Improved DTH broadcast satellite transponder performance using low delay filters

A 3-pole OMUX filter offers better group delay performance than does a 4-pole filter. With a standard DVB-S QPSK signal, the ACI from spectral regrowth is comparable for both filter types. These two results leads to the conclusion that the 3-pole filter is a better choice for the DTH satellite OMUX. Preliminary simulations with 8-PSK modulation indicate a >1 dB E_b/N_O improvement using a 3-pole rather than a 4-pole filter design. Work is also being done with a 2-pole filter performance as well as higher order (> 4-pole) designs despite the fact these incur more output insertion loss. The additional useable, low delay bandwidth can be used for more error correction and, because of the nonlinear nature of channel coding gain, will more than offset the increased insertion loss.