Class-O Base Station System with RF Pulse-Width-Modulation in Downlink and Uplink

The following paper presents a novel so-called class-O base station system with RF pulse-width-modulation in downlink and uplink. Central unit and remote unit are connected via an optical link. On the optical link, a binary RF signal is transmitted. The conversion from an analog to a binary signal is implemented using a fast pulse-width-modulator (PWM) in the RF domain. For downlink this PWM is combined with a class-S amplifier which meets the 3GPP ACLR requirements within an excellent 10dB electrical output power range. The uplink shows a dynamic range of 65dB. Lab measurements show robust optical transmission of the RF signals over up to 70km fiber. It is shown that both uplink and downlink are capable of supporting simultaneous transmission/reception of non-contiguous frequency bands. Index Terms -- Base Station, class-S amplifier, optical fiber applications, pulse-width-modulation.