A narrow bandwidth microstrip bandpass filter suitable for system-on-package integration

In this paper we present a compact microstrip bandpass filter using transmission zeros for narrowband characteristics, to be used in the carrier recovery path of a GB/s QPSK receiver. Several filters are designed operating at 20GHz with relative bandwidths (RBW) varying from 1.75% to 10%, and insertion losses varying from 3.5dB to 0.8 dB. A prototype filter is realized and good agreement between the measurement and simulation results is achieved. The applicability of the filter for system-on-package (SoP) integration is validated by a prototype wire bond connection to a thin film microstrip test structure on a Si substrate.