Furuno Electric Company Limited

Akio Funae

Koji Yano

Koji Dai

Hideki Torizuka

Takuo Kashiwa

Asao Kitabatake

Takayoshi Hirose

Masataka Yasukawa

There is provided a radar receiver that effectively prevents local oscillator signals from leaking out from an antenna. A receiverincludes a local oscillator, a mixer, a buffer amplifier, and a mode switcher. The local oscillatoroutputs a local oscillation signal LO. The mixermixes a high-frequency signal RF received by a radar antennawith the local oscillation signal LO. The buffer amplifieris disposed between the local oscillatorand the mixer. The mode switcherswitches at least between a standby mode in which power is supplied to the local oscillatorand no power is supplied to the buffer amplifierand a reception mode in which power is supplied to both the local oscillatorand the buffer amplifier

Radar receiver, and radar device equipped with same

A microwave frequency converter for a radar receiver is provided in which a frequency of a local oscillator of the microwave frequency converter can be prevented from interfering with an oscillation frequency of a magnetron included in the radar receiver and which can receive a signal from a considerably short distance. A voltage of an RF amplifier connected to the microwave frequency converter is synchronized with an oscillation output of the magnetron. The gate and drain voltages of a FET used in the RF amplifier are simultaneously switched OFF only during times before and after the magnetron performs oscillation, thereby switching an amplification function of the FET to an attenuation function thereof to increase a switching loss of the microwave frequency converter. Thereby, an excessively large power RF signal directly input from the magnetron and an excessively large power RF signal reflected from a short distance are attenuated to prevent the microwave frequency converter from being saturated, and the frequency of the local oscillator from interfering with the oscillation frequency of the magnetron.

Microwave frequency converter

A radar includes a transmitter circuit, a receiver circuit, an antenna and a circulator. The receiver circuit includes a low-noise amplifier which amplifies a received signal fed from the antenna through the circulator. A local oscillator provided in the receiver circuit generates a local oscillator signal of which frequency is approximately half the frequency of the received signal, and the local oscillator signal is amplified by a buffer amplifier. An even harmonic mixer including an anti-parallel diode pair also provided in the receiver circuit as a frequency converter mixes the received signal output from the low-noise amplifier with the local oscillator signal output from the buffer amplifier to generate and output an intermediate frequency signal.

Radar

A small and light helical antenna, with a high gain, includes arranging the dielectric cylinder with a helix conductor on the conductive plate and arranging a thin rectangular conductive plate between the lower end of the helix conductor and the feed point in a predetermined position of the conductive plate. The impedance matching is between the input impedance of the helix conductor and a power feeder. The upper and lower conductive plates constitute parallel plate waveguide space, and the probe which comes into the parallel plate waveguide space is in the lower conductive plate side, and the lower end of a thin rectangular conductive plate is connected with the lower end of a probe.

Helical antenna and helical antenna array

The invention provides a magnetron drive circuit which drives a magnetron to produce a generally rectangular-shaped narrow transmission pulse having sharply shaped rising and falling edges. The magnetron drive circuit includes a nonlinear load circuit and an active damper circuit. The nonlinear load circuit becomes on at around 80% of a peak output voltage of a pulse transformer (at which the magnetron begins to oscillate) is connected to a secondary winding of the pulse transformer in parallel with the magnetron. The active damper circuit absorbs residual energy left in the pulse transformer without any need for an absorption resistor conventionally connected between both ends of a primary winding of the pulse transformer.

Growing community of inventors

Nishinomiya, Japan

Akio Funae