S-band radar full-digital visual real-time monitoring method

Abstract

The invention provides an S-band radar full-digital visual real-time monitoring method, which adopts a special radio frequency transceiver chip and a field programmable gate array to realize joint amplitude measurement and frequency measurement through zero-fill fast Fourier transform, and comprises the following steps of: 1, receiving a radar signal, the coverage frequency band of the special radio frequency transceiver chip covers S-band radar signals; step 2, the field programmable gate array performs initialization configuration on the radio frequency transceiver chip through an SPI port, and processes the baseband radar pulse signal to obtain a signal amplitude and a frequency deviation value; step 3, sending the received signal amplitude and frequency deviation value to an upper computer for visual display through an SPI port so as to monitor the emission condition in real time; by adopting a combination mode of the single radio frequency transceiver chip and the FPGA, the size of the monitoring system is reduced, and the integration level is improved; moreover, based on a programmable gate array, a user is allowed to perform field configuration and upgrade according to requirements.

Description

Technical Field

[0001] The invention belongs to the technical field of S-band radar, and more specifically, particularly relates to a full-digital visualized real-time monitoring method for S-band radar. Background Art

[0002] Marine radar is an indispensable means for the safe navigation of ships and is equipment that is explicitly required to be installed by the International Maritime Organization and the laws of various countries. Radar performance failures, including declines caused by magnetron consumption, will pose a great safety hazard to ship navigation if they are not discovered in time. Especially when visibility is poor or when sailing in the vast ocean, how to judge whether it is a radar failure or a real lack of target echo is impossible to determine by the radar itself.

[0003] A radar performance monitor is an auxiliary device that can indicate whether the performance of a radar system has degraded. Mandatory requirements for ships to be equipped with radar performance monitors have long been in effect at home and abroad. In recent years, management departments such as the China Classification Society have made it clear that they must strengthen inspections of this function. However, traditional radar performance monitors require the use of analog discrete devices to achieve the required functions. The variety of devices is large and complex, resulting in large size and difficulty in miniaturization. In addition, analog circuit debugging is troublesome, and after the microstrip line is designed, there is very little room for adjustment. Summary of the invention

[0004] In order to solve the above technical problems, the present invention provides an S-band radar full-digital visualized real-time monitoring method to solve the technical problems in the prior art that traditional radar performance monitors need to use analog discrete devices to achieve the required functions, and the devices are of many types and complex, resulting in large size and difficulty in miniaturization; in addition, the analog circuit is troublesome to debug, and after the microstrip line is designed, the adjustable room is very small.

[0005] The purpose and effect of the S-band radar full digital visualization real-time monitoring method of the present invention are achieved by the following specific technical means:

[0006] A fully digital visual real-time monitoring method for S-band radar, using a dedicated radio frequency transceiver chip and a field programmable gate array, through zero-filling fast Fourier transform, to achieve joint amplitude measurement and frequency measurement, including the following steps:

[0007] Step 1: Receive radar signals. The frequency band covered by the RF dedicated transceiver chip includes S-band radar signals;

[0008] Step 2: The field programmable gate array initializes and configures the RF transceiver chip through the SPI port, and processes the baseband radar pulse signal to obtain the signal amplitude and frequency offset values;

[0009] Step 3: Send the received signal amplitude and the frequency offset value to the host computer through the SPI port for visual display, so as to monitor the transmission situation in real time.

[0010] In a preferred embodiment, in step 1, the received radar signal is

[0011] r(t)=s(t)·w(Tt)+n(t)

[0012] Wherein, w(t) is a window function with a pulse width of T, and the RF signal is S-band 3050±30MHz. Windowing is used to reduce spectrum leakage during fast Fourier transform, and sampling is controlled by synchronous pulses to obtain signal strength and frequency offset digitally.

[0013] In a preferred implementation, in step 2, the signal amplitude is obtained in the time domain by digital detection, and the frequency offset value is obtained by frequency discrimination.

[0014] In a preferred embodiment, the joint measurement of amplitude and frequency is achieved by using Fourier transform in the frequency domain. The Fourier transform formula is:

[0015]

[0016] The peak amplitude of the fast Fourier transform reflects the signal strength, and the peak position reflects the frequency information; according to the position and size of the signal's fast Fourier transform spectrum line, the frequency components of the time domain signal are analyzed spectrally.

[0017] In a preferred embodiment, when calculating the amplitude, the fast Fourier transform peak amplitude can reflect the intensity change of the signal. When the frequency point falls on an integer multiple of fs / N, the peak amplitude is A2, and the amplitude information can be obtained by directly taking the square root. After the peak is found, the peak value is added to the two previous and next spectral lines and the square root is taken as the signal strength.

[0018] In a preferred embodiment, the frequency resolution of the fast Fourier transform is calculated as:

[0019]

[0020] The output sampling frequency is 120MHz, and the IQ two-way signal is subjected to complex fast Fourier transform. The signal frequency and amplitude information within the range of 60MHz can be measured at one time. A 1024-point zero-filled fast Fourier transform is performed, and the frequency resolution is fs / N≈120k. Through the optimization formula:

[0021]

[0022] In the formula, I represents the highest value position, P represents the spectrum line energy, f is the signal frequency, and fs is the output sampling clock.

[0023] In a preferred embodiment, in order to be compatible with the traditional mode, an indication signal is emitted according to the obtained amplitude and phase information to display a specific indication pattern. Multiple pulses can be emitted, each with a specific interval and an amplitude difference of a specific value. The pulses are 2 to 10, the interval time is 2 to 6 us, and the phase difference value is 0 to 10 dB.

[0024] In a preferred embodiment, the absolute strength of the transmitted pulse signal is determined according to the measured radar signal strength and can be gradually decreased by a specific amplitude, wherein the decreasing amplitude is 1 dB.

[0025] In a preferred embodiment, in step three, the signal amplitude and the frequency offset value are received through a PM antenna, and the received pulse amplitude and frequency offset are uploaded, and the amplitude change and frequency offset are displayed in real time on the software interface, and a digital instrument panel can also be introduced for intuitive display.

[0026] Compared with the prior art, the present invention has the following beneficial effects:

[0027] 1. By adopting a combination of a single RF transceiver chip and FPGA, the traditional complex analog transceiver channel and cumbersome control logic circuit are replaced. This not only greatly reduces the size of the monitoring system, improves the integration, and has a more compact structure, which can better meet the needs of miniaturization and intensive equipment, especially in some application scenarios with limited space. It is of great significance; it also greatly simplifies the circuit structure and reduces the difficulty of debugging. Based on the programmable gate array, it allows users to perform on-site configuration and upgrade according to their needs, which greatly improves the flexibility of the system and user experience.

[0028] 2. In terms of signal processing algorithms, a joint frequency and amplitude measurement method based on fast Fourier transform is adopted to replace the traditional analog detection and discrimination technology. This not only improves the measurement accuracy and stability, but also has stronger anti-noise ability and performs better in low signal-to-noise ratio environments. At the same time, it can monitor the strength and frequency drift of radar signals at any time and display them visually, which not only provides a better user experience, but also makes the real-time monitoring capability far exceed the traditional method, providing a strong guarantee for the efficient operation and accurate monitoring of the radar system.

[0029] 3. Drawing on the idea of ​​software radio, it allows users to reconfigure the design on site and can upgrade the display pattern according to user needs, greatly enhancing flexibility and user experience. In terms of cost and reliability, it uses existing chip-level devices to achieve a comparable cost, but greatly improves performance. At the same time, digital design reduces the difficulty of debugging and greatly improves the yield rate, thereby effectively improving the overall cost-effectiveness and economy. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 It is a flowchart of the steps of a fully digital visualized real-time monitoring method of an S-band radar of the present invention;

[0031] Figure 2 It is a digital PM workflow diagram in a fully digital visualized real-time monitoring method of an S-band radar of the present invention;

[0032] Figure 3 It is a processing block diagram of amplitude and phase obtained by digital frequency discrimination method in a fully digital visualized real-time monitoring method of an S-band radar of the present invention;

[0033] Figure 4 It is a simulation result of measuring frequency by the frequency discrimination method in a full digital visualized real-time monitoring method of an S-band radar of the present invention;

[0034] Figure 5 It is a simulation result of measuring frequency by FFT method in a full digital visualization real-time monitoring method of S-band radar of the present invention;

[0035] Figure 6 The present invention discloses a schematic diagram of transmitting multiple pulses in a fully digital visualized real-time monitoring method of an S-band radar. DETAILED DESCRIPTION

[0036] In order to further understand the present invention, preferred embodiments of the present invention are described below in conjunction with the accompanying drawings and examples. However, it should be understood that these descriptions are only for further illustrating the features and advantages of the present invention, rather than limiting the claims of the present invention.

[0037] Example:

[0038] Please refer to Figures 1 to 6As shown, the present invention provides an S-band radar full-digital visualized real-time monitoring method. First, in terms of hardware implementation, an integrated structure of a dedicated radio frequency transceiver chip and a field programmable gate array is adopted to replace the traditional complex analog transceiver channel and the cumbersome control logic circuit, which not only greatly reduces the size of the monitoring system, improves the integration, and has a more compact structure, which can better meet the needs of miniaturization and intensive equipment, especially in some application scenarios with limited space. It is of great significance; it also greatly simplifies the circuit structure and reduces the difficulty of debugging; in terms of signal processing algorithm, a joint amplitude measurement and frequency measurement method based on zero-filled fast Fourier transform is adopted to replace the traditional analog detection and frequency discrimination technology, which not only improves the measurement accuracy and stability, but also has a stronger anti-interference ability to noise, and performs better in a low signal-to-noise ratio environment. At the same time, through the design of the programmable gate array, users are allowed to perform on-site configuration and upgrade according to their needs, which greatly improves the flexibility of the system and user experience. In terms of cost and reliability, the solution is implemented using existing chip-level devices, with comparable cost, but greatly improved performance. At the same time, digital design reduces the difficulty of debugging and greatly improves the yield rate, thereby effectively improving the overall cost-effectiveness and economic efficiency. It includes the following steps:

[0039] Step 1: Receive radar signals. A dedicated RF transceiver chip is used to achieve this function. The frequency band coverage of this chip is specially designed for receiving S-band radar signals, and can effectively capture and sample radar echo signals in this frequency band. By using a dedicated RF transceiver chip, this method has many advantages in the signal reception link compared to the traditional analog transceiver channel. First, the dedicated chip has a higher degree of integration and a smaller size, which helps to achieve the miniaturization and compact design of the entire monitoring system. Secondly, the dedicated chip has better RF performance and stronger anti-interference ability, and can more reliably capture weak radar echo signals. In addition, the design of the dedicated chip is more concise and efficient, which greatly reduces the difficulty of debugging and improves the production yield.

[0040] Step 2: After the signal receiving link, the field programmable gate array (FPGA) is used to initialize the configuration of the RF transceiver chip and process the baseband signal. The FPGA communicates with the RF transceiver chip through the SPI bus, and can flexibly configure and control its parameters. This not only ensures that the transceiver chip operates according to the expected working state, but also realizes real-time digital processing of the received radar echo signal; the FPGA integrates a special signal processing module, which can analyze the frequency and amplitude of the baseband radar pulse signal and obtain the key frequency offset and signal strength values; this FPGA-based signal processing solution has many advantages. First, as a programmable hardware platform, FPGA can adjust the signal processing algorithm at any time according to demand to realize flexible upgrading of system functions. Secondly, the parallel computing capability inside the FPGA is very strong, which can efficiently complete complex digital signal processing tasks and ensure real-time performance; in addition, FPGA has a high degree of integration and can be closely integrated with the RF transceiver chip, further improving the integration and reliability of the system.

[0041] Step 3: After completing the acquisition and digital processing of the radar echo signal, the amplitude and frequency offset values ​​are transmitted to the host computer through the SPI bus for visual display; the host computer has powerful data processing and graphics rendering capabilities, which can convert the original signal data into intuitive and easy-to-understand visualization effects, greatly improving the user's operating experience; secondly, the host computer has a richer interactive interface and display methods, which can realize multi-dimensional data display to meet different monitoring needs. In addition, the host computer can further conduct comprehensive analysis and alarm judgment on the data to provide users with more intelligent monitoring decision support.

[0042] In step 1, the received radar signal is:

[0043] r(t)=s(t)·w(Tt)+n(t)

[0044] Among them, w(t) is a window function with a pulse width of T, and the RF signal is S-band 3050±30MHz. The windowing method can reduce spectrum leakage during fast Fourier transform. Generally speaking, the rectangular window function can be directly selected without too strict requirements. By synchronously controlling the pulse signal for digital sampling, the key signal strength and frequency offset values ​​can be obtained; in addition, if the power monitoring (PM) device is installed, it is also necessary to adjust the gain Ga to make the reference arc Ar almost invisible, and save the Ga value at this time, so that the other multiple arcs can play the role of indicating the degradation of radar system performance; the whole workflow is as follows Figure 2As shown, it should be pointed out that due to the existence of frequency drift, the received signal may not fall within the 60MHz bandwidth, that is, no pulse may be detected; under the premise of correct synchronization control, the receiving frequency can be set for scanning, and only 4 times are needed to cover the 2.9GHz-3.1GHz frequency band specified by IMO, but if the peak signal is still not found and exceeds a certain detection threshold, it means that the signal is not transmitted; if multiple peaks are detected, there may be some unwanted signals, and timely alarms are also required.

[0045] In PM, the automatic gain control (AGC) function is different from the traditional automatic gain control. It just borrows this concept. Its main purpose is to monitor the strength of the transmitted signal and accurately track the change in the size of the response signal. Therefore, the key premise is to accurately measure the size of the radar antenna radiation signal; in digital PM, digital detection can be used to obtain amplitude information, and frequency discrimination can be used to obtain frequency deviation information, such as Figure 3 As shown; when implemented in the time domain, when the signal-to-noise ratio is high, more accurate amplitude information and frequency deviation information can be obtained, but the signal-to-noise ratio requirement is high; in normal operation, the detection effect is relatively good, but when the transmission performance decreases and the signal strength decreases, the effect will deteriorate rapidly. Whether it is detection or frequency discrimination, there is a certain threshold effect. When the signal-to-noise ratio is lower than the theoretical threshold, the performance will drop sharply. This is a defect that cannot be overcome by time domain detection and frequency discrimination methods, such as Figure 4 and Figure 5 As reflected in the simulation results shown; in order to solve this problem, a technology using FFT (Fast Fourier Transform) to jointly measure amplitude and frequency offset is introduced. This method can maintain high measurement accuracy even when the signal-to-noise ratio is low, thereby achieving more comprehensive and accurate monitoring of the transmission signal status.

[0046] In order to overcome the limitations of time domain detection and frequency discrimination, the Fourier transform method is used in the frequency domain to achieve joint measurement of amplitude and frequency. The Fourier transform formula is:

[0047]

[0048] The peak amplitude of the fast Fourier transform reflects the signal strength, and the peak position reflects the frequency information. By performing fast Fourier transform on the time domain signal, the spectral distribution of the signal can be obtained, thereby comprehensively analyzing the frequency components in the signal. Compared with traditional analog detection and discrimination techniques, this joint frequency and amplitude measurement method based on fast Fourier transform not only improves the measurement accuracy and stability, but also has stronger anti-interference ability against noise, and performs particularly well in low signal-to-noise ratio environments. At the same time, this method can also monitor the strength and frequency drift of the radar signal in real time and display it visually, which not only improves the user experience, but also greatly enhances the ability to monitor the operating status of the radar system, providing a strong guarantee for ensuring the efficient operation and accurate monitoring of the radar system.

[0049] In the process of using fast Fourier transform to realize joint frequency and amplitude measurement, when calculating the signal amplitude, according to the properties of fast Fourier transform, when the frequency point falls on an integer multiple of the sampling frequency fs / N, the peak amplitude is A2, and the amplitude information can be obtained by directly taking the square root; but in practical applications, due to factors such as frequency drift, the signal frequency point may not accurately fall on the ideal integer multiple frequency point. At this time, an improved method can be adopted, that is, when finding the peak amplitude, the amplitudes of the two adjacent spectral lines on the left and right sides of the peak are also taken into account, and then the square root of the average of these three amplitude values ​​is calculated as the final signal amplitude; this method can not only capture the true amplitude of the signal more accurately, but also is more robust to noise, and can suppress the influence of noise on amplitude measurement to a certain extent.

[0050] Calculate the frequency, the frequency resolution of the fast Fourier transform is:

[0051]

[0052] According to the principle of fast Fourier transform, when the output sampling frequency is 120MHz, the IQ two-way signal is subjected to complex fast Fourier transform, and the signal frequency and amplitude information within the range of 60MHz can be measured at one time. In order to further improve the resolution of frequency measurement, a 1024-point fast Fourier transform can be used for zero padding, and the frequency resolution is fs / N≈120k. However, for some signals with higher frequencies or larger frequency drifts, the frequency resolution obtained by relying solely on fast Fourier transform may not be fine enough. For this reason, an optimized frequency calculation formula can be used to further improve the accuracy of frequency measurement by considering the amplitude and energy distribution of the spectrum line. By optimizing the formula:

[0053]

[0054] In the formula, I represents the highest value position, P represents the spectrum line energy, f is the signal frequency, and f sTo output the sampling clock, this method can not only measure the center frequency of the signal more accurately, but also track dynamic frequency changes, providing more reliable basic data for subsequent signal analysis and processing.

[0055] Please refer to Figure 4 and Figure 5 As shown in the figure, compared with the time domain frequency discrimination method, the frequency domain method, namely the fast Fourier transform, is more robust in a low signal-to-noise ratio environment. The time domain frequency discrimination method is very sensitive to the signal-to-noise ratio and has an obvious threshold effect. When the signal-to-noise ratio is lower than a certain critical value, the frequency measurement error will increase sharply and cannot meet the accuracy requirements of practical applications. The frequency domain method has a better noise suppression capability due to the introduction of narrowband filtering, and can perform frequency measurement more stably even under low signal-to-noise ratio conditions. If, on the basis of the frequency domain method, an optimization formula is also used to correct the frequency measurement results, the measurement accuracy can be further improved. After this optimization process, the frequency measurement accuracy is improved in a low signal-to-noise ratio environment. The root mean square error can reach the order of 100kHz, and under high signal-to-noise ratio conditions, it can even reach the order of 10kHz, which is much better than the simple time domain frequency discrimination method. This accuracy fully meets the requirements of automatic frequency control (AFC) tracking; in contrast, the use of fast Fourier transform for frequency domain measurement not only has strong noise resistance and high measurement accuracy, but also can obtain joint information of amplitude and frequency. These numerical information can not only meet the requirements of functions such as automatic gain control (AGC) and automatic frequency control (AFC), but also can be transmitted to the host computer to achieve real-time visual display, providing richer and more reliable data support for subsequent signal analysis and processing.

[0056] Please refer to Figure 6As shown, due to the real-time upload of amplitude and frequency information, the host computer can monitor and visualize in real time whether the transmission signal meets the requirements and issue an alarm in time. In fact, it is not necessary to display the traditional pattern for real-time monitoring, but in order to be compatible with the traditional PM, it is necessary to transmit the indication signal according to the obtained amplitude and phase information. Multiple pulses can be transmitted, each with a specific time interval and a specific amplitude difference. There are 2 to 10 pulses, with an interval of 2 to 6us and a phase difference of 0 to 10dB. The amplitude can reflect the strength of the transmission signal. In view of the differences in the actual radiation power of the radar, system loss and the PM's transceiver channel, after installing the PM device, the reference arc of the two arcs should be made vague by adjusting the gain. In order to reflect the advantages of digitization, we can transmit 10 pulses, each with a 4us interval and an amplitude difference of 1dB. In this way, the display range can be reduced from 0-10dB with a 1dB step value. Similarly, the gain needs to be adjusted to make the reference arc almost invisible. In this way, the representation accuracy is more accurate and can be characterized when the decrease is small. It should be pointed out that the absolute strength of the transmitted pulse signal needs to be determined based on the measured radar signal strength. On this basis, it can be gradually reduced by a specific amplitude of 1 dB, which is relatively easy to control for digital transmission PM.

[0057] In step three, because the FFT method is used to achieve joint measurement of amplitude and frequency deviation, accurate digital information can be obtained. Therefore, it is not necessary to display a pattern to indicate performance when turned on like the traditional PM; the pulse amplitude and frequency deviation received by the PM antenna can be uploaded in real time through the SPI serial port, and the amplitude change and frequency offset can be displayed in real time on the software interface. In addition to displaying numerical values, a digital instrument panel can also be introduced, which is more intuitive and more beautiful; drawing on the idea of ​​software radio, it allows users to perform on-site configuration and reconstruction design, and can upgrade the display pattern according to user needs, greatly enhancing flexibility and user experience.

[0058] The embodiments described above are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that the technical solutions described in the aforementioned embodiments may still be modified, or some of the technical features may be replaced by equivalents. Such modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention, and should all be included in the protection scope of the present invention.

Claims

1. A fully digital visual real-time monitoring method for S-band radar, characterized in that: The joint amplitude and frequency measurement is realized by using a dedicated RF transceiver chip and a field programmable gate array through zero-filled fast Fourier transform, including the following steps: Step 1: Receive radar signals. The frequency band covered by the RF dedicated transceiver chip includes S-band radar signals. Step 2: The field programmable gate array initializes and configures the RF transceiver chip through the SPI port, and processes the baseband radar pulse signal to obtain the signal amplitude and frequency offset values; Step 3: Send the received signal amplitude and the frequency offset value to the host computer through the SPI port for visual display, so as to monitor the transmission situation in real time.

2. The S-band radar full digital visualization real-time monitoring method according to claim 1 is characterized by: In step 1, the received radar signal is r(t)=s(t)·w(Tt)+n(t) Wherein, w(t) is a window function with a pulse width of T, and the RF signal is S-band 3050±30MHz. Windowing is used to reduce spectrum leakage during fast Fourier transform, and sampling is controlled by synchronous pulses to obtain signal strength and frequency offset digitally.

3. The S-band radar full digital visualization real-time monitoring method according to claim 1 is characterized by: In step 2, the signal amplitude is obtained in the time domain by digital detection, and the frequency offset value is obtained by frequency discrimination.

4. The S-band radar full digital visualization real-time monitoring method according to claim 3 is characterized by: In the frequency domain, Fourier transform is used to realize the joint measurement of amplitude and frequency. The Fourier transform formula is: The peak amplitude of the fast Fourier transform reflects the signal strength, and the peak position reflects the frequency information; according to the position and size of the signal's fast Fourier transform spectrum line, the frequency components of the time domain signal are analyzed spectrally.

5. The S-band radar full digital visualization real-time monitoring method according to claim 4 is characterized by: When calculating the amplitude, the fast Fourier transform peak amplitude can reflect the intensity change of the signal. When the frequency point falls on an integer multiple of fs / N, the peak amplitude is A2, and the amplitude information can be obtained by directly taking the square root. After searching for the peak, add the peak value and the two previous and next spectral lines and take the square root as the signal strength.

6. The S-band radar full digital visualization real-time monitoring method according to claim 5 is characterized by: Calculate the frequency, the frequency resolution of the fast Fourier transform is: The output sampling frequency is 120MHz, and the IQ two-way signal is subjected to complex fast Fourier transform. The signal frequency and amplitude information within the range of 60MHz can be measured at one time. A 1024-point zero-filled fast Fourier transform is performed, and the frequency resolution is fs / N≈120k. Through the optimization formula: In the formula, I represents the highest value position, P represents the spectrum line energy, f is the signal frequency, and f s is the output sampling clock.

7. The S-band radar full digital visualization real-time monitoring method according to claim 6 is characterized by: In order to be compatible with the traditional mode, an indication signal is emitted according to the obtained amplitude and phase information to display a specific indication pattern. Multiple pulses can be emitted, each with a specific interval and a specific amplitude difference. The pulses are 2 to 10, the interval time is 2 to 6 us, and the phase difference value is 0 to 10 dB.

8. The S-band radar full digital visualization real-time monitoring method according to claim 7 is characterized by: The absolute strength of the transmitted pulse signal is determined according to the measured radar signal strength and can be gradually decreased by a specific amplitude, wherein the decreasing amplitude is 1 dB.

9. The S-band radar full digital visualization real-time monitoring method according to claim 1, characterized in that: In step three, the signal amplitude and the frequency offset value are received through the PM antenna, and the received pulse amplitude and frequency offset are uploaded. The amplitude change and frequency offset are displayed in real time on the software interface, and a digital instrument panel can also be introduced for intuitive display.

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