Design and Realization of a 16 QAM-Modem for a 140 Mb/s Digital Radio System Family

A 16 QAM-modem for 140 Mb/s radio systems is described, with which a spectral efficiency of 3.5 bit/s/Hz is achieved. In the digital signal processing parts extensive use is made of ECL gate arrays. Spectrum shaping according to Nyquist's criterion is performed in the IF with the aid of SAW-bandpass filters (¿ = 0.5). Experimental results obtained with this modem are reported. The incorporation of an adaptive baseband equalizer employing a complex transversal filter is discussed.