Dual-band Bandpass Filter Research Articles

Design of novel compact SISL filters with multiple TZs based on patch resonators

AbstractThis letter presents two compact filters using patch resonators based on the substrate integrated suspended line (SISL) technology platform. First, a bandpass filter (BPF) with multiple coupling schemes is designed by using a shorted‐stub‐loaded patch resonator. Two shorted stepped‐impedance resonators are working together to form the third‐order BPF. A 98.18% size reduction is achieved, and five transmission zeros (TZs) are produced by introduced mixed electric and magnetic coupling, cross‐coupling, and source to load coupling. Then, the SISL dual‐band bandpass filter (DBBPF) with six TZs is designed by using an improved slotted patch resonator. By adopting the patterned suspended substrate structure, the implemented DBBPF, featured with self‐packaging, achieves a fractional bandwidth of 52% and 10%, centered at 0.95 and 3.25 GHz with insertion losses of 0.57 and 2.89 dB, respectively.

All-Frequency Absorptive CL Dual-Band BPF With Complementary Lossy Bandstop Branches

In this brief, input-/two-port all-frequency absorptive dual-band bandpass filters (BPFs) based on complementary duplexer architecture are proposed for the first time. The design consists of a simple coupled-line (CL) based dual-band BPF section and auxiliary dual-band bandstop filter (BSF) sections with resistively terminated absorptive stubs. The dual-band BPF can transmit spectral energy in two passbands with good in-band filtering response, while the out-of-band RF-signal energy can be absorbed by auxiliary BSF sections, which indicates all-frequency absorption from dc. The impedance of the absorptive stub and the value of the resistor can be independently adjusted to enhance the absorption. The operational foundations and explicit design equations are discussed and derived. Good agreements between the simulated and measured results verify the design theory.

Monolithically-integrated 3D printed coaxial bandpass filters and RF diplexers: single-band and dual-band

AbstractThe manuscript reports on additively-manufactured (AM) coaxial-resonator-based bandpass filters (BPFs) and RF diplexers. A monolithic integration concept using stereolithography apparatus (SLA) is proposed and discussed in detail. Coupled-resonator-based synthesis alongside full-electromagnetic-based design methods is used for the design of the monolithic filters and RF diplexers. In particular, the paper discusses a new external coupling mechanism for dual-band BPFs that allow to independently control the coupling in each of the BPF passbands. Furthermore, a novel coaxial transmission line-type T-junction is proposed for the design of single- and dual-band RF diplexers. For practical validation purposes, multiple BPF and RF diplexer prototypes were designed, manufactured and tested at S- and C-band demonstrating the applicability of the proposed concept to low-cost, low-loss and low-weight RF components with complex geometrical features.

Dual Fluorescence Emission by Irradiation of Single Optical Source for Fluorescein Sodium and 5-ALA Applications

Abstract Most brain surgeries aim to completely resection a tumor. However, the arrangement of blood vessels around brain tumors is often complex. Moreover, the tumors and blood vessels have similar colors, making it difficult to identify the boundaries between them with the naked eye. Fluorescent staining is a method used to distinguish the borders between brain tumors and blood vessels. The fluorescent contrast agents commonly used to observe tumors are 5-aminolevulinic acid and fluorescein sodium, which have different surgical sensitivities, depending on the type of tumor. In this article, a dual band bandpass filter with dual-wavelength emission for 5-aminolevulinic acid and fluorescein sodium is designed, and the dual-band bandpass filter capable of inducing simultaneous fluorescence emission of fluorescein sodium and 5-aminolevulinic acid was investigated experimentally to improve accuracy, speed, and energy efficiency in clinical settings. The possibility of dual fluorescence emission with a single irradiation is proposed. The efficiency of transmission and reflection (optical density) is 98% and 0.01%, respectively, and the bandwidth is 50% in the proposed filter. The proposed fluorescent dual-band filter has the advantage of saving energy, reducing auxiliary manpower and unit costs, and reducing operating room space requirements by producing two fluorescence diagnostic effects using a single equipment.

Microstrip filters Based on Open Stubs and SIR for High Frequency and Ultra-Wideband Applications

This paper includes two new microstrip filter configurations for high frequency and Ultra-Wide Band applications. The first proposed filter is a composition of four parallel open-circuited stubs connected by optimized fractal-structured microstrip line. The filter response is a combination of three passing regions, namely low pass from 0.1 GHz to 3 GHz, band-pass from 4.5 GHz to 9 GHz and high pass from 10.5 GHz to 13 GHz, separated by two rejection regions from 3 GHz to 4.5 GHz and 9 GHz to 10.5 GHz. Deep and sharp rejection regions reaching up to -44.6 dB with 40 % fractional bandwidth (FBW) are observed with a good electrical performance. Furthermore, with a comparative table, the advantages of this proposed BSF in terms of FBW, compactness and insertion loss are compared with recently reported related studies. Secondly a dual-band band pass filter implementing a Stepped-Impedance resonator (SIR) and a modified H-shaped structure is presented. This filter is designed to operate in a low pass region up to 3.58 GHz and a band pass region from 15.38 to 21.65 GHz, with a wide stopband region between 4.46 and 14.07 GHz. The simulated and measured results are in good agreement. Compared to its peers, the compact size and low price allow for a wide application of these filter configurations, while passing frequencies allow operation in the unlicensed frequency spectrum, which is popular for high-speed communication. Keywords: Microstrip Filter, Band Pass, Band Stop, Open Stubs, SIR.

A Fast Technique for Realization of Lumped-Element Values Into 3-D Physical Layout on LTCC

This article proposes a methodology for the fast translation of ideal lumped-element values to the form of a 3-D physical layout using low-temperature cofired ceramic (LTCC) dielectric. It is explained how this approach is implemented without requiring complex formulas and uses a simulation-based process which leads to consume less optimization/tuning processing time. The proposed methodology is applied to the design of a dual-band bandpass filter (D-BPF) operating at center frequencies 2.4 and 5.2 GHz and its layout is realized in the form of 3-D physical layout. The two commercial simulators, advanced design system (ADS) and high-frequency structure simulator (HFSS), are used to simulate ideal lumped-element schematics and perform electromagnetic (EM) simulations on the LTCC layout, respectively.

A Reconfigurable Balanced Dual-Band Bandpass Filter With Constant Absolute Bandwidth and High Selectivity

A reconfigurable balanced dual-band bandpass filter (BPF) with constant differential-mode (DM) absolute bandwidth (ABW) and high selectivity is designed in this article. The proposed BPF is composed of a set of asymmetric short stub-loaded resonators (A-SSLRs) and balanced microstrip-to-slotline transition structures (MSTSs). Four varactor diodes are employed to achieve the reconfigurable characteristics with small insertion losses. By changing the coupling distances and selecting the positions of the loaded varactor diodes on A-SSLRs, the DM coupling coefficients <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$K_{i}$ </tex-math></inline-formula> and quality factors <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$Q_{i}$ </tex-math></inline-formula> of the proposed BPF can be easily controlled to keep a constant DM ABW. In the overall tuning range, a superior common-mode (CM) suppression is achieved intrinsically, and the DM responses are independent of the CM ones. Furthermore, five DM transmission zeros (TZs) are generated by the mixed-coupling and source–load coupling, which can improve the selectivity obviously. Compared with the published reconfigurable balanced BPFs, the proposed one has the advantages of constant DM ABW, smaller insertion losses, and more independent control on the two DM passbands. In order to validate the design strategies, a prototype circuit is designed, fabricated, and measured. The simulated and measured results are presented with a good agreement to verify the theory and design.

A quint mode fractal architecture based resonator and its efficacy in the design of multiband bandpass filters

This paper presents a new approach to design multiband bandpass filters (BPF) using multimode resonator topology inspired from Bamileke fractal architecture in the form of fractal shaped resonator. The proposed resonator architecture exhibits quint mode resonance behavior where resonance frequencies are determined using ABCD matrix. It offers flexibility in terms of choosing passband center frequencies precisely. Initially a second order dual band BPF is presented by suppressing higher order modes using asymmetric feed line. The same structure is used further to implement a triband and a quad band BPF where the input/output coupling circuit is modified to extract the higher order modes. Two stub loaded resonators are also embedded to improve the passband selectivity and to improve upper stopband characteristics. The design guidelines are demonstrated through the external quality factor (Qe) and coupling coefficient (k) synthesis approach. The developed filters are fabricated and measured to verify the predicted and simulated results. A close agreement is observed between them. The fabricated multiband BPFs has a very compact size, less insertion loss and good return loss profile.

A compact coplanar waveguide dual-band bandpass filters based on defected ground structures

A compact coplanar waveguide dual-band bandpass filters based on defected ground structures

Direct Synthesis Method for Dual-Band Bandpass Filters With Wide Fractional Bandwidth Range and Center Frequency Ratio

This brief proposes a direct synthesis method for dual-band filters based on frequency transformations. This method can synthesize dual-band bandpass filters (BPFs) with a large range of fractional bandwidth (8.5%-56%) and at the same time, wide center frequency ratio (2-4). A novel circuit conversion scheme is proposed to ease the difficulty of implementing complex circuit and reduce the sensitivity of S parameters to the values of the circuit elements significantly (The influence of 20% fluctuation of inductance on S <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">11</sub> is within 5dB). In order to prove the validity of the proposed method, a 3 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">rd</sup> -order narrowband dual-band BPF with center frequencies of 1 GHz and 2 GHz (small frequency ratio) and a 5 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">th</sup> -order wideband dual-band BPF with center frequencies of 0.5 GHz and 2 GHz (large frequency ratio) are designed and fabricated, the simulated and measured results have good agreement.

A reconfigurable dual-band bandpass filter using memristive switches

In this paper, a reconfigurable dual-band bandpass filter, using memristive switches, is proposed. The applied memristor is non-volatile and has low-power consumption, which could be potentially used as an RF switch. The dual-band bandpass filter is based on the dual-mode resonator with a memristor. The odd-mode and even-mode method is utilized to analyse the proposed reconfigurable filter. By loading a memristor to the optimum position of the resonator, the proposed dual-band bandpass filter’s responses can be switched. The memristor is equivalent to a low-impedance resistor in ON state and a high-impedance capacitor in OFF state. The frequency responses of the proposed reconfigurable dual-band bandpass filter can be tuned by transforming the state of two memristors. The alternative test method is used in this paper, and measured results are consistent with simulated results.

Compact fourth/third order dual‐band bandpass filter with independently controllable passbands

AbstractThis article reports a compact microstrip dual‐band bandpass filter (DBBPF) using two pairs of λ/4 short‐circuited stepped impedance resonators (SSIRs) and a stub‐loaded triple‐mode resonator (STR). The first and fourth λ/4 SSIRs not only couple with the second and third SSIRs to form the lower passband, but also serve as the feeding structure and provide source‐load coupling for the higher passband, formed by the STR. As a result, a compact filter size can be achieved, and two extra transmission zeros are created for the higher passband to enhance the passband selectivity. Meanwhile, both the center frequency and bandwidth of each passband can be controlled independently. Furthermore, the impedance and length ratios of the two pairs of λ/4 SSIRs are dissimilar to achieve wide stopband. A fourth/third order DBBPF prototype centered at 1.575 GHz (GPS) and 3.5 GHz (WiMAX) is ultimately implemented to demonstrate the design concept, and the measurements match the simulations with good consistency.

BPFs with oct-resonance and -transmission-zero realized by coupling optimization on open-loop resonator

This paper presents a series of novel designs for dual-band bandpass filters (BPFs) with excellent in-band and out-band filtering performances. By imbedding the spiral-line resonator into the coupling open-loop structures and adjusting the symmetrical structure, the second-order quad-mode BPFs are designed and then the fourth-order oct-mode dual-band BPFs. The final two designs possess eight resonant modes in the passband and also four/eight transmission zeros in the stopband, achieving a high transition-band selectivity with the roll-off rate over 1000 dB/GHz, broad out-band rejection from 1.5 GHz to 5.3 GHz (lower than 30 dB), and strong isolation between dual bands with the suppression level of 30 dB, operating at 3.2/3.4 GHz and 3.2/3.5 GHz respectively. Measured results agree well with simulations and prove the validity of the asymmetry feeders for multi-transmission-zero characteristics.

Dual-band broadside-coupled based BPF with improved performance

This paper presents a unique structure of a dual-band microstrip bandpass filter (BPF) that works at 1.25 GHz, 1.9 GHz for global positioning systems (GPS) and TV broadcast auxiliary service applications, respectively. The proposed BPF provides compactness, small fractional bandwidth (FBW), small frequency separation, and low IL. The prospective filter is constructed employing broadside-coupling techniques to achieve low insertion loss (IL). The feeding structure is accomplished utilizing a 50 Ω co-planar waveguide (CPW) scheme due to its low loss characteristics. The small 3-dB FBW is accomplished by inserting four transmission zeros (TZs). The size of the overall structure, including I/O transmission lines, is 34.9 × 23.5 mm2. The measured and simulated results fit well with each other and show an IL of 0.77 dB and 0.5 dB, and FBW of 7.6% and 8.4% at 1.25 GHz and 1.9 GHz, respectively.

Modeling and Analysis of Novel CSRRs-Loaded Dual-Band Bandpass SIW Filters

Dual-band substrate integrated waveguide (SIW) bandpass filter (BPF) operating at 6 GHz and 12 GHz is presented. The two identical complementary split-ring resonators (CSRRs) make up the resonant unit. And the two CSRRs are strongly coupled. For the first time, two resonant units are horizontally etched on the upper metal of SIW. The equivalent circuit model of the novel dual-band SIW BPF is established and analyzed in detail. To realize the miniaturization design of the filter, a dual-band half-mode SIW BPF is proposed. The center frequencies of the passbands are located at 4.56 GHz and 9.36 GHz. The filter exhibits the characteristics of higher slope selectivity, lower insertion loss, wider 3 dB fractional bandwidths and compact size.

Design of a Multilayer Dual-Band Balanced Bandpass Filter on a Circular Patch Resonator

This letter presents a novel multilayer dual-band balanced bandpass filter (BPF) design by using two perturbed circular patch resonators. The TM11 mode and TM21 mode of the resonator with odd-symmetric field distributions are explored to realize the desired differential-mode (DM) transmission and common-mode (CM) suppression. Two circular patches are properly coupled in the back-to-back form to realize a dual-passband balanced response by virtue of coupling apertures etched on the ground. In addition to the internal coupling, the above apertures are also further utilized for the undesired degenerate mode harmonic suppression. Besides, slot perturbations on the patch are introduced to perturb the TM21 resonant mode to independently adjust the center frequency of the higher passband, while the lower passband remains almost unchanged. Thus, two passbands can be flexibly controlled by simultaneously tuning the above slots and size of the patch. For validation, a dual-band balanced BPF prototype is implemented. The results indicate 18 and 26% wide fractional bandwidths centered at 5.5 and 7.5 GHz with return loss higher than 20 dB under DM operation and CM suppression higher than 40 dB over an ultra-wide frequency band.

Compact dual-band balanced bandpass filter based on circular SIW cavity

Abstract A compact dual-band balanced bandpass filter with high frequency selectivity and adjustable passband based on the perturbed circular substrate integrated waveguide cavity is firstly proposed in this paper. Two pairs of metallic vias are located at 45°direction of cavities to separate a pair of degenerate modes (TM110 modes) to achieve the differential-mode (DM) dual-band response. Moreover, the perturbation vias can also be used to control the center frequency of the second DM passband while the first one still stays unaffected. The introduction of source-load coupling makes the filter exhibit excellent selectivity. And four controllable transmission zeros appear near two DM passbands. Finally, good common-mode suppression has been got owing to the proposed balanced structure. The measured results are in accordance with the simulated ones well.

Novel Cross-Coupled Dual-Band Bandpass Filters With Compact Size Based on Dual-Mode Isosceles Right-Angled Triangular Resonators

Novel cross-coupled dual-band bandpass filters (BPFs) with compact size are proposed based on dual-mode isosceles right-angled triangular (IRAT) resonators. The dominant mode in the IRAT resonator is the TM100Z mode. By introducing posts in the resonators, an LC resonant unit is formed, which resonates at a lower frequency than the TM100Z mode. In the design of novel dual-band filters, the LC mode constitutes the first passband while the TM100Z mode produces the second passband. As cross-coupling is applied, two and eight transmission zeros (TZs) are produced in the responses of third-order and fourth-order dual-band BPFs, respectively. Two third-order cross-coupled dual-band BPFs with altered passbands and one fourth-order cross-coupled dual-band BPF are fabricated and measured. The measured results agree very well with the simulated results, demonstrating attractive advantages of the proposed BPFs such as compact size and decent performance.

3-D Printed Dual-Band Filter Based on Spherical Dual-Mode Cavity

A new dual-band bandpass filter (BPF) is designed and fabricated based on a pair of spherical dual-mode resonant cavities using 3-D printing technology. By elaborately introducing three-type metallic posts into each cavity to perturb the degenerated TM <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">101</sub> modes in a reasonable way, a dual-band coupling topology is developed in the design accordingly. Owing to the cross-coupling paths in the designed topology, two transmission zeros (TZs) are successfully introduced between the passbands, bringing out a high band-to-band isolation. Even more, TZs can also be generated by creating additional internal coupling paths to the presented dual-band coupling topology. Besides, the spherical cavity provides a higher quality factor and wider stopband, compared to that of a square or cylindrical cavity. To validate the design concept, a dual-band BPF prototype, operating at 12.0 and 12.5 GHz with respective bandwidths of 120 and 240 MHz, is implemented by 3-D printing process. The measured results exhibit good agreement with the simulated ones, showing more than 20-dB return losses and 20-dB dual-band isolation.

Microstrip Dual-Band Bandpass Filter With Wide Bandwidth Using Paper Substrate

This work presents the design and analysis of a novel dual-wideband bandpass filter (BPF) using the transversal filtering section (TFS), coupled lines (CLs), and stepped impedance stubs (SISs). Initially, a dual-band BPF employing TFS and CLs is designed. To enhance the bandwidth and selectivity, SIS units and quarter wavelength transmission lines are attached at the input and output ports. This novel filter's frequency response has six transmission zeros in the stopband and four transmission poles in each passband. A prototype with center frequencies of 1.17 and 2.4 GHz is realized on a biodegradable substrate and tested. The tested and simulated results are in high congruence, validating the proposed design circuit and theory.