High-selectivity Bandpass Filter Research Articles

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

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.

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 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.

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.

Closed-loop ring resonator topology for bandpass filter applications

&lt;p class="Pa41"&gt;This paper presents a single mode pseudo-elliptic bandpass resonator based on closed-loop ring topology. The resonator is built from six quarter wavelength transmission lines to form a square closed-loop ring structure. This structure creates transmission zeros at the lower and upper sidebands so that high selectivity bandpass filter response is achieved. The advantage of this topology is that the design is less complex since no perturbation is needed on the ring lines for creation of transmission zeros. Higher-order filters can be constructed by introducing quarter-wavelength coupled-lines, coupled at both input and output of the closed-loop ring resonator. For proof of concept, the filters are designed at 10 GHz up to 3&lt;sup&gt;rd&lt;/sup&gt; order, simulated using full-wave electromagnetic simulator on microstrip substrate, &lt;em&gt;FR-4&lt;/em&gt; with characteristics given as &lt;em&gt;Ԑr &lt;/em&gt;= 4.70, &lt;em&gt;h &lt;/em&gt;= 1.499 mm and &lt;em&gt;tan δ &lt;/em&gt;= 0.012. The filters are simulated and responses are found to be agreeable with the proposed idea.&lt;/p&gt;

28-GHz High-Selectivity Bandpass Filters With Dual-Behavior Resonators Using GaAs Technology

In this article, the design and implementation of two 28-GHz millimeter-wave on-chip high selectivity bandpass filters with coupled dual-behavior resonators are proposed. The proposed bandpass filters consist of coupled dual-behavior resonators with open/shorted stubs. Two and three out-of-band transmission zeros can be realized for the two bandpass filters. Two on-chip millimeter-wave bandpass filters are designed and fabricated for verification. The measurement results show that the insertion losses are both less than 2.2 dB at the center frequency. The sizes of the designed filters are $2.556\,\,\text {mm}\times 1.23$ mm and $3.155\,\,\text {mm}\times 1.47$ mm, respectively, including the pad.

A high selective tri-band bandpass filter with switchable passband states

AbstractA new class of switchable bandpass filter using PIN diodes is presented in this paper. The design aims at achieving a multistate switchable bandpass filtering characteristics between the passbands centered at 2.4, 3.5, and 5.2 GHz. The proposed filter is designed by assembling two λg/2 open-ended and four short-ended λg/4 uniform impedance resonators. The open-ended resonator generates a fixed passband at 3.5 GHz, whereas the short-ended resonators loaded with PIN diodes are independently controlling the ON and OFF characteristics of the passband centered at 2.4 and 5.2 GHz. The transmission zeros around each passband are produced without employing any additional circuit. The filter sample is fabricated and tested for experimental verification. A good agreement has been observed between EM-simulated and measured results. The designed filter has a compact size of 0.20 λg × 0.15 λg at 2.4 GHz.

QUASI-ELLIPTIC MICROSTRIP FILTER

Currently, modern telecommunication and radio-electronic systems widely use wireless information transmission technologies over the radio channel. Therefore, an urgent task is to ensure electromagnetic compatibility of a large number of simultaneously operating radio facilities using high-selective bandpass filters. This paper presents circuit solutions for microstrip filters using incomplete inclusion of loads and communication elements. This construction makes it possible to obtain additional attenuation poles in the near zone of the stop band, which frequencies are determined by the load inclusion factor. It is proposed to include a capacitor in the middle of the microstrip communication line to improve the selective properties. This made it possible to increase the order of the filter at constant dimensions. The frequency characteristics of a high-selective quasi-elliptic filter are given.

High‐selectivity bandpass filter using six pairs of quarter‐wavelength coupled lines

A novel high-selectivity bandpass filter (BPF) with multiple transmission poles (TPs) and transmission zeros (TZs) using six pairs of quarter-wavelength coupled lines has been presented. By employing two pairs of side-coupled lines and four pairs of open/shorted coupled lines, high roll-off skirt characteristic, and good stopband rejection can be achieved with five TPs and six TZs. Theoretical analysis is explained and simulated results are illustrated for this high-performance filter. Finally, a BPF example with a centre frequency of 1.9 GHz and a 3 dB fractional bandwidth of 9% is designed, fabricated, and measured. It is shown that the measured lower and upper stopband rejections are better than 38 and 16 dB, respectively. Good agreement between the simulations and measurements validates the design method.

High selective microstrip bandpass filter and diplexer with common magnetic coupling

A new common magnetic coupling structure has been proposed. A high selective microstrip bandpass filter and a diplexer with the common magnetic coupling and 0° feeding have been developed. A pair of transmission zeros can be generated by 0° feeding, while an additional transmission zero can be produced by the common magnetic coupling structure and can be controlled/adjusted by the electric/magnetic couplings. The proposed diplexer has been fabricated and measured, and the measurement shows a channel insertion loss of <1.3 dB, and an isolation of not <34 dB. The measured results agree with the prediction.

Low phase noise oscillator stabilised by high quality factor AFSIW resonators

A novel X-band low phase noise oscillator is proposed by taking advantage of the enhanced quality factor of air-filled substrate integrated waveguide (AFSIW) resonators. A pair of AFSIW resonators is embedded in a feedback loop, which forms a high-selectivity bandpass filter, to greatly reduce the phase noise of a heterojunction FET oscillator. A prototype is designed, fabricated and measured. At an output signal of 9.85 GHz, the phase noise is −146.8 dBc/Hz and the figure of merit is −210.6 dBc/Hz at 1 MHz offset frequency. An improvement of about 10 dB in phase noise performance is obtained compared with published substrate integrated waveguide resonator-based oscillators.

Compact, high selectivity and wideband bandpass filter with multiple transmission zeros

This paper presents the design of a compact, high selectivity and wideband bandpass filter based on signal interference technique. The proposed filter consists of open coupled line and stepped impedance modified Π-type (SMΠ) transmission line with short circuited stubs in transmission path 1 and path 2, respectively. Due to the superposition of signals of the two transmission paths, a fourth-order wideband bandpass filter with six transmission zeros can be obtained from 0 to 2f0 (f0 is the operating frequency). A bandpass filter prototype centring at 0.9 GHz, with 3 dB fractional bandwidth of 50% is designed, fabricated and tested. Good agreement is found between the simulated and experimental results.

Compact UWB bandpass filter with dual-notch bands using asymmetric tri-section stepped impedance resonator

In this study, a novel high selective UWB band pass filter (BPF) with dual notch band is presented. UWB BPF is realized using stub-loaded multiple-mode resonator (MMR). The MMR is constructed by loading a quintuple mode open stub at the centre in an asymmetric tri-section stepped impedance resonator (ATSSIR). Five modes, including two odd modes and three even modes, placed within UWB band. Two transmission zeros generated by the fractal stub improve the passband selectivity greatly. Two half wavelength long fractal Hilbert resonators are embedded near I/O line to achieve notch bands at 5.1 and 5.9 GHz. Aperture-backed interdigital coupled-lines are implemented to improve the coupling. The proposed prototype is fabricated and tested. The measured insertion loss is observed to be within 1.5 dB over the passband. By virtue of two transmission zeros (TZs), on either side of the passband, at 5.1 and 5.9 GHz, respectively, the passband selectivity is achieved with measured roll-off factor at around 34 dB/octave. The out-of-band rejection of the filter is greater than 22 dB up to 18 GHz. The simulated results are in good agreement with the measured responses.

Coupled CRLH transmission lines for compact and high selective bandpass filters

A compact size and high selective bandpass filter is presented in this paper. The filter is designed to serve at 3.5 GHz with two transmission zeros at 3.35 GHz and 3.85 GHz. The filter is designed as two gap capacitor coupled to two coupled composite right–left handed transmission lines. The coupled lines were designed to demonstrate a zeroth order phase at 3.5 GHz. Also, the transmission zeros were achieved as a consequence of the electrical/magnetic couplings between the two coupled transmission lines. The employed cell, filter design equations are emphasized. The filter S-parameters were extracted based on the circuit model, full wave simulation, and experimental measurements. A good agreement between modeled, simulated, and measured results is achieved. The measured center frequency of the bandpass filter is 3.55 GHz and 100 MHz bandwidth which is suitable for WiMAX applications. Also, the filter has low measured insertion loss which does not exceed 1 dB within passband. Finally, the filter has advantages of compactness (size is 20 3 18 mm2) which is only 50% compared to conventional non-selective one-stage coupled line filter.