Compact Dual-/Tri-/Quad-Band banpass filters using shorted stub loaded stepped-impedance resonator
In this article, the shorted stub loaded stepped-impedance resonator (SSLSIR) with the individually tunable first even resonant mode and first odd resonant mode is applied to design dual-, tri-, and quad-band bandpass filters (BPFs). The SSLSIR dual-band BPF with asymmetrical coupling is realized using the first even resonant modes and the first odd resonant modes of a set of SSLSIRs. Then, the high-impedance feeding lines of SSLSIR dual-band BPF is modified to produce a new passband, and thus a new tri-band BPF is realized. The proposed quad-band BPF consists of two sets of SSLSIRs with symmetrical coupling. Each of the designed circuits occupies a very compact size and has a good in-band out-of-band performance. Good agreements are observed between the simulated and measured results.  2015 Wiley Periodicals, Inc. Int J RF and Microwave CAE 25:601609, 2015.
quad-band bandpass filter dual-band tri-band phase shifter