Patent ID: 6847255

Claim:
A complex single sideband zero IF down-converter frequency demodulator or frequency discriminator/comparator, comprising: means for receiving and splitting a local oscillator (LO) signal of frequency ω 0 to two components: the in-phase component and the quadrature component; means for receiving and splitting an input signal of carrier frequency ω c , to two components: the in-phase component and the quadrature component; means for multiplying each one of the said in-phase and quadrature LO signal components with each one of the said in-phase and quadrature input signal components, for generating a total of four different converted input signals; means for combining (adding or subtracting) in two pairs the said four converted signals, producing two lower single sideband signals: the in-phase signal I − (t) and the quadrature signal Q − (t); means for delaying each of the said in-phase I − (t) and quadrature Q − (t) signals by substantially same time delay τ, providing respective delayed baseband signals I − (t−τ) and Q − (t−τ); means for multiplying the said delayed signals with the said un-delayed signals, to generate two multiplication products I − (t−τ)Q − (t) and I − (t)Q − (t−τ); means for combining (subtracting) the said two multiplication products, providing the demodulated baseband signal BB(t); means for outputting the said demodulated baseband signal; means for generating a local oscillator signal of frequency ω 0 , which is related to frequency ω c and time delay τ by equation (ω c −ω 0 )τ≅nπ, where n=0,±1,±2, . . . .