An N-phase vector synthesis demodulator employing N number of mixers is presented. The received signal is mixed with locally generated N number of phase-shifted carrier signals at the N mixers, the individual phases of which are successively and equally 360/N shifted. The final in-phase (I) and quadrature-phase (Q) signals are zero-force synthesized from the demodulated N-phase vector signals. Compared with the conventional I/Q demodulator that obtains the I and Q signals directly from two mixers of 0 and 90 carrier signal phases, the multi-phase demodulator provides significantly high linearities in the demodulated I and Q signals as the zero-force synthesizer performs an optimal combining of the N-phase demodulated signals while minimizing distortions, interferences, and noise.

Disclosed is a microwave cavity resonator used as a phase change (phase modulation) to intensity change (intensity or amplitude modulation) converter. Certain aspects and embodiments include resonant circuits, such as a resistor, inductor and capacitor (RLC) circuit. Certain aspects and embodiments convert changes in phase to changes in output voltage to perform analog demodulation of a phase modulated microwave carrier. Certain aspects and embodiments use resonance when the reactive components of the circuit (capacitive and inductive components) are equal in magnitude and 180 degrees out of phase with one another, thereby cancelling out the reactance component of the circuit's impedance.