Multi-frequency automatically tunable high-frequency ground wave radar system and automatic tuning method

Abstract

The application discloses a kind of multi-frequency automatic adjustable high-frequency ground wave radar system and automatic adjusting method, system includes multi-band transmitter, full-band receiving antenna array, multichannel receiver and control unit;Preset detection frequency band is divided into low-frequency long-distance detection group and high-frequency medium and near distance detection group, multichannel receiver is divided into two ways by power divider and is accessed to corresponding channel group, utilize FPGA to realize single analog-digital conversion channel and process two frequency band signals simultaneously;Control unit selects optimal non-multiple frequency band in two groups, controls double frequency and works simultaneously and adjusts frequency band combination according to real-time ocean parameter.The application gives consideration to long-distance coverage and near-shore high-precision detection, reduces hardware cost, realizes all-weather full-sea condition high-quality ocean environment detection.

Description

Technical Field

[0001] This invention relates to the field of radar technology, and in particular to a multi-frequency automatically adjustable high-frequency ground wave radar system and an automatic adjustment method. Background Technology

[0002] High-frequency ground wave radar is the core equipment of the three-dimensional marine environmental monitoring network. It can realize all-weather, large-scale, and low-cost detection of marine dynamic elements such as wind, waves, and currents on the sea surface. It plays an irreplaceable role in marine disaster prevention and mitigation, marine resource development, and the protection of maritime rights.

[0003] Currently, high-frequency ground wave radars generally adopt a single-site, single-frequency-band operating mode. The commonly used transmission frequency bands and their corresponding performances in the industry are as follows: 4MHz–5MHz band, with a maximum detection range of 300km, suitable for long-range, large-area detection; 7MHz–8MHz band, with a maximum detection range of 200–250km; 13MHz–16MHz band, with a maximum detection range of 60–100km; and 24MHz–26MHz band, with a maximum detection range of 20km, suitable for high-precision near-shore detection. There is an inherent contradiction between the detection range, accuracy, and applicable sea states of different frequency bands: low-frequency electromagnetic waves have low propagation attenuation on the sea surface and a long detection range, but their longer wavelength results in low sensitivity to small-scale sea surface undulations and poor detection accuracy, making them only suitable for detecting large-scale ocean phenomena such as typhoons and large eddies under high sea states; high-frequency bands have high detection accuracy, but large propagation attenuation and a short detection range, making them only suitable for fine-grained detection under low sea states.

[0004] In practical applications, the electromagnetic environment and sea state are constantly changing. Over a 24-hour period, different frequency bands are affected to varying degrees by factors such as ionospheric changes and electromagnetic interference. Furthermore, daily fluctuations in sea state from 18:00 to 9:00 the following day significantly alter the sensitivity of ground-wave radar to sea surface roughness. These factors lead to unstable echo signal strength in single-band radar, resulting in a substantial decrease in the effectiveness of detecting ocean currents, winds, and waves. This results in problems such as short detection range, small detection area, and low detection accuracy during many periods, making it impossible to achieve high-quality all-weather detection.

[0005] To address these issues, some existing radar systems have implemented a degree of automatic frequency tuning. However, limited by the frequency selectivity of the antenna and receiving equipment, they can only perform very small-range frequency adjustments within a single operating frequency band. They cannot switch operating modes across large frequency bands, thus failing to fundamentally change the detection range and accuracy, and cannot dynamically adapt to the optimal operating frequency band based on real-time sea conditions. Furthermore, some multi-frequency radar solutions require independent receiving antennas and hardware channels for each frequency band, resulting in a significant increase in system hardware cost, size, and power consumption, leading to poor engineering practicality.

[0006] In summary, existing high-frequency ground wave radar technology suffers from drawbacks such as the inability to balance detection coverage and accuracy, insufficient all-weather detection capability, limited automatic frequency tuning range, poor sea state adaptability, and high hardware costs. Summary of the Invention

[0007] The purpose of this invention is to provide a multi-frequency automatically adjustable high-frequency ground wave radar system and an automatic adjustment method to solve the aforementioned technical problems in the prior art. The specific technical solution is as follows: A multi-frequency automatically adjustable high-frequency ground wave radar system, with a multi-band transmitter connected to a transmitting antenna, capable of covering multiple preset detection frequency bands, which are divided into a low-frequency long-range detection group and a high-frequency medium- and short-range detection group; The output of the full-band receiving antenna array is connected to the input of the multi-channel receiver, and the operating frequency band of the full-band receiving antenna array can cover multiple preset detection frequency bands; A power divider is installed on the multi-channel receiver. The power divider is used to split the echo signal output by each receiving antenna in the receiving antenna array into two paths, which are respectively connected to the first receiving channel group corresponding to the low-frequency long-range detection group and the second receiving channel group corresponding to the high-frequency medium- and short-range detection group. The multi-channel receiver includes an analog-to-digital converter, a field-programmable gate array (FPGA), and multiple direct digital frequency synthesizers (DDS). The FPGA is connected to the FPGA and the DDS to enable a single FPGA channel to process echo signals from two different frequency bands simultaneously. The control unit is connected to the multi-band transmitter and the multi-channel receiver respectively, and is used to select the optimal non-frequency band in the low-frequency long-range detection group and the high-frequency medium- and short-range detection group, so as to control the system to work simultaneously in two optimal frequency bands and adjust the frequency band combination according to real-time ocean parameters.

[0008] Furthermore, the multi-band transmitter is a 4-channel transmitter, with each channel of the 4-channel transmitter independently corresponding to a preset detection frequency band, capable of simultaneously outputting transmission signals of two different frequency bands.

[0009] Furthermore, the preset detection frequency bands include 4MHz~5MHz, 7MHz~8MHz, 13MHz~16MHz and 24MHz~26MHz; the low-frequency long-range detection group includes the 4MHz~5MHz and 7MHz~8MHz frequency bands, and the high-frequency medium-short-range detection group includes the 13MHz~16MHz and 24MHz~26MHz frequency bands; The multi-channel receiver is a 16-channel receiver; the first receiving channel group consists of the first 8 receiving channels of the 16-channel receiver, and its pre-filter bandwidth is 4MHz to 8MHz; the second receiving channel group consists of the last 8 receiving channels of the 16-channel receiver, and its pre-filter bandwidth is 13MHz to 26MHz.

[0010] Furthermore, the field-programmable gate array has a built-in frequency division processing module, which is connected to the output of the analog-to-digital converter unit. This module is used to separate two different frequency band signals acquired by the single-channel analog-to-digital converter unit and send them to the corresponding direct digital frequency synthesizers for matched filtering.

[0011] Furthermore, the control unit includes a signal-to-noise ratio (SNR) detection module and a sea state parameter processing module. The input terminal of the SNR detection module is connected to the output terminal of the multi-channel receiver, and the output terminal of the SNR detection module is connected to the frequency band control terminal of the multi-band transmitter, for outputting the optimal frequency band selection signal according to the echo SNR of each frequency band. The input terminal of the sea state parameter processing module is connected to the ocean parameter output terminal of the multi-channel receiver, and the output terminal of the sea state parameter processing module is connected to the frequency band switching terminal of the multi-band transmitter, which is used to adjust the signal by outputting frequency band combinations according to real-time wind, wave and current parameters.

[0012] A multi-frequency automatic adjustment method for high-frequency ground wave radar, implemented using the aforementioned multi-frequency automatically adjustable high-frequency ground wave radar system, includes the following steps: Multiple preset detection frequency bands are set up, and these preset detection frequency bands are divided into low-frequency long-range detection group and high-frequency medium- and short-range detection group according to the detection distance. The radar echo signal reflected from the sea surface is received, and the echo signal output from each receiving antenna is divided into two paths, which are respectively input into the first receiving channel group corresponding to the low-frequency long-range detection group and the second receiving channel group corresponding to the high-frequency medium- and short-range detection group. The echo signals from two different frequency bands are processed simultaneously through a single analog-to-digital conversion channel, and the corresponding frequency bands are matched and filtered by multiple direct digital frequency synthesizers. Based on the signal-to-noise ratio of the echoes in each frequency band, an optimal working frequency band is selected from both the low-frequency long-range detection group and the high-frequency medium-to-short-range detection group, and there is no harmonic relationship between the two selected optimal working frequency bands. The control system operates simultaneously in two optimal frequency bands, enabling simultaneous detection of the marine environment at long and medium-to-short distances; Based on real-time ocean wind, wave and current parameters, the combination of two optimal operating frequency bands is adaptively adjusted.

[0013] Furthermore, the specific steps for simultaneously processing echo signals from two different frequency bands through a single analog-to-digital conversion channel are as follows: digitally divide the mixed frequency band signal acquired by the single analog-to-digital conversion unit to separate the signal components of the two different frequency bands, and send them to the corresponding direct digital frequency synthesizers for matched filtering.

[0014] Furthermore, the specific steps for selecting the optimal operating frequency band based on the signal-to-noise ratio (SNR) of the echoes in each frequency band are as follows: Detection signals are transmitted sequentially in each preset detection frequency band, the SNR of the corresponding echoes is detected, and usable frequency bands with SNR higher than the preset SNR threshold are selected; in the usable frequency bands of the low-frequency long-range detection group, the frequency band with the highest SNR is selected as the first optimal frequency band, and in the usable frequency bands of the high-frequency short-range detection group, the frequency band with the highest SNR and no harmonic relationship with the first optimal frequency band is selected as the second optimal frequency band.

[0015] Furthermore, the preset signal-to-noise ratio threshold is 10–20 dB.

[0016] Furthermore, the step of adaptively adjusting the combination of the two optimal operating frequency bands based on the ocean wind, wave and current parameters obtained in real time is as follows: when the detected wind, wave and current parameters are greater than the first preset sea state threshold, the operation is adjusted to simultaneously operate in the two optimal frequency bands with the highest signal-to-noise ratio in the low-frequency long-range detection group; when the detected wind, wave and current parameters are less than the second preset sea state threshold, the operation is adjusted to simultaneously operate in the two optimal frequency bands with the highest signal-to-noise ratio in the high-frequency medium- and short-range detection group.

[0017] The multi-frequency automatically adjustable high-frequency ground wave radar system and automatic adjustment method of the present invention have the following advantages: 1. By combining frequency band grouping, hardware splitting, and algorithm fusion, the problem of traditional single-band high-frequency ground wave radar being unable to balance detection range and accuracy, and having unstable all-weather detection effects is fundamentally solved. It can achieve 300km-level long-range coverage and 20km-level near-shore high-precision detection simultaneously without multi-station networking. Furthermore, the single-AD dual-frequency processing technology avoids doubling the cost of hardware channels, improving the system's practicality and reducing costs.

[0018] 2. Through a 4-channel independent transmitter architecture, independent control and output of four typical detection frequency bands are achieved. Each channel operates without interference, which can stably support the requirement of simultaneous transmission of dual frequency bands. The independent switching and power control design of the channels not only ensures the signal quality of dual-frequency collaborative detection, but also provides a flexible hardware foundation for subsequent frequency band switching and power optimization.

[0019] 3. It adopts four common high-frequency ground wave radar frequency bands, covering all core detection needs from nearshore to offshore, and has good engineering compatibility and practicality; the 16-channel receiver is grouped by high and low frequency and configured with pre-filters for corresponding frequency bands, which effectively filters out out-of-band interference, significantly improves the signal-to-noise ratio of the input signal, and lays the foundation for subsequent high-precision signal processing.

[0020] 4. The FPGA's built-in frequency division processing module uses a purely digital approach to separate and process dual-frequency signals. Compared to traditional analog splitting schemes, it offers greater flexibility and stability without introducing additional analog noise. At the same time, this design fully utilizes the FPGA's parallel computing capabilities, further reducing the system's hardware complexity and size.

[0021] 5. The control unit is divided into two independent modules: signal-to-noise ratio detection and sea state parameter processing, thus constructing a complete two-layer automatic frequency modulation control mechanism. By first selecting available frequency bands based on signal-to-noise ratio and then optimizing frequency band combinations based on sea state, the system achieves fully autonomous operation, automatically adapting to electromagnetic environment and sea state changes without manual intervention, thereby improving the system's unattended operation capability and all-weather reliability.

[0022] 6. A complete closed-loop control method has been formed, which includes frequency band preset, signal reception and processing, optimal frequency band selection and sea state adaptive adjustment. The method has strong real-time performance, can give full play to the performance advantages of the system hardware, and ensure that the system always works in the state most adapted to the current environment, effectively improving the continuity and data quality of marine environmental detection. Attached Figure Description

[0023] Figure 1 This is a connection diagram of the multi-frequency automatically adjustable high-frequency ground wave radar system of the present invention.

[0024] Figure 2 This is a schematic diagram of the multi-band transmitter in the multi-frequency automatically adjustable high-frequency ground wave radar system of the present invention.

[0025] Figure 3 This is a schematic diagram of the multi-channel receiver in the multi-frequency automatically adjustable high-frequency ground wave radar system of the present invention. Detailed Implementation

[0026] To better understand the purpose, structure, and function of this invention, the following detailed description of the multi-frequency automatically adjustable high-frequency ground wave radar system and automatic adjustment method of this invention is provided in conjunction with the accompanying drawings.

[0027] like Figures 1 to 3 As shown, the present invention provides a high-frequency ground wave radar system with automatic adjustment of multiple frequencies. The system adopts a modular design and is mainly composed of four parts: a multi-band transmitter 1, a full-band receiving antenna array 2, a multi-channel receiver 3, and a control unit 4. The modules are connected by coaxial cables and control cables to work together to complete multi-frequency adaptive detection of the marine environment.

[0028] A multi-band transmitter 1 is connected one-to-one with four independent transmitting antennas 6, and its operating frequency band covers all preset high-frequency ground wave radar detection frequency bands. The detection signal generated by the control unit 4 is transmitted to the multi-band transmitter 1 via a coaxial cable, amplified, and then transmitted to the corresponding transmitting antenna 6 via a coaxial cable for radiation. In this embodiment, the preset detection frequency bands are divided into a low-frequency long-range detection group and a high-frequency medium-to-short-range detection group according to their detection distance and accuracy characteristics. This division is based on the basic propagation principle of high-frequency ground wave radar: the lower the frequency of electromagnetic waves, the smaller the propagation attenuation on the sea surface and the longer the detection distance, but the longer the wavelength, the lower the sensitivity to small-scale undulations on the sea surface and the poorer the detection accuracy; conversely, the higher the frequency, the shorter the detection distance, but the stronger the ability to resolve small-scale sea conditions and the higher the detection accuracy. By grouping the frequency bands, the system can simultaneously utilize the advantages of different frequency bands to achieve both long-range coverage and high-precision near-shore detection.

[0029] The full-band receiving antenna array 2 adopts an 8-element linear array structure, consisting of eight identical 3-30MHz full-band receiving antennas arranged at equal intervals. Its output is connected to the input of the multi-channel receiver 3 via a coaxial cable. A single receiving antenna can cover all the preset detection frequency bands of this system, eliminating the need for separate receiving antennas for different frequency bands, greatly simplifying the antenna array structure and reducing installation and maintenance costs. By measuring the phase difference of the echo arriving at different antenna elements, the 8-element array can accurately calculate the angle of arrival of the echo, achieving spatial resolution of sea conditions in different sea areas, a function that a single receiving antenna cannot achieve.

[0030] The multi-channel receiver 3 has a dual-power divider 5 at the front end corresponding to each receiving antenna. The power divider 5 splits the raw echo signal output from each receiving antenna into two paths with equal power, which are then connected to the first receiving channel group and the second receiving channel group, respectively. The first receiving channel group corresponds to the low-frequency long-range detection group, and the second receiving channel group corresponds to the high-frequency medium-to-short-range detection group. This hardware splitting configuration allows for parallel processing of high and low frequency signals, avoiding mutual interference between signals of different frequency bands and improving the real-time performance of signal processing. The multi-channel receiver 3 also includes an analog-to-digital converter (ADC), a field-programmable gate array (FPGA), and multiple direct digital frequency synthesizers (DDS). The FPGA is connected to the ADC and multiple DDS to enable a single ADC channel to process echo signals from two different frequency bands simultaneously. Traditional multi-frequency receiving schemes require an independent AD channel for each frequency band, and the hardware cost and size increase exponentially with the number of frequency bands. However, this embodiment achieves single-channel dual-frequency parallel processing without increasing the number of AD hardware through the digital signal processing algorithm inside the FPGA. This avoids the hardware redundancy that requires twice the number of receiving channels to complete dual-frequency processing, and reduces the hardware cost and size of the system.

[0031] The control unit 4 is implemented using an industrial control computer and is connected to the multi-band transmitter 1 and the multi-channel receiver 3 via control cables. Its functions include three aspects: first, selecting an optimal operating frequency band from both the low-frequency long-range detection group and the high-frequency medium-to-short-range detection group based on the signal-to-noise ratio of the echoes from each frequency band, strictly ensuring that the two selected frequency bands do not have a harmonic relationship to avoid harmonic interference; second, controlling the multi-band transmitter 1 and the multi-channel receiver 3 to operate simultaneously on these two optimal frequency bands, achieving dual-frequency collaborative detection; and third, dynamically adjusting the operating frequency band combination based on the ocean wind, wave, and current parameters obtained in real-time from the multi-channel receiver 3, ensuring that the system always operates in a state most suitable for the current sea state. After the system is powered on, the software of the control unit 4 automatically starts and completes the entire system initialization, all operating parameters automatically match the preset initial operating frequency band, and the multi-channel receiver 3 is controlled to enter the working state.

[0032] In a preferred embodiment, the multi-band transmitter 1 is a 4-channel solid-state transmitter, with each channel independently corresponding to a preset detection frequency band, capable of simultaneously outputting transmission signals of two different frequency bands. The four channels are independent of each other, and their switching and output power can be controlled individually to meet the requirements of simultaneous dual-frequency transmission.

[0033] The corresponding preset detection frequency bands are 4MHz–5MHz, 7MHz–8MHz, 13MHz–16MHz, and 24MHz–26MHz. Among them, 4MHz–5MHz and 7MHz–8MHz belong to the low-frequency long-range detection group, with maximum detection distances of 300km and 200–250km respectively; 13MHz–16MHz and 24MHz–26MHz belong to the high-frequency medium-to-short-range detection group, with maximum detection distances of 60–100km and 20km respectively. These four frequency bands are currently the most commonly used operating bands for high-frequency ground wave radar, covering the main detection needs from nearshore to offshore. The optimal operating frequency point within each band has been pre-calibrated and determined based on the actual environment and sea conditions at the deployment site.

[0034] The multi-channel receiver 3 employs a 16-channel all-digital receiver. The first eight receiving channels constitute the first receiving channel group, each equipped with a pre-filter with a frequency band of 4MHz to 8MHz at its input to filter out interference signals outside the low-frequency band. The latter eight receiving channels constitute the second receiving channel group, each equipped with a pre-filter with a frequency band of 13MHz to 26MHz at its input to filter out interference signals outside the high-frequency band. The pre-filters significantly improve the signal-to-noise ratio of the input signal, providing high-quality raw data for subsequent digital signal processing.

[0035] The FPGA integrates a dedicated frequency divider module, whose input is connected to the output of the analog-to-digital converter (ADC). Its working principle involves digitally filtering and dividing the mixed digital signal containing two different frequency bands acquired by a single-channel AD converter, separating the two independent frequency band signal components. These components are then sent to their respective digital signal generators (DDS) for mixing and matched filtering, ultimately yielding the baseband signals for the two frequency bands. This purely digital frequency division method offers greater flexibility and stability compared to traditional analog splitting methods, and it does not introduce additional analog noise.

[0036] The control unit 4 is internally divided into two functionally independent modules: a signal-to-noise ratio (SNR) detection module and a sea state parameter processing module. The input of the SNR detection module is connected to the output of the multi-channel receiver 3 to receive real-time SNR data from echoes in each frequency band; its output is connected to the frequency band control terminal of the multi-band transmitter 1, outputting an optimal frequency band selection signal based on the SNR of each frequency band. The input of the sea state parameter processing module is connected to the ocean parameter output of the multi-channel receiver 3 to receive wind speed, wave height, ocean current speed, and other wind, wave, and current parameters obtained through real-time inversion; its output is connected to the frequency band switching terminal of the multi-band transmitter 1, outputting a frequency band combination adjustment signal based on the severity of the current sea state. These two modules work together to form the system's dual-layer automatic frequency modulation control mechanism.

[0037] Based on the above system, the present invention also provides a multi-frequency automatic adjustment method for high-frequency ground wave radar, which is implemented using the above system and specifically includes the following steps: First, during the system initialization phase, multiple detection frequency bands for high-frequency ground wave radars are preset and divided into a low-frequency long-range detection group and a high-frequency medium-to-short-range detection group based on their detection range. The frequency band division is based on the propagation characteristics of the high-frequency ground wave radars and actual detection requirements, ensuring that the two frequency bands can respectively cover the long-range and medium-to-short-range detection ranges.

[0038] After the system starts up, transmitting antenna 6 radiates electromagnetic waves towards the sea surface, and the full-band receiving antenna array 2 receives the radar echo signals reflected from the sea surface. The echo signals output from each receiving antenna are first split into two paths by power divider 5, and input to the first receiving channel group and the second receiving channel group respectively. After being filtered by their respective pre-filters, the two signals enter the corresponding AD conversion units for digital sampling.

[0039] The digitized signal is fed into an FPGA for processing, where two echo signals from different frequency bands are processed simultaneously via a single analog-to-digital converter (ADC). Specifically, the FPGA's internal frequency division module performs digital frequency division on the mixed signal acquired by the AD converter, separating it into two signal components of different frequency bands. These two signal components are then sent to their respective digital signal processing units (DDSs) for mixing and matched filtering to obtain the baseband signals for the two frequency bands. This processing method fully utilizes the parallel computing capabilities of the FPGA, achieving real-time processing of dual-frequency signals without increasing hardware resources.

[0040] Next, control unit 4 selects the optimal operating frequency band based on the signal-to-noise ratio (SNR) of the echoes in each frequency band. The system sequentially controls the multi-band transmitter 1 to transmit detection signals in each preset detection frequency band, starting from the lowest frequency band of 4MHz to 5MHz. Simultaneously, the multi-channel receiver 3 detects the SNR of the corresponding echoes, filtering out usable frequency bands with SNR higher than a preset SNR threshold. Then, in the low-frequency long-range detection group, the frequency band with the highest SNR is selected as the first optimal frequency band. In the high-frequency short-range detection group, the frequency band with the highest SNR and no harmonic relationship with the first optimal frequency band is selected as the second optimal frequency band. Excluding frequency band combinations with harmonic relationships is to avoid high-frequency signals becoming harmonics of low-frequency signals, thus causing severe intermodulation interference and affecting the accuracy of the detection results.

[0041] After determining the optimal frequency band, the control unit 4 controls the system to operate simultaneously on both optimal frequency bands, achieving synchronous detection of the marine environment at long and medium-to-short distances. At this time, the multi-band transmitter 1 simultaneously transmits electromagnetic waves of two frequency bands, and the multi-channel receiver 3 simultaneously receives and processes the echo signals of these two frequency bands, respectively retrieving the ocean wind, wave, and current parameters within the corresponding detection range.

[0042] During the detection process, the system adaptively adjusts the combination of two optimal operating frequency bands based on the real-time ocean wind, wave, and current parameters acquired. When the detected wind, wave, and current parameters exceed the first preset sea state threshold, it indicates that the current sea state is relatively severe, with large sea surface fluctuations and long wave wavelengths. The echo detection effect directly corresponds to the wavelength of the detection frequency. The low-frequency signal of the long wave can better penetrate the waves and obtain stable and reliable echoes. Only the detection results of the low-frequency band can accurately reflect the ocean dynamics characteristics under high sea states. The system will adjust to operate simultaneously on the two optimal frequency bands with the highest signal-to-noise ratio in the low-frequency long-range detection group. When the detected wind, wave, and current parameters are less than the second preset sea state threshold, it indicates that the current sea state is relatively calm, with wave heights less than 1 meter. The high-frequency signal of the short wave can more accurately detect the small fluctuations of the sea surface and obtain more accurate wind, wave, and current parameters. The system will adjust to operate simultaneously on the two optimal frequency bands with the highest signal-to-noise ratio in the high-frequency medium- and short-range detection group. When the sea state is between the two, the system maintains the dual-frequency combination of one low and one high frequency, taking into account both detection distance and accuracy.

[0043] Furthermore, the preset signal-to-noise ratio threshold is 10–20 dB, preferably 15 dB. When the signal-to-noise ratio of the echo in a certain frequency band is lower than 15 dB, it indicates that the frequency band is severely affected by electromagnetic interference or the ionosphere, resulting in poor signal quality and inability to provide reliable detection results. Therefore, it is excluded from the usable frequency band.

[0044] The first preset sea state threshold corresponds to Beaufort level 6 and above sea state, at which time large waves appear on the sea surface, with wave heights reaching 4 to 6 meters; the second preset sea state threshold corresponds to Beaufort level 3 and below sea state.

[0045] Through the synergy of the aforementioned hardware architecture and control algorithms, this system and method can automatically adapt to different electromagnetic environments and sea state changes, thereby achieving high-quality marine environmental detection under all weather and sea state conditions.

[0046] The terms “above,” “below,” and “within” as used above include the number itself; the terms “exceeding” and “excluding” do not include the number itself.

[0047] The present invention has been further described above with reference to specific embodiments. However, it should be understood that the specific descriptions herein should not be construed as limiting the substance and scope of the present invention. Various modifications made to the above embodiments by those skilled in the art after reading this specification are all within the scope of protection of the present invention. The various specific technical features described in the above embodiments can be combined in any suitable manner without contradiction. To avoid unnecessary repetition, the embodiments of the present invention will not further describe various possible combinations.

[0048] If the embodiments of the present invention involve directional indicators (such as up, down, left, right, front, back, etc.), the directional indicators are only used to explain the relative positional relationship and movement of each component in a certain specific posture (as shown in the figure). If the specific posture changes, the directional indicators will also change accordingly.

Claims

1. A multi-frequency automatically adjustable high-frequency ground wave radar system, characterized in that, The multi-band transmitter is connected to the transmitting antenna and can cover multiple preset detection frequency bands, which are divided into low-frequency long-range detection group and high-frequency medium- and short-range detection group; The output of the full-band receiving antenna array is connected to the input of the multi-channel receiver, and the operating frequency band of the full-band receiving antenna array can cover multiple preset detection frequency bands; A power divider is installed on the multi-channel receiver. The power divider is used to split the echo signal output by each receiving antenna in the receiving antenna array into two paths, which are respectively connected to the first receiving channel group corresponding to the low-frequency long-range detection group and the second receiving channel group corresponding to the high-frequency medium- and short-range detection group. The multi-channel receiver includes an analog-to-digital converter, a field-programmable gate array (FPGA), and multiple direct digital frequency synthesizers (DDS). The FPGA is connected to the FPGA and the DDS to enable a single FPGA channel to process echo signals from two different frequency bands simultaneously. The control unit is connected to the multi-band transmitter and the multi-channel receiver respectively, and is used to select the optimal non-frequency band in the low-frequency long-range detection group and the high-frequency medium- and short-range detection group, so as to control the system to work simultaneously in two optimal frequency bands and adjust the frequency band combination according to real-time ocean parameters.

2. The multi-frequency automatically adjustable high-frequency ground wave radar system according to claim 1, characterized in that, The multi-band transmitter is a 4-channel transmitter. Each channel of the 4-channel transmitter independently corresponds to a preset detection frequency band and can simultaneously output transmission signals of two different frequency bands.

3. The multi-frequency automatically adjustable high-frequency ground wave radar system according to claim 2, characterized in that, The preset detection frequency bands include 4MHz~5MHz, 7MHz~8MHz, 13MHz~16MHz and 24MHz~26MHz; the low-frequency long-range detection group includes the 4MHz~5MHz and 7MHz~8MHz frequency bands, and the high-frequency medium-short-range detection group includes the 13MHz~16MHz and 24MHz~26MHz frequency bands; The multi-channel receiver is a 16-channel receiver; the first receiving channel group consists of the first 8 receiving channels of the 16-channel receiver, and its pre-filter bandwidth is 4MHz to 8MHz; the second receiving channel group consists of the last 8 receiving channels of the 16-channel receiver, and its pre-filter bandwidth is 13MHz to 26MHz.

4. The multi-frequency automatically adjustable high-frequency ground wave radar system according to claim 3, characterized in that, The field-programmable gate array has a built-in frequency division processing module, which is connected to the output of the analog-to-digital converter unit. The frequency division processing module is used to separate two different frequency band signals acquired by the single-channel analog-to-digital converter unit and send them to the corresponding direct digital frequency synthesizers for matched filtering.

5. The multi-frequency automatically adjustable high-frequency ground wave radar system according to any one of claims 1 to 4, characterized in that, The control unit includes a signal-to-noise ratio (SNR) detection module and a sea state parameter processing module. The input terminal of the SNR detection module is connected to the output terminal of the multi-channel receiver, and the output terminal of the SNR detection module is connected to the frequency band control terminal of the multi-band transmitter. It is used to output the optimal frequency band selection signal based on the echo SNR of each frequency band. The input terminal of the sea state parameter processing module is connected to the ocean parameter output terminal of the multi-channel receiver, and the output terminal of the sea state parameter processing module is connected to the frequency band switching terminal of the multi-band transmitter, which is used to adjust the signal by outputting frequency band combinations according to real-time wind, wave and current parameters.

6. A multi-frequency automatic adjustment method for high-frequency ground wave radar, implemented using a multi-frequency automatically adjustable high-frequency ground wave radar system as described in any one of claims 1 to 5, characterized in that, Includes the following steps: Multiple preset detection frequency bands are set up, and the multiple preset detection frequency bands are divided into low-frequency long-range detection group and high-frequency medium- and short-range detection group according to the detection distance; The radar echo signal reflected from the sea surface is received, and the echo signal output from each receiving antenna is divided into two paths, which are respectively input into the first receiving channel group corresponding to the low-frequency long-range detection group and the second receiving channel group corresponding to the high-frequency medium- and short-range detection group. The echo signals from two different frequency bands are processed simultaneously through a single analog-to-digital conversion channel, and the corresponding frequency bands are matched and filtered by multiple direct digital frequency synthesizers. Based on the signal-to-noise ratio of the echoes in each frequency band, an optimal operating frequency band is selected from both the low-frequency long-range detection group and the high-frequency medium-to-short-range detection group, and the two selected optimal operating frequency bands do not have a harmonic relationship. The system is controlled to operate simultaneously in the two optimal operating frequency bands, enabling simultaneous detection of the marine environment at long and medium-to-short distances; Based on the ocean wind, wave and current parameters obtained from real-time detection, the combination of the two optimal operating frequency bands is adaptively adjusted.

7. The method according to claim 6, characterized in that, The specific steps of simultaneously processing echo signals of two different frequency bands through a single analog-to-digital conversion channel are as follows: performing digital frequency division processing on the mixed frequency band signal acquired by the single analog-to-digital conversion unit to separate the signal components of two different frequency bands, and sending them to the corresponding direct digital frequency synthesizers for matched filtering.

8. The method according to claim 6, characterized in that, The specific steps for selecting the optimal operating frequency band based on the signal-to-noise ratio (SNR) of echoes from each frequency band are as follows: Detection signals are transmitted sequentially in each preset detection frequency band, the SNR of the corresponding echoes is detected, and usable frequency bands with SNRs higher than a preset SNR threshold are selected; the frequency band with the highest SNR in the usable frequency bands of the low-frequency long-range detection group is selected as the first optimal frequency band, and the frequency band with the highest SNR and no harmonic relationship with the first optimal frequency band in the usable frequency bands of the high-frequency short-range detection group is selected as the second optimal frequency band.

9. The method according to claim 8, characterized in that, The preset signal-to-noise ratio threshold is 10–20 dB.

10. The method according to any one of claims 6 to 9, characterized in that, The specific steps for adaptively adjusting the combination of the two optimal operating frequency bands based on the ocean wind, wave and current parameters obtained from real-time detection are as follows: when the detected wind, wave and current parameters are greater than the first preset sea state threshold, the combination is adjusted to operate simultaneously in the two optimal frequency bands with the highest signal-to-noise ratio in the low-frequency long-range detection group; when the detected wind, wave and current parameters are less than the second preset sea state threshold, the combination is adjusted to operate simultaneously in the two optimal frequency bands with the highest signal-to-noise ratio in the high-frequency medium- and short-range detection group.

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