AN ANALYSIS AND A DYNAMIC TESTING METHOD OF MICROWAVE QPSK MODULATION

Using the clockwise or anticlockwise stepping pulse code signal, the characterities of general QPSK modulation are analysed. The spectrums in several operational conditions and the admittance formulas of related two modulation circu ts are given. Several typical examples of QPSK modulation are calculated. The results are used to decide the modulation effect and phase error, and also to adjust the QPSK modulator under the dynamic testing. The experimental results are in agreement with the theortical calculations. An X band QPSK modulator is also presented. the maximum phase error is less than 4, insertion loss less than 4 dB, phase accuracy near 0.1 and transmission data rate up to 34 Mb/s.