By R. T. Hsu, T. M. Straus, and J. L. Wrona, Hughes Aircraft Company
New technologies have recently led to a substantially wider choice of both transmitters and receivers that can be utilized in local distribution microwave CATV systems. One area of particular interest to smaller CATV systems involves the increased power available from low cost multichannel block upconverter type transmitters. The highest output power with this type of transmitter is now made possible by the development of a microwave feedforward amplifier, which provides up to 10 dB improvement relative to the standard AML® Microwave Line Extender transmitter. At the other end of the application scale, the continued expansion of the number of channels carried by CATV systems in major markets has led to the expansion of AML capability to 550 MHz. In addition to incorporating the latest low noise VHF hybrids to fulfill this need in AML receivers, circuit modifications, which include a built-in microwave LNA and VHF AGC, have led to significant improvements in distortion performance without sacrificing system C/N. Design criteria are provided to guide the proper application of these new microwave components in CATV systems.