Controllable Passband Research Articles

Single-/Dual-Band Linear Polarization Converter With Independently Controllable Passband and High Selectivity

Single-/Dual-Band Linear Polarization Converter With Independently Controllable Passband and High Selectivity

Miniaturized independent controllable dual-band bandpass filter by using transversal signal interference concepts

Abstract This paper presents and validates a compact dual-band bandpass filter with independent controllable passbands and isolation. The proposed filter is constructed by two transmission paths from input port to output port. Based on the transversal cancellation mechanism of two transmission paths, dual passband with independent controllable characteristics can be approached. The transversal cancellation techniques yield extra transmission zeros, which are located at 2.56 GHz, 3.58 GHz and 4.43 GHz respectively. Therefore, two passbands centered at 2.25/3.9 GHz are divided by triple transmission zeros. These transmission zeros also improve the out-of-band suppression performance of proposed filter. The designed prototype filter is implemented and tested, the measured 3 dB passband fractional bandwidths are 12.4 % and 7.5 %, respectively, and the minimum insertion losses are 0.48 dB and 0.88 dB respectively. Additionally, the dual-band transversal filter only occupies 0.012 λ g 2 ${\lambda }_{g}^{2}$ , which λ g is the guided wavelength at 50 Ω microstrip line at 2.25 GHz.

High-Order HTS Dual-Band Differential Bandpass Filter Using Stub-Loaded Twin-Ring Resonator With Fully Controllable Passbands

High-Order HTS Dual-Band Differential Bandpass Filter Using Stub-Loaded Twin-Ring Resonator With Fully Controllable Passbands

Compact dual‐band balanced bandpass filter with controllable passbands using coplanar waveguide spiral cross resonators

AbstractIn this article, a novel coplanar waveguide (CPW) spiral cross resonators (SCRs) is introduced for creating a dual‐band balanced bandpass filter (BPF) with adjustable passbands. The resonant properties of the SCRs in both the differential mode (DM) and common mode (CM) are scrutinized. Furthermore, DM bisection offers two distinct parameters for internal coupling adjustment, enabling independent passband width control. A novel grounding wire feeding arrangement matches the external Q factor of the dual DM passbands. An additional stepped‐impedance short‐circuited conducting stub between resonators prevents excessive coupling while obtaining moderate bandwidths. Inherent CM suppression can be attained by distinguishing CM resonant frequencies distinct from the DM frequencies. To validate the design, a dual‐band balanced BPF designed and fabricated to operate at 2.42 and 5.2 GHz exhibits closely matching measured results compared to the simulated ones.

High Selectivity Dual-Band Balanced BPF With Controllable Passbands Based on Magnetically Coupled Capacitor-Loaded SIRs

High Selectivity Dual-Band Balanced BPF With Controllable Passbands Based on Magnetically Coupled Capacitor-Loaded SIRs

A novel beam-steering device based on spoof surface plasmon polaritons

In this paper, an ultra-compact T-shaped component is proposed in order to achieve a spoof surface plasmon polariton (SSPPs) dual-functional device with beam steering and multiple band-rejection filtering functions. The newly introduced T-shaped component provides an excellent multiple band-rejection filter response when combined with the SSPP transmission line (TL), and can be regarded as an excellent alternative to metamaterial particles to conceive multi-band rejection of spoof SPP waves. Multi-band rejection filters are designed by introducing different intervals among the symmetric T-shaped components. Furthermore, we designed a compact SSPP beam-steering device integrated with a multiple band-rejection filtering function. The multiple band-rejection integrated beam-steering device can also be realized by incorporating different intervals among the T-shaped components, as mentioned in the case of linear filters. Integration of the SSPP beam-steering device and band-rejection filter offers compact areas and controllable passband features, which broadens the application range of SSPPs. In conclusion, the proposed T-shaped component is an outstanding addition toward the advancement of highly efficient ultra-compact dual-functional plasmonic devices.

Compact Wideband Absorptive Filtering Power Divider With a Reused Composite T-Shape Network

This paper presents a compact structure for the filtering power divider (FPD) with wide absorptive bandwidth as well as good isolation between the output ports. A composite T-shape network that consists of a pair of resistors and a central shorted stub is used for realizing good isolation and absorption simultaneously. The isolation resistors that are essential in the FPD can be shared to absorb the signal reflected back to the input port. To enhance the absorption performance, only one synergistic absorptive stub is required and added to the input port. It allows the absorption performance to be independently controllable without affecting the passband response. The dual functions of wideband filtering response and power division are achieved by integrating the power divider and the bandpass filter using a compact three-line coupled structure. A pair of shorted stubs loaded at the ends of coupled-feed lines for outputs can provide controllable passband bandwidth and transmission zeros. To verify the proposed design concept, the multifunctional FPD with the compact structure is fabricated and measured. Good agreements between the measured and simulated results verify the calculated predictions.

Design of dual-band BPFs with high selectivity

Abstract In this article, two dual-band microstrip bandpass filters (BPFs) with high selectivity and independently controllable passbands are designed based on three parallel-coupled lines (TPCLs). The first BPF proposed in this paper is achieved by employing a pair of folded F-type resonators (FFRs) and conventional TPCL structure. By adjusting the above parameters of each FFR, the center frequencies of the two passbands can be controlled easily. In the meantime, TPCL can enhance the coupling between the source and load, and introduce multiple transmission zeros (TZs), which can conduce to a higher selectivity. To obtain superior selectivity, the second BPF is designed based on a novel TPCL. The novel TPCL is based on the traditional one, which further enhances selectivity since transmission paths are doubled. In order to achieve miniaturization and enhance coupling, FFRs are folded. In addition, four transmission zeros (TZs) are generated to improve the selectivity of the two passbands. The measured results of the fabricated BPFs centered at 2.45/3.5 GHz agree well with the simulated ones, which validates the proposed design method.

An Endfire Controllable-Filtering Antenna Based on Spoof Surface Plasmon Polaritons

In this letter, a planar endfire filtering antenna with a controllable passband and a high gain based on spoof surface plasmon polaritons (SSPPs) is proposed. Its radiating part consists of three pairs of sector-shaped patches and I-shaped directors which are linked with the end of SSPPs feeding line. As demonstrated, the filtering performance of the proposed antenna can be easily adjusted by changing the size of all the branches with metal vias, round-shaped, and π-shaped resonators. A prototype operating in 8–9 GHz is fabricated and tested to verify the design, which reveals an average gain of 8.6 dBi, an out-of-band suppression level of more than 12 dB, and a profile of 0.014–λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> . Good agreement is achieved between the simulated and measured results. Simple and controllable design methods and good performance indicate its significance in modern communication systems.

Dual-Band Bandpass Filter With Controllable Stopband Bandwidth

A novel dual-band bandpass filter (BPF) is proposed with independently controllable transmission zeros (TZs) which can realize widely tunable stopband bandwidth (BW). The planar microstrip filter consists of a three-degree L-C ladder lowpass filter loaded with two unsymmetrical shorted stubs which are used to produce different TZs. By tuning the parameters of the two unsymmetrical shorted stubs, the TZs can be independently controlled. Therefore, the BPF has independent controllable center frequencies (CFs), passband bandwidths, and stopband bandwidths between adjacent passbands. All the L-C values in the equivalent circuit of the proposed filter are optimized to fulfill the design specifications. For demonstration, a dual-band BPF is designed. The measured results show good agreement with the simulated ones.

Compact, flexible and highly selective wideband complementary FSS with high angular stability

AbstractThis article presents a novel miniaturized (0.105λ0 × 0.105λ0) flexible complementary frequency selective surfaces (CFSS) structure with sharp band edge selectivity and very high angular stability. To explore two diverse applications as a passband and stopband filter, a novel complementary convoluted square loop (CCSL) type structure has been designed and investigated on ultrathin dielectric material of thickness 0.0023λ0. The second-order wide controllable passband with fractional bandwidth of 19.23% (−3 dB) and remarkably wide stopband of 64.7% (−10 dB) and 54.8% (−20 dB) respectively have been achieved by using a cascaded resonating structure which is composed of asymmetrical meandered CCSL array, arranged on two ultrathin dielectric layers with air foam separation. This particular format would lead to sharp band edge selectivity with steep roll-off (72.43 dB/GHz) and an excellent passband selectivity factor (0.731). An equivalent lumped LC circuit in conjunction with the transmission line model has also been adopted to comprehend the physical mechanism of the proposed single layer and double layer structures. Further, better passband and stopband angular stability at an oblique incident angle of 45° and the bending characteristics have also been investigated thoroughly for the proposed flexible CFSS to check their employability in different conformal structures with WiMAX passband and WLAN stopband application.

Compact fourth/third order dual‐band bandpass filter with independently controllable passbands

AbstractThis article reports a compact microstrip dual‐band bandpass filter (DBBPF) using two pairs of λ/4 short‐circuited stepped impedance resonators (SSIRs) and a stub‐loaded triple‐mode resonator (STR). The first and fourth λ/4 SSIRs not only couple with the second and third SSIRs to form the lower passband, but also serve as the feeding structure and provide source‐load coupling for the higher passband, formed by the STR. As a result, a compact filter size can be achieved, and two extra transmission zeros are created for the higher passband to enhance the passband selectivity. Meanwhile, both the center frequency and bandwidth of each passband can be controlled independently. Furthermore, the impedance and length ratios of the two pairs of λ/4 SSIRs are dissimilar to achieve wide stopband. A fourth/third order DBBPF prototype centered at 1.575 GHz (GPS) and 3.5 GHz (WiMAX) is ultimately implemented to demonstrate the design concept, and the measurements match the simulations with good consistency.

Compact and Narrow-Band Bandpass Filter Using Spoof Surface Plasmon Polaritons

This letter presents a novel narrow-band bandpass spoof surface plasmon polarition (SSPP) filter, which has a controllable passband, good rejection, and a compact structure. It is composed of two end-extending SSPP transmission lines and a pair of L-shaped coupling branches. Both the bandwidth and the central frequency can be adjusted by changing the depth of the SSPP unit and the length of SSPP transmission line behind the coupling branches. The dispersion curves of the SSPP unit are analyzed, and the influences of some structural parameters are investigated. A SSPP band-pass filter is fabricated and measured based on the proposed method, showing a wide 3-dB fractional bandwidth of 11.2% centered at 6.25 GHz and an out-of-band rejection below -15 dB within 1-10 GHz. The measured result shows good agreement with the simulated one.

Spoof surface plasmon polariton beam splitters integrated with broadband rejection filtering function

In this paper, a new kind of spoof surface plasmon polariton (SSPP) beam splitter integrated with band-rejection filtering functions is presented. Firstly, the mechanism of single-band rejection phenomena of the SSPP transmission lines (TLs) with and without T-shaped decorations are revealed through dispersion analyses. Based on the single-band rejection filter, multi-band rejection filters are further designed by introducing different intervals between the symmetric T-shaped decorations. Furthermore, we construct a compact Y-shaped beam splitter integrated with a broadband band-rejection filtering function using the SSPP TLs, which consists of an SSPP TL with rectangular grooves and two filtering branch SSPP TLs. Multiple band-rejection integrated beam splitters can also be realized by incorporating different intervals between the T-shaped decorations. The integration of the SSPP beam splitter and band-rejection filter offers compact areas, lower insertion loss and controllable passband features. It is strongly believed that that the proposed idea will raise promising possibilities in the integration of multiple microwave functions in the same component, e.g. filtering antennas, filtering switches, multifunctional radiofrequency (RF) passive and active components capable of performing several RF analog signal-processing functions in the same circuit volume, and so on.

Miniaturized single‐/dual‐band bandpass filters based on grounded square patch resonator with controllable passbands

AbstractMiniaturized single‐/dual‐band bandpass filters (BPFs) are proposed in this paper based on one single grounded square patch (GSP) resonator. The GSP resonator is realized by introducing ring‐shaped metallic vias at the center of a patch. Owing to this specific geometry, an additional mode nominated as LC mode is generated, which makes the proposed GSP resonator operate below the fundamental resonate frequency of the non‐grounded patch, thus miniaturization has been achieved. In addition, several slots are etched on the GSP resonator to serve as perturbations and control bandwidths (BWs) and center frequencies of the filter. As a result, the designed filters have featured both compact size and independent controllability. Moreover, single‐ or dual‐band BPF can be realized by changing the location of the input/output feedlines. For demonstration, the proposed filters have been fabricated, and the measured results agree with predicted responses.

Highly compact quad‐band bandpass filter with flexibly controllable passbands

This letter reports a highly compact microstrip quad-band bandpass filter based on two folded λ/4 stepped impedance resonators and three folded dual-mode short stub-loaded resonators. The two stepped impedance resonators not only form the first passband but also serve as the feed structure and provide the source-load coupling path for the three higher passbands created by the short stub-loaded resonators. Thus, a compact size can be obtained, and three pairs of transmission zeros can be realised near the three higher passbands to improve the frequency selectivity. It has been shown that the centre frequencies and bandwidths of the four passbands can be controlled independently. A microstrip quad-band bandpass filter centred at 1.1/2.05/3/3.55 GHz is implemented and tested achieving an extremely small size of 0.07λg × 0.14λg, where λg is the guided wavelength at 1.1 GHz. This presents one of the smallest quad-band bandpass filter ever demonstrated in the literature.

Dual-/tri-band bandpass filters with fully independent and controllable passband based on multipath-embedded resonators

AbstractIn this paper, dual-band and tri-band bandpass filters (BPFs) with fully independent and controllable passbands based on multipath-embedded resonators are presented. The dual-band BPF consists of two double open-ended stub-loaded terminal-shorted resonators (DOESL-TSRs) with a common via-hole connected along the symmetric plane of the filter. Based on DOESL-TSRs, a triple open-ended stub-loaded terminal-shorted resonator (TOESL-TSR) is proposed in the design of tri-band BPFs. The resonant characteristics of DOESL-TSR/TOESL-TSR are analyzed by the numerical calculation method. The measured results of the dual-band BPF show that the center frequencies (CFs) are located at 2.595 and 5.75 GHz, respectively, with 3 dB fraction bandwidth (FBWs) of 15 and 12.8%. The measured CFs of the tri-band BPF are located at 2.545, 3.775, and 5.95 GHz, respectively, with 3 dB FBWs of 9.8, 9.3, and 5.5%. Both of the filters exhibit the merits of fully independent and controllable passbands, high selectivity, and compact size.

Analysis of DGS filters using π‐circuit model

AbstractThe design and analysis of two defected ground structures (DGS)‐based filters have been proposed in this article. The first is a multifrequency bandstop filter (BSF) which utilizes a semi‐H defect in the ground plane. This structure is then prototyped on a Rogers 4350B substrate of overall size 45 mm × 15 mm with an external SMD capacitors employed to control the resonance of the circuit for the stopband frequencies of 433, 700, and 915 MHz. An equivalent π‐circuit is modified to validate this multiband filter. The second filter is a combination of a BSF and bandpass filter in one structure. The filter operating with a controllable passband and stopband frequency is fabricated on Rogers 4350B lossy substrate. Two SMD capacitors are loaded in the filter structure to control the passband and stopband frequencies of the filter with a structure size of 20 mm x 20 mm. Finally, the equivalent circuit from the BSF is modified further to encompass the bandpass and bandstop frequency response of the proposed work.

Compact dual‐band filtering power divider with independently controllable bandwidths using shorted patch resonators

This study presents a novel dual-band filtering power divider (DB-FPD) structure with independently controllable bandwidths for dual-band application. The proposed DB-FPD structure is constructed by shorted G- and T-shaped patch resonators, and meandered slot lines are etched on shorted patch resonators to generate resonance in the upper band. The 3 dB fractional bandwidth (FBW) of designed DB-FPD structure in a lower band (upper band) can be adjusted from 5.2 to 24.2% (3.1 to 26.9%), respectively, using a substrate of 31 mil thick TLY-5. The even-/odd-mode method is adopted to demonstrate the power splitting and isolation performances. The lumped-element equivalent circuit is extracted to explain the power splitting transmission performance. Also, the coupling matrix analysis is applied to present the detailed design procedures for practical DB-FPD, with specific passband bandwidths and centre frequencies of dual passbands. Finally, the isolation performances are analysed with different isolation resistor values and loading positions. For verification, two DB-FPDs with equal absolute bandwidths (ABW) and equal FBWs are simulated, fabricated and measured for dual-band WLAN application. The measured results agree well with the simulated ones, exhibiting a favourable frequency selectivity and controllable passband bandwidths.

Compact Dual-Band Inverted-Microstrip Ridge Gap Waveguide Bandpass Filter

A compact dual-mode inverted microstrip ridge gap waveguide (IMRGW) resonator and a series of dual-band IMRGW bandpass filters (BPFs) with easily controllable passbands are proposed for the first time in this article. The resonator is embedded into the ridge of the IMRGW without disturbing the placement of the mushroom-type bed of nails. A metalized via-hole is introduced to the center of the IMRGW resonator to ground a central patch, resulting in an inverted microstrip resonance mode and a cavity resonance mode simultaneously. The cavity resonant mode is relatively insensitive to the dimensions of the central patch, while the inverted microstrip resonance is insensitive to the dimensions of the cavity enclosed by electromagnetic band-gaps (EBGs) and two rows of metalized via-holes. Therefore, the resonant frequency of the two modes can be tuned independently. The resonators can be cascaded easily with a short IMRGW transmission line. A series of IMRGW based dual-band BPF with different orders are designed, fabricated, and measured. The third-order BPF’s simulated passbands are 13.07–13.41 and 18.46–18.91 GHz with a fractional bandwidth of 2.5% and 2.3%. Low insertion losses better than 1.7 and 2.1 dB are obtained on the two passbands. The measured passbands are 13.52–13.86 and 18.9–19.34 GHz with a fractional bandwidth of 2.3% and 2.2% while the insertion losses are better than 2.5 and 2.3 dB for the third-order BPF.