A multilayer bandpass filter integrated into RF module board

A bandpass filter using multilayer structure is designed and manufactured. This filter is for the DECT handset RF module, hence must be compact, easy for mass-production, and low cost. This design uses standard (yet lowloss) FR4 board (/spl epsiv/r=4.8) and tapped I/O for the ease of manufacturing. A zero is introduced at the image frequency. Its multilayer structure occupies only three layers, and allows the filter to be integrated into the RF module board, while its tapped I/O increases manufacturing tolerance, and is easy for connection.