Novel On-Chip Wideband Filtering Power Dividers With High Selectivity and Ultra-Wide Out-of-Band Suppression in LTCC Technology

This brief presents a novel design of the lumped-element chip-type wideband filtering power divider (WFPD) using the low-temperature cofired ceramic (LTCC) technology. Firstly, the modified
$\boldsymbol{\pi }$
-type lumped impedance matching structure utilized to generate a bandpass response and realize the impedance transformation is proposed for the first time. Then the hybrid resonant blocks are connected to the output ports to create two transmission zeros (TZs) to enhance the selectivity. Furthermore, ultra-wide out-of-band rejection can be obtained without extra harmonic suppression structures. A general design procedure is given based on the rigorous derivation. For verification, a prototype for the proposed WFPD operating at 2.5 GHz with the overall size of
$4.0\times 4.1\times1.3$
mm3 is designed, simulated, fabricated, and measured. The insertion loss (IL) of 0.69 dB, fractional bandwidth (FBW) of 54.4% (
$|{S}_{11}| < -15$
dB), and 20-dB rejection of the upper stopband up to 13 GHz can be achieved.