Carrier Frequency Independent RF Photonic QPSK Modulator

An RF photonic quadrature phase-shift keying (QPSK) modulator is conceived and demonstrated practically. The modulator has the ability to operate with any RF carrier frequency within an ultra-broad frequency range. This is achieved via utilization of a broadband Hilbert transformer. The transformer enables wideband 90 ^° phase shifts required for QPSK to be realized. The carrier frequency independent operation of this modulator makes it a perfect candidate for many applications such as electronic warfare transmitters operating based on frequency hopping. An operational frequency range of 9.8-30.2 GHz was achieved.