By Norman J. Slater And Douglas J. Mcewen, Cablesystems Engineering
The last few gears have seen cable television technology leap from 300 MHz, thirty-five channel capacity to 450 HBz, sixth channel capacity and beyond. New technologies which use two amplifiers in the post amplifier stage are now being used to reduce the level of composite triple beat in extended bandwidth systems. The two amplifiers are arranged in parallel or in a feedforward configuration and reduce post-amplifier composite triple beat levels by 5 dB and 18 dB respectively.
Test results are presented which show that second order distortion can be the limiting distortion in a sgstem carrying more than fiftg channels.
An analysis is then performed to confirm that second order distortion should be of verg real concern to designers of both amplifiers and systems. This analysis also shows that active equipment using parallel or feedforward post amplifiers give a disappointing improvement in second order distortion performance.