Spectrum shaping SAW filters for high-bit-rate digital radio.

The structure of a QAM radio system is explained. Some novel designs that demonstrate the current status of spectral shaping SAW (surface acoustic wave) filters are presented. Compensation of second-order effects is discussed. Experimental results for a filter for a 140-Mb/s 16 QAM cochannel system with a roll-off factor of 0.19 are shown. Two other examples of filters for a 140-Mb/s, 64 QAM system with a 35% relative bandwidth are also presented.