Substrate Integrated Waveguide Filter Research Articles

A U-band cascaded quadruplet quartz glass SIW filter based on double row vias coupling window

A U-band Substrate Integrated Waveguide (SIW) Cascaded Quadruplet (CQ) filter is designed based on low-cost quartz glass planar integrated circuits process with limited depth-to-diameter ratio and via spacing, which challenge the control accuracy of coupling coefficients. To address this issue, a double-row vias coupling structure control strategy is proposed to enhance the precision of coupling coefficient control. Cascaded quadruplet topology based on the proposed coupling structure with asymmetric coupling window is designed to improve the passband selectivity and harmonic suppression. The filter exhibits −3dB relative bandwidth of 4.6 % (1.94 GHz) at a central frequency of 42.2 GHz, insertion loss of 4.2 dB and rectangular coefficient (−20 dB BW/−3dB BW) of 1.47.

A miniaturized and low-loss Q-band SIW bandpass filter based on evanescent-mode in wafer-level packaging process

This paper presents a miniaturized Q-band substrate integrated waveguide (SIW) bandpass filter (BPF) on a silicon-based wafer-level packaging (WLP) process. By incorporating capacitive quasi-coplanar waveguide (CPW) feeding structures and complementary split-ring resonators (CSRRs), the SIW operates in an evanescent-mode below the lower cutoff frequency and then achieves miniaturization. The efficient conversion of wave-modes, mutual excitation among multiple capacitive structures, and extremely short transmission paths, collectively resulting in the proposed BPF exhibiting low insertion loss. Furthermore, the area of fabricated filter has been reduced by 88.96 % compared to the requirement of the cutoff frequency. The measured results show that the minimum insertion loss is 1.24 dB, the return loss is better than 15 dB, and the 3 dB passband covers from 29.6 to 47.8 GHz (FBW is 47 %). These results indicate that, the proposed filter effectively solve the issues of large areas in SIW filters and high losses in silicon-based integrated or packaging processes.

A Multifunctionality Reconfigurable HMSIW Filter by Using EBG Structure and Diodes for C/X-Band Application

This letter presents a multifunctionality reconfigurable substrate-integrated waveguide (SIW) filter embedded in a microstrip line. The proposed filter used an electromagnetic bandgap structure (EBG) to compact the size and improve the electromagnetic features. The SIW filter consists of a three-cell EBG with metallic circular-shaped connected to the ground through cylindrical vias. Firstly, the base SIW structure offers a wide passband filtering response, and then, to obtain selective passband, wide band rejection, and controllable resonance frequencies, a three-cell EBG along with four diodes has been attached. The filter is designed and printed on a Rogers 4003 substrate with a thickness of 1 mm and is experimentally validated for functionalities operated at three modes with an average 3 dB bandwidth of 115 MHz in each frequency. In addition to that, two transmission zeros (TZ) have been produced in the upper band frequency. The filter’s response is also tunable by turning the diode off or on and changing the main parameters of EBG, the gab, and the position between cells. The study explores resonance frequency alterations in a three-state system of on/off. By eliminating or diminishing specific modes, and incorporating diodes, distinct resonance behaviors are observed. Moreover, shifting frequency resonance in a multiparameter system has been investigated. Increasing B1 induces a significant shift to lower values, while an increase in D1 leads to a decrease in the first and second resonance frequencies and an upward shift in the third. The designed filter has been fabricated and tested to compare and confirm simulated responses. Simulation and measurement results are in good agreement. The S-parameters of measured results gained a good response (>15 dB) within the passbands and stopbands and an insertion loss of 1.5 dB suitable for 5G and Wi-Fi systems.

A technique for the passband and stopband control of wideband band-pass substrate integrated waveguide (SIW) filters designed with elliptic stepped impedances

In this paper, a design technique based on a stepped impedance synthesis is proposed for the first time for the passband and stopband control of band-pass filters in substrate integrated waveguide (SIW) technology. The structure of the band-pass filters is implemented by means of elliptic patterns etched on the top side of the SIW, which work as impedance inverters. The design method consists of previously mapping the height of the elliptic patterns and the phase shift (cut-off angle) of the SIW lines, connected to the input and output ports of the ellipses, as a function of the passband and stopband characteristics of various stepped impedance SIW filters, to then select the design parameters of the band-pass SIW filter that achieve the desired frequency response. This new approach is applied to the design of two fourth-order Chebyshev stepped impedance band-pass SIW filters with different passband and stopband characteristics. One of the band-pass SIW filters is characterized by a fractional bandwidth FBW1 = 14.5% and a spurious-free range SFR1 = 2.8 GHz, while the other filter has a FBW2 = 22.3% and a SFR2 = 1.55 GHz. Both band-pass filters were designed with a SIW TE10 mode cut-off frequency and a higher passband cut-off frequency fixed at fcTE10 = 2.85 GHz and fc,H = 3.9 GHz, respectively. Electromagnetic (EM) simulations showed that the lower passband cut-off frequency fc,L can vary with respect to fc(TE10) by 13.6% and that the first spurious frequency can appear higher than fc,H by 69.3%. The measurement results agreed well with the EM simulations, thus confirming that this method can be useful to design high-performance wideband Chebyshev stepped impedance band-pass SIW filters with a high degree of control on the passband and stopband characteristics.

Realization of a Wide Stopband Filter Using the Weakest Electric Field Method and Electromagnetic Hybrid Coupling Method

To enhance filter performance in terms of stopband, we propose a wide-stopband substrate-integrated waveguide filter based on the rejection of higher-order modes. The filter establishes the inner and outer coupling windows at the mode’s weakest electric field to achieve mode suppression. Simultaneously, we employ the electromagnetic hybrid coupling theory to analyze the electromagnetic distribution of the particular modes and determine the dimensions of the coupling circular apertures and slits based on the extracted coupling coefficients to attain suppression of the specific modes. The filter successfully suppresses all higher-order modes having resonant frequencies below that of the TE150 mode, as demonstrated by simulation results. We conducted measurements and found that the filter has a center frequency of 4.78 GHz, a bandwidth of 100 MHz with a -3 dB attenuation, and a stopband of -25 dB that extends up to 16.62 GHz (i.e., 3.48 times the center frequency). Simulation and measurement results demonstrate a good correlation. This method, compared to other SIW filters, is easy to design, has a wider stopband range, can be readily applied to practical microwave communication systems, and has potential applications.

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.

A compact fifth-order SIW BPF based on TSV technology with high selectivity

In this paper, a fifth-order Substrate Integrated Waveguide (SIW) filter using Through-Silicon Via (TSV) technology is proposed. The slots on the top and bottom redistribution layers (RDL) of the filter provide negative coupling and a finite transmission zero (FTZ). This effectively improves stopband attenuation. Asynchronous tuning is applied to the coupling path of this component. The center frequency of the filter is 3.6 GHz (fractional bandwidth is 3.50 %). The minimum insertion loss is 1.58 dB, the minimum return loss is 23.6 dB, and the overall size is 1.855 × 1.316 mm2. The simulation results show that the proposed SIW filter can achieve better in-band characteristics and selectivity with the similar size or smaller size as compared to the SIW filter operating at the similar frequency.

Wide-Stopband Substrate Integrated Waveguide Filters Based on Single-Mode Cavities With Multiple-Cross Slots

A novel design method for wide-stopband substrate integrated waveguide (SIW) bandpass filters (BPF) is proposed, which is realized by combining TE102-and TE101-based single-mode cavities with multiple-cross slots (MCSs). To demonstrate the proposed method, a planar SIW BPF with MCSs is proposed firstly. The ingenious MCSs have no effect on resonant modes, but have a great impact on non-resonant modes resulting in staggered their resonances. Thus, the stopband performance can be improved significantly and unload quality factors are not deteriorated simultaneously. To realize size-reduced wide-stopband SIW filters, a multiple-layer SIW filter is proposed on the basis of the planar filter. Finally, two SIW filters are fabricated and measured to verify the performance of the proposed SIW filters and the design method.

Microwave Frequency Offset Induced by Subsurface Damage in Abrasive-Machined Semiconductor Ceramic Waveguide

Ceramic waveguide components play a critical role in modern microwave semiconductor systems. For the first time, this work reports experimental results obtained when dielectric ceramics are abrasive-machined into waveguide components. This process will cause subsurface damage (SSD), resulting in a deviation in their working frequency which can degrade the performance of the system. For a substrate-integrated waveguide (SIW) resonator working at 10.1 GHz, SSD with a depth of 89 um can cause a maximum frequency offset of 20.2%. For a mm wave component working at 70 GHz, the corresponding frequency offset could increase to 169%. Three resonator SIW filters with SSD are studied, and the results demonstrate that the frequency offset induced by SSD can reduce the pass rate of the filters from 95.4% to 0%. A theoretical analysis is performed to reveal the mechanism and to offer a quantitative estimation of the limiting range of the offset caused by SSD. Feasible methods for reducing the offset caused by SSD, such as structure design, processing optimization, and material reinforcement, are discussed.

Miniaturized Dual-Band SIW-Based Bandpass Filters Using Open-Loop Ring Resonators

This article presents two novel architectures of dual-band substrate-integrated waveguide (SIW) bandpass filters (BPFs). Initially, two identical open-loop ring resonators (OLRRs) were coupled face-to-face on the top of the SIW cavity to realize a dual-band single-pole BPF. To obtain two-pole dual-band characteristics, two OLRRs resonant units were assembled horizontally within the top metal layer of the SIW, which is a technique used for the first time in the literature. For demonstration purposes, two types of SIW filters loaded with OLRRs were designed and fabricated. The proposed filters feature an extremely compact size, a low insertion loss, and good selectivity. The single- and two-pole filters have an overall size of 0.012λg2 and 0.041λg2, respectively. The simulated and measured circuit responses are in good agreement.

Design of Miniaturized SIW Filter Loaded with Improved CSRR Structures

In recent years, Split-Ring Resonators (SRRs) and Complementary Split-Ring Resonators (CSRRs) have gained significant attention for their unique electromagnetic properties, such as negative permeability and negative permittivity, making them promising candidates for advanced microwave devices. This paper presents the design and analysis of a substrate-integrated waveguide (SIW) filter using CSRR structures for miniaturization. The improved CSRR unit can be easily integrated on the surface of the SIW, making it an ideal candidate for the design of compact SIW filters. In this paper, an improved CSRR-loaded SIW filter is designed and analyzed based on its equivalent lumped parameter model. A filter with a center frequency at 22.6 GHz is designed. Several transmission zeros (TZs) are also realized to improve the skirt selectivity of the filter. The design process involves theoretical analysis and electromagnetic simulations to optimize the dimensions of the CSRR resonators to achieve the desired filter characteristics. The measured and simulated results show good agreement, confirming the effectiveness of the proposed improved CSRR-loaded SIW filter. The successful implementation of the improved CSRR-loaded SIW filter demonstrates its potential for achieving miniaturization and enhanced performance in advanced microwave applications.

Substrate Integrated Waveguide Filter With Flexible Mixed Coupling

This article investigates flexibly using mixed coupling in substrate integrated waveguide (SIW) filters to efficiently improve selectivity. To this end, a mixed coupling structure is proposed, which can be used as a universal coupling module to efficiently produce transmission zeros (TZs) in an inline/conventional SIW filter without degrading the superiority of SIW. On this basis, a trisection with mixed cross-coupling is further proposed, which encloses all the structures inside two general SIW cavities and can be used as a universal cavity module to efficiently produce a quasi-elliptic response in an inline/conventional SIW filter without degrading the superiority of SIW. Three prototypes are designed, fabricated, and measured, and the results agree with the expectations well. The proposed techniques should facilitate the development of high-performance SIW filters in microwave/wireless circuits and systems.

Using Mixed Coupling to Realize Wide Stopband Multilayer Substrate Integrated Waveguide Filter

Mixed coupling has been used in substrate integrated waveguide (SIW) filters to eliminate the transmission of spurious modes. However, the elimination only applied to the first spurious mode. Here, we propose a new mixed coupling structure that consists of slots for magnetic coupling and holes for electric coupling. Using it as the inter-coupling structure, the total coupling/transmission of multiple spurious modes can be zero. This brief presents a prototype that is a multilayer SIW filter working in TE101 (f0). Theoretically, all the spurious modes below TE404 of this prototype can be eliminated efficiently, which is verified by an experiment result showing a stopband extended to 4.02 f0. The proposed technique not only extends the stopband of SIW filters but also the application scope of mixed coupling. It should facilitate the development of high-performance SIW filters in wireless/microwave circuits and systems.

Miniaturized silicon-based substrate integrated waveguide filter for 6G applications

Based on Through-Silicon Via (TSV) technology, a Substrate Integrated Waveguide (SIW) bandpass filter with ultra-compact size is presented for sixth-generation (6G) mobile communication applications. The proposed filter is proposed by the way of the generalized Chebyshev filters and coupling matrix reconfiguration. The measurement results reveal that the out-of-band rejection is better than 25 dB with frequencies up to 1.059 f0. In addition, the proposed filter has the center frequency of the passband at 0.371 THz with bandwidth of 0.0183 THz. The size is only 0.496 × 0.33 mm2.

Two-Layered Cross-Coupled Post-Loaded SIW Filter With Microstrip Ports

In this brief, we propose a new structure for reducing the number of substrates of a post-loaded substrate-integrated waveguide (SIW) resonator filters with microstrip ports. For using fewer substrates, the proposed structure has microstrip ports and each capacitive gap (the dielectric gap between one side of each post and the ground) on one side of the filter structure, which has not been reported to date. Hence, it does not necessitate another substrate designated for the implementation of the dielectric-filled gaps for the capacitive posts of post-loaded resonators. In addition, a new cross coupling structure for SIW resonators is also presented in this brief. Negative couplings can be easily implemented by using the proposed slot structure.

Relative Permittivity Measurement of Microliter Volume Liquid Samples through Microwave Filters

This paper proposes a concept of dielectric characterization of low-volume liquid samples using the coupling coefficient of filters. The concept is validated through a two-pole substrate integrated waveguide filter in which the liquid under test is mounted on the coupling section between the two resonators. Unlike the conventional resonator perturbation method reported many times in the literature, this technique uses the coupling coefficient for sensing. The liquid sample is collected in a capillary tube and carefully positioned on the coupling section of the filter; the coupling coefficient of the two resonators varies compared to the relative permittivity of the sample; thus, an empirical model is established. The proposed sensor has been tested to compute the permittivity of different alcohols. Binary solutions of ethanol and water have also been characterized to calculate the volume ratio and relative permittivity as a proof-of-concept. The obtained results show that the proposed sensing technique is capable of characterizing a low quantity of liquids (≈44 µL) with good accuracy, and a worst case measured error of only 6.8% is noted. The ease of integration with other circuitry, low cost, reusability with no deterioration, and adaptability of the proposed sensor makes it a suitable choice for the chemical as well as for the pharmaceutical industry.

LOW-COST C-BAND SIW BANDPASS FILTER USING FR4-EPOXY SUBSTRATE

This paper describes a substrate integrated waveguide (SIW) filter built on an Fr4-Epoxy substrate with a dielectric constant 4.4 and a height of h=1.6mm. SIW-based devices have piqued the interest of researchers in recent years due to their low loss, small size, and low cost. The goal is to simulate and realize a SIW filter for C-band applications. The designed filter is analyzed using the reflection coefficient S11 and electric field distributions. We used the HFSS simulator. According to the findings, there is a high degree of agreement between the simulated and realized filters. The results also show that the filter has a very good response. It also shows a bandwidth of 6.3GHz around the C-band frequencies. This filter's pass-band ranges from 5.39 to 6.83GHz, with an insertion loss of 4.2dB and a return loss of 45.49dB.

Evanescent‐mode bandpass filter using D‐shaped slotlines for spurious harmonic suppression

AbstractA novel miniaturized evanescent‐mode substrate integrated waveguide (SIW) bandpass filter with D‐shaped slotlines for spurious harmonic suppression is proposed in this letter. Closed‐form equations for the proposed evanescent‐mode SIW cavity are summarized and two D‐shaped slotlines are etched together as a pair by the face‐to‐face style to obtain the designed lowpass feature, which could be utilized to improve the out‐of‐band spurious harmonic rejection level. To validate the feasibility of this method, a miniaturized evanescent‐mode SIW filter with D‐shaped slotlines is designed and measured. The measured results show that this filter operates at 1.05 GHz with 2.4 dB insertion loss and 3.8% bandwidth. The out‐of‐band spurious rejection is lower than 16 dB up to 11 times of the higher cutoff frequency of the passband. All test results are in good agreement with the simulation results.

Compact Low-Loss Half-Mode Substrate Integrated Waveguide Filter With Controllable Transmission Zeros

Two novel planar filters with controllable mixed electromagnetic couplings are developed in this brief for C band operation. They are implemented with the half mode substrate integrated waveguide (HMSIW) technology. Owing to the half mode SIW cavity, both of the filters exhibit a compact size. The size of filter I is <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$0.53\,\,{\boldsymbol{\lambda }}_{\mathbf {0}} \times 0.30 {\boldsymbol{\lambda }}_{\mathbf {0}}$ </tex-math></inline-formula> , while the size of filter II is <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$0.47\,\,{\boldsymbol{\lambda }}_{\mathbf {0}} \times 0.28 {\boldsymbol{\lambda }}_{\mathbf {0}}$ </tex-math></inline-formula> . ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${\boldsymbol{\lambda }}_{\mathbf {0}}$ </tex-math></inline-formula> represents the wavelength in the free space at the center frequency). A wide passband response with a quasi-elliptic characteristic and good out-of-band rejection is realized due to the transmission zeros (TZs) introduced by the etched slot structures on the top metal layer. By modifying the dimensions of the structure, the strength of the electric and magnetic coupling can be independently controlled, and consequently the position of TZs is controllable to achieve desired stopband response with high selectivity. As a validation of the concept, one prototype is fabricated and tested. Excellent agreement is observed between the simulated and measured results.

Substrate Integrated Waveguide Filters in Glass Interposer for mmWave Applications

This letter presents the first demonstration of substrate integrated waveguide (SIW) filters in glass interposers for <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$D$ </tex-math></inline-formula> -band (110–170 GHz). The material stack-up consists of 100- <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu \text{m}$ </tex-math></inline-formula> -thick Asahi Glass Company (AGC) ENA1 glass with 15- <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu \text{m}$ </tex-math></inline-formula> -thick Ajinomoto Build-up Films (ABF GL102) laminated on both sides. To demonstrate different frequency responses, cavities with two different shapes (square and rectangle) are used to design the filters. The cavities are fed using center coupled microstrip lines. Semi-additive process (SAP) is used to fabricate the filters. The diameter and pitch of the via side wall are designed to be 70 and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$170 ~\mu \text{m}$ </tex-math></inline-formula> , respectively. The measured results are in excellent agreement with the simulation models. At ~130 GHz, first-, second-, and third-order square SIW filters show 1.54-, 2.7-, and 4.2-dB insertion loss, respectively. The relative bandwidth for the square filters is 12.8%, 9%, and 8.8%, respectively. The first- and second-order rectangular SIW filters show 1.65- and 2.85-dB insertion loss, respectively, and the relative bandwidth for these filters is 9.5% and 9%, respectively.