Carrier to noise ratio measurement circuit

Claim 1

A carrier power to noise power ratio measurement circuit, comprising a bandpass filter (301) for band-limiting an input signal, a first branching circuit (310) for branching the output of the bandpass filter (301) to produce two outputs; a first π/2 phase shifter (308) for rotating the phase of one of the two outputs of the first branching circuit by n/2 radians; an amplitude-limiter (302) for limiting the amplitude of the output of the first π/2 phase shifter (308); a second π/2 phase shifter (309) for rotating the phase of the output of the amplitude-limiter (302) by another π/2 radians; a second branching circuit (311) for branching the output of the second π/2 phase shifter to produce two outputs; a delay circuit (303) for delaying one of the two outputs of the second branching circuit (311); a third branching circuit (312) for branching the output of the delay circuit to produce two outputs; a first multiplier (305) for producing a product of one of the two outputs of the third branching circuit (312) and the other output of the first branching circuit (310); a third π/2 phase shifter (306) for rotating the phase of the other output of the third branching circuit (306) by π/2 radians; a second multiplier (304) for producing a product of the output of the third n/2 phase shifter (306) and the other output of the second branching circuit (311); a first averaging circuit (501) for averaging the output of the first multiplier (305); a first squaring circuit (502) for squaring the output of the first averaging circuit (501); a second squaring circuit (503) for squaring the output of the second multiplier (304); a second averaging circuit (504) for averaging the output of the second squaring circuit (503); and a divider (503) for dividing the output of the first squaring circuit (502) by the output of the second averaging circuit (504).