ELECTRONICALLY TUNEABLE FIBER-OPTIC RECEIVER FOR NARROW BAND MICROWAVE SIGNAL RECEPTION

摘要

The optical receiver has a photodiode (10) which is reverse biased by a voltage supply (14). The voltage supply provides a variable bias voltage determined by a control unit (16) and the photodiode is matched to the load (22) by an impedance matching circuit (12). The photodiode exhibits large capacitance changes over a range of bias voltages and may be implemented using a Schottky barrier or P<+>N photodiode. By changing the bias voltage, the photodiode capacitance changes to vary the tuned frequency of the receiver. The matching circuit cancels the reactive component to the photodiode impedance and matches the resistive component of the load. The photodiode may have a doping profile in which an intrinsic or lightly doped region of width greater than the average photon penetration depth is located next to the junction. After the intrinsic region, the doping profile may be selected to achieve linear tuning. This doping profile gives linear tuning without sacrificing photodiode conversion efficiency.