High-selectivity Bandpass Research Articles

A Modified High-Selective Frequency Selective Surface Designed by Multilevel Green’s Function Interpolation Method

A compact high-selective band-pass frequency selective surface (FSS) with the unit cell less than λ/7 is presented. For the simulation of the structure, the multilevel Green’s function interpolation method (MLGFIM) using Floquet theory is adopted to accelerate the calculation of the complex unit cell. The radial basis function (RBF)-QR method is used in the interpolation, which makes the shape parameter in the RBF function not required to be retested for different periodicity. In this design, with an aperture coupling structure between the top and bottom layers patterned by triangular patches and meander lines, the FSS has two transmission zeros (TZs) on both sides of the pass-band and achieves a steep roll-off rate of 192 dB/GHz. Consequently, the FSS has high selectivity and out-of-band suppression, besides profiting from the low profile and symmetric geometry, this FSS exhibits good angular and polarization stabilities. The prototype of the proposed FSS is fabricated and good performance is obtained.

Low insertion loss open-loop resonator–based microstrip diplexer with high selective for wireless applications

This paper presents a low-insertion-loss open-loop resonator (OLR)-based microstrip diplexer with high-selective for wireless applications. We used two series capacitive gaps in the microstrip transmission line, loaded with rectangular-shaped half-wavelength OLRs, to create a high-selectivity bandpass filter (BPF). The planned BPFs are linked through a T-junction combiner, precisely tuned to align with both filters and the antenna port in order to produce the proposed diplexer. The system is implemented on a rogers TMM4 substrate with a loss tangent of 0.002, a dielectric constant of 4.7, and a thickness of 1.52 mm. The suggested diplexer has dimensions of (90×70) mm². It achieves a modest frequency space ratio of R=0.1646 in both transmit and receive modes by having two resonance frequencies of ft=2.191 GHz and fr=2.584 GHz, respectively. The simulated structure displays good insertion losses of approximately 1.2 dB and 1.79 dB for the two channels, respectively, at fractional bandwidths of 1.24% at 2.191 GHz and 0.636% at 2.584 GHz. The simulated isolation values for 2.191 GHz and 2.584 GHz are 53.3 dB and 66.5 dB, respectively.

A New Class of High-Selectivity Bandpass Filters With Constant Bandwidth and 5:1 Bandwidth Tuning Ratio

A New Class of High-Selectivity Bandpass Filters With Constant Bandwidth and 5:1 Bandwidth Tuning Ratio

Miniaturized High-Selectivity Bandpass Filter with Wide Stopband Based on Through-Glass-Via IPD Technology

Miniaturized High-Selectivity Bandpass Filter with Wide Stopband Based on Through-Glass-Via IPD Technology

A Miniaturized Low Pass Filter with Extended Stopband and High Passband Selectivity

A Miniaturized Low Pass Filter with Extended Stopband and High Passband Selectivity

Design of Ka-Band SISL High Selectivity Bandpass Filter With Controllable Zeros

In this letter, high selectivity bandpass filters (BPFs) using folded stepped-impedance resonators (SIRs) are proposed based on substrate-integrated suspended line (SISL) platform. It is easy to change the position of transmission zeros (TZs) by controlling the strength of electric/magnetic coupling, separately. Also, the structure is compact with double-layer wiring and via holes. To validate the proposed method, two SIR electromagnetic coupling BPFs are implemented on FR-4 substrates. The rectangular coefficients (BW <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$_{{20\, \text{dB}}}$</tex-math> </inline-formula> /BW <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$_{3\, \text{dB}}$</tex-math> </inline-formula> ) of the second-order and the fourth-order filters are only 2 and 1.3, respectively. In addition, air cavity, metal shielding wall, and substrate excavation methods also dramatically reduce the loss in substrates.

High selectivity and compact tunable bandpass filter using YIG material

This paper presents a novel highly selectivity tunable filter with transmission zero. Yttrium iron garnet/gadolinium gallium garnet layer structures are added to the filter structure as bandstop units to achieve transmission zero. CST Studio Suite simulates and optimizes the filter structural parameters. Transmission zero and filter passband are tuned simultaneously. Skirt selectivity can be significantly increased by placing the transmission zero at the lower side of the filter passband. The parasitic response can be suppressed by about 20 dBc when the transmission zero is located on the upper side of the filter passband. With the magnetic field shifted from 3250 to 5005 Oe, the filter tuning range is 11–16 GHz with an insertion loss of about 3.5 dB. The addition of transmission zero enhances filter selectivity and provides more flexibility in suppressing interfering signals that vary in frequency or parasitic responses at specific frequencies. This method presents an approach for designing wide tuning range filters with transmission zeros.

A novel MS to SL vialess vertical transition for high‐performance substrate integrated filter

In this paper, a novel broadband microstrip-to-stripline (MS-to-SL) vialess vertical transition structure is presented and demonstrated. Firstly, the vialess vertical transition is introduced under two kinds of transmission lines and signal transmission between them through the slotline in the middle ground layer is realized. Then, the proposed vialess vertical transition structure is applied to build up a six-pole broadband high selective bandpass substrate integrated filter with an equal ripple level. After that, for fascinating the design, its design method is analyzed, and design flow is given. Finally, the proposed filter is fabricated and measured. All the simulated and measured results match well with each other.

Frequency-Selective Rasorber Based on High-Q Minkowski Fractal-Shaped Resonator for Realizing a Low Radar Cross-Section Radiating System

In this article, a novel design of compact frequency-selective rasorber exhibiting absorption–transmission–absorption characteristics and having high passband selectivity has been proposed. A square-loop resonator with mounted lossy elements serves as the elemental broadband absorber from 4 to 12 GHz. The transmission frequency at 8.4 GHz is realized by printing a Minkowski fractal-shaped resonator with a high-Q factor on the resistive layer, which provides a transmission pole at the frequency corresponding to the passband of a double-cross-slot-shaped bandpass layer. The functioning of the proposed frequency-selective rasorbers (FSR) is explained by a corresponding equivalent circuit model. The proposed FSR exhibits higher selectivity at the passband, thus making it a suitable candidate for shielding the narrowband radiating system. Measurements performed on the fabricated prototype of a 17 × 17 unit cell array provides experimental validation. Further, a low radar cross-section antenna is realized by integrating a patch antenna with the proposed FSR, which achieves an average out-of-band monostatic radar cross-section (RCS) reduction of 11.92 and 5.04 dB in the lower (4–7.5 GHz) and upper (9.2–10.8 GHz) absorption bands, respectively, while maintaining the other antenna parameters. Furthermore, the bistatic total RCS reduction of 77% and 60% are achieved in the lower and upper frequency bands, respectively.

High-Selectivity Bandpass Filter with Controllable Attenuation Based on Graphene Nanoplates.

A high-selectivity band pass filter with controllable attenuation based on graphene nanoplates is proposed in this paper. Graphene with controllable resistance has a good uniform attenuation effect to electric field intensity. The filter utilizes quarter wavelength stepped impedance resonators and mixed electromagnetic coupling to have compact circuits and high performance. The graphene nanoplates are loaded on the microstrip resonator to reduce the electric field intensity, which results in a flat attenuation in the passband. In addition, the filter has two transmission zeros, which lead to a strong selectivity. Finally, a high-selectivity bandpass filter with controllable attenuation is formed. By changing the bias voltage of graphene, a controllable attenuation of 1.64–11.13 dB can be achieved in the working passband centered at 1.36 GHz. In order to validate the concept, the prototype is fabricated and measured. The measurement results are in good agreement with the simulation results. The proposed high-selectivity bandpass filter with controllable attenuation based on graphene nanoplates has widely potential in reconfigurable wireless communication systems and radar systems due to its high integration and versatility.

Miniaturized high selectivity bandpass filter based on hairpin two-conductor stripline resonators

A resonator based bandpass filter miniature design formed by two U-shaped metal strip conductors located at different sides of a suspended dielectric substrate is developed. In each conductor one end is grounded to the screen and the other is free. A resonators are connected in pairs with overlapping sections of strip conductors, it leads not only to the reduction in the dimensions of the device, but also to the increase in its selectivity due to transmission zeros near the passband. The prospects of the proposed design are proved by the measured characteristics of the 6th-order filter made on a substrate with the relative permittivity er = 80 (TBNS-ceramic) and the thickness of 0.5 mm. The filter passband central frequency f0 = 150 MHz, and the fractional bandwidth Δf/f0 = 25 %, while the size of the device is only 42 × 20 × 8.25 мм3 (0.02λ0 × 0.01λ0 × 0.005λ0, where λ0 is the wavelength at the center frequency f0). The filter has high slope steepness and a wide stopband, which extends up to the frequency of 3f0 at the level of –50 dB.

High-Selectivity Bandpass Filter Based on Two Merged Ring Resonators

High-Selectivity Bandpass Filter Based on Two Merged Ring Resonators

High selective wideband bandpass filter with mixed-coupled resonators

Novel electric and magnetic mixed-coupled resonators and a general design method for high selective wideband bandpass filters are presented in this paper. Transmission zeros are introduced in the filters for high selectivity, and the location of the transmission zeros can be adjusted without passband characters changing. To verify the design method, an eighth-order mixed-coupled filter is designed, fabricated and measured; the measured results show higher rejection compared with the conventional interdigital filters. Good agreements are obtained between simulated and measured results.

A high-selectivity double-mode SIW bandpass filter utilizing the modified parallel coupled microstrip lines

ABSTRACT In this article, a high-selectivity double-mode substrate integration waveguide bandpass filter utilizing modified parallel coupled microstrip lines (MPCML) is presented. The designed method is analyzed in detail. Six metal vias are designed to perturb TE-101 mode and TE-103 mode. The resonant frequency of the perturbed TE-101 mode is shifted to high frequency, close to that of TE-102 mode, which caused the formation of passband. The resonant frequency of the perturbed TE-103 mode is shifted to high frequency, improving out-of-band performance. Simultaneously, the coplanar waveguide structure is used to adjust the external quality factor. Two rectangular slotlines are introduced to adjust center frequency and bandwidth slightly. Two rectangular stubs are designed for better source and load matching. Three transmission zeros (TZs) are obtained to improve the selectivity. The designed MPCML promotes the generation of TZs. Another TZ is obtained by the coupling between TE-102 mode and TE-103 mode. The designed filter operates at 14.4 GHz with bandwidth of 800 MHz. The measured return loss is better than 15 dB, and the minimum insertion loss is 1.60 dB. The measurement is agreed with the simulation.

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.

High selectivity and wideband bandpass filtering impedance transformer

An impedance transformer (IT) with wideband and high selectivity is presented in this paper. Three transmission poles were obtained within the passband and provides a wide passband response. Moreover, there are two transmission zeros (TZs) close to the passband that were achieved by a shunt parallel coupled line and provide high selectivity. For validation of proposed circuit, the ITs were designed at a center frequency (f0) of 3.5 GHz using an impedance-transforming ratio (r) of 5 and 10. For r = 5, |S21| and |S11| are 0.36 dB and 28 dB at f0, respectively. Within the passband, |S21| and |S11| are better than 0.65 dB and 18 dB, respectively. The TZs at 2.65 GHz (0.76f0) and 1.22f0, close to the passband, were measured with attenuation better than 37 dB. The out-of-band attenuations are higher than 20 dB from DC to 2.77 GHz of the lower stopband and from 4.16 GHz to 9.73 GHz of the higher stopband. For r = 10, |S21| = −1.4 dB and |S11| = −23 dB were measured at f0. An 18 dB return loss was obtained from 3.415 GHz to 3.694 GHz (FBW = 7.96%).

Diplexer-Integrated SPDT Switches With Multiple Operating Modes Using Common Fractal Stub-Loaded Resonator

This article presents a method to design new diplexer-integrated single-pole double-throw (SPDT) switches for composite time division duplexing (TDD) and frequency division duplexing (FDD) requirements. The common fractal stub-loaded resonator (F-SLR) is employed to provide four magnetic coupling paths to introduce the mixed electric and magnetic coupling (MEMC) for every channel. Together with the cross-couplings, the ON-state channel with high selectivity bandpass response can be achieved. As examples, a third-order diplexer-integrated SPDT switch and a fourth-order diplexer-integrated SPDT switch operating at 0.9/1.8 GHz are designed and fabricated. These two diplexer-integrated SPDT switches have three major operating modes, i.e., the 0.9-GHz bandpass filter (BPF)-integrated SPDT switch operating mode, the 1.8-GHz BPF-integrated SPDT switch operating mode, and the 0.9-/1.8-GHz diplexer-integrated SPDT switch operating mode. In the design, the loaded positions of p-i-n diodes on the uniform impedance resonators of 0.9-GHz channel are optimized to improve the OFF-state rejection bandwidth. Measured results also show that these two diplexer-integrated SPDT switches have low ON-state passband insertion loss, high port-to-port isolation, and compact circuit size.

Balanced Dual-Band Superconducting Filter Using Stepped-Impedance Resonators With High Band-to-Band Isolation and Wide Stopband

A balanced dual-band and wide-stopband high-temperature superconducting (HTS) bandpass filter (BPF) with deep stopband rejection is designed using modified stepped impedance resonators (SIRs) in this brief. The center frequencies of the two differential-mode (DM) passbands can be controlled by adjusting two electrical length ratios of the proposed SIR, while keeping the third spurious frequency far away for wide-stopband design. An inherent common-mode (CM) suppression can also be obtained due to the discriminating CM resonant frequencies different from the DM ones. Multiple transmission zeros (TZs) are achieved to realize high passband selectivity and enhanced DM stopband by multipath coupling and shunt stubs loaded on the I/O ports. The proposed balanced dual-band filter operating at 1.78/4.0 GHz is eventually fabricated using HTS YBCO thin films on a MgO substrate, which can significantly lower the insertion losses. The circuit was measured at the temperature of 77 K, which shows maximum insertion losses of 0.42/0.37 dB and a DM stopband of 5.0f <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1</sub> <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">d</sup> with 40-dB attenuation, respectively.

Design of High-Selective Printed-Ridge Gap Waveguide Filter Using Source–Load and Cross Couplings

In this letter, high-selective bandpass filters, in the printed ridge gap waveguide technology, are presented. The filters are designed to perform 4.68% fractional bandwidth at center frequency $f_{0}$ = 24.78 GHz. In the proposed filters, to obtain high selectivity, a cross-coupling between the nonadjacent resonators and also a coupling between the input and output ports to create an extra pair of transmission zeros in the transfer function of the filters are used. Finally, the filters are fabricated, and their scattering parameters are measured to verify the simulation results.

Filtering rat‐race couplers with impedance transforming characteristics based on terminated coupled line structures

In this study, a series of rat-race couplers with bandpass filtering responses and impedance transforming characteristics are presented based on novel coupled-line structures. Firstly, a novel filtering rat-race coupler core circuit is proposed by introducing coupled-line structures into conventional rat-race coupler. Then, a series of rat-race couplers with enhanced filtering responses and stopband rejections are constructed by employing various types of impedance transformers. The even- and odd-mode methods are adopted to explain the operating mechanisms. Finally, a filtering rat-race coupler prototype with a fractional bandwidth of 35.2% is designed and measured. The measured results show high passband selectivity, good out-of-band rejection and isolation performances, which is attractive for practical application.