阅读说明：本技术 一种小型化单片气象雷达设计方法 (Design method of miniaturized single-chip meteorological radar ) 是由 徐艳 于 2021-08-16 设计创作，主要内容包括：本发明专利提供了一种小型化单片气象雷达设计方法,基于AD9361系列芯片的小型化单片气象雷达设计方法,所述小型化单片气象雷达适用但不限于国家布网雷达补盲,人工影响天气作业指挥,区县级短时、超短时临近预报,军用单兵背负气象观测领域。(The invention provides a design method of a miniaturized single-chip meteorological radar, which is based on an AD9361 series chip and is suitable for, but not limited to, national grid arrangement radar blind compensation, artificial influence on weather operation command, district-county short-time and ultra-short-time nowcasting and military single-soldier backpack meteorological observation.)

1. A design method of a miniaturized single-chip meteorological radar is characterized by comprising the following steps: the method comprises the following steps:

step A: the assembled single-chip meteorological radar comprises an antenna feeder line, a transmitter-receiver assembly, a signal processor, a servo system, a frequency synthesizer and a display control terminal, wherein the antenna feeder line is connected with the transmitter-receiver assembly, the signal processor is respectively connected with the antenna feeder line, the servo system, the frequency synthesizer and the display control terminal, and the signal processor comprises: the digital intermediate frequency receiver based on the AD9361, the FPGA circuit and the ARM circuit; the antenna feeder comprises one of a parabolic antenna, a microstrip antenna, a waveguide slot antenna and a phased array antenna; the transmitter-receiver assembly consists of a transmitting module and a receiving module, the transmitting module and the receiving module are respectively connected with the frequency mixing unit, the transmitter-receiver assembly is externally connected with a frequency conversion unit, and the algorithm in the signal processor is a meteorological signal processing algorithm;

and B: two independent receiving channels and two independent transmitting channels are defined inside the AD9361, and are defined as a receiving channel RX1, a receiving channel RX2, a transmitting channel TX1 and a transmitting channel TX 2;

and C: using the receive channel RX1 and the transmit channel TX1 for a radar mode of operation; the receiving channel RX2 and the transmitting channel TX2 are used in a radar calibration mode, specifically:

radar working mode: the radio frequency switch S1 is set to position 2 for selecting a transmit signal, the transmit waveform is output by T1, while the radio frequency switch S2 is set to position 1 for selecting a transmit pulse sampling signal coupled from the transmit channel; the variable attenuator of the transmitter-receiver assembly is used for attenuating the transmitted waveform sampling signal to ensure that the transmitted waveform sampling signal is positioned in the proper working range of the transmitter-receiver assembly, so that the saturation of a receiving channel is avoided; at the trailing edge of the transmitted trigger pulse, the radio frequency switch S1 is placed in position 1, so that the radar is in a receiving state;

radar calibration mode: when the radar is in a calibration mode, the transmitting channel 2 is used for generating a radio frequency calibration signal; at this time, the radio frequency switch S1 is placed in position 1 for selecting a reception signal, the calibration signal waveform is output from T2, and at this time, the radio frequency switch S2 is placed in position 2; the internal calibration generates a digital calibration signal by a signal processor, and generates an intermediate frequency calibration label by a DAC and an intermediate frequency filter;

and C: defining an intermediate frequency calibration signal to be injected from the front end of an AD9361 for calibrating the channel consistency of an intermediate frequency processing circuit, wherein the intermediate frequency calibration signal is subjected to up-conversion by a transmitter receiver component to form a radio frequency calibration signal for being injected from the radio frequency front end of a receiving channel 1; by utilizing the detection characteristic of zero intermediate frequency in the AD9361, the input radio frequency signal is down-converted and then directly converted to zero intermediate frequency through an IQ orthogonal branch, digital processing is carried out, AD9361 output data is defined to be downloaded to FPGA at the speed of 50Mbit/s, and after matched filtering processing is carried out in FPGA, the data is extracted and then output through an optical network port at the speed of 12.5 MHz;

step D: an AD9361 internal receiving channel RX1 is defined for receiving signal processing, a receiving channel RX2 is defined for transmitting pulse sampling processing, a transmitting channel TX1 is defined for transmitting signal generation, a transmitting channel TX2 is defined for calibration signal generation, and calibration detection of an RX1 channel is realized; the digital calibration signal generated by the TX2 comprises a noise source, a continuous wave signal and a delayed copy of a transmitting signal, a calibration channel and a working channel work independently, and the radar work is not influenced by removing the calibration function.

Technical Field

The invention belongs to the technical field of radar systems, and particularly relates to a design method of a miniaturized single-chip meteorological radar based on an AD9361 series chip.

Background

With the development of economy in China, the construction of a weather radar monitoring network is greatly developed, the weather radar is adopted to monitor and early warn the disaster weather conditions, the industrial and agricultural development is guaranteed to be one of the most effective disaster prevention means, the weather radar monitoring network plays an important role in the aspects of disaster weather monitoring and early warning, obvious social, economic and ecological benefits are obtained, and although the weather radar technology in China obtains the development and the remarkable performance of the long foot, some problems still exist at present, and the weather radar monitoring network mainly comprises: 1) the mainstream weather radar in the weather industry in China comprises a new-generation weather radar, a dual-polarization weather radar, a phased array weather radar and the like, and the market price ranges from two million to ten million. The high price determines that the radar is deployed in a city level unit, and in mountainous areas with complex terrain, due to the shielding reason, the distribution of the existing weather radar monitoring station network cannot meet the monitoring requirement on the meteorological disasters, and cannot realize seamless space coverage, especially in the monitoring of medium and small-scale disastrous weather and the comprehensive monitoring and early warning of sudden and local meteorological disasters. 2) In the current weather modification system of China, artificial rainfall, hail suppression and other work are mainly implemented by prefectural meteorological departments and depend on the guidance of city or provincial meteorological radars. For the rapidly changing convective weather conditions, radar observation data of a city or an upgraded radar often has no real-time performance and accuracy, and cannot finely guide the weather operation artificially influenced, so that the weather operation efficiency artificially influenced is reduced, and the weather operation effect artificially influenced is seriously influenced; 3) the county-level meteorological station has few observation means, is limited by personnel and expenses, does not have the condition of equipping a large-scale new-generation weather radar or a dual-polarization weather radar, but has the requirements of short-time and ultra-short-time weather forecast.

In view of the fact that the traditional radar mainly comprises an antenna feeder line, a transmitter, a receiver, a signal processor, a servo system and terminal equipment, wherein the antenna feeder line is mainly used for receiving and transmitting electromagnetic waves, the transmitter is used for generating or amplifying the electromagnetic waves, the receiver is mainly used for receiving the electromagnetic waves of target reflection echoes, the signal processor is used for processing echo signals and extracting useful information and controlling the working time sequence of the radar, the servo is used for radar rotation, and the display and control terminal provides a user interface for controlling the radar to work and displaying the observation result of the radar.

Disclosure of Invention

Aiming at the explanation of the background technology, the invention provides a design method of a miniaturized single-chip weather radar, which is based on an AD9361 series chip and is suitable for being used in multiple fields.

In order to achieve the purpose, the invention provides the following technical scheme:

a design method of a miniaturized single-chip meteorological radar comprises the following steps:

step A: the assembled single-chip meteorological radar comprises an antenna feeder line, a transmitter-receiver assembly, a signal processor, a servo system, a frequency synthesizer and a display control terminal, wherein the antenna feeder line is connected with the transmitter-receiver assembly, the signal processor is respectively connected with the antenna feeder line, the servo system, the frequency synthesizer and the display control terminal, and the signal processor comprises: the digital intermediate frequency receiver based on the AD9361, the FPGA circuit and the ARM circuit; the antenna feeder comprises one of a parabolic antenna, a microstrip antenna, a waveguide slot antenna and a phased array antenna; the transmitter-receiver assembly consists of a transmitting module and a receiving module, the transmitting module and the receiving module are respectively connected with the frequency mixing unit, the transmitter-receiver assembly is externally connected with a frequency conversion unit, and the algorithm in the signal processor is a meteorological signal processing algorithm;

and B: two independent receiving channels and two independent transmitting channels are defined inside the AD9361, and are defined as a receiving channel RX1, a receiving channel RX2, a transmitting channel TX1 and a transmitting channel TX 2;

and C: using the receive channel RX1 and the transmit channel TX1 for a radar mode of operation; the receiving channel RX2 and the transmitting channel TX2 are used in a radar calibration mode, specifically:

radar working mode: the radio frequency switch S1 is set to position 2 for selecting a transmit signal, the transmit waveform is output by T1, while the radio frequency switch S2 is set to position 1 for selecting a transmit pulse sampling signal coupled from the transmit channel; the variable attenuator of the transmitter-receiver assembly is used for attenuating the transmitted waveform sampling signal to ensure that the transmitted waveform sampling signal is positioned in the proper working range of the transmitter-receiver assembly, so that the saturation of a receiving channel is avoided; at the trailing edge of the transmitted trigger pulse, the radio frequency switch S1 is placed in position 1, so that the radar is in a receiving state;

radar calibration mode: when the radar is in a calibration mode, the transmitting channel 2 is used for generating a radio frequency calibration signal; at this time, the radio frequency switch S1 is placed in position 1 for selecting a reception signal, the calibration signal waveform is output from T2, and at this time, the radio frequency switch S2 is placed in position 2; the internal calibration generates a digital calibration signal by a signal processor, and generates an intermediate frequency calibration label by a DAC and an intermediate frequency filter;

and C: defining an intermediate frequency calibration signal to be injected from the front end of an AD9361 for calibrating the channel consistency of an intermediate frequency processing circuit, wherein the intermediate frequency calibration signal is subjected to up-conversion by a transmitter receiver component to form a radio frequency calibration signal for being injected from the radio frequency front end of a receiving channel 1; by utilizing the detection characteristic of zero intermediate frequency in the AD9361, the input radio frequency signal is down-converted and then directly converted to zero intermediate frequency through an IQ orthogonal branch, digital processing is carried out, AD9361 output data is defined to be downloaded to FPGA at the speed of 50Mbit/s, and after matched filtering processing is carried out in FPGA, the data is extracted and then output through an optical network port at the speed of 12.5 MHz;

step D: an AD9361 internal receiving channel RX1 is defined for receiving signal processing, a receiving channel RX2 is defined for transmitting pulse sampling processing, a transmitting channel TX1 is defined for transmitting signal generation, a transmitting channel TX2 is defined for calibration signal generation, and calibration detection of an RX1 channel is realized; the digital calibration signal generated by the TX2 comprises a noise source, a continuous wave signal and a delayed copy of a transmitting signal, a calibration channel and a working channel work independently, and the radar work is not influenced by removing the calibration function. .

In the technical scheme, the meteorological signal processing algorithm is a mature processing algorithm in the meteorological radar industry.

The invention relates to a design method of a miniaturized single weather radar based on an AD9361 series chip, which is suitable for but not limited to the field of national grid arrangement radar blind compensation, artificial influence weather operation command, district-county-level short-time and ultra-short-time proximity forecast and military single-soldier borne weather observation.

Drawings

In order to more clearly illustrate the embodiments of the patent of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below, it is obvious that the drawings in the following description are only some embodiments of the patent of the present invention, and other drawings can be obtained by those skilled in the art without inventive exercise.

FIG. 1 is a schematic block diagram of a radar;

fig. 2 is a block diagram of local oscillator input/output ports;

FIG. 3 is a block diagram of transmitter and receiver components;

FIG. 4 is a received signal processing block diagram;

FIG. 5 is a schematic diagram of a distance dead zone of a long and short pulse combination solution;

FIG. 6 is a schematic diagram of the generation of a transmit pulse phase encoded signal;

fig. 7 transmit pulse sampling processing and calibration signal generation schematic.

Detailed Description

The technical solutions of the present invention will be described clearly and completely with reference to the accompanying drawings of the present invention, and it is obvious that the described embodiments are only some embodiments of the present invention, not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given in the present patent application without inventive step, shall fall within the scope of protection of the present patent application.

According to the embodiments shown in fig. 1 to 7, a method for designing a miniaturized monolithic weather radar includes the following steps:

step A: the assembled single-chip meteorological radar comprises an antenna feeder line, a transmitter-receiver assembly, a signal processor, a servo system, a frequency synthesizer and a display control terminal, wherein the antenna feeder line is connected with the transmitter-receiver assembly, the signal processor is respectively connected with the antenna feeder line, the servo system, the frequency synthesizer and the display control terminal, and the signal processor comprises: the digital intermediate frequency receiver based on the AD9361, the FPGA circuit and the ARM circuit; the antenna feeder comprises a parabolic antenna, a microstrip antenna, a waveguide slot antenna and a phased array antenna; the transmitter and receiver assembly consists of a transmitting module and a receiving module, and the transmitter and receiver assembly is connected with the frequency mixing unit. The main function of the antenna is to radiate a transmitting signal to a space and receive a reflected echo signal from the space, the antenna can adopt various system forms, and the antenna design adopts a technology mature in the radar industry.

The main function of the transmitter and receiver assembly is that the radar antenna receives signals, after low noise amplification, the radio frequency signals are down-converted to receive intermediate frequency signals, and the received intermediate frequency signals are output to the driving digital intermediate frequency receiver. The function of the transmitting component is to up-convert the transmitted waveform of the transmitted intermediate frequency signal to a radio frequency and to power-amplify the radio frequency signal.

The signal processor includes: the digital intermediate frequency receiver comprises a digital intermediate frequency receiver based on an AD9361, an FPGA circuit and an ARM circuit, wherein the digital intermediate frequency receiver has the main functions of modulating a transmitting signal and demodulating a receiving signal, the receiving signal is digitally sampled, the receiving signal is converted into a baseband signal after orthogonal down-conversion and is output to a signal processing module, and the signal processing module processes echo data to obtain meteorological data.

Another function of the digital if receiver is to convert the transmit signal waveform generated by the signal processor to an intermediate frequency to generate a transmit intermediate frequency waveform, which is output to a transmitter-receiver assembly (transmitter-receiver assembly) and up-converted to generate a transmit rf signal.

The main function of the FPGA circuit is to generate a transmitting signal waveform and perform signal processing on a received zero intermediate frequency signal.

The ARM circuit mainly realizes the configuration control and communication functions of AD9361 related registers.

And B: two independent receiving channels and two independent transmitting channels are defined inside the AD9361, and are defined as a receiving channel RX1, a receiving channel RX2, a transmitting channel TX1 and a transmitting channel TX 2;

and C: using the receive channel RX1 and the transmit channel TX1 for a radar mode of operation; the receiving channel RX2 and the transmitting channel TX2 are used in a radar calibration mode, specifically:

radar working mode: the radio frequency switch S1 is set to position 2 for selecting a transmit signal, the transmit waveform is output by T1, while the radio frequency switch S2 is set to position 1 for selecting a transmit pulse sampling signal coupled from the transmit channel; the variable attenuator of the transmitter and receiver component is used for attenuating the transmitted waveform sampling signal to ensure that the transmitted waveform sampling signal is positioned in the proper working range of the transmitter and receiver component, so that the receiver channel is prevented from being saturated; at the trailing edge of the transmitted trigger pulse, the radio frequency switch S1 is placed in position 1, so that the radar is in a receiving state;

radar calibration mode: when the radar is in a calibration mode, the transmitting channel 2 is used for generating a radio frequency calibration signal; at this time, the radio frequency switch S1 is placed in position 1 for selecting a reception signal, the calibration signal waveform is output from T2, and at this time, the radio frequency switch S2 is placed in position 2; the internal calibration generates a digital calibration signal by a signal processor, and generates an intermediate frequency calibration label by a DAC and an intermediate frequency filter;

and C: defining an intermediate frequency calibration signal to be injected from the front end of an AD9361 for calibrating the channel consistency of an intermediate frequency processing circuit, wherein the intermediate frequency calibration signal is subjected to up-conversion by a transmitter receiver component to form a radio frequency calibration signal for being injected from the radio frequency front end of a receiving channel 1; defining and utilizing the detection characteristic of zero intermediate frequency inside the AD9361, carrying out down-conversion on an input radio frequency signal, then directly carrying out frequency conversion to the zero intermediate frequency through an IQ (in-phase quadrature) branch circuit, carrying out digital processing, defining that AD9361 output data is downloaded to an FPGA (field programmable gate array) at the rate of 50Mbit/s, carrying out matched filtering processing in the FPGA, then extracting, and outputting through an optical network interface at the rate of 12.5 MHz;

step D: an AD9361 internal receiving channel RX1 is defined for receiving signal processing, a receiving channel RX2 is defined for transmitting pulse sampling processing, a transmitting channel TX1 is defined for transmitting signal generation, a transmitting channel TX2 is defined for calibration signal generation, and calibration detection of an RX1 channel is realized; the digital calibration signal generated by TX2 includes a noise source, a continuous wave signal, a delayed copy of the transmit signal.

According to the above technical solution, the present invention discloses an embodiment as follows:

the radio frequency agility integrated chip AD9361 integrates a radio frequency mixer and a digital processing system, and comprises 2 multiplied by 2 independent receiving and transmitting channels; the receiving local oscillator frequency range is 70MHz to 6.0GHz, and the transmitting local oscillator frequency range is 47MHz to 6.0 GHz. The bandwidth of each channel is 200KHz to 56 MHz. Each independent channel employs a direct conversion receiver that converts the incoming radio frequency signal directly to a baseband IQ signal, which is then digitized. Each receiving module contains independent AGC dc offset correction, orthogonality correction, and digital filtering. Each channel contains a large dynamic range ADC that digitizes the received IQ signal and produces a 12-bit digital signal through a programmable decimation filter. The transmitting channel also uses a direct conversion structure, and can generate a transmitting waveform with an error vector amplitude smaller than-40 dB. The phase-locked loop is integrated inside, low-power fractional order frequency synthesis can be provided for a transmitting channel and a receiving channel, in the embodiment, the working frequency range of the AD9361 can reach 5.6GHz, the working frequency of the radar is 13.6GHz, and in order to enable the AD9361 to adapt to the working frequency of the radar, an external frequency converter is needed. The frequency converter works at 13.6GHz, and after frequency mixing by the local oscillator Lo1, the frequency is shifted to 2.1GHz intermediate frequency. In order to enable the AD9361 to work better, an external local oscillator Lo2 is used for driving the AD9361, so that the local oscillator needs to generate three signals, namely 1, a first local oscillator Lo1 and the frequency of 11.5 GHz; 2. a second local oscillator Lo2, frequency 2.1 GHz; 3. coherent clock signals: 10 MHz-100 MHz; the radar adopts Ku wave band and X wave band integrated design, local oscillator frequency, intermediate frequency, digital intermediate frequency receiver, signal processor do not change, only need change the converter from up-conversion to down-conversion, select the wave filter of corresponding frequency channel simultaneously for use, the radar operating frequency channel just can change the X wave band into by the Ku wave band. In the invention, the AD9361 internally comprises a 2 x2 independent transceiver module, and an AD9361 transceiver channel (RX2/TX2) is used for transmitting pulse sampling signal processing and calibration signal generation. The AD9361 receive path RX2 is used to convert the transmit pulse sample signal (transmit pulse sample signal) to digital baseband and further processed in the FPGA, which is only active during the transmit pulse. The TX2 of the AD9361 channel is used to generate an if calibration signal with a center frequency of 2.1GHz, which is up-converted by the transmitter-receiver assembly to generate a calibrated rf calibration signal and injected from the rf front end of the RX channel 1 into the RX channel RX 1.

In the present invention, the radar antenna may take the form of a multiple system, and according to one embodiment of the present invention, the radar takes the form of a feed forward parabolic antenna. The radar can be configured in two basic ways: the single polarization can be horizontal polarization or vertical polarization, the polarization mode is mainly determined by the radar target characteristics, and for meteorological radar, the horizontal polarization mode is generally selected. The dual polarization comprises a horizontal polarization mode and a vertical polarization mode, and the antenna adopts a dual polarization feed source, which belongs to the conventional technical means in the field.

The transmitter and receiver assembly of the invention is composed of a transmitting module and a receiving module, wherein the transmitting module and the receiving module are independently designed, and are respectively provided with an independent frequency mixing unit (for the transmitting module, the frequency mixer is an up-converter, and for the receiving module, the frequency mixer is a down-converter), and the transmitting module and the receiving module are driven by the same local oscillation signal Lo 1.

In a signal processor, a digital intermediate frequency receiver carries out AD sampling on an intermediate frequency signal, changes the intermediate frequency signal to zero intermediate frequency, outputs (I, Q) data, the signal processor carries out estimation and formatting on meteorological target parameters by means of a classical meteorological signal processing algorithm, the meteorological signal processing algorithm belongs to a mature technology, a radar adopts a digital pulse compression mode and carries out extraction in two stages, the first-stage extraction is carried out in an AD9361, and the rate after extraction is 25 MHz; the second stage of pulse compression processing is performed in the FPGA, and the signal processor hardware performs pulse compression at a rate of 25MHz, then decimates at twice the rate, and transmits through the optical network port at a rate of 12.5 MHz.

The radar adopts a long pulse waveform to improve the detection capability, but has a larger close-range blind area. In order to eliminate the influence of the blind area, a long pulse and a short pulse can be linked, the long pulse and the short pulse have different carrier frequencies, and the total bandwidth requirement is B1+ B2+ BG-B. Where B1 is the bandwidth of the first pulse, B2 is the bandwidth of the second pulse, and BG is the guard bandwidth.

The meteorological target has a large dynamic range, strong secondary echo interference exists when the radar works in a close-range mode, in order to eliminate the secondary echo, the radar can suppress the secondary echo in a mode of sampling and transmitting a phase coding signal, a block diagram is generated according to the phase coding signal, and the working waveform of the radar can be a phase coding waveform or not.

According to the technical scheme, the radar function can be changed by changing the signal processing algorithm, namely, the meteorological signal processing algorithm in the signal processor is changed into a point target processing algorithm mature in the radar industry, and the meteorological radar can be changed into a point target detection radar for detecting the point target. The radio frequency circuit can be replaced, the switching of the radar working frequency can be realized under the condition that other parts of the radar are not changed, and the radar can work in an S wave band, a C wave band, an X wave band, a Ku wave band, a K wave band, a Ka wave band, a V wave band and a W wave band; by modifying the feed source into a dual-polarized feed source and adding a completely consistent receiving and transmitting channel, the radar can be expanded into a dual-polarized radar.

The above description is only for the specific embodiments of the present invention, but the protection scope of the present invention is not limited thereto, and any person skilled in the art can easily think of the changes or substitutions within the technical scope of the present invention, and shall be covered by the protection scope of the present invention. Any miniaturized monolithic radar adopting the upgraded chip AD9371 and the similar chip design belongs to the protection scope of the patent.