Ultra-wideband Filter Research Articles

Band-pass filters based on photonic crystal

Multilayer photonic crystal structures with bleaching layers are being investigated. In order to calculate the characteristics of ultra-wideband filters on their basis, T-lines lossless model was used. Amplitude-frequency characteristics for the synthesized filters of 5th, 11th and 17th orders are given. It is proved that by a significant increase in filter N order, the difference between the connection coefficients of central resonators’ layers’ becomes negligible. This makes it possible to develop 27-order filter, in which almost half of the layers are realized by periodic interchange of only two identical high-contrast materials. The investigated band-pass filters, including the ones on a glass substrate, have high frequency-selective properties at a relative bandwidth of 80%.

Compact circular-patch-based bandpass filter for ultra-wideband wireless communication systems

Ultra-wideband (UWB) is a radio technology that enables low-power-level, short-range, and wide-bandwidth communication, and it has been widely applied in personal area networks, precision geolocation, medical, surveillance, and vehicular radar systems. Since Federal Communications Commission released the unlicensed use of the UWB range (3.1–10.6GHz), a significant attention has been paid to the development of UWB devices, particularly UWB bandpass filters. In this paper, we propose a novel UWB bandpass filter based on circular patch resonator that is grounded by via and perturbed by slits and defected ground structures. The resonator’s behaviour is analysed in detail and it is shown that its specific configuration allows a flexible control of the three lowest resonant modes, which are used to form UWB passband. To demonstrate the potential of the resonator, a UWB filter has been designed, fabricated, and measured. The filter is characterized by the insertion loss lower than 1dB and return loss higher than 17dB within the passband, as well as by very small group delay variation of only 0.07ns. Also, the filter exhibits suppression higher than 19dB up to 30GHz, and very small overall dimensions of only 0.31λg×0.31λg, and thus it outperforms other published UWB filters.

Circularly slotted flower shaped UWB filtering antenna with high peak gain performance

In this paper two UWB (Ultra Wide Band) antennas and a UWB filter are reported. First antenna is circularly-slotted-flower-shaped (CSFS) patch antenna and second one is CSFS antenna combined with flower-shaped UWB bandpass filter called CSFS UWB filtering antenna. Proposed CSFS antenna achieved improved peak gain at higher UWB band with large bandwidth (up to 12GHz). For further enhancement in frequency characteristic a flower-shaped multiple mode resonator (MMR) filter is combined with CSFS UWB antenna. Designed proposed filter is fabricated and measured. It gives better transmission characteristics over the entire UWB band. The integrated design of filter with UWB antenna is fabricated and measured experimentally. Proposed filtering antenna gives better frequency response and achieved high peak gain 9.8 dBi at 8.8GHz with good out of band rejection capability. The overall performances are presented and compared with other related works. The proposed filtering antenna has advantages of good out of band gain reduction, sharp cut off at both band edges of the UWB passband and omnidirectional radiation pattern in H-plane.

A three-mode microstrip resonator and a miniature ultra-wideband filter based on it

An original microstrip resonator design with a strip conductor split by a slot at one of its ends is investigated. It is demonstrated that at the optimal slot sizes, when the eigenfrequency of the second oscillation mode hits the center between the first and third oscillation modes, the resonator can work as a thirdorder bandpass filter. The structure formed from only two such resonators electromagnetically coupled by split conductor sections is a miniature six-order wideband filter with high selectivity. The test prototype of the filter with a central passband frequency of ~1.2 GHz and a passband width of ~0.75 GHz fabricated on a substrate ~(45 × 11 × 1) mm3 in size with a permittivity of 80 is characterized by minimum loss in a passband of 0.5 dB. The parametric synthesis of the filter structure was performed using electrodynamic analysis of the 3D model. The measured characteristics of the test prototype agree well with the calculated data.

Ultra-Wideband Filter with Dual Notch Bands Based on Ring Resonator

ABSTRACTAs the ultra-wideband system is easy to be interfered by narrow-band signals, an Ultra-wideband (UWB) bandpass filter for the rejection of wireless local area network and satellite communication signals is proposed. The main resonant structure was composed of an open stubs loaded ring resonator. The cascaded open stubs increased a resonant frequency and improved the selectivity of the filter. Two notch bands were realized by coupling W-shaped short stub loaded resonators and etching complementary split rings resonators. The notch frequencies could be obtained by adjusting the size of two band-stop resonators. The UWB bandpass filter was then simulated, fabricated, and tested. Simulation results are in sound agreement with measured results. Both show that the filter has a compact size with a wide upper stopband, and dual notch bands are centered at 5.8 and 8.0 GHz, respectively, which suppressed the interference from a wireless local area network and satellite communication signals in the UWB passband.

Highly selective integrated filter antenna for UWB application

ABSTRACTAn ultrawideband (UWB) integrated filter antenna (IFA) with enhanced selectivity is proposed. A circular radiating patch is electromagnetically coupled to a UWB filter. The design provides a fractional bandwidth of 109.5% covering the entire UWB region (3.1–10.6 GHz). The peak gain of the IFA varies between 3.0 and 4.0 dBi in the desired band with efficiency of more than 90%. The gain of proposed structure is same as that of a reference standalone monopole antenna in the desired frequency band, with a decrease beyond the cut‐off frequencies. The subsystem described in this article is compact, as it does not involve any additional line to integrate the antenna and filter. © 2017 Wiley Periodicals, Inc. Microwave Opt Technol Lett 59:1032–1037, 2017

Hybrid Microstrip/Slotline Ultra-Wideband Bandpass Filter with a Controllable Notch Band

An ultra-wideband (UWB) bandpass filter (BPF) with a controllable notch band is presented by using hybrid microstrip/slotline structure. Firstly, a slotline resonator with symmetrically loaded stubs is fed by two microstrip lines to produce a UWB bandpass filtering response. Secondly, a microstrip triangular loop resonator is externally loaded over the slotline, and a notch band is introduced in the UWB passband. The notch band is determined by the perimeter of the loop resonator. Thirdly, two patches are added as the perturbation element to the corners of the microstrip resonator to excite a pair of degenerate modes. Bandwidth of the notch band can be tuned by properly selecting the patch size. Circuit model for the microstrip resonator loaded slotline is given and studied. Finally, the filter is designed, simulated, and measured. Measured results have agreed well with the simulated ones, demonstrating that a UWB filter with a controllable notch band has been realized.

A New Class of Highly-Miniaturized Reconfigurable UWB Filters for Multi-Band Multi-Standard Transceiver Architectures

Modern wireless communication systems typically employ multiple frequency bands for several standards. A new class of miniaturized ring filters with tuning capability is introduced for this purpose. The proposed filter structure is based on a single multi-mode resonator with variable section impedances in microstrip technology. The bandwidth of the filter can be significantly extended to cover the whole ultra wideband (UWB) frequency range with high adjustability. Moreover, a tunable bandnotch is introduced within the filter response, which can be arbitrarily placed according to the required application. Varactor and PIN diodes are also utilized to facilitate a high tuning capability throughout the different filter characteristics with respect to bandwidth, center frequency, and bandnotch frequency. Based on the symmetry of the filter, even-odd mode analysis is applied to investigate the different filter design characteristics. In addition, a comprehensive transmission line model is investigated within this paper which showed excellent agreements with full-wave simulations and measurements. The implemented UWB filter is investigated with respect to its frequency-domain characteristics and group delay response. The realized filter has a fractional bandwidth of more than 119% with a low group delay. All measured results are in a very good agreement with analysis and simulations. The overall filter dimensions, including housing, do not exceed 25 mm $\times 25$ mm.

Full-Wave Analysis of Ultrahigh Electromechanical Coupling Surface Acoustic Wave Propagating Properties in a Relaxor Based Ferroelectric Single Crystal/Cubic Silicon Carbide Layered Structure

This paper describes a full-wave analysis of ultrahigh electromechanical coupling surface acoustic wave (SAW) of Y-cut X propagating Pb(In1/2Nb1/2)O3-Pb(Mg1/3Nb2/3)O3-PbTiO3 (YX-PIMNT) single crystals on a cubic silicon carbide (3C-SiC) substrate. There are several eigenmodes including shear horizontal (SH) and Rayleigh SAWs. Based on the finite-element method (FEM), the phase velocity (vp) and coupling factor (K2) of SAWs varying with the top electrode thickness, thickness, and Euler angle (θ) of the YX-PIMNT substrate have been investigated. K2 of SH SAW can reach an extremely high value of 75.9%. The proper control of structural parameters can suppress unwanted responses caused by other modes without deteriorating the coupling factor. The large K2 value of SH SAW and suppression of unwanted responses have highly promising applications in developing ultrawideband and tunable SAW filters. Finally, the performance of 3C-SiC and 6H-SiC as substrates was investigated, and 3C-SiC was identified as a more attractive substrate candidate than 6H-SiC.

Highly compact UWB bandpass filter based on composite right/left-handed transmission line and meander fractal like ring slot in ground

An ultra-wideband (UWB) highly compact bandpass filter with extremely high passband bandwidth is presented. The proposed structure is made using three-staged stepped-impedance lines and a composite right/left-handed transmission line (CRLH-TL) synthesized with meander fractal like ring slot in the ground and series capacitive gap in conductor strip. The capacitive gap in conductor strip and meander fractal like ring slot in the ground plane play major role for controlling the lower and higher cut-off frequencies. The equivalent circuit model of proposed filter is demonstrated and lumped parameters are extracted. A prototype is fabricated to experimentally validate the performance of proposed filter. The proposed UWB filter has extremely wide −10 dB return loss passband bandwidth from 3.14 to 18.26 GHz with relative bandwidth of 142% and insertion loss better than 0.5 dB. Also it achieves a wide upper-stopband from 19.7 to 24.4 GHz with insertion loss better than 13.0 dB, return loss <1.5 dB and sharpened rejection skirts outside the passband at both lower and upper frequency ends. Good agreement is found between simulated and measured results with measured group delay variation in the passband <0.65 ns.

A Compact Broadside Coupled Notched Band UWB Filter with Wide Upper Stopband

ABSTRACTA broadside coupled ultra-wideband (UWB) bandpass filter (BPF) with notched band and wide upper stopband is proposed and implemented. Initially, a broadside coupled UWB filter structure with good passband characteristics is developed. To this, split ring resonator (SRR) metal lines of half guided waveguide length are coupled to generate passband notch. Later, stub lines are embedded in the input and output (I/O) feeding lines whose attenuation poles suppress the spurious harmonics and widen the stopband. Finally, the proposed structure is fabricated and measured which establishes the authenticity of the full-wave electromagnetic response. The passband extends from 2.85 to 11.3 GHz with stopband of width 18 GHz and depth greater than 18 dB. The variation of group delay is less than 0.42 ns in the passband. The proposed structure is small in size measuring 11.08 × 11.7 mm2.

Ultra-wideband filtering of spoof surface plasmon polaritons using deep subwavelength planar structures.

Novel ultra-wideband filtering of spoof surface plasmon polaritons (SPPs) is proposed in the microwave frequency using deep subwavelength planar structures printed on thin and flexible dielectric substrate. The proposed planar SPPs waveguide is composed of two mirror-oriented metallic corrugated strips, which are further decorated with parallel-arranged slots in the main corrugated strips. This compound structure provides deep subwavelength field confinement as well as flexible parameters when employed as a plasmonic waveguide, which is potential to construct miniaturization. Using momentum and impedance matching technology, we achieve a smooth conversion between the proposed SPPs waveguide and the conventional transmission line. To verify the validity of the design, we fabricate a spoof SPPs filter, and the measured results illustrate excellent performance, in which the reflection coefficient is less than −10 dB within the −3 dB passband from 1.21 GHz to 7.21 GHz with the smallest insertion loss of 1.23 dB at 2.21 GHz, having very good agreements with numerical simulations. The ultra-wideband filter with low insertion loss and high transmission efficiency possesses great potential in modern communication systems.

Using intrinsic zero to notch satellite signals in UWB filter

In this paper, an ultra-wideband (UWB) filter with a notch band using T-shaped step impedance resonator loaded with cross-shaped open stubs has been presented. The notch band is formed by utilizing intrinsic zero. The characteristics of the new quad-mode resonator have been analyzed using odd-even mode analysis method. It can be shown that it is the intrinsic zero that generates the notch band. In addition, wide tunable notch band form 5–9.3 GHz can be achieved. A UWB filter with a notch band centered at 6.25 GHz using the proposed quad-mode resonator has been designed, fabricated, and tested. Experiment results show that the attenuation in notch frequency is >22 dB while the return loss of the simulation and measurement results are 22 dB/20 dB and 14.5 dB/11.2 dB in the lower and upper passband, respectively, which illustrate that the simulation and measurement results are in agreement.

An ultra-wideband (UWB) bandpass filter with complementary split ring resonator for coupling improvement

This paper presents a novel, compact & low cost ultra-wideband (UWB) bandpass filter (BPF) using folded coupled stepped impedance resonator (SIR) pairs and a complementary split ring resonator (CSRR). Based on the advantage of symmetry of the structure, the odd-even mode decoupling scheme is applied for the analysis of different resonant modes which is generated by the coupled SIR pairs. The overall coupling of the proposed BPF is made stronger by placing a modified CSRR unit cell in the ground plane and it is confirmed through circuit analysis, coupling architecture & field distribution analysis. The proposed UWB filter provides 108% measured 3dB fractional bandwidth (FBW) & insertion loss 1.6–2.1dB in the passband (2.6–10GHz) with a minimum flat group delay of 0.2ns. The proposed UWB BPF is fabricated using commercially available FR4 substrate (εr=4.4 , h=0.8mm) and a good agreement is found between the simulated and measured results.

Compact UWB BPF with a Tunable Notched Band based on Triplemode HMSIW Resonator

A novel triple-mode resonator based on the half-mode substrate integrated waveguide (HMSIW) structure is proposed to design the ultra-wideband (UWB) filters. The UWB filter topology is given by analyzing the resonant frequencies of the three modes and the signs of the coupling between the three modes and the input/output ports. With the filter synthesis method, a triple-mode UWB filter with passband from 3.1-10.6 GHz is effectively realized with two transmission zeros at the upper stopband. To block the existing undesired narrowband radio signals in FCC UWB range, a notched band can be easily generated and controlled by a loaded stub-capacitor. For demonstration, an UWB filter with a tunable notched band from 3.7 to 7.7 GHz and compact size is designed and fabricated. Both simulated and measured results indicate that the proposed new filter has the properties of wide tuning range of the notched band and sharp roll off.

Ultra-wideband ladder filters using zero-th shear mode plate wave in ultrathin LiNbO3 plate with apodized interdigital transducers

There are two kinds of plate waves propagating in a thin plate, Lamb and shear horizontal (SH) waves. The former has a velocity higher than 15,000 m/s when the plate is very thin. On the contrary, 0th SH (SH0) mode plate wave in an ultrathin LiNbO3 plate has an electro-mechanical coupling factor larger than 50%. Authors fabricated an ultra-wideband T-type ladder filter with a relative bandwidth (BW) of 41% using the SH0 mode plate wave. Although the BW of the filter fully covers the digital TV band in Japan, it does not have sufficient margin at the lower and higher end of BW. Besides, periodic small ripples due to transverse mode in pass-band of the filter were observed. In this study π-type ladder filters were fabricated by changing the pitch ratio of interdigital transducer (IDT) of parallel and series arm resonators (PR(IDT)) to control the BW, and by apodizing IDTs to improve the periodic small ripples due to transverse mode. Ultra-wideband filters without periodic small transverse mode with ultrawide bandwidth from 41 to 49% were fabricated. The BWs fully cover ultrawide digital television bands in Japan and U.S.A. These filters with an ultrawide BW and a steep characteristic show the possibility to be applied to a reported cognitive radio system and other communication systems requiring an ultrawide BW.

UWB bandpass filters with triple notched band characteristics implemented using wave cancellation technique

ABSTRACTA novel planar bandpass filter structure is proposed with quasi‐elliptic response for ultra‐wideband (UWB) applications, that enables incorporation of triple notch bands within its passband response. The filter design is based on wave cancellation technique which is implemented by first splitting and then combining the signal. The split signals are processed through filtering structures that generate triple notch bands within the passband of the UWB filter response, as well as transmission zeros at the lower and upper cutoff frequencies to enhance the filter's selectivity. The UWB filter designed and fabricated has tri‐notch bands centered at 5.4, 5.8, and 8.2 GHz. The proposed filter is highly compact and miniature with dimensions of 20.7 × 9.8 mm2. © 2016 Wiley Periodicals, Inc. Microwave Opt Technol Lett 58:1875–1879, 2016

Compact multi‐mode UWB microstrip filter using meander resonator

ABSTRACTIn this paper, traditional microstrip resonator is meandered to construct a compact multi‐mode resonator (MMR). The meander resonator is very simple but convenient for ultra‐wide band (UWB) passband filter. And then, a UWB microstrip filter with six transmission poles in the passband is achieved by using only two resonators. The filter has an amplitude frequency response with a passband from 1.8 GHz to 4.7 GHz, the simulated return loss in passband is better than −20dB, and the measured one is better than −19dB. The tested insertion loss at center frequency is about 0.38 dB. Methods of adjusting the bandwidth of this new kind of UWB filter is also discussed in this paper. © 2016 Wiley Periodicals, Inc. Microwave Opt Technol Lett 58:2026–2029, 2016

Band Notched UWB-BPF Based on Broadside Coupled Microstrip/CPW Transition

ABSTRACTA planar band notched ultra-wideband (UWB) bandpass filter based on broadside coupling of microstrip/co-planar waveguide (CPW) transition is proposed and implemented. The UWB filter topology is made up of microstrip lines on the top coupled in broadside fashion to an open ended CPW in the ground plane. Dual narrow notches at 5.2 and 7.9 GHz are implemented by etching two meander shaped defected ground structures in the CPW under the microstrip lines. A wideband stopband for improved isolation is obtained with the suppression of spurious harmonics by the attenuation poles generated by the spur line structures embedded in the input and output feeding lines. The proposed structure exhibits good frequency characteristics and is of compact size.

Design of compact balanced ultra‐wideband bandpass filter with half mode dumbbell DGS

A new compact balanced ultra-wideband (UWB) bandpass filter using half mode dumbbell defected ground structure (DGS) is presented. To realise the UWB response, the `T' shape multiple-mode resonator with short-ended stub is employed. To achieve wideband common mode (CM) suppression and compact design simultaneously, the concept of half-mode DGS is introduced in the two stacked microstrip layers. Afterwards, a balanced UWB filter is designed and measured for verifying the feasibility of the presented design method. The measured results match well with the expected results which indicate the proposed filter exhibits better than -30 dB CM suppression within the DM passband covering from 3.1 to 10.6 GHz.