JPS62121379A - Synthetic aperture radar equipment - Google Patents

Abstract

PURPOSE:To execute an observation in an invisible area, and also to improve the reliability by using the titled equipment while switching both analog and digital signal transmission systems. CONSTITUTION:In case a switch 12 and a switch 3 of a switching part 1 are set to on and off, respectively, by a control signal, a receiving signal is inputted to an analog transmission part 2, converted to a transmitting signal to a ground station, and thereafter, transmitted to the ground station. Also, when the switch 12 and the switch 13 are controlled to turn off and on, respectively, the receiving signal is inputted to a phase detecting part 3, converted to I and Q video signals, recorded in a high density magnetic tape 43 of a signal processing 4, and thereafter, transmitted to the ground station through a digital transmission part 5 at the time when an artificial satellite can be seen from the ground, therefore, the observation of an invisible area can be executed. Also, in case the switches 12, 13 are turned on, both of an analog signal and a digital signal are transmitted. Accordingly, the reliability is improved by having a redundant system of a different circuit.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a synthetic aperture radar device.

[Conventional technology]

By emitting radio waves from the site torsoking radar mounted on the satellite to the ground on the side of the mobile platform, and receiving and synthesizing the reflected waves while moving, an antenna with a relatively small aperture can effectively achieve a large aperture. Synthetic aperture radar that can synthesize antennas is well known.

FIG. 2 is an operational perspective view showing the principle of operation for realizing a synthetic aperture radar using a sight torsoking radar mounted on a mobile platform.

A mobile plant form such as an artificial satellite or an aircraft that moves at a speed V along a specific route or orbit set in advance according to a desired purpose is placed at a point A at an altitude of h above the ground, with a small aperture sight torso mounted on it. The King radar antenna emits transmission pulses at regular intervals. This transmission pulse is radiated in a direction perpendicular to the traveling trajectory 11iL with the spread of the beam width β, and is received by the site Lusoking radar as a reflected wave from the area BCDE on the ground.

These reflected waves are input to the moving platform as it moves at a speed of ■, and the received signal at each point in time is monitored while observing the line 1.1' parallel to the traveling trajectory on the ground with a width of distance BC. Amplitude information and phase information are recorded as . For example, a point target P located at a direction angle φ and a distance R from the moving platform starts receiving the transmitted pulse at a point F on the traveling trajectory 1ffL of the moving plant form, and ends receiving the transmitted pulse at a point G.

The reflected wave from the point target P is received while emitting the transmitted pulse, and the received signal contains distance information as well as phase information corresponding to the constantly changing relative velocity, and by processing this received signal, these points are This outputs a set of targets as image information. The transmission pulse usually uses a linear FM pulse that modulates the frequency of RF radio waves at a constant rate of change in order to improve distance resolution. This linear F
M is part of a pulse compression technique commonly used in synthetic aperture radars to improve range resolution.This pulse compression technique reduces the pulse width instead of increasing the peak power of the transmitted pulse. By adding linear FM to this pulse, the occupied bandwidth is widened and the resolution equivalent to that of a short pulse is obtained.In range compression for image processing, it is used via a distributed delay line with an opposite frequency vs. delay time characteristic. The signal is collected at one point and output as a sharp pulse.

The mobile plant form moves along a preset trajectory at a speed of ■, and the sight torsoking radar acquires information about the relative orientation that changes one after another. Emit a transmission pulse and receive the reflected wave from the target. After a certain period of time, another pulse is transmitted at the next position, and the received signal containing the distance, relative velocity, or direction information acquired at each position one after another in this way is made to correspond to the change in the amount of phase included in the phase information. By combining these two antennas, it is possible to provide a function as a synthetic aperture radar that can effectively achieve the same effect as using an antenna with a long aperture diameter.

In the case of synthetic aperture radar, the traveling direction and azimuth direction of the flying object)
The resolution, that is, the azimuth resolution δ1, is expressed by the following equation, where the antenna azimuth direction dimension is .

δ1−□ The resolution in the direction perpendicular to the traveling direction of the projectile (Mli M direction), that is, the distance resolution δ, is given by the following equation, where the bandwidth of the radar signal is Δf and the angle of incidence is φ. .

2 Δr Here, C is the speed of light.

[Problem that the invention seeks to solve]

Conventionally, in a synthetic aperture radar device, as shown in Fig. 3,
The received signal obtained by the receiving section 100 is transferred to two switching sections 200.
and 500, and the analog signal is transmitted to the ground via an antenna 600 via two analog transmission units 300 and 400 with the same configuration provided to ensure reliability, and is converted to digital data and subjected to image processing on the ground. I was going. For this reason, there was a drawback that the received signal deteriorated due to the influence of noise etc. on the analog signal transmission path. Furthermore, since there is no high-density analog data recording tape, there is a drawback that data in invisible areas cannot be obtained. Furthermore, in terms of reliability, conventional systems have had redundant systems (two analog transmission systems) of the same circuit, making them vulnerable to potential problems.

That is, if a problem occurs after installation, there is a possibility that both systems become unusable and the synthetic aperture radar system becomes unusable.

The purpose of the present invention is to eliminate the above-mentioned conventional drawbacks, prevent the received signal from deteriorating due to the effects on the transmission path when transmitting the received signal to the ground station, enable observation in the invisible region, and reduce the reliability. An object of the present invention is to provide an improved synthetic aperture radar device.

[Means for solving the problem] In the synthetic aperture radar device according to the present invention, the received signal is input to the switching section, and one of the following three methods can be set to M If by the control signal. It is configured as follows.

+11 Input the received signal only to the analog transmission section and transmit the analog signal to the ground station.

(2) Input the reception signal 13 only to the phase detection section, and 1. After converting it into a Q video signal and converting it into a digital signal in a signal processing section, the data is recorded and the digital data is transmitted from the digital transmission section to the ground station.

(3) The received signal is input to both the analog transmission section and the phase detection section, and both the analog signal and the digital signal are transmitted to the ground station.

With this configuration, it is possible to reduce signal deterioration on the transmission path, make it possible to observe invisible areas using the recording means, and improve the reliability by having different redundant systems.

· 〔Example〕 Next, embodiments of the present invention will be described with reference to the drawings.

As shown in FIG. 1, the synthetic aperture radar device according to the present invention includes a switching section 1, an analog transmission section 2, a phase detection section 3, a signal processing section 4, and a digital transmission section 5.
is driven by a control signal from a selection section (not shown).

The switching unit l is composed of a duplexer 11 and a switch 12.13, and the switch 12.13 is set to 0N10 by a control signal.
FF and sends the received signal to the analog transmission section 2 or the phase detection section 3. Switch 12 is ON, switch 13 is OFF
When set to , the received signal is input to the analog transmission section 2, where it is converted into a transmission signal to the ground station, and then transmitted to the ground station via the antenna. When the switch 12 is set to OFF and the switch 13 is set to ON, the received signal is input to the phase detection section 3, and the received signal is input to the phase detection section 3, and the reception LO (No. 8 and MIX
(mixed) and converted into I and Q video signals. ! .

The Q video signal is input to the signal processing section 4, and A/D converted with an arbitrary number of bits by Δ/D converters 41 and 42. This is how it was converted into digital data! .

The Q data is recorded on a high-density magnetic tape 43 in the signal processing unit 4, and is inputted to the digital transmission unit 5 by a control signal at any time when the artificial satellite carrying the synthetic aperture radar device is visible from the ground. transmitted to the ground station via This allows observation of invisible areas.

Also, both switches 12 and 13 of the switching section l are turned on.
In this case, analog transmission section 2 and digital transmission section 5
Both analog and digital signals are sent via ε
can do.

Note that the control signals for the switches 12 and 130 of the switching section 1 are sent out from the selection section.

〔Effect of the invention〕

As explained above, the present invention enables image transmission methods of analog signal transmission and digital signal transmission by switching the received signal with a switching unit, reduces signal deterioration on the transmission path, and facilitates observation of invisible areas. This has the effect of increasing reliability by making it possible and having a redundant system of different circuits.

[Brief explanation of drawings]

Fig. 1 is a block diagram showing an embodiment of the present invention, Fig. 2 is a diagram for explaining the principle of a general synthetic aperture radar, and Fig. 3 is a block diagram of a conventional synthetic aperture radar. be. l...Switching unit, 2...Analog transmission unit, 3...Phase detection unit, 4...Signal processing unit, 5... Digital transmission section, 6...
π/2 phase shifter, 11... Demultiplexer, 12.13.
...Switch, 41.42..., A/D converter, 43...High-density magnetic tape.

Claims (1)

[Claims] In a synthetic aperture radar device mounted on a satellite, there is a switching unit that switches connection circuits using control signals, an analog transmission unit that transmits the received analog signal to the ground, and a phase detection unit that converts the received analog signal into I and Q video signals. Department and
a signal processing unit that converts the I and Q video signals into digital signals with an arbitrary number of bits and records them on a high-density magnetic tape;
It is equipped with a digital transmission section that transmits digital signals to the ground, and can be configured to use one of three methods: when transmitting only analog signals to the ground, when transmitting only digital signals, when transmitting both analog and digital signals. A synthetic aperture radar device comprising a selection section that selects based on a control 1 signal.