Tri-band Filter Research Articles

Compact Tri-Band Bandpass Filter with Wide Upper Stopband Based on Spoof Surface Plasmon Polaritons and Open-/Short-Circuited Stubs

In this paper, a new U-shaped ring spoof surface plasmon polariton (SSPP) structure is proposed as part of a bandpass filter (BPF) combined with short-circuited stubs (SCSs). The U-shaped ring unit offers miniaturization and multiple adjustable parameters. Furthermore, the lower and upper cutoff frequencies of the passband for the BPF can be adjusted by modifying the structural parameters of the SSPP units and SCSs, respectively. To validate the design, a prototype filter was first created with a frequency range of 2 to 3.7 GHz for the passband and an extended stopband that reached up to 15 GHz. On the basis of the designed BPF, a tri-band filter was realized by introducing multiple transmission zeros by loading multiple open-circuited stubs (OCSs) onto the transmission portion of SSPPs. The center frequencies of the three passbands were 1.20 GHz, 2.03 GHz, and 2.96 GHz, respectively. At the same time, the upper stopband rejection reached up to 12 GHz with an attenuation of −30 dB, about 10 times the center frequency of the first passband. The experimental results demonstrate a strong correlation between the measured and simulated outcomes, thereby validating the proposed structure and design methodology. Notably, the filter measures only 0.38λg × 0.13λg, highlighting its compact size as a significant advantage.

A Millimeter Wave Triband Bandpass Filter Using Stub-Loaded Hexagonal Patch with Complementary Spiral Resonator

In this paper, a triband bandpass filter has been proposed for millimeter wave and 5G applications. The filter design is progressed using a complementary spiral resonator superimposed on a hexagonal patch measuring about 7 mm × 4.2 mm × 0.8 mm. employing Rogers 5880 as substrate with εr = 2.2. This triband filter is highly selective with sharp rejections emulating bandwidths of about 1.3 GHz, 2.5 GHz, and 1.8 GHz capable of supporting millimeter wave and 5G communications. The qualifying parameters of filter-like insertion loss have been realized between −0.6 dB and −0.16 dB and return loss between −19.12 dB and −28 dB for the corresponding three bands. Moreover, the performance attainment of the filter has been verified from the surface current distribution of the filter. The filter resonates at millimeter wave frequencies of 29.6 GHz, 32.5 GHz, and 35.8 GHz portraying a triband response. The simulated and measured results substantiated very well with each other.

Design of tri-band filtering power divider with out-of-band transmission zeros based on frequency transformation method

In this brief, a novel tri-band filtering power divider with a pair of out-of-band transmission zeros is presented. It mainly consists of tri-band filter matching structures, transmission lines introducing transmission zeros, and isolation resistors. Through even- and odd-mode analyses, general design equations for the three parts can be derived separately. By applying coupled lines, the circuit size is further compact. For verification, a third-order tri-band filter PD working at three independent bands with a pair of out-of-band TZs θz = 60° is designed. Good agreement between the measured and simulated results is attained so as to successfully validate the correctness of the proposed design approach.

A compact tri-band bandpass filter using asymmetrical stub-loaded resonator

ABSTRACT This paper proposes a novel compact tri-band bandpass filter based on two coupled asymmetrical stub-loaded resonators (ASLR). The proposed filter can achieve three resonant frequencies by tuning uniform impedance line, short-circuit stub, and open-circuit stub, respectively. In addition, the asymmetrical stub can be loaded at any position of the main branch, which will facilitate the circuit design for no impedance of special ratio is needed, and the design bound can be alleviated. Meanwhile, thanks to its simple structure, the whole filter occupies an area of 0.021 λg 2 based on RO4350B substrate, much smaller than other similar tri-band filters. Measurement results show that the filter achieves fractional bandwidths (FBW) of 7.5%, 6.4% and 4.2%, respectively for three bands. The proposed filter is small and can achieve a high-frequency selectivity at 2.45 GHz, 3.5 GHz and 5.25 GHz, corresponding to Bluetooth, World Interoperability for Microwave Access (WiMAX) and Wireless Local Area Network (WLAN), respectively. The proposed filter will find a wide application in wireless communications thanks to its attractive advantages.

Sharp roll‐off triband microstrip bandpass filter with wide stopband for multiband wireless communication systems

Design of a novel triband bandpass filter is presented for wireless communications systems. The filter is based on inter-coupled stepped impedance resonators and inter-digitally coupled to the input/output ports. The configuration of the filter circuit consists of open-loop resonators that are electromagnetically coupled to each other using inverted T-shaped open stubs. The intrinsic characteristics of filter structure generates five transmission zeros that results in triband bandpass response exhibiting sharp selectivity, high inter-band isolation and a wide out of band rejection. Unlike other triband filters reported recently in literature the proposed single layer filter does not require any short-circuited plated through hole which can introduce fabrication complexity and therefore production costs. Moreover, the triband structure can be configured to provide passbands with identical 3-dB fractional bandwidth and whose center frequency can be equally spaced. In the proposed prototype design presented here the passband frequencies are set to 3.6, 4.6, and 5.6 GHz that corresponds to WiMAX, 5G, and WLAN applications. The consequence of employing open-circuited transmission lines in the design results in a relatively large structure, which can be overcome by employing higher dielectric constant substrate. The proposed triband filter was designed to achieve identical 3-dB fractional bandwidth of 11.9%. Measured results confirm inter-band isolation better than 30-dB. The theoretical model is consistent with the measured results.

A Balanced Tri-Band Substrate Integrated Waveguide Bandpass Filter With High Selectivity

This paper proposed a balanced tri-band bandpass filter (BPF) with high selectivity based on substrate integrated waveguide (SIW) technology. The tri-band filtering response and multiple transmission zeros (TZs) are attained by elaborately merging cascaded quadruplet (CQ) topology and split topology. The proposed balanced tri-band bandpass filter is designed, which integrates high selectivity differential-mode (DM) transmission and good common-mode suppression by cleverly placing TE102-mode SIW cavity on the symmetric plane. To verify the proposed concept, a prototype of balanced tri-band BPF operating at 9.33, 9.67, and 10.02 GHz has been implemented. Measured results show eight TZs at out of DM passbands and more than 35 dB CM suppression within the DM passbands, which agree well with the simulated results.

Design and implementation of miniaturized tri-band microwave bandpass filter

PurposeThis paper is aimed to study the design of a miniaturized filter with tri-band characteristics. In this paper, perturbation is used to realize circuit miniaturization and multi-band by exploiting the inductive property. During this process, vias are added for twofold benefit, namely, circuit miniaturization and enhanced frequency selectivity at high frequency. Thus, with the introduction of the shorting via, the single-band dual-mode bandpass filter is converted into a tri-band filter with a smaller electrical size.Design/methodology/approachThis paper presents the design and characterization of a miniaturized two-port filter with tri-band operating characteristics. The proposed filter is constructed using a square patch resonator operating at 5.2 GHz with a capacitively coupled feed configuration. A square perturbation is added to the corner of the square patch to achieve diagonal symmetry and to excite dual mode. The perturbation offers a sharp transmission zero defining bandwidth of the proposed filter. In addition, a shorting post is introduced to achieve an 88% size reduction by lowering the operating frequency to 1.8 GHz.FindingsThe prototype filter has insertion less than 1.2 dB and return loss better than 12 dB throughout all the realized frequency bands. The prototype filter is fabricated and the simulation results are validated using experimental measurements. The realized fractional bandwidths of the proposed bandpass filter are 11/5.6/1 at 1.8/4.6/5.85 GHz, respectively. The quality factor of the proposed antenna is greater than 80 and a peak Q-factor of 387 is realized at 5.85 GHz. The high Q-factor indicates low loss and improved selectivity. The rejection levels in the stopband are greater than 20 dB.Originality/valueThe results indicate that the proposed filter is a suitable choice for low-power small-scale wireless systems operating in the microwave bands. The realized filter has the smallest footprint of 0.36λeff × 0.19λeff where λeff is the effective wavelength calculated at the lowest frequency of operation.

Design and Optimization of Tri-Band Open Loop Resonator Filter for BT, WiMAX, WLAN and Wi-Fi Applications

The consumer wireless frequency spectrum is getting denser and overlapping so may signals can cause interference and less data speed. There is need to either switch to new channel or to use newer technologies available. As per FCC new 6GHz band is now open for WLAN & Wi-Fi networks and to filter out other signals a microwave filter could the best mate. This paper proposed a tri-band microstrip filter having rectangular resonator with open loop has been evaluated. Because of its tiny size, lighter weight, cheaper cost, and superior performance, microstrip filters are often chosen over lumped filters at higher frequencies. The construction, refinement, and implementation of a modular tri-band bandpass filter have examined in this research. The proposed low-profile tri-band MS filter with three resonators designed for BT, WiMAX, WLAN and Wi-Fi microwave applications. The physical size of the filter is 30×15 mm2 . The designed filter has full ground and substrate is of FR-4 material having 4.3 dialectic constant and 1.6 mm thickness. The filter is made of four rectangular resonators of diverse dimension. Resonators are arranged in symmetrical geometry. Proposed tri-band bandpass filter is having negative group delay which facilitates the feedforward amplifier circuits. Filters with NGD also helps to reduces the physical size of the microwave circuits. The proposed tri-band filter has passband characteristics on 2.37GHz, 5.36GHz, and 6.15GHz with the insertion loss of 1.03dB, 1.6dB, and 3.67dB having return loss of 23.3dB, 18.56dB, 12.8dB, and 21.87dB. Filter exhibits good fractional bandwidth of 21.92%, 6.68%, and 4.36% respectively. Proposed filter has 2 transmission zeros. The tested and simulated results of |S11| and |S21| parameters are quite identical which shows the excellent matching of physical parameters. Keywords - Tri-band, band-pass filter, NGD, rectangular resonators, BT, WiMAX, WLAN, Wi-Fi.

Measuring surface temperatures of different types of fly ash samples using a CCD camera

In this work, an optical emission-based two-color method was experimentally investigated for the measurement of surface temperatures of different types of fly ash samples using a CCD camera. A heating system consisting of a Hencken flat-flame burner, a narrow piece of stainless steel wire mesh to separate the flame and the ash samples to be studied, and a thermocouple to record the temperature, was used to heat fly ash samples. A color camera equipped with a tri-band filter was used to capture radiation images. Fly ash samples collected from three kinds of coal-fired boilers were heated and imaged at different temperatures. The chemical compositions, elements, and particle size distributions were analyzed. The emissivity ratios of the wavelengths corresponding to the R and G optical channels and permitted by the tri-band filter were experimentally determined. A two-color method was subsequently used to calculate the average surface temperatures with relative errors within ?2% in the experiments, and an uncertainty analysis was conducted. Surface temperature distributions were also calculated and presented. The results demonstrate that the emission-based two-color method can be used to determine reliable average surface temperatures and surface temperature distributions when the radiation emitted from the ash samples is obviously greater than the ambient light. The results also show that the method has a lower limit of temperature measurement, which will lessen with the use of larger apertures and a higher radiation capacity of the ash samples to be studied.

Design of Miniaturized Tri-Band Microstrip Bandpass Filter Using Meandered Stubs for WLAN and Wi-Max Band

In this paper, a miniaturized tri-band microstrip bandpass filter is designed using three sets of shorted stub-loaded stepped impedance resonators (SSLSIRs). One pair of resonators have meandered short stub-loaded resonator (MSSLSIR) to further reduce the dimensions of the whole tri-band filter. The operating frequencies of the SSLSIRs and MSSLSIR are designed for the applications in the WLAN (2.45/5.2 GHz) and Wi-MAX (3.5 GHz) systems, respectively. The proposed filter is advantageous in terms of size miniaturization up to 0.013 × 0.012 (is guide wavelength) and in terms of good control over the passbands. The simulated and measured results are both in good agreement.

Design of tri-band bandpass filter using uniform impedance resonators loaded with different impedance stubs

ABSTRACT This paper presents a design of a compact tri-band bandpass filter simply using a pair of the uniform impedance resonator loaded with an open-circuited stub. By introducing the variable impedance of the open-circuited stub, the proposed design has additional design parameter of the impedance ratio to adjust the resonant modes of the used resonator, so as to more easily achieve the different frequency bands. The resonant frequencies of the oddmode and evenmode of the used resonator are analyzed first in this study. A tri-band filter example is designed at the center frequencies of 1.9, 3.58, and 5.75 GHz, which can be used in 4 G system, 5 G communication system, and wireless local area network, respectively. The designed filter is simulated, fabricated, and then measured. The measurement shows that the insertion loss |S21|, return loss |S11|, and 3 dB fractional bandwidth for the three passbands are less than 0.25/0.37/0.9 dB, larger than 30/15/15 dB, and 17.5/12.2/8.9%, respectively. Moreover, by using the interdigital coupling of the used resonator, four transmission zeros are generated near the passband edges at 1.47, 2.56, 4.05, and 6.48 GHz, realizing high selectivity and high isolation. The measurement is consistent with the simulation, confirming the design concept.

A tri-band filter with controllable frequency and transmission zeros using dual-stubs loaded resonators

ABSTRACT This paper presents a high band selectivity tri-band bandpass filter with controllable frequency and transmission zeros. This tri-band bandpass filter is mainly constructed by using two pairs of dual-stubs loaded resonators in a symmetrical structure. Three passbands could be independently controlled to achieve the desired frequency and have transmission zeros created close to the passbands to improve the band selectivity. Three resonant models are provided in the proposed filter to obtain different passband frequencies. The passbands of the designed filter are designed at 1.82, 2.44, and 3.49 GHz, which can be used for global system for mobile communications (GSM), wireless local area network (WLAN), and Worldwide Interoperability for Microwave Access (WiMAX), respectively. The simulated results and measured results of the designed tri-band bandpass filter have a good agreement.

Tri‐band superconducting filter based on crossed resonators with controllable coupling and feeding structures

In this article, a compact tri-band high-temperature superconducting filter with controllable coupling and feeding structures based on crossed resonator which consists of two-end-open UIR with a short stub and an open stub shunted at the resonator center is proposed. Due to the symmetrical structure of the proposed resonator, the odd- and even-mode analysis method can be used to derive their resonance frequencies. Then, a capacitance-loaded microstrip line is added between the resonators to flexibly control the bandwidths. Furthermore, one tapped line and one coupled line are utilized to realize the acquired external coupling under prior specifications. For demonstration, a tri-band filter operating at 1.6 GHz (Global Positioning System), 2.45 GHz (Wireless Local Area Networks), and 3.5 GHz (WiMAX) is designed, analyzed using the electromagnetic simulator, and fabricated using an YBa2Cu3Oy thin film on an MgO substrate. The measured results agree well with the simulated ones.

A miniaturized tri-band bandpass microstrip filter using multiple resonators with sharp skirts

AbstractIn this paper, a miniaturized tri-band bandpass microstrip filter using stub loaded rectangular ring resonator (SLRRR)，shorted stub loaded stepped impedance resonators (SSLSIR), and stepped impedance resonators (SIR) with sharp skirts is presented. Two SSLSIRs are embedded paralleled inside SLRRR to generate a quasi-elliptic response at second and third passband. The odd-even fundamental resonant mode and first high-order resonant mode of the SIRs are exploited to generate tri-band response. Three bandwidths can be controlled independently due to different signal paths. Extra transmission zeros are introduced by the configuration of 0° feed structure. Sharp skirts are achieved at the upper edge of each passband by λg/4 lines which are loaded at the I/O ports. An example of the proposed tri-band filter operating at 2.76 GHz/5.7 GHz/7.63 GHz for TDD-LTE/WLAN/VSAT applications is implemented and fabricated. The simulation and measurement show a good agreement.

Reconfigurable Cavity Bandpass Filters Using Fluid Dielectric

A novel method for the development of a reconfigurable cavity bandpass filter using fluid dielectric is proposed. Dielectric material can produce an effective permittivity ε <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">eff</sub> of the resonant mode when it is loaded into the cavity. Thus, a tube filled with fluid dielectric, e.g., distilled water, can achieve controlled and reversible ε <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">eff</sub> by adjusting the amount of water in the tube. The same manner of resonant frequency can be achieved as the resonant frequency is related to ε <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">eff</sub> , and then frequency tuning is realized. The fluid property can realize easier and faster tuning mechanism than conventional solid dielectric. As ε <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">eff</sub> is affected by the loaded dielectric parallel to the electric field, a triple-mode resonator with resonant modes TE <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">101</sub> , TE <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">011</sub> , and TM <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">110</sub> , which have orthogonal electric fields, is investigated to realize tri-band reconfiguration. The ε <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">eff</sub> , as well as the resonant frequencies, corresponding to each mode can be individually controlled by adjusting their related water posts. Then, reconfigurable single-band and tri-band bandpass filters are designed. A reconfigurable tri-band cavity filter using a triple-mode cavity resonator and fluid dielectric with individual and continuous frequency tuning is reported for the first time. Finally, the reconfigurable tri-band filter is fabricated and measured to validate the concept.

A New Family of Multiband Waveguide Filters Based on a Folded Topology

In this article, we describe a new family of multiband waveguide filters based on a folded topology. The folded topology allows to use the filters of different orders and the introduction of transmission zeros. The design of the multiband filter is based on the aggressive space mapping (ASM) technique and is able to take into account manufacturing details, such as round corners and tuning elements. The filter structure is validated by designing, manufacturing, and measuring a triband filter. The agreement between simulations and measurements is shown to be excellent, thereby fully validating both the filter topology and the design process.

Miniaturized SIW Cavity Tri-Band Filter Design

This letter presents a novel tri-band filter design using an ultraminiaturized substrate-integrated waveguide (SIW) cavity operated at evanescent mode. Two miniaturized SIW cavities in a face-to-face form are vertically stacked to build the proposed tri-band filter. The top and bottom metal layers form the cavity’s broadside walls, and the middle layer possesses three identical patches which are formed by evenly trisecting a circular patch. These patches are shorted to the cavity’s bottom wall through one, two, or four via-holes. The patches together with the host cavity exhibit three frequency-distinct resonances that create the filter’s triple passbands. The resonance frequencies are independently controlled, and six passband-edge transmission zeros are created for good selectivity. The filter size is only $0.22\,\,\lambda _{d} \times 0.22\,\,\lambda _{d}$ , and the measured in-band minimum insertion losses are 2.31, 2.25, and 3.01 dB for the first, second, and third bands, respectively. It is believed that the proposed tri-band filter has obtained the best circuit area efficiency in the SIW tri-band filter category.

Microstrip dual mode multi-bandpass filters based on tree fractal slotted resonator for wireless communication

Dual mode microstrip multi-bandpass filter is proposed with tree fractal slot on a square patch resonator. The tree fractal slotted resonators are generated from conventional square patch using an iterative tree fractal generator method. A single square patch is used for realizing both dual and tri-bandpass filters exploiting the dominant, higher order and its corresponding degenerate resonant modes by the tree fractal iteration on the diagonal unequal slots on the square patch.The resonant peaks, transmission zeros and bandwidth of the pass bands can be tuned by varying the length and width of the fractal slot. By optimizing various parameters dual mode dual and tri-band pass filters are simulated, fabricated and measured. The proposed filter finds application in wireless communication devices and falls in the bands of GSM, WLAN, Bluetooth, Zigbee, WiMax and WiFi.

New Dual-/Tri-Band Bandpass Filters and Diplexer With Large Frequency Ratio

To satisfy the simultaneous requirements of future wireless communication systems on short-range high-speed data transmission and long-distance basic coverage, the coexistence of the millimeter-wave and microwave technologies becomes the inexorable trend. However, it is difficult for the existing dual-/ tri-band filter configurations to achieve a frequency ratio larger than three. In this paper, the new use of aperture coupling mechanism is proposed to combine two bandpass elements for dual-/tri-band operation with large frequency ratio but comparable sizes. For this purpose, a microwave BPF with wide stopband up to millimeter-waveband is implemented based on the complementary frequency response characteristics of the stepped-impedance resonator bandpass filter and low-pass filter. The millimeter-wave BPF can be simply designed using the air-filled substrate-integrated waveguide circular cavities, which exhibit the natural low-frequency cutoff characteristics. Based on the proposed design concept and two BPF elements, the dual-/ tri-band bandpass filters with frequency ratio up to 12.59 and 12.7 were designed, fabricated, and measured. Owing to the independence of the two elements, a diplexer with large frequency ratio can be simply implemented based on the previous dual-band filter. All the simulation and measured results are in good agreement, validating the proposed structures.

Design Method for Multiband Filters With Compact Configuration in Substrate Integrated Waveguide

In this paper, a design method for multiband bandpass filters with compact configuration in substrate integrated waveguide is proposed by combining the single-band/dual-band synthesis method and the multimode resonator theory. The designed filters could generate multiple filtering passbands without expanding their entire physical size. In addition, all the passbands could be efficiently synthesized and designed with any prescribed order in theory, which has been rarely reported in multiband filters, especially in the design of quad-band filters. As examples, one third-order quad-band filter and one third-order tri-band filter are designed, fabricated, and measured. Good agreement is attained between their simulated and measured S-parameters, and both the two sets of results have verified the feasibility of the proposed design method and attractive performances of the designed multiband filters.