Upper-stopband Performance Research Articles

A Wide Stopband Dual-notched Bands UWB Filter Based on A Novel Composite Right/left Handed Transmission Line

Background:: As one of the key components of ultra-wideband (UWB) system, UWB filter has important research significance. However, the current UWB filter still has the problem of a narrow stopband and cannot suppress the interference signals in the passband Objective:: In this paper, a novel UWB bandpass filter is proposed, which has wide stopband characteristics and good out-of-band rejection performance and implements a notch function for the WLAN band and the X satellite communication band in the passband to improve the antiinterference performance. Method:: The filter adopts a novel composite right/left handed transmission line (CRLH-TL) structure to realize the passband characteristics with low insertion loss (< 0.8dB). The anticoupled line structures generate two transmission zeros (TZs) in the upper stopband, which improves the upper stopband performance of the filter. The short circuit step impedance resonators (SIRs) and the asymmetric coupling structure generate a notched band in the passband respectively. Results:: The simulated and measured results show that the 3dB passband range is 3.4-11.0 GHz, the out-of-band rejection is more than 20 dB in the stopband range of 12.8-28 GHz, and the dualnotched bands are located at 5.86 GHz and 8.0 GHz respectively. The measured results are basically consistent with the simulated results. Conclusion:: Compared with the existing filters, the proposed filter has outstanding advantages and has a wide range of application prospects in the field of indoor UWB positioning system.

Wideband and Highly Selective BandPass Filter Using Substrate Integrated Waveguide Technology for Ku-Band Applications

A new compact design of bandpass filter using substrate integrated waveguide (SIW) is proposed and analyzed in this paper. It offers good in-band return loss, low insertion loss, wide passband, and high stopband attenuation. The filtering response is achieved by loading a couple of inverted tuning fork-shaped defected ground structures (DGS) on the bottom of the SIW cavity. DGS is utilized to enhance the upper stopband performance. To validate, the filter is fabricated using Rogers RT/Duroid 5880 with 0.508 mm thickness and tested. The filter has a center frequency of 15.44 GHz with 19% fractional bandwidth (FBW). The return loss is more than 20 dB and the insertion loss is about 1.2 dB. It finds its application in Ku band satellite communication.

Study on a Multi-Point Differential Feeding Strategy for Design of Filtering Patch Antennas With Stopband Enhancement

In this article, a novel multi-point differential feeding technique is introduced and applied in the design of filtering patch antennas with a wide upper stopband. Different from the traditional differential feeding structure, the proposed method has four physical feeding points on the patch. Our analysis results indicate that the proposed feeding approach can not only effectively excite the desired fundamental TM <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$_{\mathbf {01}}$ </tex-math></inline-formula> mode but also flexibly allow for the elimination of high-order modes by selecting suitable feeding positions. Just relying on this feeding method, unwanted harmonic radiations can be totally removed up to <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$4{f} _{\mathbf {0}}$ </tex-math></inline-formula> without any additional elements. For demonstration, a prototype of a stacked patch antenna with filtering response has been then designed. With resorting to the proposed feeding scheme, both driven and stacked patches are indeed able to support good excitation of TM <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$_{\mathbf {01}}$ </tex-math></inline-formula> mode with other harmonics to be suppressed, leading to a wide upper stopband performance. In addition, several radiation nulls are generated in the stopband to improve the filtering selectivity. Measured results agree well with the simulated ones, indicating that the designed differential antenna possesses enhanced fractional impedance bandwidths, high in-band gains, low cross polarization, as well as intrinsic wide stopband rejection, further verifying the proposed feeding concept.

Ultra-compact half-mode substrate integrated waveguide bandpass filters with IRCSRR metamaterial on reinforced hydrocarbon polymer ceramic composites

In this work, metamaterial-enabled ultra-compact evanescent-mode half-mode substrate integrated waveguide (HMSIW) bandpass filters are developed by loading inner-rotary complementary split-ring resonator (IRCSRR) on reinforced hydrocarbon polymer ceramic composites substrate. In the proposed IRCSRR, inner-rotary slots are etched inside the conventional complementary split-ring resonator (CSRR) metamaterials to enhance the product of equivalent inductance and capacitance without occupying extra circuit area. Therefore, the proposed HMSIW-IRCSRR filters can obtain more size reduction with the same operation frequency as compared with the conventional CSRR-based ones. Similar as the conventional CSRR case, the evanescent-mode transmission below the dominant cutoff frequency of HMSIW can be produced by the negative permittivity effect of IRCSRR, and a transmission zero (TZ) at the upper stopband can be simultaneously generated by the mutual coupling between HMSIW and IRCSRR. Then, to improve the upper stopband performance, source-load coupling topology is utilized in the two-pole filters, which can produce multiple extra TZs. Meanwhile, multiple microstrip L/T-shaped open stubs are employed to introduce hybrid low-pass effect to further extend the upper stopband much wider. To demonstrate the availability of the aforementioned concepts, a series of HSMIW-IRCSRR filters are experimentally designed, fabricated and verified. Measured results shows that both ultra-compact sizes and excellent frequency-selecting performance are achieved simultaneously, as well as good agreement with simulations, all of which illustrating quite good promises for the practical radio frequency and microwave applications.

A sixth‐order SIW bandpass filter based on combining single‐ and dual‐mode cavities with high selectivity at Ka‐band

In this paper, a novel substrate integrated waveguide quasi-elliptic bandpass filter is proposed by combining single- and dual-mode cavities. Two single-mode cavities with TE101 mode are directly coupled to the dual-mode resonance cavity which employs a pair of disturbing metallic via-holes to make the resonant points of TE101 and TE102 mode in one passband. Based on the conventional box-like topology, two additional single cavities are used to achieve wider bandwidth and simplify the design difficulty. In addition to two transmission zeros (TZs) realized by the cross-coupling technology, nonreasoning node will generate an additional TZ at a higher frequency to improve the upper stopband performance. Finally, a sixth-order filter, having the passband frequency of 24.25–27.5 GHz for 5G application, with three TZs, is simulated, fabricated and measured to demonstrate and verify the proposed structure. The test results show the insertion loss is 1.7 and 3 dB bandwidth is 3.37 GHz. The three TZs improve out of band rejection of the filter.

Bandpass Filter With Ultra-Wide Upper Stopband on GaAs IPD Technology

In this brief, a novel bandpass filter (BPF) with ultra-wide upper stopband performance is proposed and implemented on gallium arsenide (GaAs) integrated passive device (IPD) technology. Firstly, the proposed BPF is designed by introducing a <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\boldsymbol{\pi }$ </tex-math></inline-formula> -section to achieve an ultra-wide upper stopband. Following that, the working principle of achieving this ultra-wideband upper stopband performance is further investigated. Finally, to demonstrate the claimed performances, this BPF with a size of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$1.63 {\mathrm {\times }}0.62$ </tex-math></inline-formula> mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> has been fabricated on GaAs IPD technology and measured by on-wafer probing. The measured BPF with a 3-dB fractional bandwidth (FBW) of 95.3% (1.7-4.8 GHz), exhibits the expected performances, especially the superior upper stopband suppression level better than 20 dB until 110 GHz (34.6 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${f} _{0}$ </tex-math></inline-formula> ). The simulated and measured results of the BPF are in reasonably good agreement, thus firmly validating the claimed superior performances of the BPF in terms of good frequency selectivity and ultra-wide upper stopband.

Miniaturized tri-notched wideband bandpass filter with ultrawide upper stopband suppression

Stepped impedance resonator (SIR) and its derivative resonators are widely used in the design of microwave filters. However, many spurious modes will be introduced into the stopband, resulting in lower upper stopband suppression and performance degradation. Based on the principle of slit line, a method to enhance the upper stopband suppression is proposed and verified by a miniaturized tri-notched wideband bandpass filter based on stub loaded ring resonator (SLRR) and shorted-stub loaded SIR (SSLSIR). The wideband is formed by coupling SLRR and interdigital lines, which has a rectangular DGS on the back of the substrate. Three notched bands with controllable positions in the passband can be produced by inserting two different SSLSIRs inside and outside the SLRR. Four slit lines are loaded on the low impedance stub of SSLSIR to adjust the high-order modes close to the transmission zeros (TZs). The operating frequency of the filter is 2.2–7.6 GHz, and the three notched bands are located at 2.97 GHz, 5.75 GHz and 6.46 GHz, respectively. The measurement results show that the − 20 dB enhanced upper stopband of the filter can reach 32 GHz, which proves that the filter has the characteristic of ultrawide upper stopband suppression while keeping the miniaturization.

Compact dual‐polarized filtering antenna with enhanced bandwidth for 5G sub‐6 GHz applications

A broadband dual-polarized filtering antenna with a compact size and high skirt selectivity for fifth-generation (5G) sub-6 GHz applications is proposed in this paper. The antenna is composed of two feeding networks and four shorted patches, which is based on a slot-aperture excitation scheme. By employing the novel defected ground LC resonator structures (DGLCRSs) and two different types of open-ended structures, the proposed dual-polarized antenna realizes satisfactory filtering performance as well as an improved operating bandwidth simultaneously. During which, four radiation nulls are generated at the both band edges and can be individually controlled. To further enhance the upper stopband performance, four pairs of meander-shaped slots are inserted on the patches symmetrically, which introduces another controllable radiation null. The working mechanism for achieving the filtering responses is provided. A fabricated prototype and experimental results demonstrate that an impedance bandwidth of 42.9% (3.3–5.1 GHz) is first obtained in a low-profile dual-polarization structure, covering the entire 5G N77/N78/N79 bands. The measured gain is about 8.1 dBi within the passband, while the stopband suppression is better than 16 dB up to 1.85 fc. These merits make the proposed antenna quite potential for the 5G new radio communication systems.

Highly‐tunable and wide stopband microstrip bandpass filters

This paper presents the design of a highly-tunable single-ended and balanced filter with improved upper stopband performance. The proposed filters are designed using a spurline and a U-shaped stepped impedance resonator (SIR) with a varactor diode connected to the open-circuited end. A spurline is introduced in both designs to achieve wide stopband performance by suppressing the higher-order modes. The proposed filters have high tunable ranges (single-ended: 2.35-3.99 GHz; balanced: 2.39-4 GHz), low insertion losses (IL) (single-ended: 0.07-0.2 dB; balanced: 0.21 to 1.1 dB) and wide upper stopband performance (single-ended: 3.79f1 with a rejection level higher than 20 dB; balanced: 3.79f1 with a rejection level higher than 20 dB). Performance of both filters are experimentally validated by comparing the experimental results with the simulated ones. Both filters can cover most of the fifth-generation (5G) wireless communication bands with different biasing voltages (capacitance). When both filters are compared with state-of-the-art filters, the proposed filters are found to achieve high tunable ranges with low IL and wide upper stopband performance.

Design of sextuple-mode triple-ring HTS UWB filter using two-round interpolation* *Project supported by the National Natural Science Foundation of China (Grant No. 61471094).

A single-stage ring resonator capable of introducing six modes within the ultra-wideband (UWB) passband is presented. The sextuple-mode resonator consists of three rings and three sets of stepped-impedance open stubs. Based on this sextuple-mode resonator, a UWB filter fed by the interdigital-coupling line (ICL) is designed. And we propose a two-round interpolation method to obtain the filter’s initial dimensions. The designed filter is fabricated on a double-sided YBCO/MgO/YBCO high-temperature superconducting (HTS) thin film for demonstration. The experimental results show that this UWB filter produces eight resonances in the passband eventually, which effectively improves the in-band reflection and the band-edge steepness. Moreover, the upper stopband performance is enhanced due to the transmission zeros (TZs) generated by the stepped-impedance open stubs and the ICL structure. The measured good performance verifies the practicability of the two-round interpolation approach, which can also be extended to other odd–even-mode filter designs.

UWB bandpass filter with compact size and wide upper stopband

AbstractA novel ultra‐wideband (UWB) bandpass filter (BPF) with a very compact size and improved out‐of‐band performance is proposed in this letter. The main circuit structure is a composite right‐/left‐handed transmission line unit cell, which has UWB bandpass characteristic as well as compact size. Moreover, two anticoupled line structures added at both ends of the unit cell can produce a new resonant mode and three transmission zeros, so the passband response and upper stopband performance can be improved. The proposed filter is implemented and measured, which shows its 3 dB passband ranges from 3.3 to 10.9 GHz with a fractional bandwidth of 110.9%. Its insertion loss is about 0.6 dB at the centre frequency, while the return loss is better than 13 dB. In addition, the measured results also show the proposed filter has a wide stopband from 11.4 to 30 GHz, whose rejection level is greater than 18 dB. The size of the filter is only 7.4 × 6.4 mm, equal to 0.22 × 0.20 λg. Both the simulated and measured results are in good agreement.

Tunable SIW Bandpass Filters With Improved Upper Stopband Performance

This brief propose the design and measurement of tunable, highly selective and wide-stopband microwave filters using substrate integrated waveguide (SIW) technology. A two pole filter is designed using optimized cavity parameters. Two higher order (4-pole) filters are designed by connecting two cavities vertically and horizontally through coupling slots. In this way, four poles are achieved in two cavities, in which the proposed filter produces $2\times \text{N}$ poles in N cavities. A varactor diode is employed in both configurations to make the filters tunable. The proposed filters have wide upper stopband performance [20 dB up to $4.8f_{1}$ (Filter 1) and 20 dB up to $4.2f_{1}$ (Filter 2)], lower insertion losses [0.2-1.1 dB (Filter 1) and 0.2-1.5 dB (Filter 2)] and good tunability ranges [2.7–3.4 GHz (Filter 1) and 3.1–3.9 GHz (Filter 2)]. In order to validate the proposed design, a prototype is fabricated on RT/duroid 5870 substrate and measured. The simulated results accord closely with the measured results.

Realisation of compact quasi‐elliptic bandpass filters based on coupled eighth‐mode SIW cavities

A novel basic quasi-elliptic response bandpass filter in quadruplet based on coupled TE 101 -mode-based eighth-mode substrate integrated waveguide (EMSIW) cavities is proposed and analysed firstly. The negative cross coupling is achieved by the nature of coupled fringe electric-field components of the first and fourth cavities. Then, based on the proposed basic quadruplet structure, two methods using a step-impedance resonator and meandered feeding lines, respectively, are introduced and analysed to realise S-L coupling to improve the upper stopband performance further. Finally, two possible structures with quasi-inline and quasi-folded layouts, respectively, are proposed to realise sixth-order EMSIW filters. Five EMSIW filters are designed, fabricated, and measured to demonstrate and verify the proposed structures. The proposed filters have the advantages of compact size, good out-of-band rejection and realisation of higher-order filtering function. The size of the realised 4th-/6th-order filter is less than . The out-of-band rejection higher than 28 dB can reach 2.32 f 0 .

Compact multi‐order bandpass filter with high stopband rejection performance

This Letter presents a multi-order bandpass filter (BPF) based on unit cells, which are constructed by coupled lines and microstrip stubs. This BPF unit cell features ultra-wide upper stopband and excellent stopband rejection performance. The external quality factors and coupling coefficients of unit cells are analysed in detail for multi-order BPF design, where transmission lines are adopted as a coupling structure for easy post-fabrication tuning. Following filter coupling matrix theory, two- and three-pole Chebyshev-response BPFs are designed and measured, centred at 1.0 GHz with 3-dB fractional bandwidth of 10%. Experimental results demonstrate excellent out-of-band rejection performances. In two-pole BPF, the upper stopband can reach 4.8 GHz (4.8 f 0 ) with the rejection level of 37 dB. In three-pole BPF, within the stopband frequency of 3.4 GHz (3.4 f 0 ), the rejection level is better than 55 dB, while the upper stopband can be extended to 6.5 GHz (6.5 f 0 ) with the suppression level of above 26.8 dB.

Design of wideband comb shape substrate integrated waveguide multimode resonator bandpass filter with high selectivity and improved upper stopband performance

In this article, a wideband bandpass filter (BPF) is designed using the comb slotted substrate integrated waveguide (SIW) cavities. The comb-shaped slots engraved on the SIW cavity are used to constitute a novel multiple-mode resonator (MMR) that accomplishes a wide passband of operation. Further, a Jerusalem cross defected ground structure (DGS) is introduced to miniaturize it and enhance filter performance in the pass band and stop band. The filter is fabricated on RT/Duroid 5880 having dielectric constant 2.2 and tested to prove the validity of design. The filter achieves 3 dB fractional bandwidth of 48%, return loss above 14 dB and insertion loss of 1.1 dB in the passband. Also, the proposed filter has steep selectivity and wide upper stopband with 25 dB attenuation from 16.7 to 24 GHz.

High-Temperature Superconducting Multimode Ring Resonator Ultrawideband Bandpass Filter

This letter presents a new multimode ring resonator ultrawideband (UWB) bandpass filter by loading a microstrip line on the vertical symmetrical plane of a ring resonator and a pair of stepped-impedance open stubs at the center of this microstrip line. Five modes are allocated within UWB band, and a pair of transmission zeros are introduced to improve the passband selectivity. By adopting the parallel-coupled lines, not only suitable external coupling is achieved, but also the performance of upper stopband is improved. This quintuple-mode high-temperature superconducting UWB filter is designed on a 0.5-mm-thick MgO substrate with double-sided YBCO films. The measured results show that 3-dB bandwidth covers 1.57–6.51 GHz, the return loss is better than 10.70 dB, the out-of-band rejection is greater than 24.75 dB in the lower stopband, and the upper stopband with 20-dB attenuation level is extended to about 9 GHz.

Wideband Bandpass Filter with High Selectivity and an Adjustable Notched-band Adopting a Multi-mode Resonator

AbstractA wideband bandpass filter (BPF) with an adjustable notched-band and high selectivity is proposed. The proposed BPF consists of a multi-mode resonator (MMR), twoλ/2 resonators, and I/O feed lines with 50 ohm characteristic impedance. The MMR, connected as a whole by a wide stub, is composed of one I-shaped resonator and two open-loop resonators. Tightly coupling is built between MMR andλ/2 resonators. I/O feed lines are directly connected with twoλ/2 resonators, respectively. Due to the use of tapped-line coupling, one transmission zero (TZ) is formed near low-edge of aim passband. High-edge of passband with one attendant TZ can be tuned to desired location by adjusting bottom-side position of used wide stub or bottom-side length of I-shaped resonator in MMR. The top-side length of I-shaped resonator is applied to improve upper stopband performance and shift undesired resonant mode of MMR near high-edge of aim passband to proper frequency point. The notched-band in aim passband is dominated by top-side position of wide stub in MMR. Good agreement is observed between simulated and measured results.

HIS‐based bandpass filter with improved upper‐stopband performance

A bandpass filter (BPF) with improved upper-stopband performance has been studied and implemented with the aid of a ground plane based on high impedance structures (HIS). The microstrip structure of the filter on the top layer consists of three-order cascaded cross-shaped resonators loaded by folded split ring slots. The ground plane contains two groups of 2 × 5 lattice metallic mushroom array, showing high impedance at the spurious band so that the upper-stopband bandwidth of the BPF can be effectively broadened. The HIS-based ground can independently control the stopband without affecting passband performance. Experimental results demonstrate that the BPF exhibits an extremely broad stopband region from 15.5 to 49.2 GHz with a rejection level above 20 dB.

Compact microwave planar band pass filter

The need for the compactness of microwave filter at high frequency application has lead to the design of microwave planar band pass filter which passes certain range of frequencies. The aim of this paper is to study and implement a compact microwave planar band pass filter operates in 3.1GHz-10.6GHz which is the ultra-wide band range. It uses multiple mode resonator (MMR) and inter digital coupled lines to improve upper stop band performance and coupling degree. Simulation of the proposed microwave filter structures is done with the help of HFSS (High Frequency Structure Simulator) software.

Bandpass filters with improved upper stopband performance using dual-behaviour resonators

Two novel bandpass filters with improved upper stopband using a pair of dual-behaviour resonators (DBRs) are presented in this paper. By utilising coupled lines and open stubs, the second harmonic can be eliminated easily. Extended DBRs with different lengths are used to obtain more transmission zeros to suppress the third and fourth harmonic. 15-dB rejection level in the upper stopband from 1.3f0 to 2.72f0 and 5.2f0 (f0 is the centre frequency of the passband) can be obtained for the two proposed bandpass filters, respectively. Two planar bandpass filters (3-dB fractional bandwidths 9.3%, 8.9%) are designed and fabricated. Good agreements are presented for the theoretical and measured results, which show good in-band filtering performances and high selectivity.