The Research Of Digital Signal Processing Methods In Phase Noise Measurement Technology

Phase noise is an important technique index of the communication equipments, microwave device and radar. This paper studies the digital signal processing method in phase noise measurement system, which makes the amount of the data calculation decreasing in phase noise measurement process and make the test system to measure the phase noise signal source effectively.This paper studies the digital signal processing method of the phase demodulation in the phase noise measurement system. First, the scheme of the phase noise measurement is briefly introduced and the phase demodulation method is used in this system. And then the digital design technique of the loop filter and the frequency difference elimination algorithm are introduced in detail. In the paper, the poly-phase structure is used to design the loop filter. With the poly-phase structure, the order of the loop filter is reduced and the amount of the filter calculation is reduced too. The amount of the poly-phase filter is5.058%of the direct filter. The frequency of the signal-under-test source and the reference source must be equal and quadrature in the phase demodulation system. But the phase loop lock could not always ensure that the signal-under-test is exactly equal in frequency to the reference signal in actual measurement. It will generate the frequency difference signal between the signal-under-test and the reference signal. In order to eliminate the frequency difference and extract the phase noise signal, the frequency difference elimination algorithm is introduced in this paper. The results of the simulation and the experiment show that the frequency difference is eliminated and the phase noise signal is extracted effectively. And then the requirement on frequency stability of the reference source can be lowered and the cost of the measurement system can be reduced.