A Radiofrequency Demodulator with an Electrically Quadrature Phase Tuning for M-QAM Digital Radio Links

This paper describes the design of a M-QAM radio-frequency demodulator, where a phase shifter is placed in one of the two channels (I or Q) to minimize the quadrature phase error between them by means of an automatic control loop. Measurements results are shown for an implementation realized in the 6.4-7.1 GHz band for a 16 QAM 140 Mbits/s radio link.