Compact UWB Bandpass Filter Using Stub-Loaded Multiple-Mode Resonator

A compact microstrip-line ultra-wideband (UWB) bandpass filter (BPF) using the proposed stub-loaded multiple-mode resonator (MMR) is presented. This MMR is formed by loading three open-ended stubs in shunt to a simple stepped-impedance resonator in center and two symmetrical locations, respectively. By properly adjusting the lengths of these stubs, the first four resonant modes of this MMR can be evenly allocated within the 3.1-to-10.6 GHz UWB band while the fifth resonant frequency is raised above 15.0GHz. It results in the formulation of a novel UWB BPF with compact-size and widened upper-stopband by incorporating this MMR with two interdigital parallel-coupled feed lines. Simulated and measured results are found in good agreement with each other, showing improved UWB bandpass behaviors with the insertion loss lower than 0.8dB, return loss higher than 14.3dB, and maximum group delay variation less than 0.64ns in the realized UWB passband     

Compact UWB Bandpass Filter With Improved Upper-Stopband Performance

In this letter, a novel ultra-wideband (UWB) bandpass filter with compact size and improved upper-stopband performance has been studied and implemented using multiple-mode resonator (MMR). The MMR is formed by attaching three pairs of circular impedance-stepped stubs in shunt to a high impedance microstrip line. By simply adjusting the radius of the circles of the stubs, the resonant modes of the MMR can be roughly allocated within the 3.1-10.6 GHz UWB band while suppressing the spurious harmonics in the upper-stopband. In order to enhance the coupling degree, two interdigital coupled-lines are used in the input and output sides. Thus, a predicted UWB passband is realized. Meanwhile, the insertion loss is higher than 30.0 dB in the upper-stopband from 12.1 to 27.8 GHz. Finally, the filter is successfully designed and fabricated. The EM-simulated and the measured results are presented in this work where excellent agreement between them is obtained.     

Compact UWB bandpass filter using ring open stub loaded multiple-mode resonator

A novel ultra-wideband (UWB) bandpass filter with a compact size, improved upper-stopband performance and reduced radiation loss has been studied and designed using a multiple-mode resonator (MMR). The MMR is formed by attaching three pairs of ring open stubs in shunt to a high impedance microstrip line. By simply adjusting the radius of the circles of the ring stubs, the resonant modes of the MMR can be roughly allocated within the 3.1?10.6 GHz UWB band while suppressing the spurious harmonics in the upper-stopband. Meanwhile, the insertion loss is higher than 20.0 dB in the upperstopband from 11.7 to 33.5 GHz in simulation. Finally, the filter is fabricated and measured. The EM-simulated and measured results are presented and excellent agreement between them is obtained.     

Short-circuited CPW multiple-mode resonator for ultra-wideband (UWB) bandpass filter

An ultra-wideband (UWB: 3.1-10.6 GHz) bandpass filter (BPF) on coplanar waveguide (CPW) is proposed, designed and implemented. A nonuniform CPW multiple-mode resonator with short-circuited ends is constructed and its first three resonant modes are properly allocated around the lower-end, center and higher-end of the specified UWB band. This CPW resonator is then driven at two ends by two parallel-coupled CPW lines with dispersive inductive coupling degree. By properly reallocating the enhanced coupling peak toward the UWB's center, a five-pole CPW BPF with one full-wavelength can be eventually constituted. Its UWB bandpass performance is characterized and optimized on the basis of a simple transmission-line network. Predicted results are confirmed by experiment. Measured results achieve the insertion loss <1.5dB and group delay variation <0.35ns in the realized 3.3 to 10.4GHz UWB passband.     

Analytical design of a microstrip UWB BPF with sharp rejection

This paper presents a new Ultra-WideBand (UWB) BandPass Filter (BPF) using half-wavelength (??/2) Stepped-Impedance Stub-Loaded Resonator (SISLR). Analytical equations derived by the even-odd mode analysis show the new filter has two tunable transmission zeros at both sides of the passband to provide a sharp rejection and seven transmission poles inside the passband to achieve U.S. UWB performance. For verification, a UWB BPF is designed, fabricated and measured. The measured results show that the fabricated filter has a -3 dB fractional bandwidth from 3.0 GHz to 10.9 GHz and its insertion loss less than 0.9 dB over the whole passband. Furthermore, the new filter exhibits a simple topology, sharp rejection, and deep stopband suppression.     

Ultra-wideband bandpass filter with hybrid microstrip/CPW structure

A novel ultra-wideband (UWB) bandpass filter (BPF) is presented using the hybrid microstrip and coplanar waveguide (CPW) structure. A CPW nonuniform resonator or multiple-mode resonator (MMR) is constructed to produce its first three resonant modes occurring around the lower end, center, and higher end of the UWB band. Then, a microstrip/CPW surface-to-surface coupled line is formed and modeled to allocate the enhanced coupling peak around the center of this UWB band, i.e., 6.85GHz. As such, a five-pole UWB BPF is built up and realized with the passband covering the entire UWB band (3.1-10.6GHz). A predicted frequency response is finally verified by the experiment. In addition, the designed UWB filter, with a single resonator, only occupies one full-wavelength in length or 16.9mm.     

Capacitive-Ended Interdigital Coupled Lines for UWB Bandpass Filters With Improved Out-of-Band Performances

This letter presents a novel ultra-wideband (UWB) microstrip bandpass filter on a microstrip line with improved out-of-band performances. A multiple-mode resonator (MMR) is first constituted to equally allocate its first three resonant frequencies in the 3.1–10.6-GHz UWB band. Two capacitive-ended interdigital coupled lines are then formed to assign their transmission zero towards the fourth-order resonant frequency of this MMR, thereby suppressing the first spurious passband. Moreover, two outer arms in the interdigital lines are properly tapered to compensate the phase imbalance or group delay near the UWB upper-end relying on extra capacitive-ended stubs. And finally, two UWB filters with one- and two-MMRs are designed and implemented to experimentally demonstrate the improved out-of-band performances, i.e., widened/deepened upper-stopband and sharpened rejection skirts outside the UWB passband.     

Compact UWB bandpass filter with improved upper-stopband performance

a compact microstrip-line ultra-wideband (UWB) bandpass filter (BPF) using aperture-backed interdigital coupled lines and a stub-loaded folded stepped-impedance resonator (SLFSIR) is presented. in the design, the first four resonant frequencies of this SLFSIR are properly adjusted to be placed evenly within the UWB while the fifth resonant frequency is raised above 16.0 GHz to improve upper-stopband performance. furthermore, the aperture-backed interdigital coupled lines can create a transmission zero to cancel the fifth resonant mode of the SLFSIR to make a wider upper-stopband as well as raising the coupling degree to relax the tight line spacing. after optimisation of this filter, good UWB bandpass behaviour is theoretically realised and experimentally confirmed.     

Implementation of Compact UWB Bandpass Filter With a Notch-Band

An ultra-wideband (UWB) bandpass filter on microstrip line with notch-band, compact-size and improved upper-stopband performances is presented and implemented. A modified non-uniform resonator is at first formed by transversely attaching three pairs of impedance-stepped stubs. Its resonance behavior is thoroughly characterized so as to allocate the first three resonant frequencies within 3.1-10.6 GHz band while suppressing spurious harmonics in the upper-band. As this resonator is linked at two sides with two feed lines via interdigital coupled lines with enhanced coupling degree, a preferred UWB passband is realized. Then, one of two arms in the coupled-line sections is largely extended and folded, aiming to create a notch band at the frequency of 5.6 GHz by virtue of out-of-phase transmission cancellation. Two filter prototypes are optimized and fabricated to demonstrate the notch-band-included and upper-stopband-improved UWB bandpass performances.     

Ultra-wideband bandpass filter using back-to-back microstrip-to-CPW transition structure

A novel ultra-wideband bandpass filter is proposed on a back-to-back microstrip-to-CPW transition structure. A multiple-mode resonator on a CPW is formed to allocate its first three resonant modes around the lower-end, centre and upper-end of the 3.1 to 10.6 GHz UWB passband. Its two sides are fed by two microstrip-to-CPW transitions with enhanced frequency-dispersive coupling degree. The designed filter exhibits good UWB passband behaviour with insertion loss <0.5 dB and group delay variation <0.35 ns.     

Compact Ultra-Wideband Bandpass Filter Using Dual-Line Coupling Structure

This letter presents a novel compact ultra-wideband (UWB) microstrip bandpass filter with spurious response suppression. A dual-mode ring resonator is constituted to allocate its first two resonant frequencies in the UWB band, and the dual-line parallel-coupled structure is used in this compact UWB filter, which is expected to achieve much tighter coupling degree. Simulated and measured results are found in good agreement with each other, showing a wide passband from 4.9 to 10.9 GHz, 15 dB return loss bandwidth of about 5 GHz, minimum insertion loss of 0.49 dB at 7.3 GHz, and wide upper stopband with more than 20 dB attenuation up to 20 GHz.     

Planar microstrip UWB bandpass filter using U-shaped slot coupling structure

A compact planar microstrip UWB bandpass filter is proposed. It is realised by cascading a lowpass filter and a highpass filter. A transmission line with U-shaped slots coupled with two DGS units on the back of the circuit board has the characteristic of highpass, while a periodic uniform DGS array has the characteristic of lowpass. Combining these two structures, a new UWB bandpass filter (BPF) is fabricated and measured. Measured results show that the proposed BPF has wide bandwidth from 3.0 to 10.9 GHz, all the measured return loss less than 13 dB in the passband. The BPF achieves a wide stopband with 18 dB attenuation up to 18.0 GHz     

Small Ultra-Wideband (UWB) Bandpass Filter With Notched Band

A compact ultra-wideband (UWB) bandpass filter (BPF) with notched band has been proposed and implemented in this letter. H-shaped slot is studied and adopted to tighten the coupling of inter-digital capacitor in order to improve the BPF's performance. Three pairs of tapered defected ground structures (DGS) are formed to assign their transmission zeros towards the out of band signal, thereby suppressing the spurious passband. Combining these two structures we obtain a small sized UWB BPF. Meander line slot is developed to reject the undesired wireless local-area network (WLAN) radio signals. An experimental UWB filter with notched band was fabricated with 35% less length as compared to an embedded open-circuited stub. The measured BPF insertion loss is less than 1.0 dB throughout the pass band of 2.8 to 10.8 GHz, the variation of group delay less than 0.20 ns in this band except for the notched band, and a wide stopband bandwidth with 20 dB attenuation up to at least 20.0 GHz.     

Coplanar Waveguide Bandpass Filters With Compact Size and Wide Spurious-Free Stopband Using Electromagnetic Bandgap Resonators

This work presents a novel coplanar waveguide (CPW) bandpass filter (BPF) that uses electromagnetic bandgap (EBG) resonators to reduce the size and suppress the harmonic responses. The propagation characteristic of the EBG structure is investigated by its associated equivalent circuit model. Compared with the conventional half-wavelength resonator at 5GHz, the EBG resonator is 60.5 % more compact. Based on the EBG CPW resonators, the inductively-coupled two-pole BPF with 3.8% 3-dB bandwidth and 2-dB insertion loss at 5GHz is implemented. This structure generates a 59.6% reduction in size and suppresses a second harmonic passband when compared with a conventional filter. To eliminate the third harmonic response, the proposed EBG CPW BPF further incorporates two EBG structures into its input and output ports and has the merit of a small circuit area     

Ultra-Wideband (UWB) Bandpass Filters With Hybrid Microstrip/Slotline Structures

A novel ultra-wideband (UWB) bandpass filter is presented using back-to-back microstrip-slotline transition and triple-mode slotline resonator. A uniform slotline resonator is constructed with a length of one full wavelength at the central frequency. Two microstrip feed lines are then placed above the slotline resonator to make up a back-to-back microstrip-slotline transition, where two intersection points are equally located at one quarter-wavelength away from two short-ends. By properly stretching the microstrip line lengths, an ultra-wide passband is constituted with the lower/upper cut-off edges dominated by the first/third resonant modes.By forming a W-shaped slotline resonator, introducing a cross coupling and cascading two lowpass filters, two UWB bandpass filters with improved out-of-band performances are designed, fabricated and measured. Measured results achieve a 2.56-to-10.90 GHz or 124% passband with return loss >12.04 dB, group delay variation <0.58 ns, sharpened rejection skirts and extended upper-stopband.     

Compact ultra-wideband bandpass filter using broadside coupled hairpin structures on multilayer liquid crystal polymer substrate

A novel ultra-wideband (UWB) bandpass filter (BPF) using a broadside- coupled hairpin structure and multilayer organic liquid crystal polymer (LCP) technology is presented. To suppress stopband harmonic response, folded stepped impedance structures were adopted as hairpin resonators in the design. The proposed filter has been investigated numerically and experimentally. Multilayer LCP technology was used to implement designed UWB BPF. Good agreement between simulated and measured results of the proposed filter was observed. They show that the fabricated UWB BPF has a good performance, including a small insertion loss, a flat group delay with a variation within 0.1 ns in most of its passband, a wide stopband from 11.0 20.0 GHz with a high rejection level up to 20.0 dB, and a very compact size of 9.8 x 7.5 mm (0.36 lg x 0.27lg, where lg is the guided wavelength of 50 V microstrip line at 6.85 GHz).     

一种新型超宽带带通滤波器的设计

针对超宽带(UWB)系统易受无线网络信号干扰及传统的超宽带带通滤波器阻带较窄,不能有效抑制谐波的问题,提出了一种新型的UWB带通滤波器,该滤波器由两级交指梳状耦合谐振器级联组成,通过增加耦合指的个数来实现陷波特性,然后在两个交指谐振器的中间添加一个槽线锥形谐振器,使该滤波器具有抑制高次谐波特性,达到拓宽高阻带的效果,同时由于槽线谐振器的加入,陷波频段的抑制电平进一步提高.实验结果证明,所设计的滤波器既能保证3.1～10.6 GHz频段内的插入损耗小于3 dB,陷波频段为5.7～5.8 GHz,陷波频段的抑制电平高达-43 dB,同时又能拓宽高频阻带.     

A Novel Wideband Bandpass Filter Using A Cross-Shaped Multiple-Mode Resonator

A novel wideband bandpass filter (BPF) using a cross-shaped microstrip multiple-mode resonator (MMR) is presented in the letter. The MMR is composed of a section of open-ended microstrip-line and a pair of short-ended stubs. Its three resonant modes are used to construct the passband of the proposed BPF. And two coplanar waveguides are used as the input/output transmission-lines to improve the coupling between the MMR and input/output transmission-lines. The filter has been investigated numerically and experimentally. Both simulated and measured results show that the filter has a good performance, including controllable bandwidth from 66% to 114%, low insertion loss (lower than 0.78 dB), and a small group delay variation.     

基于新型谐振器的超宽带带通滤波器

采用两个新型四阶阶梯阻抗谐振器设计出一种新型超宽带带通滤波器,四个1/4波长的耦合线被平行放置于输入输出端,起到增加耦合强度的作用,三个谐振频率被调整在超宽带带宽(3.1 GHz～10.6 GHz)内。通过优化后,该滤波器在通带内具有五个传输极点,频带宽度在3.6 GHz～10.5 GHz,通带内回波损耗优于15 dB,最小插入损耗为0.6 dB,满足超宽带的传输要求。仿真结果显示,文中设计的滤波器具有小型化、低插入损耗和较好的带外特性等优点。     

Compact tri‐wideband bandpass filter with multiple transmission zeros

This paper presents a tri‐wideband bandpass filter (TWB‐BPF) with compact size, high band‐to‐band isolation, and multiple transmission zeros (TZs). The proposed TWB‐BPF is based on a multiple‐mode resonator (MMR), which is interpreted by the method of the even‐ and odd‐mode analysis technique. The MMR can excite 11 resonant modes, where the first two modes comprise the first passband, the next four modes form the second passband, and the last five modes are used to generate the third passband. In addition, 10 TZs are yielded to obtain high band‐to‐band isolation and wide stopband suppression characteristics up to 14.95f_c1 (f_c1 is the center frequency of the first passband). To verify the proposed filter, a TWB‐BPF with 3‐dB fractional bandwidths (FBWs) of 37.4%, 43.5%, and 40.4% is designed, fabricated, and measured.