BROAD-BAND (GREATER-THAN-OR-EQUAL-TO-20 GHZ) LASER-DIODE-BASED OPTOELECTRONIC MICROWAVE PHASE-SHIFTER

We demonstrate a new type of broad-band microwave phase shifter with s uperior performance at frequencies up to 20 GHz. This is implemented b y simply adding an offset voltage prior to the loop filter (LF) in a l aser-diode-based digital optoelectronic phase-locked loop (OEPLL), Acc urate control of the phase of microwave signals with a continuously tu nable range exceeding 640 degrees (similar to 3.6 pi) is achieved. The phase fluctuation and long-term drift of ally desired phase shift are as small as +/-0.4 degrees and 0.08 degrees, respectively, at 20 GHz, The relative phase instability can be maintained within 0.09 degrees while operating in a phase-shift-keying (PSK) scheme, We also demonstr ate accurate control of relative phase difference between dual phase-l ocked microwave sources using the phase shifter. Our results indicate potential application of this broad-band optoelectronic phase shifter in a phased-array antenna system.