CN217360300U

CN217360300U - Passive bistatic synthetic aperture radar system

Info

Publication number: CN217360300U
Application number: CN202221179153.3U
Authority: CN
Inventors: 冯为可; 胡晓伟; 郭艺夺; 蒲涛; 路复宇
Original assignee: Air Force Engineering University of PLA
Current assignee: Air Force Engineering University of PLA
Priority date: 2022-05-17
Filing date: 2022-05-17
Publication date: 2022-09-02
Anticipated expiration: 2032-05-17

Abstract

The utility model relates to the technical field of radar equipment, in particular to a passive bistatic synthetic aperture radar system, which comprises a non-cooperative irradiation source, a reference antenna, a measuring antenna, a programmable track, a track controller, a first low noise module, a second low noise module, an oscillation controller, a first amplifier, a second amplifier, an oscilloscope and an upper computer; the reference antenna, the first low-noise module, the first amplifier and the oscilloscope form a reference channel; the measuring antenna, the second low-noise module, the second amplifier, the oscilloscope and the programmable track form a measuring channel; the oscillation controller carries out synchronous processing on signals of the reference channel and the measurement channel; and the upper computer controls the track controller and the oscilloscope, stores the signals acquired by the oscilloscope and finally completes imaging and displacement estimation processing. The non-cooperative irradiation source emission signals are used for imaging and displacement estimation, frequency distribution is not needed, flexibility is high, and cost is low.

Description

Passive bistatic synthetic aperture radar system

Technical Field

The utility model relates to a radar equipment technical field, concretely relates to passive bistatic synthetic aperture radar system.

Background

In recent years, a Ground-based Synthetic Aperture Radar (GB-SAR) has been widely used for imaging and displacement estimation of surface mine slopes, landslides, buildings, bridges, dams, and the like, as an important remote sensing tool, with a precision of millimeter or sub-millimeter. A Passive Bistatic synthetic aperture radar (PB-GB-SAR) system replaces a transmitter of an existing GB-SAR system with an existing opportunity radiation source in the environment, and has the advantages of no need of frequency allocation, high flexibility, low cost and the like. According to the working frequency, the resolution and the fuzzy function of the system, the PB-GB-SAR system based on the geostationary satellite digital television signal has great development potential, and the realization principle is simple. However, the PB-GB-SAR system has two key issues to be solved in order to achieve target imaging and displacement estimation.

1. How to obtain two paths of coherent receiving channels based on the existing hardware such as a commercial antenna, a low-noise module, an amplifier and the like, thereby reducing the development cost of a system.

2. The PB-GB-SAR belongs to a bistatic radar system, and a geometrical structure different from the existing GB-SAR must be considered in the imaging and displacement estimation processes.

SUMMERY OF THE UTILITY MODEL

In order to solve the technical problem, the utility model adopts the following technical scheme:

the technical scheme is that the passive bistatic synthetic aperture radar system comprises a non-cooperative radiation source, a reference antenna, a measuring antenna, a programmable track, a track controller, a first low-noise module, a second low-noise module, an oscillation controller, a first amplifier, a second amplifier, an oscilloscope and an upper computer; the reference antenna receives the signal of the non-cooperative irradiation source, sequentially passes through the first low-noise module and the first amplifier, and forms a reference channel after being sampled by an oscilloscope; the measuring antenna receives a signal of the non-cooperative irradiation source reflected by a target, sequentially passes through a second low-noise module and a second amplifier, and then is sampled by an oscilloscope to form a measuring channel; the first low noise module and the second low noise module are synchronized through the oscillation controller; the measuring antenna is arranged on the programmable track and is controlled by the track controller; and the upper computer controls the track controller and the oscilloscope, stores the signals acquired by the oscilloscope, and performs imaging and displacement estimation processing.

In a further aspect, the non-cooperative illumination source is selected from digital television signals transmitted by geostationary satellites.

The further technical scheme is that the reference antenna is a 45 cm parabolic antenna, and the working frequency is 11.71 to 12.75 GHz.

The technical scheme is that the measuring antenna only uses a feed horn of the parabolic antenna as a receiving antenna so as to obtain wider beam width for synthetic aperture processing.

A further solution is that the measuring antenna is mounted on the programmable track, creating a synthetic aperture with fixed spacing in the horizontal and/or vertical direction.

The technical scheme is that the oscilloscope is an Agilent 54855A Infiniium oscilloscope, and the signal sampling rate is 10 GSamples/s.

According to a further technical scheme, the oscillation controller is composed of a 25 MHz oscillator and two 74HC04 and is used for outputting three sets of in-phase and anti-phase signals and inputting the three sets of in-phase and anti-phase signals into phase-locked loops of the first low-noise module and the second low-noise module.

In a further embodiment, the reference antenna is located in a fixed position or moves with the measurement antenna, and the observation angle is directed to the geostationary satellite.

Compared with the prior art, the beneficial effects of the utility model are that:

the non-cooperative irradiation source emission signals are used for imaging and displacement estimation, frequency distribution is not needed, flexibility is high, and cost is low; the system cost can be reduced by adopting hardware such as the conventional commercial antenna (a reference antenna and a measuring antenna), a low-noise module (a first low-noise module and a second low-noise module) and an amplifier (a first amplifier and a second amplifier); the oscillation controller can realize synchronization of two receiving channels, and is beneficial to improving coherent processing time of a reference channel and a measurement channel; the simplified geometric structure and the plane wave approximation are adopted for imaging processing, high-resolution images of different targets can be obtained, and target displacement can be estimated with sub-millimeter accuracy.

Drawings

Fig. 1 is a schematic structural diagram of the passive bistatic synthetic aperture radar system of the present invention.

Fig. 2 shows the general geometry of the imaging of the passive bistatic synthetic aperture radar system of the present invention.

Fig. 3 is a simplified geometry for imaging by the passive bistatic synthetic aperture radar system of the present invention.

Fig. 4 is a circuit diagram of the oscillation controller of the present invention.

Icon: the system comprises a non-cooperative illumination source 1, a reference antenna 2, a measuring antenna 3, a programmable track 4, a track controller 5, a first low noise module 6, a second low noise module 7, an oscillation controller 8, a first amplifier 9, a second amplifier 10, an oscilloscope 11 and an upper computer 12.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

Example (b):

fig. 1-4 show a preferred embodiment of a passive bistatic synthetic aperture radar system according to the present invention, in which a passive bistatic synthetic aperture radar system specifically includes a non-cooperative illumination source 1, a reference antenna 2, a measuring antenna 3, a programmable track 4, a track controller 5, a first low noise module 6, a second low noise module 7, an oscillation controller 8, a first amplifier 9, a second amplifier 10, an oscilloscope 11, and an upper computer 12;

the reference antenna 2 receives the signal of the non-cooperative irradiation source 1, sequentially passes through the first low noise module 6 and the first amplifier 9, and forms a reference channel after being sampled by the oscilloscope 11;

the measuring antenna 3 receives signals of the non-cooperative irradiation source 1 reflected by the target, sequentially passes through the second low noise module 7 and the second amplifier 10, and is sampled by the oscilloscope 11 to form a measuring channel;

the first low noise module 6 and the second low noise module 7 are synchronized by the oscillation controller 8;

the measuring antenna 3 is arranged on the programmable track 4 and is controlled by the track controller 5;

the upper computer 12 controls the track controller 5 and the oscilloscope 11, stores the signals acquired by the oscilloscope 11, and performs imaging and displacement estimation processing.

In the utility model, the structure of the PB-GB-SAR system is shown in figure 1. The reference antenna 2 is a 45 cm parabolic antenna, the gain is about 34 dB, and the working frequency is 11.71 to 12.75 GHz. In the measurement channel, synthetic aperture processing is performed to obtain a wider beam width, and only the feed horn of the parabolic antenna is used as a receiving antenna. Two low noise modules with different local oscillators (first low noise module 6 and second low noise module 7, respectively) are synchronized by an oscillator controller 8. The received signal is amplified using two signal amplifiers (first amplifier 9, second amplifier 10, respectively) with an operating frequency from 10 to 2600 MHz and a gain from 26 to 34 dB. The measuring antenna 3 is mounted on a programmable track 4 to produce a synthetic aperture with fixed spacing in the horizontal and/or vertical direction (antenna movement step 5 mm). The two paths of signals are collected by a four-port digital storage oscilloscope 11 (Agilent 54855A Infiniium oscilloscope), and the signal sampling rate is set to 10 GSamples/s to avoid the distortion of signal sampling. Finally, the data are transmitted to the upper computer 12 for off-line signal processing, namely target imaging and displacement estimation.

In this embodiment, a stationary orbit digital television satellite (N-SAT-110) at 110 degrees east longitude using the ISDB-S standard is used as the non-cooperative illumination source 1. The frequency of the N-SAT-110 satellite digital television signal is in a Ku band (12.27-12.75 GHz), 12 channels are provided, each channel has a bandwidth of 34.5 MHz, the total bandwidth is about 474.5 MHz, and the distance resolution of the maximum 0.32 m can be provided.

The general geometry of PB-GB-SAR imaging is shown in fig. 2, with PB-GB-SAR receiving the illumination signal and the target reflection signal using two channels (i.e., a reference channel and a measurement channel). The reference antenna 2 is located in a fixed position with its angle of view directed towards the satellite. In this case the y-direction can be determined by the connection between the satellite to the reference antenna 2. To achieve high azimuthal resolution, the measurement antenna 3 moves along a linear track. Thus, the x-direction can be defined as: a direction perpendicular to the y-direction on a plane determined by the antenna movement direction and the y-direction. In practice, the reference antenna 2 can be moved together with the measuring antenna 3, with the aim of making the direction of movement of the antenna parallel to the x-axis, in order to more easily determine the position of the antenna and to simplify the imaging process, as shown in fig. 3.

The present embodiment selects a synthetic aperture length of 1.2 m to balance signal-to-noise ratio and data acquisition time. Since the antenna moves along the track and data needs to be transmitted from the oscilloscope 11 to the upper computer 12, the data acquisition time for 241 measurements (1.2 m, 5mm step) is about 15 min.

To obtain a sufficient signal-to-noise ratio, a long coherent accumulation time is required. However, the two low noise blocks of the reference and measurement channels have different local oscillators, resulting in different frequencies and phases of the two received signals. Thus, if longer coherent accumulation is used, the incoherence of the two paths will not cause the signal-to-noise ratio to increase or decrease. For a single measurement where phase information is not important, the frequency difference between the two low noise blocks can be estimated by a fourier transform based method. For PB-GB-SAR imaging, the phase difference between the two low noise blocks (first low noise block 6 and second low noise block 7) needs to be corrected in order to add together the data from multiple measurements to improve the signal-to-noise ratio of the range compression result, or to process the data from different antenna positions for azimuth compression.

The circuit for controlling the oscillator 8 is shown in fig. 4. Wherein, a 25 MHz oscillator and two 74HC04 construct a special Pierce oscillator, and three groups of in-phase and anti-phase signals are output and input into the phase-locked loops of the first low-noise module 6 and the second low-noise module 7. Based on the control oscillator, the frequency and phase synchronization between the first low noise block 6 and the second low noise block 7 can be kept stable for several tens of minutes, and thus can be used for target imaging and displacement estimation processing of the PB-GB-SAR.

Although the invention has been described herein with reference to a number of illustrative embodiments thereof, it should be understood that numerous other modifications and embodiments can be devised by those skilled in the art that will fall within the spirit and scope of the principles of this invention. More specifically, various variations and modifications are possible in the component parts and/or arrangements of the subject combination arrangement within the scope of the disclosure, the drawings and the appended claims. In addition to variations and modifications in the component parts and/or arrangements, other uses will also be apparent to those skilled in the art.

Claims

1. A passive bistatic synthetic aperture radar system, comprising: the device comprises a non-cooperative illumination source (1), a reference antenna (2), a measuring antenna (3), a programmable track (4), a track controller (5), a first low-noise module (6), a second low-noise module (7), an oscillation controller (8), a first amplifier (9), a second amplifier (10), an oscilloscope (11) and an upper computer (12);

the reference antenna (2) receives signals of the non-cooperative irradiation source (1), sequentially passes through the first low-noise module (6) and the first amplifier (9), and is sampled by the oscilloscope (11) to form a reference channel;

the measuring antenna (3) receives signals of the non-cooperative irradiation source (1) reflected by the target, sequentially passes through the second low-noise module (7) and the second amplifier (10), and is sampled by the oscilloscope (11) to form a measuring channel;

-said first low noise module (6) and said second low noise module (7) are synchronized by said oscillation controller (8);

the measuring antenna (3) is mounted on the programmable track (4) and is controlled by the track controller (5);

and the upper computer (12) controls the track controller (5) and the oscilloscope (11), stores signals acquired by the oscilloscope (11), and performs imaging and displacement estimation processing.

2. A passive bistatic synthetic aperture radar system according to claim 1, wherein: the non-cooperative illumination source (1) is selected from digital television signals transmitted by geostationary satellites.

3. A passive bistatic synthetic aperture radar system according to claim 1, wherein: the reference antenna (2) is a 45 cm parabolic antenna with a working frequency of 11.71 to 12.75 GHz.

4. A passive bistatic synthetic aperture radar system according to claim 1, wherein: the measuring antenna (3) uses only the feed horn of the parabolic antenna as a receiving antenna.

5. A passive bistatic synthetic aperture radar system according to claim 1, wherein: the measuring antennas (3) are mounted on the programmable tracks (4) creating a synthetic aperture with fixed spacing in horizontal and/or vertical direction.

6. A passive bistatic synthetic aperture radar system according to claim 1, wherein: the oscilloscope (11) is an Agilent 54855A Infiniium oscilloscope, and the signal sampling rate is 10 GSamples/s.

7. A passive bistatic synthetic aperture radar system according to claim 1, wherein: the oscillation controller (8) is composed of a 25 MHz oscillator and two 74HC04, and is used for outputting three sets of in-phase and anti-phase signals and inputting the three sets of in-phase and anti-phase signals into phase-locked loops of the first low-noise module (6) and the second low-noise module (7).

8. A passive bistatic synthetic aperture radar system according to claim 1, wherein: the reference antenna (2) is located at a fixed position or moves together with the measuring antenna, the observation angle being directed towards the geostationary satellite.