FMCW radar signal generation device and FMCW radar working method

Abstract

The invention discloses an FMCW radar signal generation device and an FMCW radar working method. The FMCW radar signal generation device comprises a PLL chip module integrated with a VCO, a time sequence control module, a signal shielding / zero setting module, a signal synthesis module, a signal receiving and transmitting acquisition module and a baseband signal processing module. The PLL chip module integrated with the VCO is formed by connecting a plurality of small-bandwidth VCO units in parallel, the input end of each small-bandwidth VCO unit is connected with the time sequence control module through a switch, the output end of each small-bandwidth VCO unit is connected with a digital gating circuit, and the outputs of all the digital gating circuits are connected with the signal synthesis module; the signal synthesis module is connected with the signal transceiving acquisition module, and the signal transceiving acquisition module transmits the intermediate frequency signal to the baseband signal processing module. By using the large-bandwidth PLL chip integrated with the VCO, a plurality of small-bandwidth VCOs successfully simulate a broadband FMCW radar signal in a time sequence splicing manner, so that the high-precision ranging capability is maintained while the system cost is reduced.

Description

Technical Field

[0001] The present invention belongs to the technical field of FMCW radar radio frequency signal generation and reception processing, and specifically relates to a low-cost FMCW radar that uses a large-bandwidth PLL chip with an integrated VCO to output broadband frequency modulation signals, as well as a specific process of using the radar system for ranging. Background Art

[0002] Traditional FMCW radar systems typically require the transmission of a continuous wave signal with a wide frequency modulation bandwidth to achieve high-resolution distance measurement and precise target positioning. Wideband frequency modulation signals can provide higher range resolution, as their frequency varies continuously and linearly within the frequency modulation period, resulting in a clear relationship between the intermediate frequency (IF) generated after mixing and the target range. However, generating such wideband frequency modulation signals typically relies on a high-bandwidth voltage-controlled oscillator (VCO). Due to the very high design, manufacturing process, and component performance requirements of such VCOs, they suffer from the following major drawbacks:

[0003] 1. High Design Complexity: Wide-bandwidth VCOs must maintain excellent frequency stability and linear frequency modulation characteristics across the entire frequency modulation bandwidth, placing extremely high demands on RF circuit design. Designers must comprehensively consider factors such as temperature drift, nonlinear distortion, and electromagnetic interference, significantly increasing the overall design complexity and verification process.

[0004] 2. Expensive manufacturing costs: To meet the requirements of high bandwidth and high stability, large-bandwidth VCOs often require the use of high-performance components and precision manufacturing processes. This not only increases the cost of raw materials, but also increases the testing and calibration steps in the production process, resulting in high costs during mass production.

[0005] 3. Difficulty in implementation: Since large-bandwidth VCOs require high dynamic response and stability across the entire frequency modulation range, in actual applications, the devices produced often have poor consistency and are easily affected by environmental factors, posing a hidden danger to the stability of the overall system performance.

[0006] 4. High sweep voltage requirements pose additional challenges to power supply design: To achieve a wide frequency modulation range, a large-bandwidth VCO usually requires a higher sweep voltage. However, the limitations of existing circuit board power supply voltage and drive circuit linearity make it very difficult to provide a sufficiently high and stable sweep voltage, while also increasing power consumption and heat dissipation burdens. Summary of the Invention

[0007] The present invention aims to overcome the shortcomings of the prior art by providing an FMCW radar signal generation device that is composed of several sequentially integrated and spliced ​​small-bandwidth VCOs, each capable of stable operation within its own narrow frequency band, and is easy to manufacture and low in cost. It also provides an operating method for the radar.

[0008] The object of the present invention is achieved through the following technical solutions: an FMCW radar signal generating device, comprising a PLL chip module with an integrated VCO, a timing control module, a signal shielding / zeroing module, a signal synthesis module, a signal transceiver acquisition module, and a baseband signal processing module;

[0009] The PLL chip module with integrated VCO is composed of multiple small-bandwidth VCO units connected in parallel. Each small-bandwidth VCO unit generates a local LFM signal during a set period. A switch is provided at the input of each small-bandwidth VCO unit, and the input of each small-bandwidth VCO unit is connected to the timing control module through the switch. The signal shielding / zeroing module includes multiple digital gating circuits.

[0010] The output end of each small bandwidth VCO unit is connected to a digital gating circuit, and the outputs of all digital gating circuits are connected to the signal synthesis module;

[0011] The signal synthesis module is connected to the signal transceiver acquisition module. The signal transceiver acquisition module transmits the broadband FM signal synthesized by the signal synthesis module through the power amplifier and matching circuit, and then transmits it to the target area through the antenna, and receives the signal reflected back by the target; the received signal is mixed with the transmitted signal in the mixer, and the intermediate frequency signal is obtained through filtering; the intermediate frequency signal is then transmitted to the baseband signal processing module;

[0012] The baseband signal processing module samples the received signal through the ADC and converts it into a digital signal; then it performs windowing and FFT transformation on the digital signal, extracts the intermediate frequency value, and calculates the target distance through the frequency modulation slope.

[0013] Another object of the present invention is to provide an FMCW radar operating method, which uses the above-mentioned device to generate FMCW radar signals, comprising the following steps:

[0014] Step 1: The timing control module uses a high-precision clock to generate a control signal, set the startup timing, and preset the working period of each small-bandwidth VCO;

[0015] Step 2: According to the control signal generated by the timing control module, each small bandwidth VCO unit starts to generate an LFM signal with linear frequency modulation characteristics after being activated;

[0016] Step 3: Use the signal shielding / zeroing module to shield the signal during the initial startup period and transmit the stable LFM signal to the signal synthesis module; during the shielding period, the signal path is disconnected through the digital gating circuit, so that the output during this period is zero level;

[0017] Step 4: The signal synthesis module collects the LFM signals output by each small-bandwidth VCO unit in real time, aligns the LFM signals in the time domain using the clock provided by the timing control module, and splices the LFM signals into a continuous broadband FM signal according to the preset splicing rules;

[0018] Step 5: The signal transceiver acquisition module amplifies the broadband FM signal obtained after signal splicing through the power amplifier, and then transmits it to the transmitting antenna through the matching network, and then transmits it to the target area through the antenna;

[0019] Step 6: The transmitted signal is reflected by the target object. After receiving the signal reflected by the target object, the signal transceiver module mixes it with the transmitted signal in the mixer, and then filters out the high-frequency part, retaining only the intermediate frequency signal and transmitting it to the baseband signal processing module;

[0020] Step 7: The baseband signal processing module uses ADC to sample the intermediate frequency signal and convert it into a digital signal; then the signal is windowed; then the signal is FFTed to calculate the spectrum and the main peak frequency is found through peak detection;

[0021] Step 8: Calculate the distance of the target based on the relationship between the main peak frequency and the FM slope, completing the radar ranging process.

[0022] The beneficial effects of the present invention are as follows: by utilizing a large-bandwidth PLL chip with an integrated VCO, the present invention enables multiple small-bandwidth VCOs to be spliced ​​together in a timed manner, successfully simulating a wideband FMCW radar signal. This reduces system costs while maintaining high-precision ranging capabilities. Conventional FMCW radars typically require a large-bandwidth VCO (voltage-controlled oscillator) to generate wideband LFM signals. However, large-bandwidth VCOs are expensive due to their complex manufacturing process, and their high-frequency performance is difficult to guarantee. Because the large-bandwidth PLL chip with an integrated VCO is relatively inexpensive and easy to maintain, the hardware cost of the entire system is significantly reduced, while improving the system's maintainability and scalability.

[0023] Because the present invention uses a broadband LFM signal composed of multiple small-bandwidth VCOs, the signal is suppressed (amplitude returns to zero) in some time periods during the VCO switching process, but the main components of the target echo signal can still be ensured to return intact. At the receiving end, the intermediate frequency information is extracted through mixing. After combining it with FFT analysis, the target distance can still be accurately calculated using the formula.

[0024] By combining these optimization measures, the present invention reduces the cost of FMCW radar signal generation while maintaining its high-precision ranging capability. By filtering to remove noise, using a Hanning window to reduce spectrum leakage, and using FFT to extract the main frequency component, the intermediate frequency signal is accurately extracted, ensuring that the final ranging accuracy is not affected by the spliced ​​signal, thus meeting the application requirements of high-precision FMCW radar. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 1 is a structural diagram of the FMCW radar signal generating device of the present invention;

[0026] Figure 2 This is the working flow diagram of FMCW radar;

[0027] Figure 3 This is a diagram of the received signal processing process of the invention. DETAILED DESCRIPTION

[0028] To reduce system costs and simplify manufacturing, this paper proposes a high-bandwidth PLL chip with integrated VCOs. This chip is constructed by sequentially integrating and splicing several small-bandwidth VCOs. Each small-bandwidth VCO operates stably within its own narrow frequency band, making it easy to manufacture and inexpensive. Through precise timing control and signal splicing techniques, the outputs of these small-bandwidth VCOs can be spliced ​​together in time to form an overall large-bandwidth frequency-modulated signal. However, since each small-bandwidth VCO may exhibit unstable output during initial startup, this interference can introduce transient signal amplitude fluctuations or noise. To prevent this interference from entering subsequent processing circuits, the unstable signals are shielded or zeroed, ensuring that only stable signals are used for subsequent mixing and target ranging. At the signal receiving end, a filter is used to remove interfering signals. Since the signal is intermittent with non-integer periodicity, discontinuities appear at the signal endpoints. These discontinuities manifest as high-frequency components in the frequency domain that are not present in the original signal, resulting in spectral leakage. This paper applies windowing to the echo signal. The basic idea of ​​windowing is to multiply the signal by a window function, smoothing the signal's temporal boundaries and reducing discontinuities and spectral leakage. Finally, a fast Fourier transform (FFT) is performed on the processed echo signal to extract the intermediate frequency (IF) signal, which is then used to calculate the range, thus achieving a low-cost, high-precision FMCW radar solution.

[0029] Assume that the timing control module presets a startup time of 10 microseconds for each small-bandwidth VCO and a bandwidth of 300 MHz. The integrated VCO PLL chip contains three VCOs. This chip can then output a sawtooth wave with a sweep bandwidth of 900 MHz and a period of 30 microseconds. Assuming the target is 100 meters from the radar, the delay time τ is determined by the target distance R: τ = 2R / c, where c = 3×108 m / s is the speed of light, and the intermediate frequency signal value should be f IF =2αR / c=20Mhz.

[0030] The technical solution of the present invention is further described below with reference to the accompanying drawings.

[0031] like Figure 1 As shown, an FMCW radar signal generating device of the present invention includes a PLL chip module with integrated VCO, a timing control module, a signal shielding / zeroing module, a signal synthesis module, a signal transceiver acquisition module, and a baseband signal processing module;

[0032] The PLL chip module with integrated VCO is composed of multiple small-bandwidth VCO units connected in parallel. Each small-bandwidth VCO unit generates a local LFM signal during a set period. A switch is provided at the input of each small-bandwidth VCO unit, and the input of each small-bandwidth VCO unit is connected to the timing control module through the switch. The signal shielding / zeroing module includes multiple digital gating circuits.

[0033] The output end of each small bandwidth VCO unit is connected to a digital gating circuit, and the outputs of all digital gating circuits are connected to the signal synthesis module;

[0034] The signal synthesis module is connected to the signal transceiver acquisition module. The signal transceiver acquisition module transmits the broadband FM signal synthesized by the signal synthesis module through the power amplifier and matching circuit, and then transmits it to the target area through the antenna, and receives the signal reflected back by the target; the received signal is mixed with the transmitted signal in the mixer, and the intermediate frequency signal is obtained through filtering; the intermediate frequency signal is then transmitted to the baseband signal processing module;

[0035] The baseband signal processing module samples the received signal through the ADC and converts it into a digital signal; then it performs windowing and FFT transformation on the digital signal, extracts the intermediate frequency value, and calculates the target distance through the frequency modulation slope.

[0036] like Figure 2 As shown, an FMCW radar operating method of the present invention uses the device of the present invention to generate an FMCW radar signal, including the following steps:

[0037] Step 1: The timing control module uses a high-precision clock (such as a crystal oscillator or timer) to generate control signals, set the activation sequence, and preset the operating time of each small-bandwidth VCO; for example, VCO1 activates between 0 and 10 microseconds, VCO2 between 10 and 20 microseconds, and VCO3 between 20 and 30 microseconds. Timing control ensures that each VCO activates strictly according to the scheduled time, avoiding mutual interference and time overlap.

[0038] Step 2: According to the control signal generated by the timing control module, each small bandwidth VCO unit starts to generate an LFM signal with linear frequency modulation characteristics after being activated. Its frequency f(t) changes with time and can be expressed by the following formula:

[0039]

[0040] where f c is the carrier frequency of the transmitted signal, B is the bandwidth of the signal, assuming B = 900Mhz, the sweep time of the sawtooth signal T = 30μs, which is the sum of the working time of each small bandwidth VCO; then the transmitted signal S tx (t) can be expressed as:

[0041]

[0042] Where α=B / T is the frequency modulation slope.

[0043] Step 3: Use the signal shielding / zeroing module to shield the unstable signal during the initial startup period (for example, the first 1 microsecond after startup) and transmit the stable LFM signal to the signal synthesis module; during this shielding period, the signal path is disconnected through the digital gating circuit, so that the output during this period is zero level; after shielding the unstable period, each VCO only transmits the signal within the stable working period (for example, the signal within 1 to 10 microseconds) to the subsequent modules to ensure signal quality.

[0044] Step 4: The signal synthesis module collects the LFM signals output by each small bandwidth VCO unit in real time, and uses the clock provided by the timing control module to align the LFM signals in the time domain; and splices each LFM signal into a continuous broadband frequency modulation signal according to the preset splicing rules; assuming that three small bandwidth VCOs 1, VCO2, and VCO3 are used for splicing, and the working sweep time of each VCO is 10 microseconds, then the duration of the stable output signal of VCO1 is 1 to 10 microseconds, the duration of the stable output signal of VCO2 is 11 to 20 microseconds, and the duration of the stable output signal of VCO3 is 21 to 30 microseconds. According to the splicing rules, the three VCO stable signals are spliced ​​into a continuous LFM frequency modulation signal. At this time, the transmitted signal is

[0045]

[0046] Step 5: The signal transceiver acquisition module amplifies the broadband FM signal obtained after signal splicing through the power amplifier, and then transmits it to the transmitting antenna through the matching network, and then transmits it to the target area through the antenna;

[0047] Step 6: The transmitted signal is reflected after encountering the target object. After the signal transceiver module receives the signal reflected by the target object, it mixes it with the transmitted signal in the mixer to generate an intermediate frequency signal, which is then transmitted to the baseband signal processing module. The reflected signal is represented as:

[0048]

[0049] The delay time τ of the reflected signal is determined by the target distance R, τ = 2R / c. If the target distance is 100 meters, the delay time τ = 0.667 microseconds.

[0050] The radar's transmitted signal (local oscillator signal) and reflected signal are input into the mixer for difference frequency processing; in the mixer, the echo signal is multiplied by the local oscillator signal:

[0051]

[0052] Then, a Butterworth low-pass filter is used, and an appropriate cutoff frequency (e.g., 50 MHz) is selected to filter out the high-frequency portion, retaining only the intermediate frequency signal and transmitting it to the baseband signal processing module. The resulting intermediate frequency signal is:

[0053]

[0054] Step 7: The baseband signal processing module uses ADC (high-speed analog-to-digital converter) to sample the intermediate frequency signal and convert it into a digital signal; then the signal is windowed; and then the signal is FFT (fast Fourier transform) is performed to calculate the spectrum S IF (f) = FFT(S IF (t)), find the main peak frequency f by peak detection IF =ατ; its process is as follows Figure 3 shown.

[0055] Since the finite length of the signal will cause spectrum leakage, the present invention first uses the Hanning Window function to perform weighted processing on the signal before performing FFT to reduce spectrum leakage and improve ranging accuracy. The Hanning Window function is expressed as:

[0056]

[0057] Step 8: According to the relationship between the main peak frequency and the FM slope R = f IF c / 2α, calculate the distance to the target and complete the radar ranging process.

[0058] The core of FMCW radar's ranging function is to calculate target distance using the mixed intermediate frequency (IF) signal, rather than relying directly on the continuity of the transmitted signal. Even if the signal is partially lost, the target's echo signal still provides stable IF information within the effective FM range. As long as the IF signal's primary frequency component remains clearly discernible, even brief signal interruptions will ensure that the main peak of the spectrum remains, and the ranging result will not be significantly affected.

[0059] Those skilled in the art will appreciate that the embodiments described herein are intended to help readers understand the principles of the present invention, and it should be understood that the scope of protection of the present invention is not limited to such specific descriptions and embodiments. Those skilled in the art can make various other specific variations and combinations based on the technical teachings disclosed in the present invention without departing from the essence of the present invention, and such variations and combinations are still within the scope of protection of the present invention.

Claims

1. An FMCW radar signal generating device, characterized in that: Including PLL chip module with integrated VCO, timing control module, signal shielding / zeroing module, signal synthesis module, signal transceiver acquisition module, and baseband signal processing module; The PLL chip module with integrated VCO is composed of multiple small-bandwidth VCO units connected in parallel. Each small-bandwidth VCO unit generates a local LFM signal during a set period. A switch is provided at the input of each small-bandwidth VCO unit, and the input of each small-bandwidth VCO unit is connected to the timing control module through the switch. The signal shielding / zeroing module includes multiple digital gating circuits. The output end of each small bandwidth VCO unit is connected to a digital gating circuit, and the outputs of all digital gating circuits are connected to the signal synthesis module; The signal synthesis module is connected to the signal transceiver acquisition module. The signal transceiver acquisition module transmits the broadband FM signal synthesized by the signal synthesis module through the power amplifier and matching circuit, and then transmits it to the target area through the antenna, and receives the signal reflected back by the target; the received signal is mixed with the transmitted signal in the mixer, and the intermediate frequency signal is obtained through filtering; the intermediate frequency signal is then transmitted to the baseband signal processing module; The baseband signal processing module samples the received signal through the ADC and converts it into a digital signal; then it performs windowing and FFT transformation on the digital signal, extracts the intermediate frequency value, and calculates the target distance through the frequency modulation slope.

2. A FMCW radar operating method, using the device according to claim 1 to generate an FMCW radar signal, characterized in that: The following steps are involved: Step 1: The timing control module uses a high-precision clock to generate a control signal, set the startup timing, and preset the working period of each small-bandwidth VCO; Step 2: According to the control signal generated by the timing control module, each small bandwidth VCO unit starts to generate an LFM signal with linear frequency modulation characteristics after being activated; Step 3: Use the signal shielding / zeroing module to shield the signal during the initial startup period and transmit the stable LFM signal to the signal synthesis module; during the shielding period, the signal path is disconnected through the digital gating circuit, so that the output during this period is zero level; Step 4: The signal synthesis module collects the LFM signals output by each small-bandwidth VCO unit in real time, aligns the LFM signals in the time domain using the clock provided by the timing control module, and splices the LFM signals into a continuous broadband FM signal according to the preset splicing rules; Step 5: The signal transceiver acquisition module amplifies the broadband FM signal obtained after signal splicing through the power amplifier, and then transmits it to the transmitting antenna through the matching network, and then transmits it to the target area through the antenna; Step 6: The transmitted signal is reflected by the target object. After receiving the signal reflected by the target object, the signal transceiver module mixes it with the transmitted signal in the mixer, and then filters out the high-frequency part, retaining only the intermediate frequency signal and transmitting it to the baseband signal processing module; Step 7: The baseband signal processing module uses ADC to sample the intermediate frequency signal and convert it into a digital signal; then the signal is windowed; then the signal is FFTed to calculate the spectrum and the main peak frequency is found through peak detection; Step 8: Calculate the distance of the target based on the relationship between the main peak frequency and the FM slope, completing the radar ranging process.

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