Broadband balanced filter with high common-mode suppression and wide stopband based on SIW and SSPP

Abstract

This paper introduces a novel balanced bandpass filter that utilizes the symmetrical F-shaped groove (SFG) substrate-integrated waveguide and spoof surface plasmon polariton (SIW-SSPP) structure. This design combines lowpass SSPP unit cells within a highpass balanced dual-layer SIW structure to realize bandpass filtering response. The SFG SIW-SSPP unit cell's superior dispersion properties contribute to broad bandwidth and extensive stopband. Additionally, the balanced dual-layer SIW structure, achieved by removing a rectangular aperture from the common ground, allows for high in-band common-mode (CM) suppression and a broad CM suppression range. The proposed filter offers multiple variables to regulate the passband's lower and upper cut-off frequencies independently. A fabricated prototype of the balanced filter is tested, demonstrating superior performance compared to previously reported balanced SIW and halfmode SIW BPFs. The filter achieves a broad 3-dB fractional bandwidth of 46.55% (6.33-10.17 GHz), a wide 20-dB stopband rejection up to 2 f0 (f0: the passband's center frequency), and simultaneous broad CM suppression range (24-dB up to 4.85 f0).

Broadband Balanced-to-Balanced Filtering Power Divider Using HMSIW-SSPP Transmission Line

“…Port 2+ (3+) shares the intermediate ground plane with Port 2− (3−). The DM signal transmission and CM signal suppression are mainly accomplished through the rectangular aperture ( w a1 × l a1 ) in the middle metal layer [ 18 ].…”

“…To further investigate the operating principle of HMSIW BTB PD, Figure 4 a,b provide the schematic diagram of the electric-field (E-field) distributions under DM and CM excitations, respectively [ 18 ]. When Port 1+ and 1− are simultaneously excited with a 180° phase difference (DM driven), the DM signal’s E-field has the identical direction in the dual-layer structure, as shown in the A-A’ and B-B’ planes in Figure 4 a.…”

“…To further investigate the operating principle of HMSIW BTB PD, Figure 4a,b provide the schematic diagram of the electric-field (E-field) distributions under DM and CM excitations, respectively [18]. When Port 1+ and 1− are simultaneously excited with a 180° phase To further investigate the operating principle of HMSIW BTB PD, Figure 4a,b provide the schematic diagram of the electric-field (E-field) distributions under DM and CM excitations, respectively [18]. When Port 1+ and 1− are simultaneously excited with a 180° phase To further investigate the operating principle of HMSIW BTB PD, Figure 4a,b provide the schematic diagram of the electric-field (E-field) distributions under DM and CM excitations, respectively [18].…”

“…When Port 1+ and 1− are simultaneously excited with a 180° phase To further investigate the operating principle of HMSIW BTB PD, Figure 4a,b provide the schematic diagram of the electric-field (E-field) distributions under DM and CM excitations, respectively [18]. When Port 1+ and 1− are simultaneously excited with a 180° phase To further investigate the operating principle of HMSIW BTB PD, Figure 4a,b provide the schematic diagram of the electric-field (E-field) distributions under DM and CM excitations, respectively [18]. When Port 1+ and 1− are simultaneously excited with a 180 • phase difference (DM driven), the DM signal's E-field has the identical direction in the dual-layer structure, as shown in the A-A' and B-B' planes in Figure 4a.…”

“…To address this challenge, researchers have leveraged the SIW/HMSIW and SSPP (SIW-/HMSIW-SSPP) transmission line, resulting in the development of broadband bandpass filtering passive components like BPFs [ 12 , 13 , 14 , 15 , 16 , 17 ], balanced BPF [ 18 ], FPDs [ 19 , 20 ], filtering balun [ 21 ], diplexer [ 22 ], and filtering magic-T [ 23 ], enabling independent adjustment of lower and upper cut-off frequencies in the passband. Despite these advancements, to date, no literature has reported BTB FPDs based on SIW-SSPP or HMSIW-SSPP.…”