JPS58213268A - Synthetic aperture radar - Google Patents

Abstract

PURPOSE:To prepare an SAR system having high flexibility, by selecting optionally the number of quantizing steps in accordance with a demand, when digitizing the analog signal of a synthetic aperture radar (SAR). CONSTITUTION:A sampling signal is quantized by a quantizing part 8, and is outputted as an SAR digital signal 11 by fetching upper (m) bits by a quantizing part control signal 9. In that case, in case when picture information of a wide range is necessary, but a picture having a high quality is not always necessary, (m) is small and picture information of a narrow range is enough, but in case when a picture having a high quality is necessary, (m) is made large, and in this way, the control being rational and abounding in flexibility between a data quantity and picture quality is executed by an external control signal 12 in accordance with a demand.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a synthetic aperture radar system, and more particularly to a synthetic aperture radar system characterized by a means for quantizing a synthetic aperture radar analog signal.

Synthetic Aperture Radar
e Radar (hereinafter referred to as S A R) is a type of side-looking radar, and is an all-weather high-resolution active sensor that is mounted on a mobile platform such as an aircraft launcher or an artificial satellite and takes pictures of the surface of a pond using radio waves. In SAR, pulse compression technology is used to improve distance resolution, and synthetic aperture technology is used to improve lateral resolution. S
AR advances while transmitting and receiving radio waves obliquely to the surface to be imaged. By applying signal processing techniques to the coherent phase history obtained in this way, it is possible to obtain high resolution similar to that obtained when using a large-diameter amplifier.

Conventionally, quantization 1 is used when digitizing SAR signals (coherent phase history/analog signals) within a satellite.
Regarding /(, quantization using a specific quantization step/number has been considered.

However, when SAR is mounted on an artificial satellite, the time during which the satellite can be seen from one ground receiving station (the time during which that ground receiving station can receive SAR signals) is limited. The SAR data collected behind the scenes must be stored in a data recording system within the satellite, and then sent out from the recording system when the satellite is in a position where it can see the satellite or the ground reception station. . However, S.A.
If the R signal is quantized with a large number of quantization steps, the data will become larger, and a data recording thread with a small storage capacity can only record information about a plane object surface.

In addition, quantization with a small number of quantization steps has the disadvantage that quantization errors increase and image quality deteriorates. had not been done.

In the present invention, when digitizing BAR analog signals,
By digitizing the data at a predetermined number of quantization steps according to the program of the computer on board the satellite, rational control is performed on the conflicting gap between the amount of data and image quality mentioned above. The purpose is to provide a device that can do this.

That is, an object of the present invention is to configure a BAR system with extremely high flexibility regarding SAR image quality and data amount.

The main parts of the device according to the present invention are composed of a buffer amplification section, a low-pass filter, a sampling section, a quantization section, and a control section, and is designed to appropriately control the number of data output bits of the quantization section depending on the situation. It is configured. This appropriate control can be used, for example, if a wide range of image information is required but the image does not need to be of very high quality, or by using a small number of quantization steps, or if a narrow range of image information is required but the image is of high quality. If necessary, quantization is performed using a large number of quantization steps, and this control is stored in a computer on board the satellite and is controlled by external control signals regulated by a predetermined program. This allows for reasonable control between data amount and image quality.

Next, an embodiment of the present invention will be described with reference to the drawings. The BAR analog signal l output from the 019AR receiver is input to the /(sofa amplifier 2) of the digitizer 14, and the signal level is scaled. be exposed.

Here, a part of the output signal of the buffer amplifier 2 is used as the monitor signal 13 to feed the controller 4. In the buffer amplifier 1 and 2, dynamic At the same time as removing the DC component included in the signal, to maximize the range,
The gain of the buffer amplification section 2 is adjusted by the buffer amplification section control signal 3 from the control section 4 . Next, after low-pass filtering in a low-pass filter 5 and sampling in a sampling unit 6 controlled by a sampling unit control signal 7, the sampled signal is converted into n bits (analog/digital i) in a quantization unit 8. Quantization is performed using the maximum number of quantization steps allowed by the hardware of the conversion device, the data recording thread, and the communication capacity of the data link. The upper m bits of the signal are processed by the quantizer control signal 9 (external control signal 3 12 that enters the quantizer 8 through the controller 4 and defines the number of quantization stages of the output signal of the quantizer 8). (1≦m5n) and outputs it as a SAR digital signal 11. In this case, if a wide range of image information is required but the image does not need to be of very high quality, m should be small; if a narrow range of image information is required but a high quality image is required, . This external control signal 12 is sent out according to a program stored in a computer mounted on the satellite, and defines the optimal number of quantization steps according to the ever-changing situation (required ml situation as described above). . In addition, l in the figure
O indicates a data recording system for recording SAR digital signals.

As explained above, the device according to the present invention can arbitrarily select the number of quantization stages according to demand when digitizing a SAR analog signal, so that it can achieve a reasonable balance between SAR data limit and image quality. This makes it possible to configure an extremely flexible BAR system.

BRIEF DESCRIPTION OF THE DRAWINGS The figure is a block diagram showing an embodiment of the present invention. DESCRIPTION OF SYMBOLS 1...SA, R analog signal, 2...Buffer amplification section, 3...Buffer amplification section control signal, 4...Control section, 5...Low pass filter, 6...M series Department,
7... Sampling section control signal, 8... Quantization section, 9...
・B child conversion unit control signal, IO...data recording thread, 11.
...RAR digital signal, ]2...external control signal,
+3...Monitor signal, 14...sA R (, No. 1 digitization device. Patent applicant: Japan Space Development Agency)

Claims (1)

[Claims] In a synthetic aperture radar device mounted on a flying object such as an artificial satellite, a sampling means for sampling a synthetic aperture radar analog signal output from a receiver, and a quantization means for quantizing the sampled signal. , and control means for changing the number of Isogoization stages of the quantization means in accordance with a program stored in a computer mounted on the flying object.