An analysis and a dynamic testing method of microwave QPSK modulation

Abstract

Using the clockwise or anticlockwise stepping pulse code signal, the characteristics of general quaternary phase shift keying (QPSK) modulation are analysed. This paper gives the spectrums in several operational conditions and the admittance formulas of related two modulation circuits. Several typical examples of QPSK modulation are calculated. The modulation effect and the phase error can be decided and the QPSK modulator under the dynamic test may be adjusted by using above results. The experimental results are in agreement with the theoretical calculations. An X-band QPSK modulator is also presented. The maximum phase error is less than 4°, the phase accuracy near ±0.1°, the insertion loss less than 4 dB and the data (transfer) rate up to 68 Mb/s.