Design And Realization Of Instantaneous Frequency Measurement Module Based On New Coding Method

In the engineering application of ECM, the behavior of measuring frequency in a short time can be called Instantaneous Frequency Measurement(IFM), which is a kind of widely applied receiver working approach with important status. IFM receiver is a kind of receiver which measures the frequency of a short time signal. Due to the performances of wideband signal receiving and IFM ability, IFM Receiver has been widely applied in ECM. All the bases of IFM techniques are established in two aspects, one is a group of microwave components which has a key task to extract frequency information from external RF signal when it passes through, e.g. transform it into an instant or voltage information. The other one is a coding and processing function, which transforms the information provided by microwave front-end to digital signals to be coded and processed, thus obtaining practical and usable frequency information.A classic Frequency Measurement method is called interferometer phase-comparison :the main idea of this method is to transform the signal’s frequency to Phase and then calculate its frequency through the measurement of the Phase’s range change.Having good transient performance, this kind of method has been widely used in practice. However,its bottle-neck due to it can’t supply enough precision in measurement. This paper on the basis of research on instantaneous frequency measurement with practical projects, identified the resolution systematicly, digital signal processing parts have applied modular design and FPGA technology, and increase the accuracy of the measurement greatly.At the beginning of the thesis, the classification of frequency measuring receiver within reconnaissance receiver is introduced, the basic requirements and application of measuring frequency receiver are briefly described, then the mechanisms and composition of traditional interferometer phase-comparison method based IFM are emphasized. Based on engineering requirements of a product development project, a kind of new coding method to extract frequency information by combining A/D sampling and table looking up is put forward before prototype trial production, which makes use of most information provided by the components, then with the help of the project’s main specification, an IFM component with a bandwidth of 2GHz~4GHz is designed.The traditional way of output such frequency information is detecting the zero-crossing point first, and then forming the Garry code which will be transferred into final binary code. It needs high quality of delay-line and correlator. To predigest receiver’s production procedure and meet the mass production,the coding method of this receiver is combining A/D sampling and table looking up, which improves the precision of the IFM components, in other words, the RMSE of frequency measurement within working frequency is controlled in 3MHz(whole temperature range), and the number of the phase detector, the size of the printed circuit board and the works of debugging are superior to the IFM based on the traditional resistor loop quantization coding system obviously.