Dual-band Bandpass Filter Research Articles

Dual-Band Substrate Integrated Waveguide Filters Based on Multi-Mode Resonator Overlapping Mode Control

In this paper, a multi-mode resonator (MMR) overlapping mode control technique is proposed to realize dual-band substrate-integrated waveguide (SIW) bandpass filters (BPFs). A pair of via perturbations and two kinds of slotlines are introduced to control the overlapping modes. Five resonant modes TM110 (a pair of degenerate modes), TM210 (a pair of degenerate modes) and TM020 are perturbed to realize the dual-band filters. The degenerate modes can be rearrange by the via perturbations, and the overlapping modes can be adjusted by the slotlines. Thus, two kinds of dual-band filters can be realized in a single resonant cavity. Then a two-cavity dual-band filter is proposed to realize better out-band suppression and return loss performance. The proposed two-cavity dual-band BPF is synthesized, designed, fabricated, and measured, realizing the 3-dB fractional bandwidth (FBW) of 6.1% and 7.7% at Q-band and V-band, respectively.

Coherent dual-frequency signal generation in an optoelectronic oscillator.

Coherent dual-frequency microwave signal generation using an optoelectronic oscillator (OEO) is presented and demonstrated. In the proposed OEO, a dual-band bandpass filter (DB-BPF) is utilized to select two oscillation modes. An external signal is injected into the OEO loop with its frequency equaling the frequency interval of the two oscillation modes. Owing to the modulation nonlinearity of the Mach-Zehnder modulator, the two oscillation frequencies interact with the injection frequency. When the phase and gain conditions are satisfied within the loop, injection locking between the two oscillation signals will be established, and their phases will be synchronized. The effect of gain competition in the OEO loop, which leads to single-frequency oscillation, is suppressed. An experiment is carried out, and two frequencies, of 16.083 GHz and 9.998 GHz, are generated at the same time. The phase noise values are -140.1 and -141.0 dBc/Hz @ 10 kHz, respectively. The coherence between the generated signals and sidemode suppression performance are evaluated.

Design of a dual-band filter with high selectivity and wide stopband

ABSTRACT This paper proposes a design of dual-band bandpass filter with a high selectivity and a wide stopband, by using two ring type hairpin resonators. The equivalent circuit of the used resonator is analyzed through the analysis of odd and even modes. The designed filter can achieve dual passbands at 2.4 GHz and 3.65 GHz for wireless local area network (WLAN) and 5 G communication systems, with transmission zeros at 2.9 GHz and 5.1 GHz, realizing high selectivity. With a wideband bandstop filter on the input port, a wide stopband from 4.6 GHz to 17.3 GHz is realized.

A low profile cylindrical cavity dual-band bandpass filter with short-circuited metal pillars

This paper presents a low profile cylindrical cavity quadruple-mode dual-band bandpass filter. Five short-circuited metal pillars are loaded in a cylindrical cavity to change the electric field distributions of the original resonant modes. The changed TM010 mode and TM110+ mode form the first passband, and the changed TM110- mode and TM210+ mode form the second passband. The center frequencies of the two passbands are 3.05 GHz and 3.59 GHz, with relative bandwidths of 1.72% and 2.5%, respectively. The first passband can be adjusted independently, and the stopband range of the proposed bandpass filter is relatively wide. By using the degenerate modes, two transmission zeros are introduced to improve the selectivity of the proposed bandpass filter. The use of TMmn0 mode effectively reduces the height of the cavity. The fabricated cavity bandpass filter is measured, and the measured results are accordance with the simulated ones.

Compact dual-band narrowband bandpass filter with small frequency ratio

Abstract A compact but very simple dual-band bandpass filter (BPF) based on just five pairs of coupled lines is designed in this paper. It can be examined using the even- and odd-mode method because of its symmetry structure. Six transmissions zeros (TZs) can be obtained and calculated by using input impedance analysis. For demonstration, a dual-band narrowband BPF example with center frequencies at 0.94 and 1.12 GHz is fabricated and measured. The 3-dB fractional bandwidths of two passbands are 2% (0.93–0.95 GHz) and 3.4% (1.1–1.14 GHz), whose frequency ratio of upper-band to lower-band is very small. The measurement results agree with the simulation results, confirming the design process.

Realization of a novel dual-band bandpass filter with coupled series gaps and stepped impedance complementary split ring resonators

In this article, a bandpass filter (BPF) is proposed by etching stepped impedance complementary split ring resonators (SICSRRs) pairs in parallel with series gaps on the top side of a coplanar waveguide (CPW). The Nicolson-Ross-Weir (NRW) method is used to analyze the left-handed (LH) behavior of the filter. The effects of the resonators parameters on the left-handed BPF are studied. The parameters and number of the resonators are adjusted properly to obtain the desired filter characteristics. Split ring resonators (SRRs) are magnetically coupled to the BPF to realize a novel left-handed dual-band bandpass filter. Besides, The dual-band filter is described by means of the lumped-element equivalent circuit model. Also, the quasi-static analysis is used to obtain the equations for the resonant frequencies of the resonators. The efficient electrical size of the dual-band filter is 0.51λg × 0.42λg where λg represents the guided wavelength at the first passband center frequency. The prototype of the compact dual-band BPF is fabricated and measured. The measured results reveal low insertion loss and high return loss at the passbands along with wide upper stopband attenuation. The measured result is in a good agreement with the corresponding simulation result.

Design of a Compact Quad-Channel Microstrip Diplexer for L and S Band Applications

In this paper, two novel dual-band bandpass filters (BPFs) and a compact quad-channel diplexer working at 1.7/3.3 GHz and 1.9/3.6 GHz are proposed. In the proposed diplexer design, triangular loop resonators and rectangular loop resonators are used together to reduce the circuit size and improve diplexer performances. Insertion loss (IL) and return loss (RL) of the proposed diplexer are better than 0.8 dB and 21 dB, respectively, at these four operating frequencies. Output ports isolation parameter is better than 30 dB. With the achieved specifications, the proposed diplexer can be used in L and S band applications.

A compact diamond-shaped dual-band bandpass filter with multiple transmission zeros

In this paper, a compact diamond-shaped dual-band bandpass filter with seven transmission zeros in the stopband and two poles in each passband is designed, analyzed, and implemented. The proposed filter consists of coupled lines and stepped impedance open stubs. Theoretical analysis based on lossless transmission line theory is carried out to verify the transmission zero frequencies. A filter prototype with center frequencies of 1.17 GHz and 2.85 GHz is fabricated to exhibit the feasibility of the design. The prototype is printed on a 0.79 mm Rogers RT Duroid 5880 with a dielectric constant of (ϵr = 2.2) and occupies an area of 0.29λg×0.17λg, where λg is the guided wavelength at the first center frequency. The experimental results show a 3-dB fractional bandwidth of 13.65% and 3.5% at low and high center frequencies, respectively. The simulated and experimented frequency responses are consistent with each other.

A Frequency Independently Tunable Dual-Band Bandpass Filter With Large Frequency Ratio and Ultra-Wide Stopband

To meet the demand for simultaneously supporting the microwave and millimeter-wave technologies in emerging industrial wireless systems, research on dual-band components with a large frequency ratio has been conducted recently. However, it is challenging to implement independent frequency tunability on bandpass filters with both compactness and high performance. This article presents a dual-band bandpass filter with a large frequency ratio, independently tunable frequencies, and an ultrawide stopband. This is achieved by artfully incorporating a harmonic-controllable varactor-loaded microstrip BPF and a wide-stopband dielectric-loaded cavity BPF with the bandgap-embedded aperture coupling mechanism. Extremely compact size can be achieved without additional filtering elements. Two pairs of transmission zeros can be allocated beside two passbands for good selectivity due to the separate path and cross-coupling in the resonators. For validation, a prototype is designed, fabricated and measured. It can provide two independent tunable frequency ranges (3.22–3.52 GHz and 25–27.06 GHz), exhibiting a large frequency ratio up to 8.3. Mid-band suppression better than 20 dB and ultra-wide stopband up to 32.5 GHz with 20 dB suppression level are achieved. Low insertion loss and good selectivity can also be observed.

Design of dual-band BPFs with high selectivity

Abstract In this article, two dual-band microstrip bandpass filters (BPFs) with high selectivity and independently controllable passbands are designed based on three parallel-coupled lines (TPCLs). The first BPF proposed in this paper is achieved by employing a pair of folded F-type resonators (FFRs) and conventional TPCL structure. By adjusting the above parameters of each FFR, the center frequencies of the two passbands can be controlled easily. In the meantime, TPCL can enhance the coupling between the source and load, and introduce multiple transmission zeros (TZs), which can conduce to a higher selectivity. To obtain superior selectivity, the second BPF is designed based on a novel TPCL. The novel TPCL is based on the traditional one, which further enhances selectivity since transmission paths are doubled. In order to achieve miniaturization and enhance coupling, FFRs are folded. In addition, four transmission zeros (TZs) are generated to improve the selectivity of the two passbands. The measured results of the fabricated BPFs centered at 2.45/3.5 GHz agree well with the simulated ones, which validates the proposed design method.

A Switchable Bandpass Filter for Broadband, Dual-Band and Tri-Band Operations

In this brief, a novel microstrip switchable bandpass filter (BPF) is presented. By switching RF p-i-n diodes on/off, the proposed topology could provide three different filtering states: broadband bandpass filter (BBPF), dual-band bandpass filter (DBPF) and tri-band bandpass filter (TBPF). For each state, the relationship between bandwidths and return losses are newly analyzed by proposed algorithm, then the design charts can be easily summarized. In order to improve selectivity and stopband rejection, two cascaded proposed topologies are also considered and discussed briefly. For demonstration, two switchable circuits are designed, fabricated and measured in the experiment. Simulated and measured results are matched very well.

A low-loss dual-band bandpass filter using open-loop stepped-impedance resonators and spur-lines for sub-6 GHz 5G mobile communications

<abstract><p>This article presents the design of a low-loss microstrip dual-band bandpass filter with improved inter-band isolation and selectivity for 5G sub-6 GHz mobile communications. The proposed filter utilizes the two first resonance mode frequencies provided by the stepped-impedance resonator to generate its two passbands at 3.6 GHz and 3.5 GHz, and spur-lines located before the input/output ports to improve the isolation and selectivity between passbands. The filter is designed using an RT/Duroid 5870 substrate with a relative permittivity of 2.33 and a thickness of 0.79 mm, manufactured and tested to validate the proposed design. The experimental results show that the filter operates at 3.61 GHz and 5.51 GHz with a 3-dB fractional bandwidth of 12.74% and 16.7%, respectively. Insertion losses at the two passbands center frequencies are 0.6 dB and 0.9 dB. In addition, the proposed filter has the advantage of covering the licensed and unlicensed 5G bands and provides a simple structure without using vias or DGS structures.</p></abstract>

Development of highly selective compact high-temperature superconducting quad-band bandpass filter using interdigital feeding structure for radio astronomy

Astronomers at the Mizusawa Very Long Baseline Interferometry Observatory of the National Astronomical Observatory of Japan are promoting the development of broadband receivers in the ultra-high frequency (UHF) band. The presence of extensive radio frequency interferences (RFI) in the UHF band hinders continuous broadband radio observations in this band. A promising technical solution to this problem is to use a superconducting multi-band bandpass filter as it enables the bundling of several RFI-free bands. We have developed a high-temperature superconducting compact quad-band bandpass filter (QB-BPF) at 0.7, 1.4, 1.6, and 2.1 GHz with low loss and steep cutoff characteristics for broadband receivers. That consists of two six-pole dual-band bandpass filters. We have devised an interdigital feeding structure with a high degree of freedom that enables the external quality factor to be designed individually for each band. A compact QB-BPF was fabricated using double-sided YBa2Cu3Oy thin films on a 36.4 mm × 42.0 mm (0.22λ g × 0.25λ g) Al2O3 substrate. The measurement results agreed well with the simulated ones, indicating that the QB-BPF overcomes the problem of extensive RFI in the UHF band.

Design of miniaturized single and dual-band bandpass filters using diamond-shaped coupled line resonator for next-generation wireless systems

AbstractThis paper presents a multi-mode resonator (MMR) for next-generation wireless systems that achieves single and dual-band bandpass filter (BPF) responses using a split-ring dual-path structure. The proposed BPF design is realized by employing two pairs of parallel couple lines and two symmetrical step-impedance open-circuited stubs (SIOCS). SIOCS are used to improve selectivity and increase the number of transmission zeros/poles. The proposed single-band BPF exhibits an ultra-wideband (UWB) response having a center frequency of 7.5 GHz, a minimum insertion loss of less than 0.48 dB, and a maximum return loss of 25.35 dB. The proposed UWB BPF has a stopband suppression of 39.34 dB up to 18 GHz and a 3 dB fractional bandwidth of 48.23%. Moreover, a dual-band BPF has been accomplished by utilizing the same architecture while slightly changing the MMR structure and adding more coupling. The center frequency (bandwidth) of the dual broadband BPF is 7.40 GHz (2.40 GHz) and 14.15 GHz (1.7 GHz), respectively. The measured minimum insertion loss is less than 0.23 dB and a return loss of less than 16.8 dB with 3 dB FBWs of 32.4 and 12.1%. Finally, two prototypes are fabricated to validate the proposed characteristics. The BPF's simulated and measured results are in good agreement.

Dual-Band Bandpass Filter With Independently Tunable Attenuation Characteristics Using Graphene Nanoplates

A dual-band bandpass filter (BPF) with independently tunable attenuation based on graphene nanoplates is proposed. By utilizing dual coupling paths, the 1.2- and 2-GHz frequency bands realized by the multimode resonant structure can be completely controlled. The graphene nanoplates loaded close to the resonator are responsible for independently tunable attenuation. Meanwhile, the influence of the loaded graphene nanoplates on the original dual-band BPF is analyzed in detail. New branches are added to achieve a stronger coupling of source, load, and passband. Due to good separation of the dual coupling paths and the controllable attenuation of graphene to the signal, a novel dual-band BPF with independently tunable attenuation is obtained. The measured results show that the dual-band BPF achieves independently tunable attenuation of about −4 dB in two passbands with a low reflection of less than −10 dB.

Miniaturized Dual-Band Filter Using Dual-Mode Dielectric Waveguide Resonator

This letter presents a novel miniaturized dual-band bandpass filter (BPF) using a dual-mode dielectric waveguide resonator (DWR). The DWR is a cylinder dielectric block with the surface being silver-coated. The two modes are TM010 and TM011 modes, which are used to construct the two passbands. The frequency of them can be adjusted by changing the radius and the height of the cylinder DWR and the frequency space can be controlled independently. The BPF is composed of three cylindrical cavities, which are arranged in an equilateral triangle. The three cavities construct a cascaded trisection (CT) unit, which creates a transmission zero (TZ) at the upper side of the two passbands. Finally, a dual-band BPF using DWR is simulated, manufactured, and measured to exhibit the feasibility of the proposed design. Their results are in good agreement, showing good performance, such as miniaturization, good return loss (RL), and upper stopband selectivity.

Multilayer packaging dual‐band balanced bandpass filter based on dual‐mode substrate integrated waveguide cavities with split‐type topology

A new design method of the dual-band balanced bandpass filter (BPF) using multilayer packaging dual-mode substrate integrated waveguide (SIW) cavities is proposed. Split-type coupling topology based on dual-mode resonators is developed for the design. Firstly, a single-band balanced filter with perturbed metal vias is designed. The TE201 mode and the TE202 mode perturbed by the metal vias can form a passband. Secondly, an additional metal vias perturbed SIW cavity with the same dual-mode is placed in the lower layer for the bandstop function. A dual-band balanced BPF with split-type coupling topology is successfully realised. Compared with the traditional cascaded single-mode form, the proposed dual-mode split-type design has more compact size and can be more easily extended to multi-passbands. To verify the proposed method, a dual-band balanced filter operating at 13.3 and 14.2 GHz is designed, fabricated and measured. The designed dual-band balanced filter has good filtering performance including differential mode passband transmission and common mode rejection. Measured results show good agreements with simulated ones.

Balanced Dual-Band HTS BPF With Controllable Frequency Ratio and Transmission Zeros Using Mixed Cross-Coupling

In this brief, a fourth-order balanced dual-band high temperature superconducting (HTS) bandpass filter (BPF) is presented based on modified stub-loaded resonators (SLRs). Firstly, the differential mode (DM) and common mode (CM) resonant characteristics of the modified SLRs are analyzed. Under DM operation, two types of mixed cross-coupling topologies are constructed by placing the spiral modified SLRs and their DM equivalent structures in an appropriate way. Then, a dual-band response with controllable center frequencies, bandwidths, and transmission zeros (TZs) is achieved. Under CM operation, an effective CM suppression circuit is proposed for improving the in-band CM suppression level. Finally, for verification, a fourth-order balanced dual-band HTS BPF with center frequencies of 3.494/4.797 GHz and insertion loss of 0.26/0.21 dB is designed and fabricated on MgO substrate with double-sided YBCO thin films. The measured results agree well with the simulated ones, and the BPF shows the attractive features of low insertion loss and good out-of-band rejection.

Dual-Path Coupled-Line Dual-Band Bandpass Filter with Synthesis

A dual-band bandpass filter topology based on the use of dual-path coupled lines is presented. It exhibits a 2nd order dual-band response with three transmission zeros that gives a wide separation of the passbands, and from the rejection bands. A simplified circuit diagram of the topology is proposed along with a global synthesis that can be used to control the transmission zeros, the center frequency, and the bandwidth of the passbands, by varying the length and impedance of the filter elements. The filter topology was implemented in the design of two dual-band microstrip filters on TRF45 substrate to validate the idea. Measurement results show that the center transmission zero is at 2.55 GHz, and the two passbands are centered at 1.81 GHz and 3.02 GHz. It provides isolation of up to 31 dB between the passbands. Keywords—Dual-mode, dual-band, microstrip, bandpass filters.

Planar single-/dual-band bandpass filters based on new perturbed multi-mode SIW circular cavity

In this paper, new single- and dual-band bandpass filters are implemented based on the perturbed multi-mode substrate integrated waveguide (SIW) circular cavity. For the single-band filter, the TM mode, TM mode, and TM mode are simultaneously utilized to realize the triple-mode resonance response, of which both the bandwidth and central frequency can be flexibly adjusted by allocating the perturbation position properly. Meanwhile, for the dual-band operation, the TM mode, TM mode, and TM mode are arranged to realize the lower passband, whereas the TM and TM modes are excited to generate the upper passband. The working principle of the filters' coupling topology is explained in detail. For concept verification, both the triple-mode single-band and multi-mode dual-band filters are designed, manufactured and measured, with the measurement results are separately in good agreement with the corresponding simulations.