Dual-band bandpass filter and diplexer based on double-sided parallel-strip line

In this paper, a dual-band bandpass filter (BPF) and a diplexer based on double-sided parallel-strip line (DSPSL) with an inserted conductor plane are proposed. The novelty of the proposed structure lies in the use of the isolation feature of the inserted conductor plane to provide two transmission paths for the RF signals; meanwhile no extra combination circuits for the two paths are required. The two paths on the top and bottom layers, using the dual-mode slotted-patch resonators operating at different frequencies, generate two passbands for the proposed dual-band BPF. To further demonstrate the idea, a diplexer without extra combination circuits is successfully designed. The simulated and measured results of the proposed dual-band BPF and diplexer are presented to verify the proposed idea.