Front end filter design for the newly acquired spectrum from the FCC

The recent release by the US Federal Communications Commission (FCC) of additional spectrum for the use of cellular service has introduced some interference concerns. The frequency allocation is such that blocks of frequencies from each of the service providers will be embedded within the frequency spectrum of the other service provider. This presents a problem to the system designer to provide adequate filtering to minimize the interference between service providers, by designing the ideal filter with an immediate transition from very low loss to high rejection. This is so because FCC frequency allocation provides no guard band between service provider frequency bands. Efforts to meet these demanding filtering requirements are reported. Several approaches have been investigated and procedures and results are discussed