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This paper presents a miniaturized bandpass filter (BPF) with characteristics of wider passband and stopband rejection using substrate integrated waveguide (SIW) technology. Slot loading mechanisms deployed on the upper layer of SIW and defective ground structure (DGS) on the ground plane are utilized to achieve wider passband and stopband respectively. The slots on the top layer along with DGS significantly enhances the selectivity of the filter by generating three transmission zeros (TZs) on the upper side of the passband. The proposed filter is simulated using full-wave simulators and the performance is validated through fabrication and testing of the prototype. The proposed SIW filter exhibits a low insertion loss of 1.52 dB over a wider passband from 9.17 GHz to 20.31 GHz with a 3 dB fractional bandwidth (FBW) of 76%. Further, a wider upper stopband is achieved with the rejection of more than 16 dB in the frequency range of 23 GHz to 40 GHz. The filter provides a flat group delay response of approximately 0.19 ns over the wider passband. The electrical size of the fabricated prototype is 1.05λg × 0.67λg, where λg denotes the guided wavelength in the dielectric substrate for the designed center frequency of 16 GHz. [ABSTRACT FROM AUTHOR]

This paper presents a novel design of miniaturized substrate-integrated waveguide (SIW) filter loaded with a pair of unit-cell resonators. Two identical open-loop resonators are connected face-to-face to form a unit-cell. A pair of unit-cells is engraved on the surface of the SIW to develop an evanescent-mode bandpass filter. The proposed unit-cells behave as an electric-dipole and produce a passband smaller than the waveguide frequency. This reduction in resonant frequency allows us to achieve size miniaturization. An equivalent electrical-circuit model is developed and investigate for characterization of passband and transmission-zero. This filter structure is then employed to develop a SIW planar diplexer. Two SIW filter structures loaded with unit-cells are excited with a T-shaped feed line to achieve lower and upper channels of the diplexer. To demonstrate the analysis, both SIW filter and diplexer loaded with open-loop resonators are implemented and fabricated. The proposed SIW filter and diplexer prototypes exhibit size miniaturization, low insertion-loss and high-selectivity due to evanescent-mode transmission and sub-wavelength resonators. The measurement responses are very similar to the simulation responses. [ABSTRACT FROM AUTHOR]

In this paper, a novel design of highly compact power divider employing substrate-integrated waveguide (SIW) is proposed for dual-band applications. The double-ring asymmetric complimentary split-ring resonators (CSRRs) are utilized to obtain dual-band operation. The asymmetric double-ring CSRRs create mixed magnetic and electric coupling resulting two distinct resonating frequencies which exhibits bandpass behaviour below the resonating frequency of the cavity. The resonating passbands can be designed individually by varying the dimensions of the proposed CSRRs. In addition, the position ofoutput ports can be varied to achieve arbitrary power division. To demonstrate the proposed analysis, three prototypes (two equal power division and one unequal power division) of dual-band SIW power dividers are designed and fabricated. Measurement performance provides a good consistency with that of simulated one. The circuit areas of the fabricated prototypes 1, 2 and 3 excluding microstrip transitions are 0.053λg², 0.088λg² and 0.033λg², respectively. The proposed design process exhibits dual-band performance with smaller circuit-area, suitable isolation and hence appropriate for dual-band communication services. [ABSTRACT FROM AUTHOR]

In this paper, a new type of dual-frequency impedance transformer is presented for ultra-high transforming ratio. The proposed configuration consists of parallel coupled-line, series transmission lines and short-ended stubs. The even and odd-mode analysis is applied to obtain the design equations and hence to provide an accurate solution. Three examples of the dual-frequency transformer with load impedance of 500, 1000 and 1500 Ω. are designed to study the matching capability and bandwidth property. To prove the frequency agility of the proposed network, three prototypes of dual-frequency impedance transformer with transforming ratio of 10, 20 and 30 are fabricated and tested. The measured return loss is greater than 15 dB at two operating frequencies for all the prototypes. Also, the bandwidth is obtained more than 60 MHz at each frequency band for all the prototypes. The measured return loss is found in good agreement with the circuit and full-wave simulations. [ABSTRACT FROM AUTHOR]