Miniaturized central station realization incorporating multi-Gbps modulation schemes for intermediate frequency over fiber downlink transmission

An affordable, simple and energy-efficient 10 GHz IF-over-Fiber system was investigated. We present here the design of a printed circuit board for a central station (CS) used in intermediate frequency (IF) over fiber downlink transmission. The CS inherently consists of IQ mixer, which facilitates quadrature modulation desirable to increase the spectral efficiency of the analog transmitted RF data. The IQ mixer is used for upconverting a 2.5 GHz complex baseband of the I & Q quadrature modulation. Amplifiers are incorporated at the inputs of I and Q as well as at the IF output of the IQ mixer to achieve output power of about 23 dBm, needed for driving the optical modulator. The IQ modulator has low noise figure of 2.5 dB. External laser intensity modulation and direct detection by photodiode at the base station (BS) are implemented. 5 Gbps optical modulated data at 10 GHz IF is transmitted over optical fiber mitigating the typical chromatic dispersion effects of fiber optical communication. The IF signal detected by the photodiode will be upconverted at the BS to 60 GHz carrier frequency and wirelessly transmitted to the mobile station (MS). In this paper, we present measurement and performance results of the miniaturized CS for the 2.5 GHz baseband input frequency. The power consumed by the CS (without laser) is estimated to be less than 1.5 W.