Compact Wideband Bandpass Filter Research Articles

Compact wideband filter with wide stopband using transition-free spoof surface plasmon polaritons

In this article, a newly spoof surface plasmon polaritons (SSPPs) is proposed and used to design a compact wideband bandpass filter (BPF). Different from the traditional SSPP unit cell with one-shaped structure, the unit cell of the proposed SSPPs consists of an H-shaped slotline and a bilateral T-shaped slotline. Benefiting from the hybrid structure, no transition portion is needed for impedance matching in the design of the microwave filter, which highly reduces the horizontal size of the SSPPs-based filter. The transition structure of microstrip to slotline provides a capacitance with a highpass frequency response, which enables the realization of a passband by cooperating with the natural lowpass property of SSPPs. Also, the upper and lower cutoff frequencies of the proposed filter can be adjusted independently by the key parameters. Besides, a wide upper stopband can be obtained by properly designing the SSPPs unit cell and the microstrip to slotline structure. Finally, a well-designed BPF operated at 1.3–6.2 GHz and its upper stopband rejection reaching 20 GHz is fabricated and measured. The test results are in good agreement with the simulations, which verifies the feasibility of the proposed structure and design method.

Compact Wideband Groove Gap Waveguide Bandpass Filters Manufactured with 3D Printing and CNC Milling Techniques.

This paper presents for the first time a compact wideband bandpass filter in groove gap waveguide (GGW) technology. The structure is obtained by including metallic pins along the central part of the GGW bottom plate according to an n-order Chebyshev stepped impedance synthesis method. The bandpass response is achieved by combining the high-pass characteristic of the GGW and the low-pass behavior of the metallic pins, which act as impedance inverters. This simple structure together with the rigorous design technique allows for a reduction in the manufacturing complexity for the realization of high-performance filters. These capabilities are verified by designing a fifth-order GGW Chebyshev bandpass filter with a bandwidth BW = 3.7 GHz and return loss RL = 20 dB in the frequency range of the WR-75 standard, and by implementing it using computer numerical control (CNC) machining and three-dimensional (3D) printing techniques. Three prototypes have been manufactured: one using a computer numerical control (CNC) milling machine and two others by means of a stereolithography-based 3D printer and a photopolymer resin. One of the two resin-based prototypes has been metallized from a silver vacuum thermal evaporation deposition technique, while for the other a spray coating system has been used. The three prototypes have shown a good agreement between the measured and simulated S-parameters, with insertion losses better than IL = 1.2 dB. Reduced size and high-performance frequency responses with respect to other GGW bandpass filters were obtained. These wideband GGW filter prototypes could have a great potential for future emerging satellite communications systems.

A wideband bandpass filter with wide upper stopband attenuation containing multiple resonators

AbstractA compact wideband bandpass filter with a wide passband and very‐wide out‐of‐band suppression is presented. The filter is constructed from a central rectangular‐ring resonator with two open stubs placed around it symmetrically. In addition, tri‐section stepped‐impedance resonators are symmetrically distributed on both sides of the two open stubs, and two symmetrical funnel‐shaped resonators are included to enhance out‐of‐band suppression. The out‐of‐band performance of filter is very good, with a suppression level greater than 20 dB up to 25.72 GHz. The center frequency of the filter is 5.84 GHz, with a fractional bandwidth of 115.8%. Good agreement between the simulations and measurements validates the design principle.

Compact wideband bandpass filter based on coupled line stub with high selectivity

Two bandpass filters with the cross shaped resonator and parallel coupled lines are proposed. It has two fixed transmission zeros (TZ) which are located at 0 and 2pi. With the assistance of two types of parallel coupled line, two bandpass filters have other two TZs. Two TZs only depend on the odd and even mode impedance of open parallel coupled line stubs or short parallel coupled line stubs. By adjusting the odd- and even-mode impedance values, two TZs can be adjusted and the frequency selectivity of the bandpass filters are improved. Two bandpass filters are fabricated and measured. The experimental results are basically consistent with the simulation results, which verifies the filter design method.

Compact high‐selectivity high‐temperature superconducting wideband bandpass filter using triple‐mode stub‐loaded loop resonator

A triangle triple-mode stub-loaded loop resonator (SLLR) is proposed in this letter and used for wideband filter design. Also, this SLLR can produce multiple transmission zeros for high-selectivity bandpass filter (BPF) design without adding extra circuit unit. To verify the unique characteristics of the proposed SLLR, a compact wideband BPF is designed and fabricated using high-temperature superconducting YBCO thin films on a MgO substrate. Furthermore, a novel meander structure is introduced to realize compact size and strong input/output coupling design. The measured results show that the 3-dB fractional bandwidth is of 50.6% (2.55-4.28 GHz), and the selectivity factor of the passband is 0.87 with a maximum insertion loss of 0.07 dB, indicating good agreement with the theoretical expectation.

Compact Wideband BPF With Wide Stopband Using Substrate Integrated Defected Ground Structure

In this letter, a compact wideband bandpass filter (BPF) with a wide stopband is proposed based on the substrate integrated defected ground structure (SIDGS) and folded stepped-impedance resonator (FSIR). Such a SIDGS resonator can not only allocate a specific resonance with compact size but also introduce the different harmonic positions compared with a traditional microstrip line resonator. Meanwhile, due to the discrepant harmonic positions of proposed SIDGS and FSIR, a wide stopband response can be achieved using a compact stacked-coupled scheme. To verify the mechanism, a miniaturized wideband BPF operating at 1.69 GHz (i.e., f <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> ) is implemented and fabricated. A measured wide stopband up to 11.8 f <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> with a 20-dB rejection level is achieved.

Application of a Stub-Loaded Square Ring Resonator for Wideband Bandpass Filter Design

In this paper, a stub-loaded square ring resonator (SLSRR) is analyzed and applied to design a very simple and compact wideband bandpass filter structure. Resonant modes dependent on the structure parameters of the SLSRR are analyzed first, and then the first two modes are used to achieve a required passband. The input and output terminals are supplied with high impedance and strong coupling to provide sufficient coupling energy. Two wideband filter examples are designed, manufactured, and measured using the SLSRRs. The first filter is a wideband filter with a wide upper stopband, and the second filter is a dual wideband filter with a notched stopband between two passbands. The two filter examples are designed, fabricated, and measured to verify the design concept and present the advantages of easy design and a simple and compact structure.

Design of compact wideband bandpass filter with broad stopband using hybrid HMSIW and open‐circuit tri‐section stepped impedance resonators

AbstractA compact wideband bandpass filter (BPF) with broad stopband using hybrid half‐mode substrate integrated waveguide (HMSIW) resonator and open‐circuit tri‐section SIRs (OTSIRs) is proposed. A BPF with 3 transmission poles (TPs) and 3 transmission zeros is obtained by cascading the HMSIW resonator and OTSIRs using J and K inverters. A demonstrated wideband BPF with the stopband up to 4.4 times the designed center frequency for a 20 dB rejection level is designed, fabricated and measured. The measured results verify the predicted attractive features.

Design and analysis of a super compact wide-band bandpass filter based on metamaterial resonators

In this paper, a novel compact wide-band bandpass filter (BPF) with a wide frequency range is presented. This filter consisting of a multi-mode resonator (MMR) and four metamaterial unit-cells benefits from a very compact size. Unit-cells based on a complementary spiral resonator (CSR) including a metallic via, improve both upper and lower stopband rejection and compensate the insertion loss (I.L) within the passband altogether. This wide-band filter presents a 3-dB bandwidth of 7.7 GHz, ranging from 3 GHz to 10.7 GHz and the Insertion loss is less than 0.7 dB over the passband. The measured results are in good agreement with both the full-wave electromagnetic simulation and the proposed circuit model results. The dimension of the fabricated filter is 0.128 λ × 0.1 λ (i.e., 5.6 × 4.4 mm2). This filter is considerably compact compared to the other wide-band bandpass filters with the same substrate.

A &lt;inline-formula&gt; &lt;tex-math notation="LaTeX"&gt;$C$ &lt;/tex-math&gt; &lt;/inline-formula&gt;-Band Compact Wideband Bandpass Filter With High Selectivity and Improved Return Loss

In this letter, a C-band compact wideband bandpass filter (BPF) with high selectivity and improved return loss (RL) is proposed. Two pairs of short-circuited stubs are employed on a transmission-line model to generate three transmission poles and two transmission zeros (TZs), where the odd- and even-mode analysis is used to analyze the resonant frequencies of the BPF. By applying the transversal signal-interference technique, two additional TZs can be generated in the upper and lower stopbands, respectively. The measured results show that the 3-dB fractional bandwidth is 62.8% at the center frequency of 5 GHz. The RL and the insertion loss within the passband are better than 22 and 0.6 dB, respectively. Moreover, the roll-off rate is up to 100 dB/GHz.

A Novel Wideband Bandpass Filter using H-shaped DGS

&lt;p&gt;This paper presents a novel compact wide-band bandpass filter (BPF) having good selectivity. It is designed using a dual-plane structure which consists of a parallel-coupled microstrip line on the upper surface and three H-shape defected ground structures (DGS) on the ground plane. By adding three H-shape DGS units on the ground plane, then properly adjusting their dimensions and position, the bandwidth and selectivity of the designed filter can be significantly improved. A compact prototype of wide-band microstrip bandpass filter has been designed, fabricated and measured for the wireless systems applications. The filter exhibits a center frequency at 4.8 GHz, passband from 2.8 GHz to 6.8 GHz with best insertion loss and return loss of 0.8 dB and 40 dB, respectively. The measured results agrees well with the theoretical expectations validating the proposed design.&lt;/p&gt;

Compact wideband bandpass filter with equiripple response in both magnitude and delay

Aiming at the reduction of the in-band delay variation, a wideband bandpass filter with equiripple response in both magnitude and group delay is presented and studied. The filter is composed of one section of end-connected coupled line and two short-circuited shunt transmission line stubs, all of them are uniform and equal in electrical length. Design formulas are given to calculate the characteristic impedances of the lines to meet the filtering specifications. By changing the coupling strength of the coupled line section, the group delay can be controlled to be equiripple in band, while the remaining equiripple response in magnitude unchanged. For verification, a filter sample is fabricated and measured. In experiment, it exhibits a delay variation of 0.11 ns and minimal insertion loss of 0.2 dB within its passband (|S11| < −14 dB) from 0.48 to 1.46 GHz, which validates the theoretical predictions.

Compact spiral band pass filter with low group delay

AbstractA complementary coupled spiral transmission line with center via is proposed to design band pass filter with compact and simple profile, low group delay, and low insertion loss. A compact wideband band pass filter is designed and fabricated for demonstration which has 26% bandwidth, 0.3 dB insertion loss, and compact size as 0.41 × 0.23 λg with very low group delay, 0.28 ns. These good specifications prove the capability of the proposed approach to design of band pass filter compared with the literatures.

Compact wideband bandpass filter using quad mode resonator

This paper presents a compact wideband bandpass filter for TETRA band applications. The proposed filter design is based on a quad mode resonator designed using small rectangular loop loaded with four Stepped Impedance Stubs (SISs) and a short circuit stub. The four modes of the resonator help in generating a wide passband. The use of SISs makes the filter compact. In addition to four transmission poles, the resonator inherently generates a transmission zero above the higher end of passband. Two transmission zeros are generated by the input/output coupling which helps in increasing the selectivity and also for achieving wide stopband. This filter provides a 3 dB fractional bandwidth of 30.33% and maximum insertion loss of 1.3 dB at the center frequency 0.36 GHz with a compact size of 0.125 λg × 0.085 λg (4.1 × 2.78 cm2).

Compact quasi-elliptic wideband bandpass filter using mixed coupling lumped-element dual-resonance resonators

ABSTRACTThis paper presents a quasi-elliptic wideband bandpass filter (QEWB-BPF) constituting a pair of lumped-element dual-resonance resonators (LE-DRRs) with mixed electric and magnetic coupling (MEMC). Two resonant modes of proposed LE-DRR can be controlled separately. Due to virtual ground in LE-DRR, the cancelling effect of two paths of MEMC, and inductive perturbation, four TZs are realized around the passband. As an example, a QEWB-BPF with measured central frequency (CF) at 1.82 GHz and 3 dB fractional bandwidth (FBW) of 24.4% is designed and fabricated. The measured minimal insertion loss (IL) is 0.95 dB, and a 30 dB rejection upper stopband from 2.11 to 4.79 GHz is also obtained. The fabricated QEWB-BPF has a compact circuit size of 0.133λg × 0.215λg.

Compact wideband bandpass filter based on double-T-shaped stub loaded resonator and loading technique for zero-voltage point

In this article, a double-T-shaped stub centrally loaded uniform impedance resonator (UIR) is introduced and its resonant characteristics are well clarified, which provided a simple approach for triple-mode wideband bandpass filter (BPF) design. The double-T-shaped stub consists of a T-shaped stub at the center of UIR and two shunt uniform-impedance stubs at the T-shaped stub. Furthermore, loading technique for zero-voltage point is employed to guide design procedure from UIR to the proposed resonator. The resonant frequencies of the first three modes for the resonator can be free to adjust by the length of the UIR and the two kinds of stub. Finally, a compact wideband BPF is designed, fabricated, and measured. The measured results are in good agreement with the full-wave simulation results. The realized wideband filter exhibits a 3 dB fractional bandwidth of 69.1% with good in-band filtering performance, wide stopband, and sharp out-of-band rejection skirt.

Compact Wideband Bandpass Filter for TETRA Band Applications

This letter proposes a compact wideband bandpass filter using Short Circuited line Loaded Triangular Stub Resonator (SCLTR). The SCLTR makes the filter compact and simultaneously shifts the harmonics to higher frequencies. Six transmission poles generated by six resonators provide wide passband bandwidth and three Transmission Zeros (TZs) escalate the selectivity of the bandpass filter response. Two transmission zeros are created by virtue of Simultaneous Electric and Magnetic Coupling (SEMC) and one because of source to load cross coupling. The designed and fabricated filter is very compact with a size of $0.127 \lambda _{g} \times 0.133 \lambda _{g}$ , providing −3 dB fractional bandwidth of 20.5% and wide stopband bandwidth from 0.42 to 1.55 GHz. The experimental results are in compliance with the simulated results, which show that the filter is viable for practical use.

Triple mode spiral wideband bandpass filter using symmetric dual‐line coupling

A compact wideband bandpass filter at the centre frequency of 5.77 GHz with 78% fractional bandwidth is presented. An especial coupling structure along with a novel triple mode spiral resonator designed based on modal analysis is used to provide a flat wide passband with excellent skirt characteristics. To verify the efficiency of the filter, a prototype is fabricated, tested and compared with some of the most recent works.

Miniaturised highly selective bandpass filter with very wide stopband using meander coupled lines

A compact wideband bandpass filter with a very wide stopband for terrestrial radio (TETRA) band applications is proposed. The proposed filter employs two types of resonators: one is tri-section half wavelength stepped impedance resonator (SIR) and the other is stub-loaded shorted ring resonator. The proposed filter has adopted SIRs and meandering technique in achieving miniaturised size. Spur-lines and tapped feeding techniques are infused in the filter to suppress harmonics so as to achieve wide stopband. Cross-coupling is introduced in the filter for acquiring good selectivity. This highly selective filter has a miniaturised size of 0.09 × 0.12λg (28 × 36.8 mm2) with a wide stopband up to 8.75f0 (f0 is the centre frequency of filter) with 25 dB harmonics suppression level.

Design of High-Temperature Superconducting Wideband Bandpass Filter With Narrow-Band Notch Resonators for Radio Telescope Application

This paper presents a compact wideband bandpass filter (BPF) integrating with two narrow-band notch resonators, for preventing the wideband communication system from interfering. The wideband filter adopts an asymmetric stub-loaded multimode resonator to obtain a bandwidth of 66.7%, with excellent passband fluctuation. In addition, two multiloop resonators are used to implement a 0.56% narrow-band. To illustrate its usefulness, a high-temperature superconducting wideband BPF with built-in narrow-band notch resonators is designed. It is fabricated on 20.8 mm × 16.15 mm YBCO films deposited on a 0.5-mm-thick MgO substrate with a relative permittivity ϵr of 9.78. The proposed wideband filter works at L-band, i.e., 1–2 GHz, and the return loss is greater than 19 dB. The notch-band resonator centered at 1.805 GHz provides more than 25 dB maximum attenuation for avoiding interferences from the global system for mobile communication. Finally, the circuit is measured, and the results agree well with the simulations.