JPH0450995B2 - - Google Patents

Description

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

[Conventional technology]

In radar devices such as synthetic aperture radar (SAR) mounted on platforms of aircraft and artificial satellites, the reception start time of a received signal changes due to changes in the altitude or attitude of the platform. The timing of the reception start time had to be set by command based on the platform's orbit (altitude) information and attitude information.

[Problem that the invention seeks to solve]

For this purpose, when you want to acquire SAR data in an invisible region, the attitude data and orbit data of the platform are sent to the ground using a telemeter in order to set a command for the reception start time based on the predicted orbit (altitude) information. There were some flaws that I had to live with.

Another drawback is that the S/N ratio of the acquired data deteriorates when there is a sudden change in attitude or orbit of the platform.

The present invention solves the above-mentioned drawbacks and makes it possible to generate high-quality images by generating the reception start time of a received signal in a radar device mounted on a platform such as an aircraft or an artificial satellite. It provides equipment.

[Means for solving problems]

The present invention provides a radar device such as a synthetic aperture radar mounted on a platform such as an aircraft or an artificial satellite, which includes a frequency generating section that generates a necessary frequency within the radar device, and a pulse stretching section that generates a chirp signal. , a transmission amplification section that converts the frequency of the chirp signal that is the output signal of the pulse expansion section and amplifies it to a predetermined level, and a transmission amplification section that sends the transmission signal that is the output signal of the transmission amplification section to the antenna section and demultiplexes the received signal from the antenna section. an antenna section that emits a transmission signal to the ground and receives a reflected signal from the ground; and a reception section that amplifies the output signal of the transmission and reception switching section and sends the received signal to a signal processing system and a pulse compression section. , a pulse compression section that compresses pulses and has a filter having frequency versus time characteristics opposite to those of the reception section and the pulse expansion section;
A level detection section that detects the level of the pulse-compressed received signal, a timing generation section that generates the reception time timing based on a clock signal from the time when the level detection section exceeds a predetermined level, and the output of the frequency generation section. It has a clock generator that generates a clock signal from the signal.

〔Example〕

FIG. 1 is a circuit diagram showing an embodiment of the present invention.

The present invention includes an antenna section 11, a transmission/reception switching section 12,
Receiving section 13, transmission amplification section 14, pulse expansion section 1
5, a frequency generator 16, a pulse compressor 17, a level detector 18, a timing generator 19, and a clock generator 20.

The frequency generating section 16 generates a frequency required within the radar device such as the pulse expanding section 15, the transmission amplifying section 14, and the receiving section 13. The pulse expansion section 15 pulse-modulates the CW signal from the frequency generation section 16, and performs linear frequency modulation using a filter having frequency versus time characteristics as shown in a in FIG. 2 to generate a chirp signal. The signal is sent to the transmission amplification section 14. The transmission amplification section 14 converts the frequency of the chirp signal, which is the output signal of the pulse expansion section 15 , based on the CW signal from the frequency generation section 16 , amplifies it to a predetermined level, and sends it to the transmission/reception switching section 12 . The transmission/reception switching section 12 sends a transmission signal, which is an output signal of the transmission amplification section 14, to the antenna section 11. The antenna section 11 includes a transmission/reception switching section 12
The transmission signal which is the output signal of is radiated to the ground, the reflected signal from the ground is received, and the received signal (reflected signal) is sent to the transmission/reception switching unit 12. The transmission/reception switching section 12 sends the received signal to the receiving section 13 . The receiving section 13 frequency-converts the received signal based on the CW signal from the frequency generating section 16 and sends it to the signal processing system and the pulse compression section 17.

The pulse compression unit 17 includes a filter having a frequency versus time characteristic opposite to that of the transmitted signal as shown in b in FIG. 2, and performs pulse compression on the received signal, as shown in c in FIG. A signal is output. The level detection section 18 detects the level of the pulse compression signal and sends timing information of a predetermined level to the timing generation section 19. Timing generator 1
9 sends the timing of the reception start time to the receiving section 13 and the signal processing system based on the clock signal from the clock generating section 20. The clock generator 20 generates a clock signal from the CW signal from the frequency generator 16.

〔Effect of the invention〕

With the configuration described above, the present invention generates the timing of the reception start time of a received signal in a radar device mounted on a platform such as an aircraft or an artificial satellite, and obtains a high-quality image. It provides equipment.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing an embodiment of the present invention, and FIGS. 2 a to 2 c are diagrams showing the principle of pulse compression. 11... Antenna section, 12... Transmission/reception switching section, 1
3... Receiving section, 14... Transmission amplification section, 15... Pulse expansion section, 16... Frequency generation section, 17... Pulse compression section, 18... Level detection section, 19... Timing generation section, 20... Clock generator.

Claims (1)

[Claims] 1. In a radar device such as a synthetic aperture radar mounted on a platform such as an aircraft or an artificial satellite, there is a frequency generation section that generates the necessary frequency within the radar device, a pulse expansion section that generates a chirp signal, and a pulse extension section that generates a chirp signal. A transmission amplification section that converts the frequency of the chirp signal that is the output signal of the expansion section and amplifies it to a predetermined level, and sends the transmission signal that is the output signal of this transmission amplification section to the antenna section and demultiplexes the received signal from the antenna section. a transmission/reception switching section, an antenna section that emits a transmission signal to the ground and receives a reflected signal from the ground, and a reception section that amplifies the output signal of the transmission/reception switching section and sends the reception signal to a signal processing system and a pulse compression section. , a pulse compression section that compresses the received signal by having a filter with a frequency vs. time characteristic opposite to that of the pulse expansion section; a level detection section that detects the level of the pulse-compressed received signal; The present invention is characterized by comprising a timing generation section that generates a reception start time timing based on a clock signal from a time when a predetermined level is exceeded, and a clock generation section that generates a clock signal from the output signal of the frequency generation section. radar equipment.