Third-order Substrate Integrated Waveguide Research Articles

Compact Hybrid Bandpass Filters Using Substrate-Integrated Waveguide and Stripline Resonators

This article presents a novel class of compact hybrid bandpass filters (BPFs) using substrate-integrated waveguide (SIW) and stripline resonators. As the stripline resonators are inserted between two SIW cavities, they are able to increase the filtering order without occupying any additional area. This is beneficial for circuit miniaturization. To verify the concept, several third-order hybrid filters with various responses are designed by combining a half-wavelength stripline resonator (HWSLR) or a full-wavelength stripline resonator (FWSLR) and two SIW resonators. Their sizes are reduced by more than 33% compared with standard third-order SIW filters. In addition, a class of fourth-order box-like hybrid filters with two flexible transmission zeros (TZs) is also proposed by using the HWSLR and FWSLR simultaneously. Compared with previously reported box-like SIW filters, a size reduction of more than 65% is obtained. Three filter prototypes are fabricated and measured for validation.

Wide-Stopband SIW Filters Using Modified Multi-Spurious Modes Suppression Technique

A modified multi-spurious modes suppression technique is proposed to realize wide-stopband substrate-integrated waveguide (SIW) bandpass filters (BPFs), which is to set the external ports and internal coupling windows to the positions of weakest electric fields of specific spurious modes. To extend the stopband as wide as possible with the limited design degrees of freedom, different feeding and coupling positions are fully exploited to reject unwanted modes in specific cavities. By suppressing the out-of-band spurious peaks as much as possible and removing the first unsuppressed spurious resonance to the farthest position, the widest stopband can be achieved intrinsically. A second- and a third-order SIW BPFs are synthesized, designed, fabricated, and tested as demonstrations, realizing the stopbands of $2.51{f} _{0}$ and $3.85{f} _{0}$ with the rejection level better than 25 dB and 20 dB, respectively.

Compact planar substrate‐integrated waveguide diplexers with wide‐stopband characteristics

Compact planar substrate-integrated waveguide (SIW) diplexers with wide-stopband characteristics are presented for the first time based on collaborative multispurious mode suppression techniques including the harmonic staggered technique, centered coupling windows, and offset-centered output ports. The coupling scheme using common dual-mode resonator coupled with multiple single-mode resonators is adopted here to eliminate the T-junctions for size and loss reduction, and the dual-mode coupling controlling technique we previously proposed is also employed to allocate the fractional bandwidths (FBWs) of the two channels flexibly based on the FBW design graph. Additionally, by combining the harmonic staggered technique, centered coupling windows, and offset-centered output ports, good out-of-band rejections can be achieved and excellent wide-stopband characteristics have been implemented intrinsically. Two prototypes including second-order and third-order SIW diplexers are synthesized, designed, fabricated, and tested as demonstrations, extending the stopbands to 1.78f1 and 2.04f1 with the rejection levels better than 17.5 and 20 dB, respectively.

Compact bandpass filter with wide-stopband using substrate integrated waveguide cavities and short-circuited coplanar line

AbstractThis article presented a compact bandpass filter with wide-stopband performance. Two substrate integrated waveguide (SIW) cavities and a short-circuited coplanar line introduced between the two cavities are used to realize a compact third-order bandpass filter. The passband is generated by combining the resonant frequency of TE101 mode of the SIW cavities and the fundamental resonant frequency of the short-circuited coplanar line. The size of the proposed filter reduces significantly in comparison with conventional third-order SIW filters. Moreover, the center frequency (CF) and the bandwidth of the filter can be controlled by adjusting the structural parameters of the filter. In addition, the first higher-order mode TE102 of the SIW cavity is suppressed by minimizing the coupling of TE102 mode in order to obtain wide-stopband performance. The proposed filter is designed, fabricated, and measured, and the simulation and measurement results show a good agreement. The filter exhibits compact size, low loss, and a rejection higher than 20 dB up to 1.94f0.

Compact inline substrate integrated waveguide filter with enhanced selectivity using new non‐resonating node

A high selective inline substrate integrated waveguide (SIW) filter based on novel stepped-impedance non-resonating node (NRN) is presented. The stepped-impedance NRN is realised by inserting a stepped-impedance substrate integrated coaxial line resonator into the volume of a third-order SIW filter. It introduces extra signal transmission path between source and load. Thus, one more transmission zero (TZ) is produced compared with conventional NRN that further improves the selectivity of the filter. Also, the proposed filter achieves a compact circuit size as the stepped-impedance NRN is embedded in the SIW cavity without occupying extra layout. To validate the proposed concept, a prototype filter with two TZs locating at both the lower and upper stop-bands, is designed, fabricated and measured. The measured results are well consistent with the simulation ones.

Compact substrate integrated waveguide transversal filter with mixed source–load coupling

This study proposes a compact implementation of substrate integrated waveguide (SIW) transversal filter with mixed source and load coupling. One dual-mode microstrip resonator, etched on the top metal layer of SIW cavity, is utilized to achieve transversal topology. Therefore, four transmission zeros can be obtained by introducing mixed sourced and load coupling, which is realized by inter-digital slot structure. A third-order SIW transversal filter sample is fabricated using printed circuit board technology, and its measured S-parameters have good agreements with the simulated ones.

A SIW filter with asymmetric frequency response by non-resonating node

In this paper, a novel substrate integrated waveguide (SIW) filter with asymmetric frequency response by using a non-resonating node (NRN) is proposed. The NRN was first implemented as a strongly detuned SIW resonator. This filter can realize a transmission zero either in the upper or in the lower stopband, and only positive coupling coefficient between each resonator and NRN is required. A third-order SIW filter with the center frequency of 15 GHz was constructed and measured, in which bandwidth is 300 MHz. The measured results agree well with the simulated results.

Miniaturized and high-selectivity substrate integrated waveguide (SIW) bandpass filter loaded by complementary split-ring resonators (CSRRs)

This paper presents an effective technique to obtain miniaturized and high-selectivity substrate integrated waveguide (SIW) bandpass filters by loading complementary split-ring resonators (CSRRs) at the SIW cavities. The existence of the CSRR enables a considerable reduction of the resonance frequency of a conventional SIW cavity thanks to the coupling effect between CSRR and SIW cavity. Besides, a sharp roll-off is generated in a higher stopband due to the characteristics of CSRRs. To demonstrate the operation principal, the second- and third-order SIW bandpass filters are fabricated using standard printed circuit board technology, showing advantages of compact size, good selectivity, easy fabrication, and integration with other circuits. The measured -parameters agree well with the simulated ones.

Design of Substrate Integrated Waveguide (SIW) Elliptic Filter with Novel Coupling Scheme

A novel fourth-order substrate integrated waveguide (SIW) quasi-elliptic filter with novel coupling scheme is presented in this paper. A microstrip resonator (MR) with two grounded ends is introduced into the filter design. It not only acts as a resonator, but also brings different direct couplings between MR and SIW resonator. Then, quasi-elliptic response can be obtained easily. The proposed filter has better frequency selectivity than the conventional third-order SIW filter. A filter sample is fabricated on single-layer printed circuit board (PCB) technology. Good agreements are obtained between its measured- and simulated S-parameters.

Compact Coplanar Waveguide-Incorporated Substrate Integrated Waveguide (SIW) Filter

A novel third-order substrate integrated waveguide (SIW) filter incorporated with a coplanar waveguide (CPW) is presented in this paper. The CPW not only acts as a resonator, but also brings mixed coupling between two SIW resonators. It is shown that the filter has two transmission zeros and wide stopband, which is very compact in comparison with conventional third-order SIW counterpart. Good agreement is obtained between its measured and simulated S-parameters.