Ultrafast Microwave Frequency Measurement Based On Electro-optic Tunable Fabry-perot Etalon

In radar systems and electronic warfare systems, microwave frequency measurement is widely used for detecting and classifying unknown signals. Compared with conventional electrical approaches realizing microwave frequency measurement, photonics-based approaches like optical channelizer, frequency-amplitude mapping and optical scanning receiver have the advantages such as wide instantaneous bandwidth, low loss, and immunity to electromagnetic interference. Among these approaches, optical scanning receiver is the most popular one. However, the scanning receivers now reported are scanned by mechanical tuning, electric heating, scanning microwave signal or frequency shifting recirculating delay line, which have a long scanning time and a low scanning speed. Facing this problem, the thesis introduces electro-optic fabry-perot elation to microwave photonics, proposes ultrafast microwave frequency measurement based on electro-optic fabry-perot elation, and makes theoretical analyses and experiment research on the performance of the system.The thesis first demonstrates the principal of frequency meas urement based on electro-optic fabry-perot elation. In this chapter, related basic theoretical knowledge is illustrated and main performance parameters and their determinants are analyzed. Then, the author designs and fabricates the core device of this system, electro-optic fabry-perot elation. The performance of electro-optic fabry-perot elation is tested, and the results show that it works well, with a scanning frequency of 1 MHz. At last, a single-EOFP microwave frequency measurement system is demonstrated to test the performance and feasibility of this approach. The test shows that the system can work well with a measurement range of 3.2 GHz, and a scanning voltage of 7.0 V. The accuracy is ±0.025 GHz when the voltage sweeping speed is 0.1 MHz. The accuracy decreases with the increase of scanning frequency. When the voltage sweeping speed is 1.0 MH, the accuracy decreases to ±0.1 GHz. Besides, we put forward an approach using two electro-optic fabry-perot elations with different FSRs to improve the measurement range of the system with single elation. Theory and simulation show that the range is expanded from 3.2 GHz to 54 GHz without losing accuracy and speed. The accuracy and range is limited by the loss caused by our technological level. With an advanced technological system, the measurement range and accuracy of the system can be double enhanced.Compared with other frequency scanning measurement systems, the system has a very simple structure without extra scanning microwave signal source, pump laser or long fiber and only needs a sawtooth wave scanning voltage whose peak-to-peak value is 7.0 V. The system has low requirements for the photodetector, it can be used to detect frequency information of the signals with very short duration and has a very good application prospects.