By Martin Lee & Keith Mothersdale, Channell Corporation
With the advent of two way communications over Hybrid Fiber Coax (HFC) networks, new technical demands are being made of conventional element of the coax drop. Products originally engineered and designed to accommodate forward path transmissions only are increasingly being used in two way systems. In these networks high level reverse path transmissions hold the key to future revenue growth and proliferation of services offered by cable operators. This paper examines a specific problem, Intermodulation, as it relates to transmission of high level reverse path signals through RF passive products. The factors contributing to Intermodulation Distortion occurring are explained in detail and a variety of solutions currently being pursued by passive product manufacturers are presented. Isolation performance of RF passives is also discussed as it relates to optimizing reverse path stability and managing intermodulation. In conclusion, passive product design criteria is presented which should be considered carefully in the selection of next generation passives.