Leakage signal cancellation circuit of linear frequency modulation continuous wave radar

Abstract

The invention discloses a leakage signal cancellation circuit of a linear frequency modulation continuous wave radar. A transmission signal is transmitted by an antenna via a circulator; an input end of a first coupler is connected with the transmission signal; a through end of the first coupler is connected to the circulator; a coupled end of the first coupler is connected to an input end of a second coupler; a through end of the second coupler is connected to a signal input end of a vector modulator; a coupled end of the second coupler is connected to a phase shifter; the phase shifter is connected to an LO (Local Oscillator) signal input end of a quadrature mixer; leakage signal in the circulator is input to a third coupler; a through end of the third coupler is connected to a fourth coupler; a coupled end of the third coupler is connected with an output end of the vector modulator; a through end of the fourth coupler is connected to a receiver; a coupled end of the fourth coupler is connected to an RF (Radio Frequency) signal input end of the quadrature mixer; two differential signals output by the quadrature mixer are connected to the vector modulator via a differential operational amplifier, an active low pass filter and a summing circuit respectively; and the summing circuit and offset voltage carry out additive operation.

Description

technical field [0001] The invention belongs to the technical field of radio frequency microwave circuits, and is suitable for linear frequency modulation continuous wave system radar, especially for single antenna linear frequency modulation continuous wave radar system. Background technique [0002] The biggest challenge for continuous wave radar is how to achieve sufficient isolation between transceivers. Since the transmitting and receiving of the continuous wave radar is carried out simultaneously, the influence of the transmitter on the receiver cannot be eliminated by using the transmitting and receiving switch like the pulse radar. Therefore, the most serious disadvantage of continuous wave radar is the leakage of transmitted signals. For pulse radar, using the transceiver switch can separate the transmission and reception in time, that is, do not receive when transmitting, and do not transmit when receiving. In the continuous wave radar, the transmission and recep...

AI Technical Summary

Problems solved by technology

In the continuous wave radar, the transmission and reception are carried out simultaneously, and the detection power needs to be within 10 watts when the transmission power is several watts. -6 The useful target echo signal of W magnitude or even lower will cause two serious problems: (1) the noise of the transmitted signal will overwhelm the useless signal; (2) the signal leaked into the receiver will reduce the sensitivity of the receiver

This is why pulsed radars have dominated and CW radars have been limited since the beginning of radar use

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