Microstrip dual-band bandpass filter based on the cul-de-sac topology

This paper presents a dual band filter implemented with microstrip open loop resonators using a cul-de-sac configuration covering the bands 1895–1960 MHz and 1995–2067 MHz. The undesired cross-couplings of its central core quartet of resonators are weak enough to not damage the overall filter response. The resulting filter offers a higher level of miniaturization by comparison with other extended dual-band topologies implemented with the same kind of resonators. The filter covers the desired passbands with insertion-losses lower than 1.8 dB and return-losses better than 10 dB.