Low BER radio design for wireless local loop applications

High performance full duplex 1.4 to 2.8 GHz radios for wireless local loop telephony application have been developed and are described. The radios are designed to handle both QPSK modulation and spectrally efficient quadrature amplitude modulation (QAM) at a bit error rate of 1E-06. The radios are a critical component in a very sophisticated FDMA system that is currently installed and operational in several countries throughout the world. The system offers copper quality voice service to subscribers and is capable of supporting advanced digital services such as ISDN. The radios are designed to transmit over distances as great as 50 km. The base station radio achieves a nominal output power of approximately 1 Watt. The remote station radio located at the subscriber's residence achieves a nominal output power of approximately 0.5 Watts. The transmitter amplifiers in both the base and remote radios are operated at approximately 5 dB of cutback to preserve linearity which is especially critical in the QAM mode. The power managed system requires 60 dB of ALC range.