Microwave phase shifter implemented in photonic technology

There are many applications where a very wideband phase shifter is required. Analog pre-distorters to linearize Ka-band amplifiers require a frequency-independent phase shift over at least 1 GHz. The same requirement applies to phased-array antennas or antenna feeds, as well as direct radiating array antennas. Most electrical phase shifters have a fixed operating frequency, discrete phase shift steps (e.g., 5-bit control) and some frequency and temperature dependent responses which result in sub-optimum system performance. The requirements in the 50/40 GHz band will be even more demanding where the bandwidth to be covered could extend up to 5 GHz. The use of photonic technology mitigates the limitations of electrical phase shifters. Operation over a wide range of frequencies (e.g., 4 to 50 GHz) using a single design is possible, and a flat phase response over many GHz's can be achieved. This paper discusses the use of novel microwave photonic technologies to enhance the performance of a broadband phase shifter with respect to power, mass, volume, electromagnetic interference and compatibility of future on-board satellite subsystems. The targeted phase shifter is equally applicable to analog linearizers, phased-array antennas/feeds or other smart antenna schemes where relative phase shifts are required. The results of a prototype phase shifter are presented showing a broadband response over several GHz. Limitations of this device and justification for an integrated version will be discussed. Finally, preliminary results for an integrated device are presented.