Compact Ultra-wideband Bandpass Filter Research Articles

A compact, flexible and transparent UWB bandpass filter with silver nanowires

The advent of ultra-wide band (UWB) technology has made bandpass filters omnipresent. Current approaches to designing bandpass filters cannot provide transparent and flexible bandpass filters to meet their increasing demands for various applications. In this new work, a flexible and transparent UWB bandpass filter with silver nanowires printed on flexible polyethylene terephthalate (PET) substrates is designed. The filter structure is formed by connecting three pairs of open-circuited rectangular stubs. Proper coupling of these stubs is used to obtain the desired UWB passband. The proposed design operating from 1.05 to 10.75 GHz with an extremely wide stopband up to 50 GHz and a rejection level of 11.4 dB is demonstrated in the measured results. Furthermore, it was observed that the measured results matched well with the simulated results. These improved results indicate that our design strategy will provide a way to design highly efficient flexible UWB filters. This flexible filter may serve as a potential candidate for increasing the flexibility of indoor electronic applications.

Design of a Compact Ultra-Wideband Microstrip Bandpass Filter

A compact ultra-wideband bandpass filter based on a multilayer printed circuit board (MPCB) structure is proposed in this paper. RO4450F prepreg is used to bond three RO4350B dielectric substrates with different thicknesses in the MPCB structure. The upper surfaces of the three dielectric substrates are respectively provided with copper-coated structures with different patterns. The blind holes and the defected ground structure (DGS) are added to the MPCB of an ultra-wideband bandpass filter. Two groups of loaded quarter-wavelength terminal-open stubs introduce two transmission zeros, which improves the roll-off rates and stopband characteristics, while simple DGS composed of rectangular slots introduces two resonance points in the passband to improve the return loss. Simulation and measurement are consistent. The insertion loss at the center frequency of 12.795 GHz is 0.58 dB and the fractional bandwidth of 3 dB is 40.33% from 10.215 GHz to 15.375 GHz. This bandpass filter can be widely used in wireless and satellite communication.

Highly compact UWB-BPF with a wide notch-band using a rectangular ring structure and two Y-shaped open stub resonators

A miniaturized ultra-wideband bandpass filter (UWB-BPF) with a high rejection notched band is proposed in this article. It is composed of a rectangular ring with two grounded vias, a microstrip line with two open radial stubs, a pair of interdigital feedlines with two lumped capacitors and two open-loaded Y-shaped stub resonators (YSSR), as well as a defected ground structure (DGS). This filter was simulated and fabricated by using a practical printed circuit board (PCB) process with the substrate of FR4. The measurement results agree well with the simulation data. The measured 3-dB passbands cover 2.73–4.36 and 6.82–11.78 GHz, the in-band insertion loss is less than 1.13 dB except at the edges of the bands, and the return loss is better than 10 dB. It is found that the filter’s lower and upper transmission zeros occur at 0.8 and 13.95 GHz with the magnitudes of −87.2 and −45.6 dB, respectively. This makes the filter exhibit high selectivity with the steep skirt characteristics. It is also worth noting that the proposed filter possesses a wide 10-dB notch band ranging from 4.87 to 6.93 GHz with the highest rejection of 46.3 dB at 5.9 GHz. This feature can effectively and simultaneously inhibit the unwanted signals coming from the C-band 5G mobile communication, 5-GHz WiFi, WLAN, and 6-GHz satellite systems. Furthermore, the presented filter is highly compact with the dimensions of 13.2 mm × 11.8 mm and has a very wide upper stopband spanning from 13.4 to 28 GHz with rejection of 20 dB or higher.

A surface-to-surface transition based UWB bandpass filter with triple in-band notches

A Compact Ultra-Wideband (UWB) bandpass filter (BPF) designed using the surface-to-surface transition mechanism and with triple passband transmission zeros (TZs) is proposed. The geometry of basic structure consists of two microstrip lines placed facing each other on the top plane coupled with a short circuited co-planar waveguide (CPW) in the bottom plane. This basic architecture develops a UWB response with two transmission zeros (TZs) at lower/higher passband edges, which exhibits good frequency characteristics. Later, complementary folded split ring resonator (CSRR), split ring resonators (SRRs) and folded split ring resonators (FSRRs) are appended to the basic architecture to generate triple passband notches so as to circumvent interferences. A hardware prototype is finally developed and its response tested against the simulated data. The triple-notched BPF is compact covering a physical area of only 14 × 11.4 mm2.

Compact UWB BPF With Broad Stopband Based on Loaded-Stub and C-Shape SIDGS Resonators

In this letter, two types of substrate-integrated defected ground structure (SIDGS) resonators (i.e., loaded-stub and C-shape resonators) are proposed for the ultra-wideband (UWB) bandpass filter (BPF) design. Coupled SIDGS resonators can generate four transmission poles to achieve the UWB response with low insertion loss in a compact size. Besides, the spurious cancellation with a broad stopband is achieved by mutual suppression of separated harmonics from the SIDGS resonators. In addition, the lowpass units (LPUs) embedded in the microstrip feed-lines are utilized to further improve the BPF stopband rejection. To verify the mechanism, a compact BPF operating at 6.85 GHz (i.e., the passband center frequency <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> ) with 0.6-dB insertion loss and 3-dB fractional bandwidth (FBW) of 114% is implemented and fabricated. The measured stopband extends to <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$9.7f_{0}$ </tex-math></inline-formula> with a rejection level more than 26 dB.

Design of a Compact Ultra-Wideband Bandpass Filter Using Inductively Compensated Parallel-Coupled Lines

An ultra-wideband bandpass filter (UWB-BPF) using inductively compensated parallel-coupled lines (ICPCL) is presented in this article. It consists of three circuits: a high-pass filter (HPF), a lowpass filter (LPF), and a transmission line. The HPF and the LPF are independently synthesized from the ICPCL. The proposed filter can suppress unwanted frequencies in the upper stopband and increase the skirt slope of the frequency response in the transition bands. The fabricated UWB-BPF with compact size provides good passband performances, with insertion loss of better than −0.49 dB and return loss of better than −12 dB in the frequency range of 2.92–10.95 GHz (the bandwidth of 8.03 GHz). The 107% bandwidth is achieved. In addition, the proposed filter can suppress the spurious frequencies at 2f0, which is greater than 30 dB. The measured results accord well with the simulation results. The novelty of the paper is the introduction of the ICPCL for the construction of the compact UWB-BPF.

Modeling of a compact ultra-wideband bandpass filter with a single notch using DGS and DMS technology

A compact, low loss microstrip ultra-wideband (UWB) bandpass filter (BPF) with a narrow notch band is proposed in this article for using wireless communication applications within the unlicensed UWB range reported by the Federal Communications Commission. A systematic approach is presented to establish the UWB-BPF structure followed by a narrow notch within it. The UWB-BPF response is achieved by integrating a defected structures-based lowpass filter and a short-stepped impedance stub-based highpass filter. The narrow notch band is obtained by embedding two-stepped impedance stubs. The physical dimensions of the stubs can be optimized to select a specific frequency for the notch band. The UWB-BPF structure without the notched band, having a center frequency of 3.69 GHz, provides a fractional bandwidth (FBW) of 157%. The stopband suppression is −26 dB and it is broadened up to 15 GHz. On the other hand, the notched band response is obtained at 5.8 GHz with an FBW of 49.78% which is used for avoiding interference from the wireless local area network. The proposed structures are fabricated and measured for experimental validation.

A Pythagorean tree fractal shape stub-loaded resonator as a UWB bandpass filter with wide stopband

AbstractA compact ultrawideband (UWB) bandpass filter (BPF) is designed by harnessing the efficacy of a Pythagorean tree fractal shape stub-loaded resonator. The design inherently provides the passband transmission poles, which make it convenient to be used in wide passband filtering circuits. The number and the position of the resonating modes can be controlled by increasing the iterations of the Pythagorean tree, as analyzed using odd- and even-mode analysis. Design steps of the BPF are detailed. The designed UWB BPF takes up a small circuit area of (12.13 × 9.59) mm2. The proposed design is fabricated and measured to verify the simulated results. The stopband is extended up to 17.5 GHz with a maximum attenuation of 15 dB.

Design of a Super Compact UWB Filter Based on Hybrid Technique with a Notch Band Using Open Circuited Stubs

This paper presents a new design of a super compact Ultra wideband (UWB) band-pass filter (BPF) with rejection of X-band satellite applications. For covering the UWB bandpass, the proposed filter is realized using hybrid technique which is achieved by using a Microstrip-Coplanar waveguide-Microstrip transition. The basic structure consists of a modified microstrip in the top layer and CPW in the bottom layer. Later, open-circuited stubs are embedded in the top to implement in-band transmission zeros (TZ) so as to circumvent interference. The simulated results show that the UWB bandpass filter has a high adaptation (S11 ≤ −18 dB) and insertion loss better than 0.4 dB at the passband. The impedance bandwidths are about 114% (3–11 GHz) with upper stopband extends to more than 14 GHz with a depth of greater than 38 dB. In addition, the UWB BPF shows a flat group delay performance with a variation of about 0.15 ns over the entire bandwidth. A prototype of the filter is fabricated and tested. Good agreement is achieved between measurement and simulation. The proposed UWB BPF is compact in size with overall dimensions of 14 by 9.2 mm2. Consequently, the obtained results prove that the presented filter is suitable for UWB wireless devices.

Compact UWB Half-Mode SIW Bandpass Filter With Fully Reconfigurable Single and Dual Notched Bands

Compact ultra-wideband (UWB) bandpass filters based on the half-mode substrate integrated waveguide (SIW) with fully reconfigurable single and dual notched bands are proposed in this article. The lower stopband of the UWB bandpass filter is formed by the intrinsic cutoff frequency of the half-mode SIW, and transmission zeros in the upper stopband are created by utilizing three U-shaped slot resonators. Coupling microstrip resonators loaded by varactor diodes are placed along the open side of the half-mode SIW and microstrip feeding line to construct the in-band notches. By controlling the bias voltages and the size of resonators, fully reconfigurable single and dual notched bands can be obtained. Moreover, the frequency and bandwidth of each notched band can be controlled independently. To demonstrate the proposed technique, five and seven distributed coupling microstrip resonators are first applied to obtain the fully reconfigurable single notched band with the suppression level of 30 and 36 dB, respectively. Then, reconfigurable dual notched bands are demonstrated by changing the bias voltages using the same prototype with seven resonators. At last, nine resonant cells with two sets of different sizes are shown to design reconfigurable dual notched bands with frequency tuning range covering almost the full UWB passband.

Design of Compact UWB Filter Using Parallel-coupled Line and Circular Open-circuited Stubs

This article encompasses the design of compact ultra-wideband (UWB) bandpass filter with low insertion loss and high selectivity using circular open-circuited stubs (COSs). Low insertion loss from two COSs and Multiple Mode Resonator (MMR) from three pairs of parallel-coupled lines are constituted to obtain the UWB band. The proposed filter has multiple resonant frequencies in the passband and two transmission zeros perceived at stop band/passband transition edges. It has a 3-dB fractional bandwidth of 110% and it covers the entire UWB band of 3.1–10.6 GHz. The measured passband insertion loss and group delay are 0.35 dB and 0.42 ns, respectively. Moreover, the presented filter is a single-layered structure since it is more comfortable to be integrated into a printed circuit board (PCB). The simulated and measured performance of the presented filter is in good agreement. The filter finds its application in low power handling single-layered PCBs, unlicensed short and medium distance communications.

Compact Ultra-Wideband Bandpass Filters Achieved by Using a Stub-Loaded Stepped Impedance Resonator

In this paper, we develop a bandpass filter using a stub-loaded stepped impedance resonator (SLSIR) and calculate the even and odd resonant modes of this type of resonator using the input impedance/admittance analysis. In this study, two impedance ratios and two length ratios are operated as the design parameters for controlling the resonant modes of the SLSIR. Several resonant mode variation curves operating three resonant modes with different impedance ratios and two length ratios are developed. By tuning the desired impedance ratios and length ratios of the SLSIRs, compact ultra-wideband (UWB) bandpass filters (BPFs) can be achieved. Two examples of the UWB BPFs are designed in this study. The first example is UWB filter with a wide stopband and the second one is dual UWB BPF, namely, with UWB performance and a notch band. The first filter is designed for a UWB response from 3.1 to 5.26 GHz having a stopband from 5.3 to 11 GHz, with an attenuation level better than 18 dB. The second filter example is a dual UWB BPF with the frequency range from 3.1 to 5 GHz and 6 to 10.1 GHz using two sets of the proposed SLSIR. The measured results have insertion loss of less than 1 dB, and return loss greater than 10 dB. Furthermore, the coupling structures and open stub of the SLSIR also provide several transmission zeros at the skirt of the passbands for improving the passband selectivity.

A Compact UWB Bandpass Filter with WLAN Band Rejection Using Hybrid Technique

A compact Ultra-wideband (UWB) band-pass filter (BPF) based on a hybrid technique using a CPW-Microstrip-CPW transition is designed with WLAN band rejection. The proposed bandpass filter is mounted on a Rogers RO4350 substrate with a thickness of 0.508 mm. The presented UWB bandpass filter has good bandpass quality with 20 dB return-loss bandwidth from 2.9 to 12.2 GHz and insertion loss better than 0.5 dB with group delay UWB BPF about 0.22 ns. We can note that this latter is flat in the entire bandpass which indicates that the filter is efficient. . In addition, by implementing the closed-ring resonators (CRRs) on the bottom plane, we observe an appearance of the notched band. The center and bandwidth of the notched band can be controllable by adjusting the length and width of the CRRs. Thus, the presented filter can be beneficial for low profile future wireless communication systems. Simulation of this proposed filter is carried out on CST MWS software.

Compact reconfigurable triple notch ultra-wideband bandpass filter for cognitive radio system

This paper introduces a compact ultra-wideband (UWB) bandpass filter (BPF) with two switchable external notch structures which avoids the interference between the UWB communication with worldwide interoperability for microwave access (WiMAX) and wireless local area network (WLAN) systems, suitable for cognitive radio (CR) applications. The first external notch structure is modified C-shaped structure which generates a sharp rejection at 3.5 GHz to avoid interference with WiMAX system and second external notch structure is back to back T-shaped structure which creates sharp rejection notch bands at 5.2 GHz and 5.8 GHz frequencies for WLAN systems. The filter reconfiguration is achieved by varying the conductance of microstrip line. The response of the proposed structure shows sharp rejections at one WiMAX and two WLAN bands. The bandpass filter covers frequency of UWB system from 3.1 to 10.7 GHz having very low passband insertion loss. The proposed UWB BPF is designed, simulated, fabricated and tested to validate the results. A good agreement is achieved between simulation and experimental results.

Compact reconfigurable triple notch ultra-wideband bandpass filter for cognitive radio system

This paper introduces a compact ultra-wideband (UWB) bandpass filter (BPF) with two switchable external notch structures which avoids the interference between the UWB communication with worldwide interoperability for microwave access (WiMAX) and wireless local area network (WLAN) systems, suitable for cognitive radio (CR) applications. The first external notch structure is modified C-shaped structure which generates a sharp rejection at 3.5 GHz to avoid interference with WiMAX system and second external notch structure is back to back T-shaped structure which creates sharp rejection notch bands at 5.2 GHz and 5.8 GHz frequencies for WLAN systems. The filter reconfiguration is achieved by varying the conductance of microstrip line. The response of the proposed structure shows sharp rejections at one WiMAX and two WLAN bands. The bandpass filter covers frequency of UWB system from 3.1 to 10.7 GHz having very low passband insertion loss. The proposed UWB BPF is designed, simulated, fabricated and tested to validate the results. A good agreement is achieved between simulation and experimental results.

Compact ultra-wideband bandpass filter based on composite right/left-handed transmission line with improved out-of-band performance

ABSTRACTThis paper presents a novel compact ultra-wideband (UWB) bandpass filter (BPF). It consists of two composite right/left-handed transmission line (CRLH-TL) unit cells and an anti-coupled line structure. The CRLH-TL unit exhibits good passband performance with a compact size. By cascading the anti-coupled line structure, a wide upper stopband is obtained. The measured fractional bandwidth and insertion loss are 113.9% and 0.52 dB, respectively. Moreover, a broad stopband from 14 to 30 GHz with a high rejection level of 20 dB is obtained. The whole size is 14.4 mm × 10.2 mm. The simulated and measured results agree well.

A hybrid surface-to-surface transition-based UWB-BPF with multiple in-band interference suppression

AbstractA compact ultra-wideband (UWB) bandpass filter (BPF) based on surface-to-surface transition technology with features of extended stopband and integrated interference mitigation characteristics is proposed. The basic structure consists of a modified multiple-mode resonator (MMR)-based co-planar waveguide in the ground surface and coupled in broadside manner with the microstrip lines on the top surface. Later, two open-circuited stubs are embedded in the feeding lines and two complementary split ring resonators are etched in the MMR to implement multiple in-band transmission zeros so as to circumvent interference. A prototype is fabricated and measured to validate the results obtained in simulation. The proposed UWB-BPF is compact in size with overall dimensions of 17.82 by 11.08 mm2.

Compact UWB filter with narrow notched band based on grounded circular patch resonator

In this paper, a compact ultra-wideband (UWB) band-pass filter (BPF) with a single narrow notched band is proposed. This filter is designed using a novel multiple-mode resonator (MMR) based on a grounded circular patch resonator (GCPR). The proposed MMR generates three main resonances and two transmission zeros (TZs). A semi-lozenge slot (SLS) is proposed to control resonant frequencies and obtain UWB operation. The 3dB notched band is achieved from 5.65-5.8 GHz by connecting an arrowhead stub inside the filter. The UWB filter has been simulated, fabricated and measured. The dimension of the designed filter is about 0.31 × 0.31 λg × λg.

Theoretical Based Design of Ultra-Wideband Filter with Dual Band-Notch

In this paper, a compact ultra-wideband microstrip band-pass filter with single/dual-notched bands is proposed. The filter is theoretically designed based on a multiple-mode resonator which consists of a short circuit stub loaded-ring resonator. A multi stepped impedance resonator is also applied to reject unwanted in-band frequencies and extend the upper-stopband. The proposed filter is analyzed by utilizing graphs according to odd- and even-mode method. The resonant modes are allocated between 3.1 GHz to 10.6 GHz and transmission zeros are adjusted at upper stopband to create a sharp roll-off and suppress the spurious harmonics, as well as a compact physical size. Full-wave simulations are performed for three types of filters, with and without notch-bands, to verify theoretical results. The measurement results demonstrate that not only − 3 dB fractional bandwidth is more than 120% and but also at least − 20 dB suppression can be achieved at upper-stopband.

A compact UWB band-pass filter with a notch band using multi-mode stub-loaded resonators (MM-SLR)

AbstractIn this paper, an ultra-wideband (UWB) band-pass filter (BPF) with a sharp notch band is presented. The UWB BPF consists of modified elliptical-ring and multi-mode stub-loaded resonator (MM-SLR). By adding the asymmetric tight coupled lines resonator via input/output (I/O) lines, it can be achieved UWB band-pass response. With adding two bends to the middle resonator, a notch band at 6.86 GHz is created, so that it can be controlled using the mathematical formulas (MF). In the meantime, the equivalent circuit of the middle resonator is obtained using L–C analysis. Measured results of fabricated filter have the advantage such as ultra-wide pass band (flandfHof the defined UWB pass band are 3.776 and 10.42 GHz, which satisfy the requirements of FCC-specified UWB limits), compact size, low insertion loss &lt;0.65 dB and the stop band of the proposed filter is from 11.1 to 16.32 GHz with attenuation of −39.8 to −42.14 dB, respectively. The proposed UWB filter is realized using the substrate with dielectric constant of 2.2 and substrate height of 0.787 mm. Experimental verification is provided and good agreement has been found between simulation and measurement results.