Development and demonstration of 12.4 Ghz sige HBT mixer for radio over fiber applications

Abstract

This work involves in conveying of an optically modulated intermediate frequency (IF) over fiber by employing the frequency up-conversion technique at the base station (BS), while the local oscillator (LO) signal was assumed to be remote and was located at the central station (CS). The main focus of this work is the development of optical front-end receiver for radio over fiber (RoF), whereby the LO signal was sent from CS to BS using the system. At the BS, the optically generated LO signal was used to up-convert the IF signal by using a microwave mixer. The mixer was developed utilizing heterojunction bipolar transistor (HBT) as its main active component due to the high internal gain offered and to allow the frequency conversion to take place. HBT mixer configuration was successfully modeled and simulated by employing harmonic-balance technique in Microwave Office (MWO) software. It has been verified through fabrication and device demonstration. In which, with the driven LO power of 0 dBm, the simulated conversion gain of -2.8 dB to 5.2 dB was obtained at -30 dBm to -10 dBm of IF input power level. The design was practically demonstrated and up-converted RF signal of up to 12.4 GHz was achieved.