RF Photonic Vector Modulation and Demodulation Techniques for Millimeter-Wave Communications

Abstract

RF photonic techniques for modulating and demodulating microwave and millimeter-wave signals on RF carriers are theoretically analyzed and experimentally demonstrated. The two demodulating configurations utilize cascaded electrooptic phase-modulation followed by optical filtering. The spurious free dynamic ranges of these configurations are measured and a technique to intrinsically linearize the latter system to fifth-order is experimentally confirmed. Measurements are then performed at frequencies between 7 and 70 GHz that verify RF photonic based downconversion using a harmonic of the electrical local oscillator (LO). Furthermore, this architecture is extended to allow for vector demodulation of digitally-encoded signals. Results of RF photonic demodulation of 4-quadrature amplitude modulation (QAM) and 16-QAM RF encoded millimeter-wave signals are presented.

Two RF photonic techniques for generating and encoding millimeter-wave RF signals are analyzed and experimentally demonstrated. The first uses phase-modulation and optical filtering in an interferometric configuration. Phase-shift keyed encoded microwave and millimeter-wave signals are electrooptically synthesized using a harmonic of the electrical LO at data-rates of up to 6 Gbps and frequencies of up to 40 GHz. A second RF photonic scheme is developed to allow for vector modulation and upconversion using dual-drive Mach-Zehnder modulators. Vector modulation and upconversion are then shown at harmonics of the LO up to the fourth-order and at frequencies up to 60 GHz. Moreover, generation of 2.488 Gbps 4-QAM signals on a 36 GHz carrier using the second harmonic of the LO are demonstrated with this approach. Wired and wireless microwave and millimeter-wave transmission experiments are successfully conducted with the RF photonic systems detailed above in a laboratory environment.