Design and analysis of a novel instantaneous frequency measurement module based on the interferometer phase-comparison method

The design of a novel instantaneous frequency measurement module based on the interferometer phase-comparison method is proposed in this paper. Relative to heterodyne receiver, the advantage of instantaneous frequency measurement is its measurement speed. Firstly, the basic operating principle of interferometer phase-comparison method is given. And then the module is fabricated and measured. The proposed instantaneous frequency measurement module consists of amplitude limited amplified and filtered circuit, power divided circuit, phase shift network, AD and coding circuit, etc. The measurement results show that the sensitivity of this module is better than −75dBm, the frequency measurement accuracy is about 5MHz, the speed could reach about 0.1us. The total dynamic range is from −75dBm to +25dBm. The performance of the proposed module satisfies the requirement of the design, and the module has been used in some equipment. Finally, the frequency measurement error is analyzed. The frequency measurement error in some frequency points exceeds 8MHz in 85°C,because the LO power of I/Q phase detector decreases in higher temperature and cause the loss increasing. It can be solved by tuning the power of LO amplifier.