking filter needs to select large-capacitance capacitors to filter out the intermediate frequency DC signal in order to retain the Doppler signal. However, large-capacitance capacitors are difficult to integrate inside the chip and require external components. This not only limits the system integration, but also requires additional input and output pins, forming an external noise interference path, and requires enhanced interference suppression.

[0040] Based on this, the inventive concept of the present invention is to use frequency chopping technology to significantly eliminate the echo DC signal in the Doppler radar system, without using large-capacitance capacitor components, thereby reducing the complexity of chip design.

[0041] The specific implementation of the above concept is described below.

[0042] Please refer to Figure 2 A Doppler radar system provided by an embodiment of the present invention includes: a power amplifier, a low noise amplifier, a mixer, an intermediate frequency low-pass filter, an intermediate frequency amplifier, and an analog-to-digital converter. Further, the system also includes a dual-frequency oscillator, a chopping clock, a frequency chopper, and a differential chopper; wherein the chopping clock is a high-low level periodic clock signal with a preset duty cycle;

[0043] The dual-frequency oscillator is used to input the generated dual-frequency radio frequency radar carrier signal into the frequency chopper; the dual frequency includes a first frequency and a second frequency;

[0044] The frequency chopper alternately selects the radar carrier signals of the first frequency and the second frequency according to the high and low levels of the received chopping clock, and outputs them to the power amplifier and the mixer, and the mixer mixes the echo signal amplified by the low noise amplifier with the radar carrier signal to obtain an echo differential intermediate frequency signal corresponding to the radar carrier signals of the first frequency and the second frequency, and the mixer outputs the echo differential intermediate frequency signal to the differential chopper;

[0045] The differential chopper is used to output the echo differential intermediate frequency signal alternately in positive and negative directions to the intermediate frequency low-pass filter under the control of the high and low levels of the chopping clock. The intermediate frequency low-pass filter integrates and averages the echo differential intermediate frequency signal alternately input in positive and negative directions using its internal capacitor integration circuit, thereby realizing the subtraction of the echo differential intermediate frequency signals corresponding to the two frequencies. After filtering, the echo differential intermediate frequency signal is amplified by the intermediate frequency amplifier and converted into a digital signal by the analog-to-digital converter.

[0046] In the embodiment of the present invention, a dual-frequency oscillator, a frequency chopper, a differential chopper and a chopper clock are arranged in a Doppler radar system, so that the frequency chopper alternately selects the radar carrier signals of the first frequency and the second frequency under the control of the high and low levels of the chopper clock, and the mixer obtains the echo differential intermediate frequency signal corresponding to the radar carrier signals of the first frequency and the second frequency after mixing the echo signal and the radar carrier signal. Under the control of the high and low levels of the chopper clock, the differential chopper outputs the echo differential intermediate frequency signal alternately in positive and negative directions to the intermediate frequency low-pass filter, so that the intermediate frequency low-pass filter integrates and averages the echo differential intermediate frequency signal alternately input in positive and negative directions by using its internal capacitor integration circuit, thereby realizing the subtraction of the echo differential intermediate frequency signals corresponding to the two frequencies and completing the signal filtering; and by subtracting the echo intermediate frequency signals corresponding to the two frequencies, the DC voltage component in the filtered echo differential intermediate frequency signal can be made close to 0. It can be seen that even if a DC blocking filter is not used in the Doppler radar system, the intermediate frequency DC signal can be filtered out. After eliminating the DC blocking filter with a large capacitance value, the integration of the Doppler radar system can be improved.

[0047] In the embodiment of the present invention, when reducing the DC voltage component in the echo differential intermediate frequency signal, it is mainly achieved by subtracting the echo differential intermediate frequency signals of the first frequency and the second frequency. When the duty cycle corresponding to the high and low level periodic clock signals in the chopping clock is closer to 50%, the DC voltage component in the echo differential intermediate frequency signal can be reduced more strongly. Therefore, in one implementation, the preset duty cycle is 30%-70%. More preferably, the preset duty cycle is 50%.

[0048] In one embodiment of the present invention, please continue to refer to Figure 2, the frequency chopper and the differential chopper can be implemented in one of the following ways:

[0049] The two input ends of the frequency chopper are respectively connected to the two contact ends S1 and S2 of the first single-pole double-throw switch, and the output end of the frequency chopper is connected to the common end of the first single-pole double-throw switch; the two input ends of the frequency chopper are respectively input with the radar carrier signals of the first frequency and the second frequency;

[0050] The input terminal P1 of the differential chopper is connected to the common terminal of the second single-pole double-throw switch, the input terminal N1 of the differential chopper is connected to the common terminal of the third single-pole double-throw switch, the output terminal P2 of the differential chopper is connected to the contact terminal S1 of the second single-pole double-throw switch and the contact terminal S2 of the third single-pole double-throw switch, and the output terminal N2 of the differential chopper is connected to the contact terminal S2 of the second single-pole double-throw switch and the contact terminal S1 of the third single-pole double-throw switch;

[0051] When the chopping clock is at the first level, the common end of the single-pole double-throw switch is connected to the contact end S1, so that the input end P1 of the differential chopper is connected to the output end P2, and the input end N1 is connected to the output end N2;

[0052] When the chopping clock is at the second level, the common end of the single-pole double-throw switch is connected to the contact end S2, so that the input end P1 of the differential chopper is connected to the output end N2, and the input end N1 is connected to the output end P2.

[0053] It can be seen that when the chopper clock outputs different levels, the frequency chopper can alternately select the radar carrier signals of the first frequency and the second frequency, and the differential chopper can output the echo differential intermediate frequency signal alternately in forward and reverse directions to the intermediate frequency low-pass filter.

[0054] In one implementation, the first level is a high level, and the second level is a low level; or, the first level is a low level, and the second level is a high level.

[0055] The following takes the chopping clock output high and low level periodic clock signal with a duty cycle of 50% as an example to explain the chopping clock output signal, switch control and frequency after gating. Please refer to Figure 3 . The period of the chopping clock is Ts, and the high level and low level occupy half a period Ts / 2 respectively. When the chopping clock is at a high level, the switches in the frequency chopper and the differential chopper are both S1 turned on. At this time, the frequency chopper selects the first frequency f1 to pass, and the differential chopper outputs the echo differential intermediate frequency signal in the forward direction; when the chopping clock is at a low level, the switches in the frequency chopper and the differential chopper are both S2 turned on. At this time, the frequency chopper selects the second frequency f2 to pass, and the differential chopper outputs the echo differential intermediate frequency signal in the reverse direction.

[0056] Considering that the frequency chopper alternately selects carrier signals of different frequencies, and the differential chopper alternately outputs the echo differential intermediate frequency signal in positive and negative directions, noise glitches will be generated during switching. In order to filter out the noise glitches by the intermediate frequency low-pass filter in the subsequent process, in one embodiment of the present invention, the clock frequency of the chopping clock is greater than the cutoff frequency of the intermediate frequency low-pass filter. In this way, the intermediate frequency low-pass filter can directly filter out the noise glitches without affecting the echo differential intermediate frequency signal.

[0057] In order to ensure the filtering effect of the intermediate frequency low-pass filter on noise burrs, the clock frequency of the chopping clock is at least 1.5 times the cut-off frequency of the intermediate frequency low-pass filter.

[0058] The Doppler radar system provided by the embodiment of the present invention can make the DC voltage component in the echo differential intermediate frequency signal close to 0, thereby achieving the effect of eliminating the DC voltage. The principle of the Doppler radar system in the embodiment of the present invention being able to reduce the DC voltage component is described below.

[0059] For the radar carrier signal with the first frequency f1 and the second frequency f2 emitted by the dual-frequency oscillator, the echo signal expressions corresponding to the first frequency and the second frequency are respectively:

[0060]

[0061] Where IF1 is the echo signal corresponding to the first frequency f1, IF2 is the echo signal corresponding to the first frequency f2, v is the moving speed of the target, R is the radial distance between the radar and the reflecting target, C is the speed of light, B is the echo amplitude in the radar formula, and the amplitude B is proportional to R. 2 Inversely proportional.

[0062] After the differential chopper performs forward and reverse alternating output, the intermediate frequency low-pass filter uses its internal capacitor integration circuit to integrate and average the echo differential intermediate frequency signals input alternately in the forward and reverse directions, thereby realizing the subtraction of the corresponding two frequency echo differential intermediate frequency signals. The equal-amplitude subtraction signal ΔIF is:

[0063]

[0064] The following formula is obtained by summing and subtracting the above formula for equal amplitude subtraction signals:

[0065]

[0066] In one implementation, the first frequency is not equal to the second frequency. When the first frequency f1 and the second frequency f2 are close, the difference between the first frequency and the second frequency is f1-f2=Δf, and (f1+f2) / 2 is the average frequency of f1 and f2, which is between f1 and f2 and can be approximately equal to f1 or f2. In this way, the above formula after sum-difference product can be simplified in two steps:

[0067]

[0068] After the simplification in the second step, the final expression of the equal-amplitude subtraction signal is obtained. According to the final expression, the signal frequency of ΔIF is Its value is close to the Doppler frequency The echo differential intermediate frequency signal of the conventional traditional radar with the main frequency is very close in frequency value to the Doppler intermediate frequency signal obtained by the conventional Doppler radar. It is just transformed from cosine to sinine phase and the phase is shifted by 90 degrees, which will not have any effect on the result.

[0069] In the final expression, the amplitude term is Where B is the echo amplitude in the radar formula, and vt+R is the radial distance between the radar and the reflecting target at time t. In this final expression, R′ can be used to replace vt+R. From the radar formula, we can see that B is related to the radial distance R′. 2 Inversely proportional.

[0070] When the radar detection range gradually increases from the short-range range, that is, when the radial distance R′ gradually increases, the amplitude terms corresponding to different radial distances are different, specifically:

[0071] In the close-range detection range, since the stationary target in the close-range range has a small R′ and v = 0, the amplitude term can be simplified to Approximately Among them, the term B*R′ means that the amplitude term of the intermediate frequency echo signal is changed from the echo amplitude B and R′ of the conventional traditional radar. 2 It is inversely proportional, and the overall term B*R′ changes to be inversely proportional to the distance R′.

[0072] When the detection range gradually increases, that is, the radial distance gradually increases, and when the distance R' increases to , amplitude term At this time, the amplitude term is the same as the amplitude of the echo signal received by the conventional Doppler radar.

[0073] When the detection range is further increased, that is, the radial distance R' is further increased, the amplitude of the echo signal is superimposed on the traditional radar echo signal amplitude B / 2 and the sin signal is added. to π, and the sin signal is The function value decreases rapidly between π and π, causing the overall echo signal amplitude to decrease faster than that of conventional Doppler radar.

[0074] Based on this, in one embodiment of the present invention, the farthest detection distance corresponding to the optimal detection range of the Doppler radar system is 1 / 4 of the wavelength corresponding to the difference between the first frequency and the second frequency. That is to say, the farthest detection distance corresponding to the optimal detection range of the Doppler radar system can be determined according to application requirements, and the requirement for the first frequency and the second frequency can be that when 1 / 4 of the wavelength corresponding to the difference is equal to the farthest detection distance, the optimal detection range is an ideal detection range. Among them, within the optimal detection range, the amplitude is greatly reduced, and at a closer distance, the amplitude approaches 0, that is, the echo signal of a close-range stationary target is weak and will not affect the Doppler signal of a moving target at a longer distance.

[0075] Furthermore, for the velocity v = 0 of the echo signal of a close-range stationary target, and the direct feedthrough signal from the transmitter to the receiver, both correspond to a very short radial distance, that is, the R value is very small, that is, The value is close to 0. The corresponding radar echo signal amplitude is The value is also close to 0. The amplitude in the amplitude term in the conventional Doppler radar system is only determined by -B / 2. The amplitude of the DC voltage component in the DC echo signal caused by the feedthrough from transmission to reception for the Doppler radar system in the embodiment of the present invention is greatly reduced compared with the conventional Doppler radar system. The amplitude in the embodiment of the present invention is similar to the amplitude of the Doppler signal caused by the remote moving target. Therefore, in the embodiment of the present invention, the DC voltage does not need to be isolated, and can be amplified in the same way as the Doppler signal of the remote moving target, without causing system saturation caused by DC signal amplification.

[0076] In the embodiment of the present invention, since the DC voltage component in the echo differential intermediate frequency signal after filtering by the intermediate frequency low-pass filter is close to 0, even if an external DC isolation filter is not used in the Doppler radar system, the intermediate frequency DC signal can be reduced or even filtered out. After eliminating the large-capacitance DC isolation filter, the integration of the Doppler radar system can be improved, and the port required for connecting the large-capacitance capacitor device outside the chip can be further eliminated, thereby reducing the noise caused by the port.

[0077] Furthermore, the devices used in the Doppler radar system will generate relatively high low-frequency noise in the low-frequency band, such as the flicker noise of CMOS devices. The low-frequency noise generated by the Doppler radar system at the low-frequency end will increase the system signal-to-noise ratio and reduce the target recognition performance of the system. In the embodiment of the present invention, the differential chopper can realize signal differential chopping subtraction by outputting the echo differential intermediate frequency signal in a positive and negative alternating manner, and can cancel the positive and negative low-frequency noise in the system itself, thereby significantly reducing the noise inside the system and improving the target recognition performance of the system.

[0078] Furthermore, in the operation process, in addition to receiving the target echo signal of the continuous wave emitted by its own system, the Doppler radar system will also receive signals sent by various other devices. These signals will become interference signals of the radar system, thereby causing radar false alarms and missed alarms, resulting in low target recognition performance of the radar system. Based on this, in the embodiment of the present invention, the differential chopper can realize signal differential chopping subtraction by outputting the echo differential intermediate frequency signal alternately in positive and negative directions. When the frequency of the chopping clock is high enough, the corresponding interference signal can achieve positive and negative cancellation, thereby greatly reducing the interference signal received by the system.

[0079] Please refer to Figure 4 The embodiment of the present invention provides a signal processing method based on any of the above-mentioned Doppler radar systems, the method comprising:

[0080] Step 400, using the dual-frequency oscillator to generate a dual-frequency radio frequency radar carrier signal to a frequency chopper; the dual frequency includes a first frequency and a second frequency;

[0081] Step 402, controlling the frequency chopper and the differential chopper using the high and low levels of the chopping clock;

[0082] Step 404, using the frequency chopper to alternately select the radar carrier signals of the first frequency and the second frequency to be output to the power amplifier and the mixer under the control of the high and low levels of the chopping clock, and the mixer mixes the echo signal amplified by the low noise amplifier with the radar carrier signal to obtain an echo differential intermediate frequency signal corresponding to the radar carrier signals of the first frequency and the second frequency, and outputs the echo differential intermediate frequency signal to the differential chopper; the echo signal is a signal received by the system after the target reflects the radar carrier signal;

[0083] Step 406, using the differential chopper to output the echo differential intermediate frequency signal in positive and negative directions alternately to the intermediate frequency low-pass filter under the control of the high and low levels of the chopping clock, and the intermediate frequency low-pass filter uses its internal capacitor integration circuit to integrate and average the echo differential intermediate frequency signal input in positive and negative directions alternately, so as to achieve a subtraction operation of the echo differential intermediate frequency signals corresponding to the two frequencies;

[0084] Step 408: The filtered echo differential intermediate frequency signal is amplified by the intermediate frequency amplifier and converted into a digital signal by the analog-to-digital converter.

[0085] It should be noted that, in this article, relational terms such as first, second, third and fourth are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, the elements defined by the statement "comprise a ..." do not exclude the existence of other identical elements in the process, method, article or device including the elements.

[0086] The above is only a preferred embodiment of the present application. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present application. These improvements and modifications should also be regarded as the scope of protection of the present application.

Claims

1. A Doppler radar system, comprising a power amplifier, a low noise amplifier, a mixer, an intermediate frequency low pass filter, an intermediate frequency amplifier, and an analog-to-digital converter; characterized in that: The system further comprises a dual frequency oscillator, a chopping clock, a frequency chopper and a differential chopper; wherein the chopping clock is a high and low level periodic clock signal of a preset duty cycle; The dual-frequency oscillator is used to input the generated dual-frequency radio frequency radar carrier signal into the frequency chopper; the dual frequency includes a first frequency and a second frequency; The frequency chopper alternately selects the radar carrier signals of the first frequency and the second frequency according to the high and low levels of the received chopping clock, and outputs them to the power amplifier and the mixer, and the mixer mixes the echo signal amplified by the low noise amplifier with the radar carrier signal to obtain an echo differential intermediate frequency signal corresponding to the radar carrier signals of the first frequency and the second frequency, and the mixer outputs the echo differential intermediate frequency signal to the differential chopper; The differential chopper is used to output the echo differential intermediate frequency signal alternately in positive and negative directions to the intermediate frequency low-pass filter under the control of the high and low levels of the chopping clock. The intermediate frequency low-pass filter integrates and averages the echo differential intermediate frequency signal alternately input in positive and negative directions using its internal capacitor integration circuit, thereby realizing the subtraction of the echo differential intermediate frequency signals corresponding to the two frequencies. After filtering, the echo differential intermediate frequency signal is amplified by the intermediate frequency amplifier and converted into a digital signal by the analog-to-digital converter.

2. The Doppler radar system according to claim 1, characterized in that: The preset duty cycle is 30%-70%.

3. The Doppler radar system according to claim 1, characterized in that: The two input ends of the frequency chopper are respectively connected to the two contact ends S1 and S2 of the first single-pole double-throw switch, and the output end of the frequency chopper is connected to the common end of the first single-pole double-throw switch; the two input ends of the frequency chopper are respectively input with the radar carrier signals of the first frequency and the second frequency; The input terminal P1 of the differential chopper is connected to the common terminal of the second single-pole double-throw switch, the input terminal N1 of the differential chopper is connected to the common terminal of the third single-pole double-throw switch, the output terminal P2 of the differential chopper is connected to the contact terminal S1 of the second single-pole double-throw switch and the contact terminal S2 of the third single-pole double-throw switch, and the output terminal N2 of the differential chopper is connected to the contact terminal S2 of the second single-pole double-throw switch and the contact terminal S1 of the third single-pole double-throw switch; When the chopping clock is at the first level, the common end of the single-pole double-throw switch is connected to the contact end S1, so that the input end P1 of the differential chopper is connected to the output end P2, and the input end N1 is connected to the output end N2; When the chopping clock is at the second level, the common end of the single-pole double-throw switch is connected to the contact end S2, so that the input end P1 of the differential chopper is connected to the output end N2, and the input end N1 is connected to the output end P2.

4. The Doppler radar system according to claim 3, characterized in that: The first level is a high level, and the second level is a low level; or, the first level is a low level, and the second level is a high level.

5. The Doppler radar system according to claim 1, characterized in that: The clock frequency of the chopping clock is greater than the cut-off frequency of the intermediate frequency low-pass filter.

6. The Doppler radar system according to claim 1, wherein: The clock frequency of the chopping clock is at least 1.5 times the cut-off frequency of the intermediate frequency low-pass filter.

7. The Doppler radar system according to claim 1, characterized in that: The maximum detection distance corresponding to the optimal detection range of the Doppler radar system is 1 / 4 of the wavelength corresponding to the difference between the first frequency and the second frequency.

8. A signal processing method based on the Doppler radar system according to any one of claims 1 to 7, characterized in that: The method comprises: The dual-frequency oscillator is used to generate a dual-frequency radio frequency radar carrier signal to a frequency chopper; the dual frequency includes a first frequency and a second frequency; Controlling the frequency chopper and the differential chopper using the high and low levels of the chopping clock; The frequency chopper is used to alternately select the radar carrier signals of the first frequency and the second frequency to be output to the power amplifier and the mixer under the control of the high and low levels of the chopping clock, and the mixer mixes the echo signal amplified by the low noise amplifier with the radar carrier signal to obtain an echo differential intermediate frequency signal corresponding to the radar carrier signals of the first frequency and the second frequency, and outputs the echo differential intermediate frequency signal to the differential chopper; the echo signal is a signal received by the system after the target reflects the radar carrier signal; The differential chopper is used to output the echo differential intermediate frequency signal in positive and negative directions alternately to the intermediate frequency low-pass filter under the control of the high and low levels of the chopping clock, and the intermediate frequency low-pass filter uses its internal capacitor integration circuit to integrate and average the echo differential intermediate frequency signal input in positive and negative directions alternately, so as to achieve a subtraction operation of the echo differential intermediate frequency signals corresponding to the two frequencies; The echo differential intermediate frequency signal after filtering is amplified by the intermediate frequency amplifier and converted into a digital signal by the analog-to-digital converter.

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