Frequency-modulated continuous wave radar for range measuring
First Claim
1. A radar system of the frequency modulated continuous wave type (FM/CW), intended for range measuring, including a linearly frequency-modulated microwave signal generator, a transmitter-receiver antenna and deriving means for deriving a fractional signal of the transmitted wave to effect production of a local oscillation signal and for deriving a fractional signal of the received echo wave and transmission lines for transmitting the derived signals to the inputs of a mixer, the lengths of the transmission lines being adjusted so that at least the internal interference coupling signal due to the antenna reflection has, up to the mixer, the same propagation time as the local oscillation signal, characterized in that a phase control loop including an amplifier and a low pass filter is connected between the output of the mixer and a control input of a phase-shifting circuit placed in the local oscillation channel, the closed loop cut-off frequency of the control loop being lower than the frequency of the useful subtractive beat signal between the transmitted and received waves provided at the output of the mixer.
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Accused Products
Abstract
The radar includes a linearly frequency-modulated microwave frequency signal generator (1), a transmitter-receiver antenna (2) and coupling means (3, 6; 48) in order to sample a local oscillation signal and an echo signal and in order to transmit these two signals to the inputs of a mixer (5) which provides at its output a subtractive beat signal between these two signals. The line lengths are adjusted in order to produce a static adjustment of the phase between the local oscillation signal and the interference antenna reflection signal. A phase control loop including an amplifier (36) and a low-pass filter (37) is connected between the output of the mixer and an input of a phase-shifting circuit (35; 54) placed in the local oscillation channel; the closed control loop cut-off frequency is just below the frequency of the subtractive beat signal.
43 Citations
9 Claims
- 1. A radar system of the frequency modulated continuous wave type (FM/CW), intended for range measuring, including a linearly frequency-modulated microwave signal generator, a transmitter-receiver antenna and deriving means for deriving a fractional signal of the transmitted wave to effect production of a local oscillation signal and for deriving a fractional signal of the received echo wave and transmission lines for transmitting the derived signals to the inputs of a mixer, the lengths of the transmission lines being adjusted so that at least the internal interference coupling signal due to the antenna reflection has, up to the mixer, the same propagation time as the local oscillation signal, characterized in that a phase control loop including an amplifier and a low pass filter is connected between the output of the mixer and a control input of a phase-shifting circuit placed in the local oscillation channel, the closed loop cut-off frequency of the control loop being lower than the frequency of the useful subtractive beat signal between the transmitted and received waves provided at the output of the mixer.
Specification