JPS6088377A - Radar equipment - Google Patents

Abstract

PURPOSE:To make it possible to easily change the response time of the change in receiving gain, to change gain even if a S/N ratio is inferior and to keep a receiving level constant, by calculating the square average value of error voltage through the level comparison of a detection receiving signal and a reference signal to control an analogue attenuator. CONSTITUTION:In the synthetic aperture radar mounted to an artificial satellite, the part good in a S/N ratio of a receiving signal is cut off in a time window controlled by a gate signal from a controller 16 corresponding to the altitude and posture of a platform to a detector 13 and the output of this detector 13 is compared with the reference signal from the controller 16 corresponding to reference signal command in a comparator 14 while error voltage subjected to A/D conversion is supplied to the controller 16. Subsequently, the square average value voltage of time constant of error voltage is calculated and corrected corresponding to time constant command to control an analogue attenuator 11 through a gain setting circuit 17 and a D/A converter 18. By this method, a variable condenser is dispensed with and the change in a receiving gain response time is easily performed and, even if S/N is inferior, desired gain setting can be performed and a receiving level can be made constant.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a radar device, particularly to a radar device useful when applied to a synthetic aperture radar.

In radar equipment such as synthetic aperture radar (8AR) installed on aircraft and satellite platforms, there is a demand for changing the receiver gain after a certain period of time and keeping the receiver output level constant. .

In order for the gain control circuit (AGO circuit) of the receiver to operate normally, the signal-to-noise ratio (S/N) must be good to some extent. However, radar equipment mounted on artificial satellites has the disadvantage that it is not possible to achieve a signal-to-pierce ratio due to hardware problems such as limitations on the satellite's power supply capacity and the transmission power of the radar equipment's transmitter. was there.

In radar equipment, if you want to make the aging of the receiver gain change similar, that is, if you want to increase the time frequency of the AGC circuit of the receiver, the time constant is determined by the capacitance and resistance value. Should I increase the capacitor capacity?
(: The resistance value must be increased.However, the capacitor with a large capacitance that can be mounted on a satellite is f
i< (approximately 1000 μF) Furthermore, if the capacitor capacity is increased, the size, weight, and power consumption will increase, making it unsuitable for satellite loading.

Furthermore, if you want to change the response time of the receiver gain change by an arbitrary V, the capacitance of the capacitor in the AGC circuit of the receiver can be set to T.
:The drawback was that it would be difficult to implement onboard a satellite as it would require changing the IJ.

The present invention solves the above-mentioned drawbacks, and in a radar device mounted on a platform such as an artificial satellite, it is possible to arbitrarily change the response time of the receiver gain change, and at the same time, the Isa signal-to-noise ratio can be improved. The present invention provides a device that can change the gain and keep the output signal level of the receiver constant at an arbitrary level.

The present invention is a radar device such as a synthetic aperture radar mounted on a plant platform such as an aircraft carrier or an artificial satellite. a controller that generates a gate signal that can be used, a detector that detects the received signal cut off by the gate signal, and a reference signal rectangle that is output from the detected signal and a reference signal command via the controller;
A comparator that compares pressure levels, an A/D converter that converts the error voltage that is the output signal of the comparator, and a command that determines a time constant, the control is capable of calculating the root mean square value of the error π1' pressure at any time. a D/A converter that converts the gain setting signal not calculated by the gain setting circuit that sets the gain of the receiver from the average value voltage, and converts the output signal of the D/A converter into an analog signal. - Consists of an amplifier that is input to an attenuator, reduces the gain of the receiver, delays the output level of the receiver by an arbitrary amount of time, and makes it constant at an arbitrary level.

Next, embodiments of the present invention will be described with reference to the drawings.

Greasy! FIG. 1 shows a general functional block diagram of a secondary radar device. The radar device includes an antenna 1,
It is composed of a transmitter/receiver switch 2, a transmitter 3, and a receiver 4.The antenna 1 has the function of irradiating a transmitting signal to a target and receiving a received signal that is a reflected signal from the target. ,
The transmitter/receiver switch 2 has a function of transmitting and receiving a transmitting signal generated by the transmitter 1 to the antenna 1 and transmitting a received signal from the antenna 1 to the receiver 4. The transmission line 3 has the function of generating a transmission signal, amplifying it to a desired transmission output level and transmitting it to the duplexer 2), and also generating a signal necessary for the receiver 4.

The receiver 4 has a function of amplifying the received signal sent from the transmission switching device 2 to a desired level, and also processes and outputs the received signal using the signal from the transmitter 3.

FIG. 2 shows a perspective view of a lateral force monitoring radar such as a lateral monitoring radar such as a synthetic aperture radar.

The radar device is mounted on platform A of the ship Sky Sakura and Artificial Guard S@, and is mounted diagonally at 1. Irradiates waves.

The target, which is the irradiation area, is diagonal #, 81! When platform A advances, the radar device will irradiate the area between t and t'. Figure 3(a) is a diagram showing the geometry of the side-monitoring radar. The radar equipment is mounted on platform A and moves between F and G. F-IC (Distance is called Near Range Rn, and distance from A to G is called Far Range Rf.

From (a) in Figure 3, the short distance Rn and the long distance B, f are (1
) where, ILe: Radius of the earth h Altitude of the Niblat form αn: Angle of inclination ψn for short distances: Angle of elevation αf for short distances: Angle of inclination ψf for long distances: Angle of elevation θ of the ψ conjunction of long distance furrows : Antenna beam width in the distance direction (in FIG. 3) is a diagram showing the timing of the transmitted signal and the received signal. The pulse repetition frequency PRF is selected so that the received signal RX1 of the first transmission signal TXI is received between the nth and (n+1)th transmission signals. However, n is a positive integer equal to 0. If the transmission pulse width is τ1, the instant the first received signal starts is the first
FIG. 3(C) is a diagram showing the difference in the timing of the received signal due to the change in the altitude of the platform.

■ in the same figure indicates when the altitude is high, ■ in the same figure indicates when the altitude is nominal, and ■ in the same figure indicates when the altitude is low.

FIG. 4(a) is a diagram showing the relationship between the reception level of the received signal and time. Since the level of the received signal is almost proportional to the antenna pattern, the S/N ratio is better in the center of the received signal.

4) is a diagram showing the received signal in the time domain.

FIG. 5 is a circuit diagram showing a third embodiment of the present invention.

Below, I will explain and explain the Eki 5 map.

As shown in Figure 3(C), the intensity of the received signal changes as the altitude of the platform on which the radar device is mounted changes. Furthermore, even if the attitude of the platform changes, the timing of the received signal changes. Detector 1
The timing of the gate signal input to 3 is determined by inputting the altitude data and attitude data of the platform, that is, according to equation (1), ψ2ψf, αn,
By inputting the data of αf, the short range distance n and the long range Rf are calculated, and the controller 16 generates the values by performing these calculations.

In FIG. 4(1)), the shaded area indicates the timing at which a part of the received signal is gated. By dividing the timing at which a part of the receiving portion is cut off by the controller 13, the signal-to-noise ratio (S/N) can be improved with equal constraints. The voltage of the signal detected by the detector 13 is Va
and the voltage VR of the reference coefficient generated from the controller 16 is
shall be. Reference signal voltage VRp2 (determines the output level of the receiver and can be changed with the reference signal voltage command. The detected signal voltage VD and the reference signal voltage VR are compared by the comparator 14. The output signal of the comparator 14 The error voltage △V
i is A/D converted by an A/D converter 15.

The time constant command is a command that determines the gain E of the receiving and transmitting equipment, and is input to the control unit 11W16. Controller 16
, the error voltage △Vi which is the A/D converter's
The square value of the time constant of (digital signal) quality pressure V
Calculate av. This division is performed using the following formula % Formula % Here, the value of m determines the time constant.

The time constant τ can be changed using a time constant command.

The time constant τ is expressed by the following equation.

τ=m/plLF' (3) Here, PnF: Pulse repetition frequency - As an example, PnF=1000H2, m=10. 1
0.

10, time constant τ= 100m5ec, 1
sec, 10 sec. The average value of the error voltages Vav, which is the output signal of the controller 16, is input to the gain setting circuit.

The gain setting circuit 17 has a function of generating a gain setting signal that determines the attenuation level of the analog attenuator 11. The D/A converter 18 converts the gain setting signal into D.
/A conversion function. Analog attenuator 1
1 has a function of attenuating a received signal and changing the gain of the receiver in response to a gain setting signal. Amplifier 12 is an amplifier with a fixed amplification degree.

With the configuration described above, the present invention can arbitrarily change the response time of the gain change of the receiver, solve problems such as the capacitance of the capacitor, and even if the signal-to-noise ratio is poor, the receiver's response time can be changed arbitrarily. This has the advantage that the gain can be changed and the output level of the receiver can be kept constant at an arbitrary level.

[Brief explanation of drawings]

Figure 1 is a block diagram showing the configuration of the secondary radar device;
The figure is a perspective view of the side monitoring radar, Fig. 3 is a diagram showing the geometry of the other monitoring radar and the timing of the transmitted signal and the received signal, and Fig. 4 is the relationship between the reception level and time of the received signal and the time of the received signal. FIG. 3 is a diagram showing waveforms in a region. FIG. 5 is a circuit diagram showing an embodiment of the present invention. 11... Analog attenuator, 12...
...Amplifier, 13...Detector, 14...
・Comparator, 15...A/I) converter, 16...
...Controller, 17...Gain setting circuit, 18
...D/A converter. Strategy 1 Mouth 117) Line 2 Figure ffl' 1 Atsushi 3 Figure

Claims (1)

[Claims] In radar devices such as synthetic aperture radars mounted on platforms such as aircraft and artificial satellites, the altitude data and attitude data of the platform are input, and the time to cut out a part of the received signal can be changed in response to changes in altitude and attitude. A controller that generates a gate signal, a detector that detects a received signal cut off by the gate signal, and a potential level of a reference signal output from the detected signal and a reference signal command via the controller. A comparator for comparison, an A/D converter for A/D converting the error voltage that is the output signal of the comparator, and the control that can calculate the root mean square value of the error voltage at any time by a command that determines a time constant. a D/A converter that converts the gain setting signal calculated by the gain setting circuit that sets the gain of the receiver from the average voltage, and converts the output signal of the D/A converter into an analog signal. A radar device comprising an amplifier that is input to an attenuator and changes the gain of a receiver to keep the output level of a received signal constant at an arbitrary level over a given XeO time.