A compact triple-band bandpass filter with customizable frequencies

Abstract

A novel design of a customizable triple-band EBG (Electromagnetic Bandgap) bandpass filter is proposed. The EBG filter is manufactured by a conventional 2-layer PCB process in RO4350 substrate with surface mounted lumped capacitors. Specific working frequency of each band of the filter can be selected on demand by adjusting the value of corresponding capacitors, while the filter’s performance and compact design is not compromised. The experimental results show a filter with size of 28.00 × 28.00 × 1.52 mm³ in PCB achieving performance of insertion loss of 2.57 dB, 2.82 dB; return loss of 13.35 dB, 28.09 dB at two passbands with center frequencies of 2.33 GHz, 4.23 GHz respectively. Good agreement was obtained where the filter exhibited the third passband with center frequency of 1.87 GHz. The filter has band to band isolation better than 36.0 dB.