Photonic Approaches To Microwave Frequency Measurement

The frequency measurement of the input microwave signals is of critical importance for modern radar warning receivers in the field of electronic warfare (EW) Unlike the conventional receivers, the input signals are unknown for EW receivers and it is desirable to estimate the frequency of the unknown signal in a very short period of time. Instantaneous frequency measurement (IFM) system deals with that problem. With the frequencies of modern radar systems ranging from sub-gigahertz to millimeter-wave, the conventional electrical implementations may not meet the requirements of wide operating frequency range and nearly real-time response because of electrical bottleneck.The photonic techniques could overcome these above limitations due to their advantages such as wide bandwidth, light weight, low loss, and immunity to electromagnetic interference.In the second chapter of this dissertation, we propose and demonstrate a photonic approach to instantaneous frequency measurement with extended range based on phase modulation. In the measurement system, two optical wavelengths and two segments dispersion fibers are used to construct the frequency-dependent amplitude comparison functions (ACFs). Several ACFs can be utilized jointly to determine the microwave frequency without ambiguities beyond a monotonic region of the conventional one ACF. Then the measurable range of microwave frequency can be extended and the accuracy can be improved by selecting ACF with largest slope. The experiment results show that the errors are limited within±150MHz from8to20GHz frequency measurement range.The third chapter proposes a photonic microwave frequency measurement setup based on a sagnac loop with PMF.The forth chapter proposes a integrated photonic microwave frequency measurement approach based on a micro ring resonator.