Direct QPSK modulator for point-to-point radio link at 23 GHz

Abstract

The design and characteristics of a simple direct QPSK modulator for a terrestrial point-to-point radio link is presented. This modulator enables a compact, low cost and high efficiency transmitter. Good sideband suppression, greater then 25 dB is obtained in the frequency range 21.0 to 24.0 GHz, without tuning. The insertion loss is less than 8 dB in 3 GHz bandwidth and the carrier suppression is about 22 dB.