Wideband On-Chip Filter With High Selectivity and Reduced Size by Single TV Inductive Coupling

The wideband GaAs-based integrated passive device (IPD) filter with high selectivity and reduced size is proposed by utilizing single through via (TV) inductive coupling. One series and two parallel dual-mode
$\pi $
-type units containing two inductors and three capacitors are used to design the wideband fourth-order filter with two transmission zeros (TZs). Then, by combining eight TVs in three
$\pi $
-type units into only one TV, three different inductive coupling transmission paths can be generated between input and output ports, resulting in the proposed filter that can achieve five TZs near the passband, then, the higher selectivity and the lower / upper stopband suppression up to 23 dB / 32 dB can be achieved. Besides, size of the proposed filter layout with one TV is approximately 21% smaller than that of the conventional filter layout with eight TVs. In final, a prototype with 3-dB fractional bandwidth of 79.3% is designed and fabricated at 3.67 GHz (
${f}_{{0}}{)}$
. Its shape factor defined as 20-dB bandwidth / 3-dB bandwidth is only 1.25. This IPD filter occupies only
$0.011\,\,\lambda _{{0}} \times 0.017\,\,\lambda _{{0}}$
, where
$\lambda _{{0}}$
is the free-space wavelength at
${f}_{{0}}$
.