Design of a Compact Novel Stub Loaded Pentaband Bandpass Filter for Next Generation Wireless RF Front Ends

This paper presents a compact novel pentaband bandpass filter using a dual path stub loaded step impedance resonator (SLSIR). The proposed topology consists of a dual path
$\lambda $
/4 and
$2\lambda $
/3 long uniform impedance resonator centered separated by
$2\lambda $
/3 open and
$\lambda $
/12 short circuit stubs respectively. The superposition of signals from the two transmission routes results in a fifth-order pentaband bandpass response with six finite frequency transmission zeroes and out-of-band rejection of 11dB from 12 GHz up to 20 GHz. The filter produces five frequency bands at 1.06 GHz, 3.24 GHz, 5.36 GHz, 8.55 GHz and 10.78 GHz with fractional bandwidth (FBW) of 25.59 %, 22.22 %, 19.48 %, 16.03 % and 17.17 % respectively. The proposed design is fabricated on a high-frequency substrate with a physical size of (
$0.23\lambda _{g} \times 0.14\,\,\lambda _{g}$
). The new pentaband bandpass filter has a simple and compact design with good electrical performance. A fair match can be found between the simulated and experimental results.