CN104062648B - The control method of distributed network system for high-frequency earth wave radar - Google Patents

Abstract

The invention relates to a distributed network high-frequency ground wave radar system and a control method thereof. The system includes a plurality of radar sites; the radar sites are divided into radar sites containing only the transmitting subsystem, radar sites containing only the receiving subsystem, and radar sites containing both the transmitting subsystem and the receiving subsystem. The radar system adopts the linear frequency modulation continuous wave or linear frequency modulation interrupted continuous wave working system. By modulating the frequency sweep center frequency or the initial frequency sweep time of the transmitting signal, the echo signals generated by different transmitting subsystems can be transmitted in the receiving subsystem. The baseband stage achieves alias-free discrimination. The system can include two or more high-frequency ground wave transmitting-receiving pairs that work in the same frequency band and have overlapping coverage areas. On the one hand, the radar system can obtain a large amount of information, which is conducive to improving detection accuracy, coverage and detection stability. On the other hand, it makes efficient use of the limited frequency resources allocated to high-frequency ground wave radar.

Description

Control Method of Distributed Network High Frequency Ground Wave Radar System

technical field

The present invention relates to a high-frequency ground-wave radar system with a distributed network structure and its control method. Specifically, it is composed of a plurality of high-frequency ground-wave radar transmitting subsystems and receiving subsystems located in different geographic locations Distributed network high-frequency ground wave radar system and its control method.

Background technique

High-frequency radar refers to the radar whose radio frequency signal is in the high-frequency band. It is divided from the way of radio wave propagation, including high-frequency sky-wave radar and high-frequency ground-wave radar. High-frequency ground wave radar is a device that can be used to measure dynamic parameters such as wind, waves, and currents on the sea surface in a large range, and to detect ships and low-altitude aircraft. After nearly 50 years of development, it is now mature in measuring ocean surface currents. Compared with other current measurement instruments, such as drifting buoys, current meters, acoustic Doppler current profilers, etc., high-frequency ground wave radar has the advantages of large coverage area, all-weather work, real-time measurement, low operation and maintenance costs, etc. Many coastal developed countries have been widely used.

The traditional high-frequency ground wave radar is a monostatic radar in which the transmitting subsystem and the receiving subsystem are located in one place, and the radial velocity component is obtained by using the backscattered echo. In order to obtain the two-dimensional vector flow velocity, two radars with overlapping coverage areas are usually installed in two places far apart, and the radial flow velocity obtained by the two radars working independently is synthesized into the vector flow velocity. In order to allow flow velocity components in more directions to participate in vector synthesis to reduce measurement errors and improve measurement stability, more and more high-frequency ground wave radars are deployed in coastal areas, and the mutual interference between radars has become a problem that must be solved .

At present, the most commonly used method to solve the mutual interference of radars is to make the radars work in different frequency bands, that is, the method of frequency division multiplexing. This method is simple and easy to implement, but it is extremely unfavorable for the development of high frequency ground wave radar. Frequency resources in high frequency bands are extremely limited and have been allocated to many different types of users. In 2012, the World Radiocommunication Conference clarified the frequency allocation of high-frequency ground wave radar in its WRC-12 resolution, as shown in Table 1.

Table 1 Applicable frequency bands of high frequency ground wave radar serial number WRC allocated frequency (MHz) Spectrum width (kHz) Service category 1 4.438-4.488 50 secondary business 2 5.250-5.275 25 secondary business 3 9.305-9.355 50 secondary business 4 13.450-13.550 100 secondary business 5 16.100-16.200 100 secondary business 6 24.450-24.600 150 secondary business 7 26.200-26.350 150 secondary business 8 39.5-40.0 500 Main business

In order to meet a certain range resolution, high-frequency ground wave radar needs to occupy a large bandwidth. Table 2 shows the commonly used range resolution and corresponding bandwidth of high-frequency ground wave radar.

Table 2 Commonly used bandwidth and distance resolution of high-frequency ground wave radar serial number Bandwidth (kHz) Distance resolution (km) 1 20 7.5 2 30 5 3 60 2.5 4 120 1.25 5 200 0.75

Comparing Table 1 and Table 2, we can see that the frequency resources allocated to high-frequency ground wave radar are extremely limited relative to its needs. When the number of radars is large, it is impossible to allocate an independent frequency band for each radar. Moreover, this method of frequency division multiplexing also causes a huge waste of precious frequency resources.

When the number of high-frequency ground wave radars is large, in addition to suppressing their mutual interference, it is hoped that multiple radars can be organically combined to form a regional radar network, increase the total amount of data acquisition, and improve the comprehensive detection performance of the entire system , such as detection accuracy, stability, anti-interference ability, etc.

Contents of the invention

The purpose of the present invention is to solve the above-mentioned high-frequency ground-wave radar mutual interference problem. The present invention utilizes a plurality of high-frequency ground-wave transmitting subsystems and receiving subsystems to establish a distributed network high-frequency ground-wave radar, and then multiple Radars are organically combined to improve the comprehensive detection performance of the entire system.

The purpose of the present invention is achieved like this:

A distributed network high-frequency ground wave radar system, including a plurality of radar sites; the radar sites include three types, respectively, including only high-frequency ground wave transmitting subsystem radar site, only including high-frequency ground wave receiving sub-system The radar site of the system, the radar site including the high-frequency ground wave transmitting subsystem and the high-frequency ground wave receiving subsystem; the echo signal generated by one transmitting subsystem is used by multiple receiving subsystems, and one receiving subsystem uses multiple The echo signal generated by the transmitting subsystem.

The high-frequency ground wave transmitting subsystem includes a satellite navigation system signal receiving antenna, a synchronization controller, a waveform generator, a transmitter, and a high-frequency ground wave transmitting antenna;

Described synchronous controller comprises taming clock, frequency synthesizer, FPGA, taming clock, frequency synthesizer, FPGA are connected successively, taming clock is connected with FPGA, satellite navigation system signal receiving antenna is connected with taming clock, frequency synthesizer and waveform generator Connection, the FPGA is connected to the waveform generator and the transmitter respectively, and the transmitter is connected to the transmitting antenna.

The high-frequency ground wave receiving subsystem includes a high-frequency ground wave receiving antenna, a waveform generator, a satellite navigation system signal receiving antenna, a synchronization controller, an analog front end, an analog-to-digital converter, a digital signal processor, a microprocessor, a data Transmission bus, computer; Described synchronous controller comprises taming clock, frequency synthesizer, FPGA;

The tame clock, frequency synthesizer, and FPGA are connected in sequence, the tame clock is connected to the FPGA, the high-frequency ground wave receiving antenna, the analog front end, the analog-to-digital converter ADC, the digital signal processor DSP, the microprocessor, the data transmission bus, and the computer are connected in sequence , the satellite navigation system signal receiving antenna is connected to the taming clock, the frequency synthesizer, the waveform generator, and the analog front end are connected in sequence, and the FPGA is connected to the waveform generator, analog-to-digital converter ADC, digital signal processor DSP, and microprocessor respectively.

In the radar site including the high-frequency ground wave transmitting subsystem and the high-frequency ground wave receiving subsystem, the transmitting subsystem and the receiving subsystem share the satellite navigation system signal receiving antenna and the synchronization controller.

The data transmission bus adopts the universal serial bus USB.

A control method for a distributed network high-frequency ground wave radar system based on the above-mentioned system. The timing signals issued by the satellite navigation system are used between the radar sites to realize time and phase synchronization; linear frequency modulation continuous wave or linear frequency modulation interrupted continuous wave is adopted The working system adjusts the frequency sweep center frequency or the initial frequency sweep time of the transmitted signal, so that there is an instantaneous frequency difference between the signals transmitted by different transmitting subsystems, and the instantaneous frequency difference is greater than the radar information bandwidth, so that different The echo signal generated by the transmitting subsystem realizes alias-free discrimination at the baseband level of the receiving subsystem.

The control process of the radar site that only includes the launch subsystem includes the following steps:

Step 1.1, after the system is powered on, the satellite signal receiving antenna receives the signal transmitted by the satellite navigation system and transmits it to the satellite signal taming clock in the synchronization controller, and the signal output by the taming clock is multiplied by the frequency synthesizer and sent to the FPGA chip and The waveform generator is used as its working clock; at the same time, the second pulse output by the tame clock—1PPS signal and time information packet—TIP is also transmitted to the FPGA chip;

Step 1.2, if the transmitting subsystem transmits the chirp interrupt continuous wave signal, the FPGA chip generates an interrupt pulse sequence and transmits it to the transmitter; if the transmitting subsystem transmits the chirp continuous wave signal, then this operation is omitted; the FPGA chip transmits the radio frequency signal The waveform parameters are sent to the waveform generator; at the same time, the FPGA chip compares the time information indicated by the TIP with the preset time. If the preset time is reached, the latest 1PPS signal is used as a reference to generate a trigger pulse to the waveform generator;

Step 1.3, after the waveform generator is triggered by the trigger pulse, it outputs the linear frequency modulation continuous wave signal to the transmitter according to the waveform parameters set by the FPGA;

Step 1.4, if the transmitting subsystem transmits the chirp continuous wave signal, the transmitter performs power amplification on the chirp continuous wave signal generated in step 1.3, and then transmits it to the high-frequency ground wave transmitting antenna, and radiates it into space; if The transmitting subsystem transmits the linear frequency modulation continuous wave signal, and the transmitter synthesizes the linear frequency modulation continuous wave signal generated in step 1.3 and the interrupt pulse generated in step 1.2 to generate a linear frequency modulation continuous wave signal, and then radiates through the high frequency ground wave transmitting antenna go out;

The control process of the station containing only the receiving subsystem includes the following steps:

Step 2.1, after the system is powered on, the satellite signal receiving antenna receives the signal transmitted by the satellite navigation system and transmits it to the satellite signal taming clock in the synchronization controller, and the signal output by the taming clock is multiplied by the frequency synthesizer and sent to the FPGA chip and The waveform generator is used as the working clock of the FPGA chip and the waveform generator; at the same time, the second pulse output by the tame clock—1PPS signal and time information packet—TIP is also transmitted to the FPGA chip;

In step 2.2, the FPGA divides the frequency of the input clock signal generated in step 2.1 to generate the working clock of the DSP chip and the microprocessor respectively, and the sampling pulse signal passed to the analog-to-digital converter; the FPGA chip sends the waveform parameters of the local oscillator signal To the waveform generator; at the same time, the FPGA chip compares the time information indicated by TIP with the preset time, and if the preset time is reached, it will use the latest 1PPS signal as a reference to generate a trigger pulse to the waveform generator;

Step 2.3, after the waveform generator is triggered by the trigger pulse, it outputs the linear frequency modulation continuous wave signal to the analog front end according to the waveform parameters set by the FPGA;

Step 2.4, the radar echo signal enters the analog front end through the high-frequency ground wave receiving antenna, and is mixed with the local oscillator signal to obtain an intermediate frequency signal;

Step 2.5, the analog-to-digital converter samples the intermediate frequency signal, and the sampling result is sent to the DSP chip;

In steps 2 and 6, the DSP chip performs digital down-conversion and quadrature demodulation on the sampling results, and then generates a radar echo distance spectrum and transmits it to the microprocessor;

Step 2.7, the microprocessor transmits the distance spectrum data to the computer via the data transmission bus for further processing and result display;

The control process of the site that includes both the transmitting subsystem and the receiving subsystem includes the following steps:

Step 3.1, after the system is powered on, the satellite signal receiving antenna receives the signal transmitted by the satellite navigation system and transmits it to the satellite signal taming clock in the synchronization controller, and the signal output by the taming clock is multiplied by the frequency synthesizer and sent to the FPGA chip and The waveform generator is used as its working clock; at the same time, the second pulse output by the tame clock—1PPS signal and time information packet—TIP is also transmitted to the FPGA chip;

Step 3.2, if the transmission signal is a chirp interrupt continuous wave signal, the FPGA chip generates an interrupt pulse sequence and passes it to the transmitter; if the chirp continuous wave signal is transmitted, then this operation is omitted; the FPGA chip converts the radio frequency signal and the local oscillator signal The waveform parameters are sent to the RF signal waveform generator and the local oscillator signal waveform generator respectively; at the same time, the FPGA chip compares the time information indicated by the TIP with the preset time, and if the preset time is reached, the latest 1PPS signal is used as a reference , to generate a trigger pulse to the waveform generator;

Step 3.3: After the RF signal waveform generator is triggered by the trigger pulse, it outputs the linear frequency modulation continuous wave signal to the transmitter according to the waveform parameters set by the FPGA; after the local oscillator signal waveform generator is triggered by the trigger pulse, it outputs the linear frequency modulation continuous wave signal according to the waveform parameters set by the FPGA. FM continuous wave signal to the analog front end;

Step 3.4, if the transmission signal is a chirp continuous wave signal, the transmitter performs power amplification on the radio frequency chirp continuous wave signal generated in step 3.3, and then transmits it to the high-frequency ground wave transmitting antenna, and radiates it into space; if The transmitting signal is a chirp interrupted continuous wave signal, then the transmitter synthesizes the radio frequency chirp continuous wave signal generated in step 3.3 and the interrupt pulse generated in step 3.2 into a chirp interrupted continuous wave signal, and then radiates it out through the high frequency ground wave transmitting antenna ;

Step 3.5, the radar echo signal enters the analog front end through the high-frequency ground wave receiving antenna, and is mixed with the local oscillator signal to obtain an intermediate frequency signal;

Step 3.6, the analog-to-digital converter samples the intermediate frequency signal, and the sampling result is sent to the DSP chip;

Step 3.7, the DSP chip performs digital down-conversion and quadrature demodulation on the sampling results, and then generates the radar echo distance spectrum, which is passed to the microprocessor;

In step 3.8, the microprocessor transmits the distance spectrum data to the computer via the data transmission bus for further processing and result display.

Compared with prior art, the present invention has following advantage:

1. The present invention enables two or more high-frequency ground wave transmitting-receiving pairs with overlapping coverage areas to work in the same frequency band, so that the radar system can obtain a large amount of information, which is conducive to improving detection accuracy, coverage and detection stability and other performance indicators;

2. The present invention makes efficient use of the limited frequency resources allocated to the high-frequency ground wave radar.

Description of drawings

Fig. 1 is a schematic diagram of the structure principle of the present invention.

Fig. 2 is a schematic structural diagram of the transmitting subsystem of the present invention.

Fig. 3 is a schematic structural diagram of the receiving subsystem of the present invention.

Fig. 4 is a schematic structural diagram of a radar site (including transmitting and receiving subsystems) of the present invention.

Fig. 5 is a schematic diagram of the structure of the analog front end of the present invention.

FIG. 6 is a schematic diagram of Example 1 of the waveform design method of the present invention (the method of adjusting the frequency sweep center frequency of the transmitted signal).

FIG. 7 is a schematic diagram of Example 2 of the waveform design method of the present invention (the method of adjusting the initial frequency sweep time of the transmitted signal).

Fig. 8 is the example of radar station received signal distance spectrogram of the present invention; This figure is example with the distributed network radar that comprises 3 high-frequency ground wave radar stations, and wherein, (a) figure is the first radar station received signal distance Spectrum, (b) is the distance spectrum of the signal received by the second radar station, and (c) is the distance spectrum of the signal received by the third radar station.

detailed description

Below in conjunction with accompanying drawing and embodiment describe in detail:

1. Overall

Referring to Figure 1, the present invention consists of multiple radar sites. Each radar site either contains only the high frequency ground wave transmitting subsystem, or only contains the high frequency ground wave receiving subsystem, or has both the high frequency ground wave transmitting subsystem and the high frequency ground wave receiving subsystem. The echo signal generated by the signal emitted by one transmitting subsystem after being scattered by the target can be used by multiple receiving subsystems, and one receiving subsystem can utilize the echo signals generated by multiple transmitting subsystems.

Referring to Fig. 2, the transmitting subsystem of the present invention includes a satellite navigation system signal receiving antenna, a synchronization controller, a waveform generator, a transmitter, and a high-frequency ground wave transmitting antenna. The satellite signal receiving antenna, synchronous controller, waveform generator, transmitter, and high-frequency ground wave transmitting antenna are connected in sequence. The frequency synthesizer in the synchronization controller is connected to the waveform generator. The FPGA chip in the synchronization controller is connected with the transmitter.

The control method (work flow) of the launch subsystem is: (1) The satellite signal receiving antenna receives the signal issued by the satellite navigation system and transmits it to the satellite signal taming clock in the synchronization controller. (2) Satellite signal taming clock Use this signal to tame the internal clock source to make it output a stable standard frequency signal, and generate a standard pulse per second (1PPS) signal based on this frequency signal. (3) The standard frequency signal output by the taming clock is multiplied by the frequency synthesizer to a higher 100-megahertz-level clock, and then transmitted to the FPGA chip and the waveform generator as their working clock. At the same time, the 1PPS signal and TIP output by the tame clock are also passed to the FPGA. (4) FPGA writes the waveform parameters of the radio frequency signal into the waveform generator, and compares the time information indicated in TIP with the time information preset by the system. If the two are equal, after the next 1PPS signal arrives, follow the preset After the delay time value of is delayed for a certain time, a trigger pulse is sent to the waveform generator. If the transmitting subsystem generates a chirp interrupted continuous wave, the FPGA will also generate an interrupted pulse sequence to the transmitter. (5) After the waveform generator receives the trigger pulse signal from the FPGA, it generates a linear frequency modulation continuous wave signal according to the set RF signal waveform parameters and transmits it to the transmitter. (6) After the transmitter amplifies the power of the linear frequency modulation continuous wave signal, it radiates into the space through the transmitting antenna. If the transmitting subsystem generates a chirp interrupted continuous wave, the transmitter synthesizes the interrupted pulse sequence generated by the FPGA and the chirped continuous wave signal generated by the waveform generator into a chirped interrupted continuous wave signal, and then performs power amplification, and finally by The transmitting antenna radiates into space.

Referring to Fig. 3, the receiving subsystem of the present invention includes a high-frequency ground wave receiving antenna, a waveform generator, a satellite navigation system signal receiving antenna, a synchronous controller, an analog front end, an analog-to-digital converter (ADC chip), a digital signal processor ( DSP chip), microprocessor, data transmission bus, computer. Among them, the high-frequency ground wave receiving antenna, analog front-end, ADC chip, DSP chip, microprocessor, data transmission bus, and computer are connected in sequence; the satellite navigation system signal receiving antenna, synchronization controller, waveform generator, and analog front-end are connected in sequence; The synchronous controller is also connected with the ADC chip, the DSP chip and the microprocessor respectively.

The control method (work flow) of the receiving subsystem is: (1) The satellite signal receiving antenna receives the signal issued by the satellite navigation system and transmits it to the satellite signal taming clock in the synchronization controller. (2) Satellite signal taming clock Use this signal to tame the internal clock source to make it output a stable standard frequency signal, and generate a standard pulse per second (1PPS) signal based on this frequency signal. (3) The standard frequency signal output by the taming clock is multiplied by the frequency synthesizer to a higher 100-megahertz-level clock, and then transmitted to the FPGA chip and the waveform generator as their working clock. At the same time, the 1PPS signal and TIP output by the tame clock are also passed to the FPGA. (4) FPGA writes the waveform parameters of the local oscillator signal into the waveform generator, and compares the time information indicated in TIP with the time information preset by the system. If the two are equal, after the next 1PPS signal arrives, follow the preset time information. After the preset delay time value is delayed for a certain time, a trigger pulse is sent to the waveform generator. The FPGA divides the frequency of the input working clock to generate the sampling pulse of the ADC chip and the working clock of the DSP chip and the microprocessor. (5) After the waveform generator receives the trigger pulse signal from the FPGA, it generates a linear frequency modulation continuous wave signal according to the set local oscillator signal waveform parameters and transmits it to the analog front end. (6) The high-frequency ground wave receiving antenna receives the echo signal and transmits it to the analog front end. (7) The analog front-end mixes the echo signal and the local oscillator signal to obtain an intermediate frequency signal and transmit it to the ADC chip. (8) The ADC chip samples the intermediate frequency signal, and the obtained digital signal is transmitted to the DSP chip. (9) The DSP chip performs digital down-conversion and quadrature demodulation on the digital signal, and then performs Fourier transform to obtain the distance spectrum and transmit it to the microprocessor. (10) The microprocessor signal packs the distance spectrum data and transmits it to the computer via the data transmission bus. (11) The computer further processes the data and displays the final results.

Referring to Fig. 4, when the radar site includes both the transmitting subsystem and the receiving subsystem, the transmitting subsystem and the receiving subsystem share the satellite signal receiving antenna and the synchronization controller. The control method (workflow) of this radar site is: (1) The satellite signal receiving antenna receives the signal issued by the satellite navigation system and transmits it to the satellite signal taming clock in the synchronization controller. (2) Satellite signal taming clock Use this signal to tame the internal clock source to make it output a stable standard frequency signal, and generate a standard pulse per second (1PPS) signal based on this frequency signal. (3) The standard frequency signal output by the taming clock is multiplied by the frequency synthesizer to a higher 100-megahertz-level clock, and then transmitted to the FPGA chip and the waveform generator as their working clock. At the same time, the 1PPS signal and TIP output by the tame clock are also passed to the FPGA. (4) If the transmission signal is a chirp interrupt continuous wave signal, the FPGA chip generates an interrupt pulse sequence and transmits it to the transmitter; if the chirp continuous wave signal is transmitted, this operation is omitted. The FPGA chip sends the waveform parameters of the radio frequency signal and the local oscillator signal to the radio frequency signal waveform generator and the local oscillator signal waveform generator respectively. At the same time, the FPGA chip compares the time information indicated by TIP with the preset time. If the preset time is reached, it will use the latest 1PPS signal as a reference to generate a trigger pulse to the waveform generator. The FPGA divides the frequency of the input working clock to generate the sampling pulse of the ADC chip and the working clock of the DSP chip and the microprocessor. (5) After the RF signal waveform generator is triggered by the trigger pulse, it outputs the linear frequency modulation continuous wave signal to the transmitter according to the waveform parameters set by the FPGA. After the local oscillator signal waveform generator is triggered by the trigger pulse, it outputs the linear frequency modulation continuous wave signal to the analog front end according to the waveform parameters set by the FPGA. (6) After the transmitter amplifies the power of the linear frequency modulation continuous wave signal, it radiates into the space through the transmitting antenna. If the transmitting subsystem generates a chirp interrupted continuous wave, the transmitter synthesizes the interrupted pulse sequence generated by the FPGA and the chirped continuous wave signal generated by the waveform generator into a chirped interrupted continuous wave signal, and then performs power amplification, and finally by The transmitting antenna radiates into space. (7) The high-frequency ground wave receiving antenna receives the echo signal and transmits it to the analog front end. (8) The analog front-end mixes the echo signal and the local oscillator signal to obtain an intermediate frequency signal and transmit it to the ADC chip. (9) The ADC chip samples the intermediate frequency signal, and the obtained digital signal is transmitted to the DSP chip. (10) The DSP chip performs digital down-conversion and quadrature demodulation on the digital signal, and then performs Fourier transform to obtain the distance spectrum and transmit it to the microprocessor. (11) The microprocessor signal packs the distance spectrum data and transmits it to the computer via the data transmission bus. (12) The computer further processes the data and displays the final result.

2. Each component

1) Synchronous controller

The synchronous controller of the present invention includes a satellite signal taming clock, a frequency synthesizer and a field programmable gate array (FPGA) chip. The satellite signal taming clock, frequency synthesizer, and FPGA chip are connected in sequence. Wherein, the tamed clock can be a clock tamed by the GPS system, or a clock tamed by other satellite navigation systems such as Beidou. The internal clock source of the taming clock can be a constant temperature crystal oscillator, such as the Thunderbolt GPS taming crystal oscillator of Trimble Company, or an atomic clock, such as the SYN3206 Beidou taming rubidium atomic clock of Xi’an Synchronous Electronic Technology Co., Ltd. The frequency synthesizer can choose the phase-locked loop frequency synthesizer ADF4360-9 chip of AnalogDevices Company.

2) Analog front end

The analog front end of the present invention adopts a direct sampling scheme of primary frequency mixing and high frequency. Its advantages are: (1) The higher the intermediate frequency, the greater the difference between the image frequency and the signal frequency, the higher the selectivity of the RF filter to the signal, that is, the stronger the ability to suppress image interference; (2) Mixing Afterwards, the useful signal bandwidth is greatly reduced, which reduces the requirement for the sampling frequency of the ADC chip.

Fig. 5 is an implementation of an analog front end, including a radio frequency filter, a mixer, an intermediate frequency amplifier, an intermediate frequency filter, and an adjustable amplifier. The input echo signal is filtered by the radio frequency filter, mixed with the local oscillator signal, then filtered and amplified by multi-stage intermediate frequency, and finally transmitted to the ADC chip for sampling.

3) Data transmission bus

The data transmission bus of the present invention adopts the USB bus, which has the advantages of convenient use, easy expansion, small size, low cost, reliable transmission and the like. The microprocessor can choose the EZ-USB series chip produced by Cypress Company.

4) Waveform generator

The waveform generator of the present invention is implemented by a direct digital synthesizer, for example, AD9858, AD9954 and other chips from Analog Devices can be selected.

3. Waveform design

The distributed network radar system of the present invention adopts the linear frequency modulation continuous wave or linear frequency modulation interrupted continuous wave working system. By modulating the frequency sweep center frequency of the transmit signal or the initial sweep time, the echo signals generated by different transmit subsystems can be distinguished without aliasing at the baseband level of the receive subsystem.

Taking the distributed network radar composed of three high-frequency ground wave radar stations as an example, each radar station includes a transmitting subsystem and a receiving subsystem. The time-frequency distribution diagram of the transmitted signal and its echo signal scattered by the target is shown. Regardless of the radar's suppression of its short-distance echoes, the echo signals of each radar station from near to far follow its transmit signal in turn, and the farther the echo signal is, the greater the delay relative to the transmit signal is. Since the instantaneous frequency of the chirp signal is proportional to time, the greater the delay, the greater the instantaneous frequency difference between the echo signal and the transmitted signal. The instantaneous frequency difference between the farthest useful echo signal and the transmitted signal is called the information bandwidth. Figure 6 shows the information bandwidth of the three radar stations. It can be seen from Fig. 6 that the scanning period and scanning frequency band of the transmitted signals of the three radar stations are the same, but the starting time of the scanning is different, so there is an instantaneous frequency difference between the transmitted signals. After the instantaneous frequency difference is demodulated by the receiver, it will be converted into the frequency difference of the baseband signal. Although the time and frequency bands of the three radar stations overlap at the radio frequency level, as long as the instantaneous frequency difference between the transmitted signals of the radar stations is greater than the information bandwidth of each radar station, the signals of different radar stations can be distinguished at the baseband level. There is no interference from the signals of other radar stations on the backscatter echoes of the own radar station.

Fig. 7 shows an example of another waveform design method, that is, the method of adjusting the initial frequency sweep time of the transmitted signal. Still taking the distributed network radar composed of three high-frequency ground wave radar stations as an example, each radar station includes a transmitting subsystem and a receiving subsystem. All transmitted signals keep the sweep period, sweep bandwidth, and initial sweep time the same. Only fine-tuning the center frequency of the sweep frequency ensures that the difference between the center frequencies of signals transmitted by different radar stations is greater than the corresponding information bandwidth of the radar station, and at the same time far smaller than the bandwidth of the transmitted signal. Since the difference between the center frequencies of signals transmitted by different radar stations is greater than the corresponding information bandwidth of the radar stations, after demodulation by the receiver, the echo signals of different transmitted signals at the baseband level will be located in different frequency bands, thereby being distinguished.

4. Experimental results

Taking the distributed network radar including 3 high-frequency ground wave radar stations as an example, each radar station includes transmitting and receiving subsystems. The echo signals formed by each transmitting subsystem can be utilized by the three receiving subsystems, and each receiving subsystem can utilize the echo signals formed by the three transmitting subsystems. By adopting the waveform design method for adjusting the frequency sweep center frequency of the present invention, the distance spectrum diagrams of received signals obtained by the three radar stations are shown in Figure 8(a)~(c) respectively. It can be seen from Fig. 8 that on the distance spectrum diagram of the received signal of each radar station, there are echo signals generated by the transmitted signals of three radar stations, and these echo signals are located in different distance unit areas without overlapping each other. That is, there is no mutual interference. A total of 9 transmit-receive pairs are formed by the 3 radar stations, and the amount of data is greatly increased.

Claims (1)

1. the control method of a distributed network system for high-frequency earth wave radar, it is characterised in that: described radar system includes many Individual radar website；Described radar website includes three types, be respectively only comprise high-frequency ground wave launch subsystem radar website, Only comprise the radar website of high-frequency ground wave receiving subsystem, comprise high-frequency ground wave simultaneously and launch subsystem and high-frequency ground wave and receive son The radar website of system；One echo-signal launching subsystem generation is utilized by multiple receiving subsystems, and one receives subsystem System utilizes the echo-signal that multiple transmitting subsystem produces；

Described high-frequency ground wave launch subsystem include satellite navigation system signals reception antenna, isochronous controller, waveform generator, Transmitter, high-frequency ground wave launch antenna；

Described isochronous controller includes taming clock, frequency synthesizer, FPGA, and taming clock, frequency synthesizer, FPGA connect successively Connecing, tame clock and be connected with FPGA, satellite navigation system signals reception antenna is connected with taming clock, frequency synthesizer and waveform Generator connects, and FPGA is connected with waveform generator, transmitter respectively, and transmitter is connected with launching antenna；

Described high-frequency ground wave receiving subsystem includes that high-frequency ground wave reception antenna, waveform generator, satellite navigation system signals connect Receive antenna, isochronous controller, AFE (analog front end), analog-digital converter, digital signal processor, microprocessor, data transmission bus, meter Calculation machine；Described isochronous controller includes taming clock, frequency synthesizer, FPGA；

Taming clock, frequency synthesizer, FPGA are sequentially connected with, and tame clock and are connected with FPGA, high-frequency ground wave reception antenna, simulation Front end, analog-digital converter ADC, digital signal processor DSP, microprocessor, data transmission bus, computer are sequentially connected with, and defend Star navigation system signal receiving antenna is connected with taming clock, and frequency synthesizer, waveform generator, AFE (analog front end) are sequentially connected with, FPGA is connected with waveform generator, analog-digital converter ADC, digital signal processor DSP, microprocessor respectively；

Described comprise in the radar website that high-frequency ground wave launches subsystem and high-frequency ground wave receiving subsystem, launch subsystem and Receiving subsystem shares satellite navigation system signals reception antenna and isochronous controller；

Described data transmission bus uses general-purpose serial bus USB；

The time signal utilizing satellite navigation system to issue between described radar website realizes time and Phase synchronization；Use linear Continuous Wave with frequency modulation or linear frequency modulation interrupt continuous wave working system, by launching the frequency sweep mid frequency of signal or initial sweeping Frequently the moment is adjusted so that there is instantaneous frequency between the signal that different transmitting subsystems are launched poor, and this instantaneous frequency Difference is more than radar information bandwidth, so that the different echo-signal launching subsystem generation realizes in the base band level of receiving subsystem Distinguish without aliasing；

Described only comprises the radar website launching subsystem, and its control process comprises the following steps:

Step 1.1, after system electrification, satellite signal receiving antenna receives the signal that satellite navigation system is launched, and sends synchronization to Satellite-signal in controller tames clock, and the signal taming clock output is respectively transmitted to FPGA after frequency synthesizer frequency multiplication Chip and waveform generator, as its work clock；Meanwhile, pulse per second (PPS) 1PPS signal and the temporal information of clock output are tamed Bag TIP is also passed to fpga chip；

Step 1.2, if launching subsystem to launch linear frequency modulation interruption continuous wave signal, then fpga chip produces interruption pulse sequence And pass to transmitter；If launching subsystem to launch linear frequency modulation continuous wave signal, then this operation is omitted；Fpga chip is by radio frequency The waveform parameter of signal is sent to waveform generator；Meanwhile, the temporal information that TIP is indicated by fpga chip is compared with Preset Time Relatively, if arriving Preset Time, then with nearest 1PPS signal as reference, producing and triggering pulse to waveform generator；

Step 1.3, after waveform generator is triggered pulse-triggered, the waveform parameter output linearity frequency modulation arranged according to FPGA is continuous Ripple signal is to transmitter；

Step 1.4, if launching subsystem to launch linear frequency modulation continuous wave signal, the then linear tune that step 1.3 is produced by transmitter Frequently continuous wave signal carries out power amplification, is then transferred to high-frequency ground wave and launches antenna, it is radiated in space；If launching Subsystem launch linear frequency modulation interrupt continuous wave signal, then the linear frequency modulation continuous wave signal that step 1.3 is produced by transmitter with The interruption pulse synthesis that step 1.2 produces, produces linear frequency modulation and interrupts continuous wave signal, then launch antenna spoke through high-frequency ground wave It is shot out；

The described website only comprising receiving subsystem, its control process comprises the following steps:

Step 2.1, after system electrification, satellite signal receiving antenna receives the signal that satellite navigation system is launched, and sends synchronization to Satellite-signal in controller tames clock, and the signal taming clock output is respectively transmitted to FPGA after frequency synthesizer frequency multiplication Chip and waveform generator, as fpga chip and the clock of waveform generator；Meanwhile, the pulse per second (PPS) of clock output is tamed 1PPS signal and temporal information bag TIP are also passed to fpga chip；

Step 2.2, the input clock signal that step 2.1 is produced by FPGA divides, and produces dsp chip and microprocessor respectively Work clock, and pass to the sampling pulse signal of analog-digital converter；The waveform parameter of local oscillation signal is sent out by fpga chip Give waveform generator；Meanwhile, the temporal information that TIP is indicated by fpga chip, compared with Preset Time, is preset if arrived Time, then with nearest 1PPS signal as reference, produce and trigger pulse to waveform generator；

Step 2.3, after waveform generator is triggered pulse-triggered, the waveform parameter output linearity frequency modulation arranged according to FPGA is continuous Ripple signal is to AFE (analog front end)；

Step 2.4, radar echo signal enters AFE (analog front end) through high-frequency ground wave reception antenna, in obtaining after being mixed with local oscillation signal Frequently signal；

Step 2.5, analog-digital converter sends dsp chip to if signal sampling, sampled result；

Step 2,6, dsp chip carries out Digital Down Convert and quadrature demodulation to sampled result, then generates radar return distance spectrum, Pass to microprocessor；

Step 2.7, microprocessor by distance spectrum data through data transmission bus pass to computer being further processed and Result shows；

The described website not only comprising transmitting subsystem but also comprising receiving subsystem, its control process comprises the following steps:

Step 3.1, after system electrification, satellite signal receiving antenna receives the signal that satellite navigation system is launched, and sends synchronization to Satellite-signal in controller tames clock, and the signal taming clock output is respectively transmitted to FPGA after frequency synthesizer frequency multiplication Chip and waveform generator, as its work clock；Meanwhile, pulse per second (PPS) 1PPS signal and the temporal information of clock output are tamed Bag TIP is also passed to fpga chip；

Step 3.2, if launching signal is that linear frequency modulation interrupts continuous wave signal, then fpga chip produces interruption pulse sequence and passes Pass transmitter；If launching linear frequency modulation continuous wave signal, then this operation is omitted；Fpga chip is by radiofrequency signal and local oscillation signal Waveform parameter be sent respectively to radiofrequency signal waveform generator and local oscillation signal waveform generator；Meanwhile, fpga chip is by TIP The temporal information of instruction, compared with Preset Time, if arriving Preset Time, then with nearest 1PPS signal as reference, produces Trigger pulse to waveform generator；

Step 3.3, after radiofrequency signal waveform generator is triggered pulse-triggered, the waveform parameter output linearity arranged according to FPGA Continuous Wave with frequency modulation signal is to transmitter；After local oscillation signal waveform generator is triggered pulse-triggered, the waveform arranged according to FPGA Parameter output linearity Continuous Wave with frequency modulation signal is to AFE (analog front end)；

Step 3.4, if launching signal is linear frequency modulation continuous wave signal, then the RF linear that step 3.3 is produced by transmitter is adjusted Frequently continuous wave signal carries out power amplification, is then transferred to high-frequency ground wave and launches antenna, it is radiated in space；If launching Signal be linear frequency modulation interrupt continuous wave signal, then the RF linear Continuous Wave with frequency modulation signal that step 3.3 is produced by transmitter and The interruption pulse that step 3.2 produces synthesizes linear frequency modulation and interrupts continuous wave signal, then launches aerial radiation through high-frequency ground wave Go out；

Step 3.5, radar echo signal enters AFE (analog front end) through high-frequency ground wave reception antenna, in obtaining after being mixed with local oscillation signal Frequently signal；

Step 3.6, analog-digital converter sends dsp chip to if signal sampling, sampled result；

Step 3.7, dsp chip carries out Digital Down Convert and quadrature demodulation, then generates radar return distance spectrum sampled result, Pass to microprocessor；

Step 3.8, microprocessor by distance spectrum data through data transmission bus pass to computer being further processed and Result shows.