The CATV Return Amplifier

The age of high-speed data communications and multimedia application have dawned on cable television. It has brought with it a myriad of services such as high-speed data, video on demand, IP telephony, status monitoring, impulse pay-per-view.

A cable plant must be two-way ready to carry this high-speed data traffic from a variety of sources. Traditionally, in a two-way cable television plant, return amplifiers are employed to carry the reverse path signals (5 – 42 MHz). Diplex filters are used to separate the reverse signals from the forward path. A diplex filter is a Low-pass and High-pass combination. In a frequency division multiplexing (FDM) arrangement, without the use of diplex filters which are located between the input and output ports of an amplifier station, interference and oscillations between the forward and reverse path signals could occur. In a typical CATV trunk amplifier station, there are three diplex filters, (trunk in, trunk out, and Bridger out) forward amplifier, Bridger amplifier and reverse amplifier present. In a line-extender, an arrangement of two diplex filters with forward and reverse amplifiers is employed. In North America, a modern diplex filter Low-pass section would pass frequencies between 5 Mhz through 42 Mhz (reverse path) and the High-pass filter section would pass frequencies between 54 Mhz through 860 Mhz (forward path).

June 19, 2011

Continue