SIW Filtering Power Divider with Output Equal / Unequal Power Based on Embedded Isolation Network

Miniaturized SIW filtering power dividers with output equal / unequal power and quadrature phase are proposed based on embedded isolation network and hybrid multi-mode technology. For the first time, the capacitive loaded isolation network is embedded in multi-mode resonant units to construct the novel SIW filtering power divider architecture, which simultaneously realizes high-density integration, high isolation, different output power ratios and orthogonality. It should be noted that the embedded isolation network with output quadrature consists of four embedded transmission lines, two chip capacitors, and two interdigital capacitors, thus realizing the high-density integration, controllable output power ratios, output orthogonality and high isolation of the SIW filtering power divider. In addition, the fourth-order filtering response with the wide stopband and high frequency selectivity can be achieved through hybrid four-mode resonant units. Specifically, two LC modes are embedded within two SIW cavity modes (TE₁₀₁ and TE₂₀₁), which not only cause the rapid frequency decline of TE₁₀₁ and TE₂₀₁ modes but also maintain other higher-order modes largely unchanged, resulting in the wide stopband characteristic. Furthermore, multi-way cross-coupling generates two transmission zeros near the adjacent passband to achieve high frequency selectivity. After processing and testing, the design of equal/unequal filtering power dividers achieves center frequencies (<italic>f</italic>₀) at 6.03 GHz / 6.04 GHz, 3 dB relative bandwidths of 3.5% / 3.6% and output power ratios of 1 / 1.5. Their output phase differences, full-band isolation and upper stopband suppression are 90°±2.6° / 89°±4°, 20.1 dB / 19.6 dB and 20 dB @3.09<italic>f</italic>₀ / 20 dB @3.05 <italic>f</italic>₀, respectively. The sizes of these filtering power dividers are only 0.4λ_g², where λ_g is waveguide wavelength at <italic>f</italic>₀.