Design Of Bandpass Filter Research Articles

Dual Band Modified Complementary Split Ring Resonator Loaded Substrate Integrated Waveguide Based Bandpass Filter

This study presents a dual-band bandpass filter design that implements microstrip to substrate integrated waveguide (SIW) transition to decrease radiation losses. The proposed filter is designed with using four complementary split ring resonators (CSRR) to minimize its size and to gain double negative property. A bowtie shaped slot is etched inside CSRR to have a second resonance at the spectrum. After the simulation results are performed the designed filter is fabricated on a Rogers RT5880 dielectric substrate and the experimental results are compared with the simulation results. The proposed filter has center frequencies at 6.57 and 12.55 GHz with fractional bandwidth (FBW) of 22.05% and 26.29%, respectively. Moreover, the presented filter offers the best bandwidth-to-size result with the size of 0.327λg×0.352λg (where λg is the wavelength at the first passband’s center frequency).

Third-order optical bandpass filters based on structures of alternating layers of quartz and silver

Designs of optical bandpass filters have been developed on planar structures, which were obtained by vacuum deposition onto quartz glass (SiO2) substrates of three layers also of quartz, which are half-wavelength resonators separated from each other, from free space, and from the substrate by four layers of silver (Ag). The thicknesses of the Ag and SiO2 layers were determined based on the given parameters of the filter passband by parametric synthesis of one-dimensional models using electrodynamic analysis. In this case, experimental frequency dependences of the real and imaginary parts of the permittivity of silver were used. The measured frequency responses of the manufactured prototypes of red, green and purple filters are in good agreement with the responses obtained during synthesis.

Dual- and triple-band quasi-elliptic bandpass filters based on single-cavity multi-mode hybrid cavities

In this paper, a novel construction method for a single hybrid cavity is proposed for the first time, which integrates a quarter-mode substrate integrated waveguide structure into a patch cavity (QMSIWP), and a novel single-cavity multi-mode resonator is realized through the incorporation of cross-slot lines. A detailed analysis of its characteristics, combined with a specialized feed structure, leads to the design of multiple dual-band quasi-elliptic bandpass filters (BPFs) with varying frequency ratios and a triple-band quasi-elliptic BPF. The finite frequency transmission zeros (FTZs) and bandwidths (BWs) can be controlled by adjusting various parameters. For the demonstration, a triple-band quasi-elliptic BPF is fabricated and measured to validate the performance and design method of the proposed QMSIWP hybrid cavity and feed structure. The measured results agree with the synthesized and simulated results, confirming the proposed method's feasibility and universality. The proposed filter exhibits advantages such as compact size, high selectivity, and excellent group delay, which expands its application prospects and potential value.

A proposal for design of 2 – 4 GHz wideband bandpass filter using suspended substrate stripline for passive radar systems

This article proposes a solution to design of front-end bandpass filters which finds application in wideband receivers for passive radar systems. The structure employs suspended substrate stripline as base transmission lines, dual-frequency resonators, and broad-side coupling patterns to render a wideband, steep cutoff and low-loss bandpass filter that aims at replacing lossy microstrip-based or bulky waveguide-based filters. The structure is able to scale to different operating frequency ranges in electronic warfare systems.

A creative hybridization of metamaterial CSRR and multiple-mode resonators for designing a compact wideband bandpass filter for 5G/IOT/WLAN/Wi-Fi 6E applications

Abstract This article presents the design of a metamaterials-based hybrid wideband bandpass filter (WB-BPF) supporting several advanced communication applications. The suggested filter uses multiple-mode resonators (MMRs) and metamaterial complementary split-ring resonators (CSRRs). Coupling frequencies are optimized by stretching the coupled lines parallel on both sides. At the same time, the metamaterial complementary split-ring resonator (CSSR) cells are carefully tuned to improve impedance matching, reduce insertion loss, and broaden the bandwidth. The designed compact-sized bandpass filter offers a Quality factor ( Q L ) of above 1 while maintaining a wide bandwidth of 6150 MHz. The realized structure requires a small physical area of 20.2 × 10 mm2. A parametric study, field distribution analysis, and equivalent circuit model of the proposed hybrid BPF are performed. The resulting filter has an exceptional response with five transmission poles, demonstrating superior performance in the targeted frequency range. This wideband bandpass filter, operating from 3.3 GHz to 9.45 GHz, finds potential applications in the emerging fields of the Internet of Things (IoT), wireless fidelity 6 enhanced (Wi-Fi 6E), and high-speed wireless communications, particularly 5G technology, and 5 GHz wireless local area network (WLAN). This research demonstrates significant advances in the development of bandpass filters, offering compact, high-performance solutions for modern communications systems.

Design of a CPW-based SSPP band-pass filter with reflectionless notch

Abstract This work proposes a band-pass filter (BPF) with a reflectionless notch based on spoof surface plasmon polaritons (SSPPs), utilizing interdigital coupling structures and novel transmission line unit cells. This filter efficiently transmits signals within the 0.67 GHz −4.06 GHz frequency range. By analyzing the equivalent LC circuit of the novel transmission line unit cell, its dispersion relation is derived using microwave network theory, with a cutoff frequency of 4.11 GHz. By comparing its dispersion relation with that of the conventional transmission line unit cell, the miniaturization capability of the proposed unit cell can be verified. In the BPF, loading a zigzag groove onto the central transmission line can be equivalently represented as an interdigital coupling structure, generating a stopband in the low-frequency range near 0 GHz. By deriving and analyzing its S-parameters, it is shown that the bandwidth of the low-frequency stopband can be flexibly adjusted by modifying the geometric dimensions of the zigzag groove. Additionally, loading another set of interdigital coupling structures onto the transmission line generates a notch at its resonant frequency of 3.4 GHz. It is noteworthy that in this configuration, the interdigital coupling structures along with the central transmission line can be represented equivalently as a set of CPW antennas. At the resonant frequency, the atructure radiates signals into free space, forming a reflectionless notch. Based on the simulations, a physical filter was fabricated and tested, showing excellent agreement between simulations and measurements.

Design of a quad-band bandpass filter based on 13-mode resonator

ABSTRACT A quad-band microstrip bandpass filter (BPF) based on a 13-mode resonator is proposed in this article with compact size, high band‐to‐band isolation, and multiple transmission zeros (TZs). The proposed filter is constructed by two transmission paths from the input to the output port, which employs the transversal cancellation mechanism of two transition paths to introduce extra nine TZs. Therefore, a total of 12 TZs are located at 0.2, 1.8, 2, 3.88, 4.61, 5.24, 5.9, 9.26, 9.51, 12.32, 12.75, and 13.27 GHz, respectively, realizing high selectivity. Moreover, the designed filter can achieve quad passbands with centered frequency at 0.95, 2.78, 7.32, and 10.63 GHz for the requirement of multi-service in modern communication systems, with wide bandwidth of 235, 790, 2200, and 1540 MHz, respectively. The measured results agree well with the simulation results, which proves the feasibility of the design method.

Design of Compact HTS Bandpass Filter with High Selectivity Operating Above 100 k

In this manuscript, a miniature high-temperature superconductor (HTS) bandpass filter (BPF) with multi-transmission zeros (TZs), high selectivity, and great attenuation of stopband is presented. A couple of dual-mode resonator (DMR) is employed to achieve the proposed BPF, which can be characterized by using the classical even-odd mode analysis technique. The presented cascaded DMR can excite four resonant modes, which can be individually managed. Plus, a pair of intrinsic transmission zeros can be yielded at both the lower and upper edges of the passband, which results in sharp shirt performance. As an example, the HTS BPF is designed, fabricated, and tested, in which the center frequency is centred at 3.95 GHz and the 3-dB fractional bandwidth (FBW) is 2.5%. The proposed HTS BPF is implemented by using Tl2Ba2CaCu2O8 (Tl-2212) thin films which are fabricated by two-step processing and the superconducting critical temperatures (Tc) of the HTS films can reach 103 K. The design methodology is confirmed since the experimental results are in good agreement with theoretical results, showing desired bandpass characteristics, high selectivity, and the attenuation of lower and upper stopbands above −50 dB. Further, the circuit size is only 0.4 cm2.

Design and Simulation of Three-Band Microstrip Resonator Bandpass Filters for Wireless Communication Systems

Abstract This research focuses on the design, simulation, and practical implementation of three-band microstrip resonator bandpass filters for wireless communication systems. Key parameters targeted in optimizing these filters include coupling coefficient, external quality factor, and fractional bandwidth, among others. Using ANSYS HFSS software, the electromagnetic behavior of the filters was analyzed to enhance their design. The proposed filters were fabricated on RT/Duroid 5880 substrate and experimentally validated using a vector network analyzer. Experimental results were compared with simulations, demonstrating satisfactory performance at specific frequencies relevant to Wi-Fi, 5G, and radar applications. Additionally, a comparative study with other similar filters from the literature was conducted to evaluate their performance.

Design of Absorptive Bandpass Filters With General Chebyshev Response Based on λ/4 Microstrip Lines

ABSTRACTIn this brief, a synthesis design method is proposed for one‐port absorptive bandpass filters (BPFs) with general Chebyshev response and transmission zeros. The method is based on coupling matrix theory, enabling the derivation of normalized coupling matrix coefficients based on user‐defined parameters, including 3 dB bandwidth, in‐band reflection coefficient, and out‐of‐band rejection. Moreover, it offers design equations for designing absorptive filters using transmission lines, coupling lines, and stubs, all with a length of one‐quarter wavelength at the center frequency of the passband. To illustrate this method, a fourth‐order absorptive BPF with a general Chebyshev response and two transmission zeros is designed, fabricated, and measured. The experimental results verify the effectiveness of the design method.

Compact Wide‐Stopband QMSIW‐Based BPF for X‐Band Applications

ABSTRACTA novel and compact two‐pole quarter mode substrate integrated waveguide (QMSIW) based bandpass filter with ultra‐wide stopband characteristics (rejection level > 20 dB, up to 4.05f0, where f0 is the center frequency of the bandpass filter) is designed and developed in this paper. The designed second‐order filter comprises of two circular QMSIW cavity resonators. The filter is designed using the dominant TM010 mode of the circular SIW cavity. The TM010 modes of cavities are coupled through the arc‐shaped slot etched in the middle layer. To verify the present design methodology, a second‐order bandpass filter is fabricated and its characteristics are measured. The designed bandpass filter shows outstanding performance in terms of good fractional bandwidth of 14.45%, lower insertion loss of 2 dB and wider stopband behavior (rejection better than 20 dB up to 4.05f0) in a given footprint. The experimental results of the filter matches well the EM‐simulated ones.

Balanced tri- and quad-band BPFs based on SIR with improved passbands selectivity

Abstract In this paper, balanced tri- and quad-band bandpass filters (BPFs) with high selectivity and controllable center frequencies and bandwidths are proposed. In the tri-band BPF design, two differential-mode (DM) passbands are formed by utilizing a stub-loaded resonator (SLR) and a uniform impedance resonator (UIR). The coupling structure of the proposed BPF realizes the third DM passband. Moreover, the center frequencies and bandwidths of the three DM passbands can be controlled by the lengths of resonators and the gaps between the resonators. In order to improve the DM selectivity further, the source-load-coupled structure is introduced. In addition, common-mode (CM) suppression is achieved by using L-shaped balanced microstrip line to slotline transition structures, achieving the independence between CM responses and DM ones. Therefore, the design procedure can be simplified greatly. In order to validate the practicability, one balanced tri-band BPF operating at 2.5, 3.5 and 4.5 GHz is designed and fabricated. Moreover, by adding a short stub to the UIR located in the symmetrical plane, one flexible resonance frequency is generated, which is used to design the balanced quad-band BPF. By manufacturing and measurement, the measurement and simulation are in good agreement.

Design of novel multiband bandpass filters based on coupled symmetric short‐circuit stub multimode resonators

AbstractIn this letter, the working mechanism of suggested bandpass filters with connected symmetric short‐circuit stub multimode resonators is described. Because of the design flexibility, the suggested bandpass filters' centre frequencies may be modified based on the design approach. Meanwhile, the suggested bandpass filters have reduced insertion losses and compact sizes. A prototype is built and tested with six passbands centred at 1.57/2.38/3.55/5.14/5.83/6.78 GHz to confirm the design and analysis. Good agreement between the simulated, and measured results is observed, indicating that the proposed structure can be applied in the field of communication, information, and automation.

Design of HTS linear phase bandpass filter based on the inline topology

Abstract Inline topology filters have the advantages of a simple structure and fewer coupling coefficients. Based on the inline topology, this paper constructs a phase compensation topology of the filter, which can independently and controllably introduce two types of transmission zeros (TZs), and is convenient to realize the Chebyshev-like function response and compensate group delay. The finite frequency transmission zero is directly introduced through the source and load (S/L), and the real zero point is introduced and adjusted through the cross-coupling unit of the main path in this inline phase compensation topology. The two types of TZs can be introduced and regulated independently, so the side-band suppression and group delay compensation can be freely adjusted. A High-temperature superconducting (HTS) filter with inline is designed and processed with a typical structure based on application requirements. The filter introduces two pairs of symmetrical real TZs to improve sideband rejection and a pair of real TZs to control group delays to realize the linear phase. In addition, it has a small size and straightforward construction, and the results of the full-wave analysis method and the theoretical analysis approach match well with the measured results of the frequency response characteristics.

Enhancing safety in narrow-band transformerless PLC couplers with a passive symmetrical filter

As the demand for efficient data transmission over existing power infrastructure grows, power-line communication (PLC) systems have become increasingly vital. However, integrating communication signals with high-voltage power lines poses significant safety challenges, emphasizing the need for reliable, safe, and high-performance components. To address cost and safety concerns, this article introduces a symmetrical third-order band-pass filter design that employs a transformerless coupler, avoiding the expense and bulk of traditional transformers while enhancing both equipment and human safety in narrow-band PLC systems. The design, functionality, and safety considerations are discussed, with a focus on implementing a passive analog Butterworth filter, chosen for its flat frequency response in the passband. Additionally, we address the safety aspects of transformerless couplers in PLC applications, emphasizing their reliability and efficiency in maintaining signal integrity while minimizing the risks associated with high-voltage environments. Simulations validated the proposed design, confirming its effectiveness in achieving the desired frequency response. The design is cost-effective due to the elimination of the transformer and ensures safety through the strategic rearrangement of the coupler components, which isolates the power line from the communication side.

E-plane waveguide bandpass filters based on high-order modes of spoof surface plasmon polaritons

In this paper, a new design method of E-plane waveguide bandpass filter (BPF) using high-order modes of spoof surface plasmon polaritons (SSPPs) is proposed. The high-order modes of the double-layer SSPP (DL-SSPP) unit cell can be effectively manipulated by adjusting the dimensions of grounded metallic patterns in SSPP array, which mainly determines the filtering characteristics of E-plane waveguide BPFs. For improving the out-of-band rejection, two extra transmission zeros (TZs) are designed at the upper and lower stopbands of E-plane waveguide BPF, and then the operating mechanism of TZs is clearly investigated. Moreover, the filtering characteristics of the E-plane waveguide BPF with different transition parts are discussed to demonstrate the generalization of proposed design method. To verify the design feasibility, two examples of E-plane waveguide BPF are fabricated and measured. Good agreement between measurements and simulations shows that the proposed design method possesses good potential for the applications of high-performance E-plane waveguide BPF design.

An edge-coupled magnetostatic bandpass filter

The further development of 5G and 6G communication systems introduced new frequency allocations beyond 6 GHz, necessitating the development of compact bandpass filters that can operate over wide gigahertz frequency ranges. Herein, we report on the design, fabrication, and characterization of an edge-coupled magnetostatic forward volume wave bandpass filter (MSFVW). Using micromachining techniques, we fabricate both 2-pole and 4-pole filters from a yttrium iron garnet (YIG) film grown on a gadolinium gallium garnet (GGG) substrate with inductive transducers. By adjusting an out-of-plane magnetic field, we demonstrate linear center frequency tuning for a 4th-order filter from 4.5 GHz to 10.1 GHz while retaining a fractional bandwidth of 0.3%, an insertion loss of 6.94 dB, and a − 35 dB rejection level. We characterize the filter nonlinearity in the passband and stopband with IIP3 measurements of − 4.85 dBm and 25.84 dBm, respectively. In this work, we demonstrate a compact octave tunable narrowband channel-select filter with a significant degree of design flexibility and performance comparable to the state-of-the-art.

Design of a tunable center frequency and small size cavity bandpass filter by separating capacitor-loaded resonators

This paper presents a tunable center frequency and small size cavity bandpass filter design method. In this method, a capacitor-loaded open terminal coaxial resonator is employed to reduce the size of cavity filters. The resonator is designed and fabricated separately into two parts to achieve the flexible operating frequency purpose. The first part is called the base of the resonator which is simply a pillar and directly fabricated integrally with the cavity housing. The second part called the hat of the resonator is the main part causing the load capacitance in cavity filters. By using different heights of the base part or/and different shapes and sizes of the hat, the operating frequency of cavity filters can be changed flexibly. This method not only reduces the difficulty and cost of cavity filter processing but also makes cavity filters reconfigurable. To demonstrate the effectiveness of the method, a cavity filter sample with a center frequency of 3.45 GHz and a bandwidth of 80 MHz was designed, fabricated, and measured. The measured results show that the insertion loss was smaller than 1.33 dB in the whole bandwidth, one zero-point at 3.350 GHz reaching -68 dB, the rejection at 3.550 GHz was -41 dB, unloaded Q was 5,898, and the dimension of the filter was 128 mm×86 mm×23 mm.

Design of high selectivity tunable bandpass filter with switchable single‐/dual‐band responses

AbstractThis article proposes a switchable filter with four operating states, namely dual‐band mode, lower band mode, upper band mode, and all‐stop mode. The transition between these states is achieved by using positive intrinsic negative diodes, while the center frequency tuning is done by using varactors. In order to verify the design concept, a prototype has been fabricated on an F4BME substrate with a dielectric constant of 2.25 and a thickness of 1 mm, and the measured results were in agreement with the simulations. Notably, the dual‐band mode yields four transmission zeros (TZs), while the single‐band mode produces two TZs. The final circuit size of the designed filter is 0.18 × 0.14 λg, making it ideally suited for reconfigurable multi‐band communication systems.

Metal Mesh Metasurfaces as Dual-Band Bandpass Filters for Terahertz Frequencies

In the paper, we propose a new strategy to design of metal mesh filters (MMFs) based on spatial symmetry analysis of bound states in the continuum(BICs) and manipulating and control with resonances, when BICs transformed to the resonances due to spatial perturbations in the MMF structure. The design of a dual-band polarization-insensitive terahertz bandpass filter with wide upper stopband characteristics using a single conducting layer patterned with rectangular holes is presented. The transmission response of the MMF with two poles is obtained to realize dual-band characteristics and three zeros to suppress the stopband. The proposed design has achieved broadband bandpass transmission characteristics under both TE and TM polarizations with canter frequencies at 0.516THz and 0.734THz and 3dB bandwidths of 25% and 17%, respectively, and upper stopband from 0.887THz to 1.6THz with over 10dB suppression.