Quadrature splitter considerations for digital cellular radio

A quadrature splitter for converting a narrowband bandpass IF or RF signal into baseband inphase and quadrature phase signals is evaluated in a high IF cellular digital radio system with a total bandwidth of 25 MHz. The results show that the simple splitter causes spectrum residues due to the relatively small ratio of sampling frequency to total signal bandwidth. These spectrum residues result in spectrum overlap between a pair of two channels symmetrically located on either side of the center IF frequency. To accommodate the cellular radio application, two alternative splitters are designed and simulated. The improved splitters provide better performance with the cost of higher complexity. The performance and structure trade offs are presented