I. Introduction
The push towards very high bit rate wireless communication systems requires substantial spectral bandwidth. This has motivated the use of millimeter-wave (mm-wave) frequencies [1] and in particular, the unlicensed band from 57 to 64 GHz [2], [3]. Wireless communications in this frequency band are employed for short distance or indoor systems due to enormous attenuation in the atmosphere at 60 GHz [4]. Therefore, the prominent interest in microwave photonic generation of mm-wave signals such as optical heterodyning is growing rapidly [5], [6], where two or more optical modes beat on a high-speed photodiode (PD). An optical fiber is used to transmit the generated optical signals and data from the central station (CS) to the base station (BS), and owing to heterodyne process on PD, the electrical mm-wave signals are generated before distribution to mobile stations.