Substrate Integrated Waveguide Filter Research Articles

Compact wideband substrate integrated waveguide bandpass filter for X/ Ku‐band application

This article presents a novel design of a compact substrate integrated waveguide (SIW) wideband bandpass filter. The proposed bandpass filter offers wide passband, wide lower, and upper band rejection characteristics. First, the filtering response is obtained by loading a single T-shaped slot on the top of the SIW structure. Later, to achieve wide passband and wide upper band rejection, a pair of T-shaped slots has been engraved on the top surface. To demonstrate the analysis, the proposed SIW filter has been simulated, fabricated, and tested. The measured S-parameters are in good agreement with the simulated results, showing wide passband from 8.05 to 15.45 GHz within a 3-dB fractional bandwidth of 62% at a center frequency of 12 GHz. The measured return loss is fairly good (>17 dB) within the passband and an insertion loss of 0.5 dB, including the loss from two SMA connectors. The fabricated prototype has a compact size of 0.248λg2.

Novel Double-Layer SIW Filter With Mechanically Adjustable Frequency Response

In this letter, a novel reconfigurable filter concept, which is called assembly reconfigurability through rotation, is proposed for the first time to implement a high-Q filter with adjustable frequency response. Two separated printed circuit boards (PCBs) are designed and assembled together to build a double-layer substrate integrated waveguide (SIW) filter. Guided by coupling matrix synthesis, the filter is designed to have adjustable filtering features by mechanically rotating one of the boards. Specifically, by only rotating the top PCB layer to different directions, three kinds of assembly states can be achieved, resulting in variable frequency response with transmission zeros (TZs) created at below, above, or both sides of the passband. Two design prototypes, which present 2- and 3-pole responses, respectively, are simulated and measured to validate the novel idea. The results show that two compact, low-loss fully shielded filters with adjustable response shape are developed, which well verify the concept of assembly reconfigurability for filter synthesis.

A wide stopband multilayer substrate integrated waveguide bandpass filter with suppression of higher-order mode coupling

AbstractThis paper presents a compact multilayer substrate integrated waveguide (SIW) bandpass filter with wide stopband. The square SIW cavity resonators in multilayer substrates are horizontally and vertically coupled with magnetic coupling. By properly designing the coupling structure, the couplings between the higher-order resonant modes can be suppressed. Compared with the conventional single-layer SIW filters, the proposed multilayer SIW filter also exhibits a compact size. To verify the design concept, a double-layered SIW filter is fabricated and measured. The measured results agree well with the simulations. The measured results show that the upper stopband of the filter is extended to 2.73 times of the center frequency 8.02 GHz.

Compact dual-band SIW filters loaded with double ring D-shaped resonators for sub-6 GHz applications

In this paper, a compact substrate integrated waveguide (SIW) based dual-band filter which utilizes the dual resonance provided by asymmetric double-ring D-shaped resonators that are incorporated on the upper metallic layer of SIW is communicated. The two passbands are generated well below the cut-off frequency of the SIW due to evanescent mode propagation. Such propagation is responsible for the substantial miniaturization of the filter as well. Two types of two-pole dual-band filters are designed that exhibit low insertion loss, wide out-of-band-rejection, compact size, easy fabrication and integration with other microwave components. To validate the proposed idea, three filter prototypes working around 2.66 and 3.54 GHz are designed, fabricated for demonstration and experimentally tested. Parametric analysis is performed to verify the dependence of filter parameters on the proposed filter prototype. Expected agreements are achieved between the experimental and simulated results. The proposed filter finds applications in the upcoming 5G sub-6 GHz communication.

Low-Loss Low-Cost Substrate-Integrated Waveguide and Filter in GaAs IPD Technology for Terahertz Applications

A low-loss and low-cost terahertz (THz) substrate-integrated waveguide (SIW) and a SIW filter implemented in a commercially-available GaAs integrated-passive-devices (IPD) technology are proposed for THz applications. Ellipse vias penetrating through a 100- $\mu \text{m}$ thick GaAs substrate are employed to realize a low-loss SIW. The via’s orientation is designed as being transverse, instead of being longitudinal, to the propagation direction of the input wave, which can improve the insertion loss by 2.7 dB at 415 GHz due to lower signal leakage from the waveguide. The proposed SIW is able to provide simulated insertion loss of only 0.39 dB/mm, i.e., 0.14 dB/ $\lambda _{\mathrm {g}}$ , at 340 GHz. A new SIW filter structure using the ellipse vias is proposed which not only successfully realizes a low-loss fourth-order Chebyshev filter under hard design-rule-check (DRC) rules imposed by the IPD technology, but also can enhance out-of-band rejection by 10.5 dB at 390 GHz as compared with conventional waveguide filters. A slot-coupled coplanar waveguide (CPW) to SIW transition structure without any impedance tuning stub required is also proposed to measure the proposed SIW and SIW filter. The proposed transition structure can give simulated insertion loss of 0.7 dB at 340 GHz while keeping return loss better than 10 dB from 307 to 374 GHz. Eight samples are measured to demonstrate the robustness of the proposed designs against process variations. Experimental results show that the proposed transition structure with a 220- $\mu \text{m}$ long SIW and the SIW filter can provide measured insertion loss of 0.7 and 3.6 dB at 327.5 GHz, respectively. The reasons for the discrepancy between the simulation and measurement results are identified and discussed in detail. As compared with prior works, the proposed SIW and SIW filter exhibit lower loss, lower cost, higher repeatability, higher reliability, and mass-producible capability. To the best of the authors’ knowledge, this is the first demonstration of the THz SIW and THz SIW filter designs using a commercially-available and mass-producible IPD technology reported thus far.

Novi dizajn minijaturnih SIV filtera na keramičkom supstratu za c-pojas

This article presents new structures and methods of design of miniature third-order substrate integrated waveguide (SIW) bandpass filters on a high-permittivity ceramic substrate for the C-band. The aim was to appraise the feasibility of such filters by using a 3D electromagnetic (EM) simulator. The substrate integrated waveguide (SIW) offers good quality factors and electrical performances compared with other planar techniques. Its integration capabilities and fabrication cost are other benefits that make it attractive. Ceramic material offer electrical properties suitable in designing of passive devices. High relative permittivity with low dielectric losses makes it possible to miniaturize passive components while exhibiting high temperature stability, which is an important selection criterion for a filter designed to equip the payload of a satellite. Three SIW filters were designed on a Trans-Tech ceramic substrate (thickness = 254 mm, er = 90, and tand = 0.0009) with drastic specifications for space application. The first filter is composed of three SIW resonators with direct coupling, the second is composed of three SIW resonators with a cross-coupling to create a transmission zero, and the third is composed of three SIW resonators with circular holes etched on the top of the metal layer to achieve a super-wide band. The obtained results for the proposed filters are presented, discussed, and compared with relevant published literature. The proposed filter can be used to enhance the performance of microwave devices used for C-band, especially Satellite communications.

Balanced substrate integrated waveguide filters with controllable finite transmission zeros

Balanced substrate integrated waveguide filters with controllable finite transmission zeros

A Class of Box-Like Bandpass Filters With Wide Stopband Based on New Dual-Mode Rectangular SIW Cavities

This article proposes a new class of box-like substrate integrated waveguide (SIW) filters with wide stopband. First, a two-pole doublet bandpass filter with one finite-transmission zero (FTZ) is proposed using a new planar dual-mode rectangular SIW cavity, which is realized by TE201 and TE103 modes. TE102, TE202, and TE104 modes are suppressed intrinsically by arranging feeding lines at the horizontal centerline of the dual-mode SIW cavity. Then, a four-pole box-section filter with one FTZ is proposed using one dual-mode and two single-mode rectangular SIW cavities, and the two single-mode cavities have different width-length ratios to further improve the stopband performance. To further improve the cutoff skirt, a new design method for five-pole quasi-elliptic SIW filter is proposed, which is achieved by the four-pole filter loaded by one single-mode SIW cavity. Some design examples with the center frequency of 10 GHz are presented to verify the performance of the proposed dual-mode SIW filters and the design method.

Substrate integrated waveguide filter based on the magnetized ferrite with tunable capability

AbstractIn this paper, a miniaturized substrate integrated waveguide filter on the magnetized ferrite is presented. The proposed filter has a small size, high power transmission capability, relatively good bandwidth, and tunable frequency bandwidth. This filter is tunable due to the magnetic bias applied to the ferrite substrate. Compared to the tunable filters reported in previous references based on PIN diode, varactors, and mechanical changes, the proposed filter has a relatively wide adjustment on the operation frequency. Using this method dramatically reduces the complexity of the external control system. This tunable filter is optimized using the Ansoft HFSS software and then fabricated. The measured operating frequency of the filter is tunable from 5.3 to 7.15 GHz by changing the magnetic bias from 100 Oe to 1100 Oe. In the frequency range of 5.55 to 6.95 GHz, an insertion loss of less than 1.1 dB and a return loss of better than 20 dB are achieved. A good agreement between the simulation and experimental results was achieved.

Accurate Modeling of Stubs Used as Resonant Coupling Elements in SIW Filters

This letter presents an accurate model for the stubs used as frequency-dependent coupling elements in substrate integrated waveguide (SIW) filters, with the aim to generate transmission zeros (TZs) in the frequency response. The model is based on the actual modes excited in the stub, differently from the single-mode (equivalent circuit) representation used in previous works. A procedure to determine the geometrical dimensions of the stub, depending on the synthesized filters parameters, is also presented, based on the full-wave characterization of the structure. The proposed model is validated by the design and the fabrication of an SIW filter.

A compact SIW bandpass filter using DMS-DGS structures for Ku-band applications

This paper presents a design of compact SIW (substrate integrated waveguide) bandpass filter for application in Ku-band Transmit up-convert frequency (i.e., 13.7–14.1 GHz) used for satellite communications. Based on Defected Microstrip Structure-Defected Ground Structure combination (DMS-DGS), this SIW filter structure is designed to improve passband and stopband performance. By merging circular ring slot (CRS) with interdigital DGS, better passband characteristics with sharp stopband attenuation are obtained. To validate the design, the filter is fabricated using Rogers substrate. The size measures 23.8 mm × 10 mm and operates at a center frequency of 13.9 GHz. Measured results of the filter agree well with the simulated results. Also, designed BPF filter has advantage of low insertion loss, better return loss, compact size and high stopband rejection.

Miniaturized SIW filter using D-shaped resonators with wide out-of-band rejection for 5G applications

ABSTRACT In this article, substrate integrated waveguide (SIW) filter with compact size and wide out-of-band rejection is designed for 5G (sub-6 GHz) applications. To achieve the proposed filter responses, D-shaped resonators oriented face-to-face are etched out on the top layer of SIW. Due to the resonators loading, the filter provides a passband below the cut-off frequency of SIW. This decrease in the operating frequency of the filter allows us to achieve size miniaturization. To enhance the frequency responses, a double-stage SIW filter is proposed and investigated. The equivalent electrical-circuits are developed to validate the transmission responses. To support our claim, single- and double-stage SIW filters are designed, fabricated and tested. The filter prototypes achieve size miniaturization, low insertion loss and wide out-of-band responses. The measured responses are very similar to the full-wave simulation responses.

Neural network of calibrated coarse model and application to substrate integrated waveguide filter design

In this article, we propose a novel neural network of calibrated coarse model, which can obtain the optimal filter response with as little training data as possible to synthesize the entire substrate integrated waveguide (SIW) filter. By incorporating the knowledge of filter decomposition with the inverse neural network, we build a coarse model that can synthesize the dimensions of a SIW filter. However, the SIW structures are subject to a potential leakage problem due to the periodic gaps, the results of the coarse model are very different from the ideal response. We propose a novel calibrated neural network from the perspective of the coupling matrix to correct the errors generated in the coarse model. In addition, this article also proposes an equivalent de-embedding technique, which is simpler than the thru-reflect-line calibration technique to accurately extract the scattering parameters of the SIW discontinuities. An H-plane fifth order SIW filter is synthesized by the proposed model. The result shows that the SIW filter that is very close to the ideal response can be synthesized with only a few hundred training data.

Passband broadening of sub-wavelength resonator-based glide-symmetric SIW filters

Here, we discuss the virtues of glide symmetry for designing low-frequency band-pass periodic filters in substrate integrated waveguide (SIW) technology based on complementary split-ring resonators (CSRRs). Conventional (non-glide) versions of these filters have a narrow passband, due to the fact that this band is below the cutoff frequency of the background waveguide. When glide symmetry is added to the filter configuration, the low-frequency passband is significantly widened, as well as the first stopband. The dispersion properties of both conventional and glide-symmetric periodically loaded waveguides are analyzed and compared with commercial software and an equivalent circuit model. Finally, two prototypes of the proposed glide-symmetric structure have been designed and built, illustrating the potential of this technique to widen the passband and reduce insertion losses of conventional sub-wavelength CSRR-loaded SIW filters.

Super compact dual-band substrate integrated waveguide filters and filtering power dividers based on evanescent-mode technique

AbstractThis paper proposes a series of novel super compact dual-band substrate integrated waveguide (SIW) filters and filtering power dividers (FPDs) using two new compact metamaterial unit-cells. The proposed unit-cells, called COCSRRs, consist of a complementary split-ring resonator (CSRR) and an open CSRR (OCSRR). The working principle of the proposed filters and FPDs is based on the evanescent-mode technique.Based on the theory of evanescent mode, an additional passband below the waveguide cut-off can be achieved by etching the electric dipoles on the metal surface of the SIW structure. The CSRR and OCSRR unit-cells, behave as electric dipoles when excited by an axial electric field and are able to generate a forward-wave passband region below the cut-off frequency of the SIW configuration. Therefore, the proposed COCSRR unit-cells can be interpreted in term of electric dipoles, which can generate two forward-wave passbands below the cut-off frequency of the SIW structure. Although, the center frequencies of each passband can be independently controlled by changing the dimensions of the CSRR and OCSRR sections in the proposed COCSRR unit-cells. Accordingly, by loading the proposed COCSRR unit-cells on the waveguide surface, two arbitrary passbands below the waveguide cut-off frequency are achieved for WLANs and WiMAX applications. The designed SIW filters and FPD are fabricated and measured. Good agreement is observed between the simulated and measured results of the proposed filters and FPD. The proposed dual-band filters and FPD have many benefits like compact size, high selectivity, tunable passband frequencies, and easy integration with other planar technologies.

When Compactness Meets Flexibility: Basic Coaxial SIW Filter Topology for Device Miniaturization, Design Flexibility, Advanced Filtering Responses, and Implementation of Tunable Filters

Substrate integrated waveguide (SIW) technology [1], [2] is a well established and successful approach for implementing planar microwave filters with very stringent requirements in terms of quality (Q) factor and also with the ability to integrate into a system. Optimized SIW filters can reach a Q factor of 200-800 using low-loss substrates and standard fabrication procedures [3]. Furthermore, packaging and electromagnetic (EM) shielding, power-handling capabilities, and low-cost batch manufacturing are other broadly recognized strengths of this approach. However, SIW filters are still larger than most of their planar counterparts; in addition, advanced topologies are not always easy to accommodate, and filter reconfigurability usually leads to very complex implementation [4]-[6].

A novel dual-band bandpass SIW filter loaded with modified dual-CSRRs and Z-shaped slot

In this paper, a novel dual-band bandpass substrate integrated waveguide (SIW) filter has been presented by loading two modified dual complementary split ring resonators (CSRRs) and a Z-shaped slot on the top side of SIW. The modified dual-CSRR structure is obtained by folding its outer ring, adding T-shaped branch to its inner ring and placing the splits of the inner and outer rings of CSRR in the same direction. The modified structure allows the electromagnetic wave to propagate in the passband below the cutoff frequency of the waveguide. Compared with conventional CSRR of the same size, it has two passbands and work at a lower frequency. A dual-band bandpass filter is proposed by placing two proposed dual-CRSSs face-to-face on the top side of SIW. In order to improve the performance of the filter, the Z-shaped slot is introduced to enhance the electromagnetic coupling, thus increasing the transmission zero point, broadening the passband and enhancing the flatness in the band, and realizing the center frequency shift of the passband to the left. To validate the design and analysis, a dual-band bandpass SIW filter loaded with two modified dual-CSRRs and a Z-shaped slot is manufactured and measured. The first pass band of the filter has a center frequency of 1.94 GHz, a 3 dB band width of 0.28 GHz, the second pass band has a center frequency of 4.85 GHz and a 3 dB band width of 0.13 GHz, which is basically consistent with the simulation results.

Design of an Offset Posts K- band Bandpass Filter using Substrate Integrated Waveguide for Microwave Applications

In this paper, an offset posts K-band bandpass filter has been designed using substrate integrated waveguide (SIW). SIW is formed inside a dielectric material by applying a top metal over the ground plane and trapping the structure on either side with rows of plated vias. SIW is effective and efficient solution in waveguide technique. The slotted windows are cut in tapered transition of SIW filter to attain low loss. The proposed filters are designed at 23 GHz center frequency. The simulated results exhibit low losses and sharp roll off characteristics in pass band. There is good agreement between the simulated results and the experimental results. The proposed filter is suitable for use in microwave communication devices.

Wide Stopband Substrate Integrated Waveguide Filter Implemented by Orthogonal Ports’ Offset

Ideally, the orthogonal port can be effective to eliminate the TE102/TE201 spurious passband of a fundamental substrate integrated waveguide (SIW) filter using the orthogonality. However, it was not feasible in practical applications because the orthogonality of TE102/TE201 is deteriorated by the orthogonal port. Here, we propose an approach to repair the orthogonality which makes the practical orthogonal port work as the ideal one and thereby avoid the TE102/TE201 spurious passband in an SIW filter. The repair is achieved using ports’ offset almost without affecting the fundamental passband. A guideline of using the proposed technique to design a wide stopband filter based on square SIW resonators is provided. Four SIW filters with three, four, five, and six resonators, respectively, are then experimented. The measured results agree with the expectations well. An empirical equation is finally given to initialize the critical ports’ offset to facilitate the design. Compared with counterparts, the proposed technique uses a much simpler design, obtains better performance, and can be more easily implemented in practical applications.

Pedestal substrate integrated waveguide filter with both electric and magnetic cross-couplings

In this paper, the recently proposed Pedestal Substrate Integrated Waveguide (SIW) structure, consisting of evanescent-mode SIW cavities, loaded with pedestal-shaped metal inserts, is utilized to design a coupled resonator filter with both positive and negative cross-coupling. It is shown that both types of coupling, for a large range of coupling values for both, can very simply be implemented in this structure, with electric coupling obtained by means of an I-shaped strippine between pedestal tops, and magnetic coupling obtained using inductive irises. The proposed structure can also introduce mixed coupling. Graphs are presented to show the range of coupling values attainable. A proof-of-concept sixth order cross-coupled bandpass filter, with a 5 % bandwidth at 5 GHz, and both real and imaginary axis transmission zeros, are designed and measured.