JPS59184875A - Synthetic aperature radar - Google Patents

Abstract

PURPOSE:To widen an observation area without increasing the transmitting power by controlling the transmission phase of a phase shifter, and controlling the direction of an antenna beam. CONSTITUTION:The high frequency pulse power of a transmitter 2 is fed to antennas 1-1, 1-2 through a transmission and reception branching filter 3, a power distributor 5 and a phase shifter 6, and radiated to space. Also, when an excitation phase is controlled by the phase shifter 6 so that an antenna beam is directed to the direction of a coverage A at the time when a transmitting pulse 7-1 is radiated, and the antenna beam is directed to the direction of a coverage B at the time when a transmitting pulse 7-2 is radiated, and a phase of the phase shifter 6 is controlled so that the antenna beam is directed to the direction of the coverage A at the time when a reflected echo 8-1 is received, and the antenna beam is directed to the direction of the coverage B at the time when a reflected echo 8-2 is received, each reflected echo, and the transmitting pulse and the received echo are not overlapped, and the coverage A and B are covered with the whole.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a synthetic aperture radar mounted on an artificial satellite. Synthetic aperture radar is a remote sensor that can provide images with extremely high distance resolution regardless of day or night weather.

FIG. 1 is a diagram showing the operating principle of a conventional synthetic aperture radar. High-frequency pulse radio waves generated by the radar transmitter (2) are radiated in the J direction through the transmitter/receiver duplexer (3) and the antenna (1). The reflected wave from the observation area is received again by the antenna (1), passes through the transmitter/receiver splitter (3), and is received by the receiver (4). A high-resolution image is obtained by processing this received signal.

Since radar emits high-power pulse radio waves, the receiver cannot operate while the pulse is being transmitted. Therefore, the repetition frequency of the transmitted pulse fU is selected so as to satisfy the following conditions when the distance to the nearest point of the observation area as seen from the radar is RI p and the distance to the farthest point is R3.

Here, C is the speed of light and n is a positive integer.

As described above, when the pulse repetition frequency is selected, qualitatively the timing of the transmitted pulse and the received echo becomes as shown in Fig. 2, and the transmission time interval Tt υ and the receiving time width 'rr become shorter. . On the other hand, during observation, it is desirable for the observation area to be as wide as possible, but if the transmission time interval and reception time interval are made to match, the coverage area of the antenna beam will be expanded and the gain will be reduced. down. Synthesis - Loreda's l[! ! The signal-to-noise ratio of the I-image is proportional to the square of the transmission power and the antenna gain, so if the observation width is widened, the signal-to-noise ratio of the I-image is proportional to the square of the observation width. Need to increase power. This invention was made to eliminate such problems with conventional radars, and provides a means for widening the observation area without increasing transmission power. The contents of this invention will be explained in detail with reference to the following two drawings.

FIG. 3 (This is a diagram for explaining the configuration of a synthetic aperture radar which is an embodiment of the present invention. In the figure, (1) is a one-dimensional phased array antenna consisting of two or more elements, (2) is a transmitter, and (3) is a transmitter/receiver duplexer.

(4) is a receiver, (5) is a power divider, and (6) is a phase shifter.

Luxurious. (A) and CB) Coverage of U antenna beam.

That's naive. Figure 4 is a diagram showing the pulse timing, and (
7) represents two consecutive pulse trains, and (8) represents the received echo corresponding to each pulse.

In the above figure, the ^-frequency pulse power generated from the transmitter (2) is sent to the transmitter/receiver splitter (3) and the power divider (5).

and the antenna (+-1) and (
1-2) and radiates into space. By controlling the transmission phase of the phase shifter, the direction of the antenna beam can be adjusted to the observation range (
A) or the observation area (BJ) The beam direction changes to cover the observation area.The reflected wave from the observation area follows the opposite path and is received by the receiver (4) via the transmitter/receiver splitter (3). .

In Fig. 4, at the time when the transmission pulse (, 7-1) is emitted, the antenna beam is directed to the coverage area (, A), and (
7-2) is emitted when the antenna beam reaches the coverage area (B
), the excitation phase is controlled by the phase shifter (6), and at the time when one reflected echo (8-1) is received, the antenna beam faces the direction of the coverage area (A) and the reflected echo (c) ( 8-
2) If the phase of the phase shifter (6) is controlled so that the antenna beam points in the direction of the coverage area (B) at the time of receiving the signal, the mutual reflected echoes will also be the same.

Further, the transmitted pulse and the received echo are received without overlapping, and the coverage area (A) and the coverage area (B) can be covered as a whole.

Furthermore, compared to the case where an antenna with a wide beam width is used to simultaneously cover the entire coverage area, the coverage area of the antenna beam is halved, so the antenna gain is doubled, p, and the transmission pulse (7-1) and ( 7-2) requires only one-fourth the power.

Therefore, even if two pulses are emitted in succession.

The total power consumption will be halved.

As described above, according to the present invention, data covering a wide area can be obtained using a transmitter with low power consumption, and the effect is extremely large when used on a satellite.

Note that the present invention is not limited to the above-described embodiments, and can be implemented in exactly the same way by using one, for example, two transmitters to separately excite two antennas.

[Brief explanation of the drawing]

Fig. 1 is an explanatory diagram of a conventional synthetic aperture radar, Fig. 2 is a diagram showing the pulse timing in the conventional radar, Fig. 3 is an explanatory diagram of the present invention, and Fig. 4 is a diagram showing the pulse timing of the present invention. In the figure, (1) is an antenna;
(2) is a transmitter, and (4) is a receiver. (61 is the phase shifter, (7) is the transmitting noise, and (8) is the receiving echo. In the figure, the same or corresponding parts are given the same reference numerals. Agent Masuo Oiwa

Claims (1)

[Claims:] Means for emitting two or more transmission pulses in succession. A synthetic aperture radar comprising a one-dimensional phased array antenna that scans a beam in one plane and means for receiving two reflected radio waves.