Dual-band Bandpass Filter Research Articles

A novel self‐packaged DBBPF with multiple TZs for 5G sub‐6 GHz applications

AbstractIn this article, we proposed a self‐packaged dual‐band bandpass filter (DBBPF) with high isolation and low insertion loss (IL) for 5G sub‐6 GHz applications. To get high stopband suppression, multiple and controllable transmission zeros (TZs) are introduced. A pair of quarter‐wavelength stepped‐impedance resonators (QSIRs) and half‐wavelength hairpin resonators (HWHR) are introduced to form a cross‐coupled five‐star topology to generate two passbands and multiple TZs analyzed by mixed electromagnetic couplings. A pair of U‐shape resonators are designed on G6 to fully excite the resonators and introduce source/load TZs at the same time. The generation of TZs by separate electric and magnetic coupling paths (SEMCP) is discussed. The DBBPF achieves a low IL of 0.85/1.13 dB with fractional bandwidths (FBW) of 11.0%/6.9% at center frequencies of 3.45 and 4.9 GHz for 5G sub‐6 GHz applications, respectively. The total size is only 0.32 λg × 0.45 λg.

A New Method of Isolation Enhancement of Dual Band Band-Pass Filter Using Composite Mode Co-planar Waveguide Structure for 5G and Body Centric Applications

Frequency ratio or frequency difference of more than fifteen times between the two bands is difficult to realize particularly for millimetre-wave applications. This paper presents a large frequency ratio dual band band-pass filter for 5G communication and body-centric applications. The proposed filter has been studied and developed based on the mode-composite co-planar waveguide (MC-CPW). The proposed dual band band-pass filter comprises lower and higher bands designed independently with a high degree of freedom. In order to suppress the harmonics between the two bands, the lowpass filter is cascaded with the structure impedance matching to achieve the competent dual band band-pass filter response. The characteristics of the proposed dual band band-pass filter based on mode composite co-planar waveguide structure yield it as the promising and potential entrant for the multi-band operating systems particularly in 5G communication systems with body-centric applications. To certify the practicability and pre-eminence of the proposed filter, the simulated and measured results are compared and are found in good agreement with one another.

High Selectivity Cylindrical Cavity Dual-Band Bandpass Filter With Stepped Cylinders

In this brief, a quad-mode cylindrical cavity dual-band bandpass filter (CCDBPF) is proposed. Two stepped cylinders are located at the top and bottom of the cylindrical cavity. Two low-order resonant modes are generated because of two stepped cylinders, and they constitute the first passband. Two high-order modes are the low-order modes of the cylindrical cavity itself, which constitute the second passband. The center frequencies of two passbands are 1.61 GHz and 2.61 GHz, respectively. Two passbands can be independently adjusted. The first passband can be adjusted from 1.55 to 1.67GHz with insertion loss of 0.13-0.15 dB. The second passband can be adjusted from 2.48 to 2.67 GHz with low insertion loss of 0.1-0.2dB. The frequency selectivity is improved because of four transmission zeros (TZs) at 1.49 GHz, 1.89 GHz, 2.52 GHz, and 2.89 GHz. Since the stepped cylinders introduce a low-frequency passband, the miniaturization of the CCDBPF is realized. Finally, the CCDBPF is fabricated and measured. The measured frequency responses are coincident with the simulated results.

Graphene based tunable bandpass filter for terahertz spectroscopy of polymers

In this paper, a tunable dual-band bandpass filter using graphene is designed and simulated at resonant frequencies 1 THz and 1.5 THz. The proposed design consists of a series of TEM-mode transmission-line resonators which are open and short circuited in alternate orientation. The bandpass filter is designed from the lowpass Chebyshev prototype. A graphene layer is placed in between the dielectric layer and conductor layer in order to facilitate the plasmonic wave propagation. The simulation results suggest that the proposed graphene-based bandpass filter can achieve the specified frequency response. By altering the chemical potential of the graphene a shift of about 0.14 THz is observed in the transmission response of the filter. The proposed filter has the potential to be used as ultra-compact dual-band BPF in non-destructive testing in polymer processing industries.

A miniaturized dual-band bandpass filter with sharp roll-off rate using coupled lines and dual transmission lines

This paper presents a compact, high roll-off rate second-order dual-band bandpass filter with seven transmission zeros. The proposed filter design constructs of dual transmission lines, coupled lines, stepped impedance open stubs, and quarter-wavelength transmission lines. The proposed filter has a size of 0.31λg × 0.24λg and is printed on RT/duroid 5880 substrate to operate at two different frequencies (1.16 GHz and 2.71 GHz). The proposed filter is fabricated and measured, and good input matching is obtained at desired frequencies. Excellent isolation is achieved between two passbands due to the stopband effect created by the dual transmission lines. The simulated and tested frequency responses are in high agreement with each other.

A cylindrical cavity differential dual-band bandpass filter (DDBBPF) with stepped cylinders

In this paper, a differential dual-band bandpass filter (DDBBPF) is proposed. Two passbands are designed based on the fundamental mode TE111 and the first higher order mode TE112 of the cylindrical cavity. By introducing the stepped cylinders, the electromagnetic field distributions of two modes are changed. The two modes are split and the filtering performance of the two passbands is improved. Because the stepped cylinders have a great influence on TE112 mode and a small influence on TE111 mode, the second passband can be independently adjusted by changing the structural parameters of the stepped cylinders. Two center frequencies of the proposed DDBBPF are 1.78 GHz and 2.31 GHz, and both the absolute bandwidths are 40 MHz. Three transmission zeros (TZs) improve the frequency selectivity. Finally, the proposed DDBBPF is fabricated, and the simulation results are basically consistent with the measurement ones.

Designing a Compact Microstrip Dual-Band Filter with Two T-Shaped Resonators and Suitable Frequency Selectivity

A miniaturized microstrip dual-band bandpass filter (DBPF) with two T-shaped resonators is proposed. The two T-shaped resonators lead to multiple transmission zeros in the stopband and higher filter selectivity. The filter is analyzed using LC and even/odd mode analyses to determine the transmission zeros. The LC equivalent circuit and transfer function are presented. The proposed filter is symmetrical, so the electrical length and impedance values are used for odd/even mode analysis. The designed DBPF is centered at 1.9/5.54[Formula: see text]GHz and is suitable for WLAN applications. The insertion loss of the filter is less than 0.5[Formula: see text]dB and its return loss is more than [Formula: see text][Formula: see text]dB in each band. Five transmission zeros are created with an attenuation greater than [Formula: see text][Formula: see text]dB. The total area of the proposed filter is [Formula: see text][Formula: see text]mm2. To validate the proper performance of the proposed filter, it is fabricated and measured.

A dualband bandpass filter with tunable bandwidths for automotive radar and 5G millimeter-wave applications

A compact dual wideband bandpass filter for automotive radar (AR) and 5G millimeter-wave (mmWave) applications with adjustable bandwidths is presented in this work. The filter is based on microstrip dual-mode edge-coupled stub-loaded resonators (SLR). The novelty of this configuration is that it allows independent control of the bandwidths which is not obvious for many reported SLR-based filters. To achieve an overall size of 1.23λ_g× 2.02λ_g, these resonators are coupled and bent int o U-shape, T-shape, and E-shape. The U-shaped resonator, based on a quarter-wavelength transmission line, is coupled to the T-shaped element which constitutes the main feed line to obtain the dual-band response. Having a symmetrical structure, the design i s studied using the even-odd mode analysis. The layout is made using the Ansys high-frequency structural simulator (HFSS) and fabricated on Rogers RO3010 with a thickness of 1.28 mm, a dielectric constant of 10.2, and a loss tangent of 0.0022. The measured bandwidths are 660 MHz and 880 MHz at central frequencies of 23.92 GHz and 28.38 GHz respectively. The measured insertion losses are less than 3.9 dB and the return losses are greater than 17 dB in both bands. A good agreement is obtained between simulate d and experimental results.

Investigation of dual-band bandpass filter inspired by a pair of square coupled interlinked asymmetric tapered metamaterial resonator for X-band microwave applications

Investigation of dual-band bandpass filter inspired by a pair of square coupled interlinked asymmetric tapered metamaterial resonator for X-band microwave applications

Multi-band propagation of spoof surface plasmon polaritons by its high-order modes

Compact dual-band and tri-band bandpass filters (BPFs) based on high-order modes of spoof surface plasmon polaritons (SSPPs) are proposed. By using the meander line technique, the electrical size of the proposed SSPP structure was reduced by 68% compared with the traditional rectangular-grating SSPP structure. The high-efficiency passbands are excited by high-order modes of SSPPs. Therefore, dual-band and tri-band BPFs are designed by using two and three high-order modes of SSPPs, respectively. In addition, a notched band is obtained by loading three complementary split-ring resonators (CSRRs) on the bottom layer of the tri-band BPF. Thus, a quad-band BPF is achieved.

Balanced quasi-elliptic-type dual-passband filters using planar transversal coupled-line sections and their digital modeling

AbstractA class of balanced dual-band bandpass filters (BPFs) with planar transversal-signal-interference coupled-line sections is reported. In their building balanced dual-band BPF stage under differential-mode excitation, a second-order quasi-elliptic-type dual-band bandpass filtering transfer function is obtained. Specifically, from the transversal interaction among their two open-ended and virtually-short-ended half-wavelength coupled-line paths, sharp-rejection differential-mode dual passbands with several out-of-band transmission zeros at both sides are realized. To attain high common-mode suppression levels within the differential-mode passbands, two open-ended line segments are connected at the symmetry plane of the devised balanced dual-band BPF stage. Moreover, higher-order schemes based on in-series-cascaded multi-stage designs to further increase differential-mode selectivity and in-band common-mode rejection are illustrated. The operational principles and parametric-analysis design rules of the engineered transversal-coupled-line-based balanced dual-band BPF approach are detailed. Additionally, for a rigorous interpretation of their zero/pole characteristics, a digital-modeling framework is applied to them to connect RF balanced filters with their discrete-time versions. For practical-validation purposes, a microstrip prototype of two-stage/fourth-order balanced dual-band BPF is built and tested. It exhibits measured differential-mode dual passbands with center frequencies of 1.464 GHz and 2.294 GHz, 3-dB fractional bandwidths of 8.74% and 9.68%, and in-band common-mode rejection levels above 23.16 dB and 31.36 dB, respectively.

Design and Application of Novel Single- and Dual-Band Reconfigurable Microwave Components With Filter and Coupler Functions

In this article, novel single- and dual-band reconfigurable microwave component (RMC) designs with very compact circuit sizes are proposed, which can be reconfigured into multiple functions, including a bandpass filter, a bandstop filter, and a quadrature coupler. The proposed RMCs with filter and coupler functions are based on lumped elements and transistor-based switches such that they are very suitable for on-chip implementation. Specifically, the proposed 10-GHz RMC in GaAs can achieve the functions of a bandpass filter, a bandstop filter, and a quadrature coupler with a circuit size of only 1.8 mm <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\times1.35$ </tex-math></inline-formula> mm. On the other hand, the proposed 9.5/24-GHz RMC in GaAs can be reconfigured as either a dual-band bandpass filter or a dual-band quadrature coupler, while the circuit size is only 1.36 mm <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\times1.15$ </tex-math></inline-formula> mm. In addition, to demonstrate the possible application of the proposed RMC designs, a proof-of-concept 2.45-GHz radar system prototype based on a proposed 2.45-GHz RMC is implemented in PCB, which successfully integrates the functions of target speed detection and transmission in a single hardware.

A Wide Stopband Dual-Band Bandpass Filter Based on Asymmetrical Parallel-Coupled Transmission Line Resonator

A self-coupled resonator consisting of asymmetrical parallel-coupled microstrip transmission lines is proposed to design wide stopband dual-band bandpass filters. Due to the even-to-odd-mode analysis limitation to asymmetrical structure, a multiport analysis method is developed and applied to analyze the proposed self-coupled resonator and dual-band filter. According to the analysis, the proposed self-coupled resonator features a small frequency ratio of the second to the first resonances and controllable spurious responses, and its transmission zeros (TZs) are placed close to the position out-of-band spurs in order to achieve wide stopband. Moreover, a feed line consisting of tapped line loaded coupled line is investigated, resulting in flexible adjustment of the second passband external quality factor ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${ \boldsymbol Q}_{ \boldsymbol e}$ </tex-math></inline-formula> ) with a minor influence on the first passband <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${ \boldsymbol Q}_{ \boldsymbol e}$ </tex-math></inline-formula> . A dual-band BPF prototype with a frequency ratio of 1.59 is proposed and validated. It is operated at 2.34 and 3.72 GHz with the insertion loss of 1.05 and 1.86 dB, respectively. A return loss better than 20 dB is achieved at both passbands. The out-of-band rejection is better than 30 dB within the frequency range from 4.19 to 11.24 GHz, and the harmonic suppression is 39.97 dB at 14.88 GHz and 61.41 dB at 18.6 GHz. The measured results verify the analytical method presented in this article well.

Crystal structure and microwave dielectric properties of garnet-type Ca2YZr2-xTixAl3O12 ceramics for dual-band bandpass filters

Microwave dielectric ceramics with a high-quality factor are vital materials for substrates, dielectric resonators, and filters in millimeter-wave communication systems. Here, a novel microwave dielectric ceramic based on a garnet-type Ca2YZr2Al3O12 compound for bandpass filter was prepared using the solid-state reaction method. Sintering the Ca2YZr2Al3O12 ceramics at 1600 ℃ for 5 h resulted in excellent microwave dielectric properties of εr = 10.81 ± 0.16, Qf = 87,628 ± 4000 GHz and τf = −34.3 ± 0.5 ppm/℃. Increasing the Ti4+ content of the Ca2YZr2-xTixAl3O12 ceramics significantly improved the sintering process. Superior microwave dielectric properties (εr = 11.93 ± 0.15, Qf = 121,930 ± 2600 GHz and τf = −30.8 ± 0.4 ppm/℃) were obtained for Ca2YZr2-xTixAl3O12 (x = 0.3) because of its dense microstructure, large grain size and high lattice energy. The Ca2YZr2-xTixAl3O12 (x = 0.3) ceramics were used to fabricate a dual-band bandpass filter with a hairpin structure that exhibited a large return loss (|S11| > 12 dB) and a small insertion loss (|S21| < 0.73 dB). The high performance of the Ca2YZr2-xTixAl3O12 ceramics and the corresponding bandpass filter makes this material a potential candidate for millimeter-wave devices.

A Compact Dual-Band Bandpass Filter Using Coupled Microstrip Lines

In this paper, a new compact dual-band bandpass filter (DB-BPF) is proposed using parallel coupled lines. The design method is based on introducing transmission zeros (TZs) in the frequency response of a single-wideband filter. In the proposed structure, three coupled lines and a multi-mode resonator are used to realize the wide bandpass filter. Meanwhile, two coupled lines that are connected at the end and loaded by an open-circuit stub are employed to make a new notch filter. The proposed DB-BPF is designed and fabricated on Rogers RO3210 substrate for Wireless Local Area Networks (WLANs) applications. The simulation results show good agreement with measurements. The measured results exhibit two passbands centered at 2.4 and 5.2 GHz, having an insertion loss of less than 0.1 dB and 0.9 dB, respectively. Low insertion loss, compact size, and high attenuation between two passbands are the main advantages of the proposed DB-BPF.

A dual‐band filtering structure for highly selective reconfigurable bandpass filter and filtering balun

This article proposes a filtering structure consisting of two half-wavelength resonators and two open-stub loaded resonators, which generates two third-order passbands. Multiple transmission zeros are introduced by the newly developed coupling scheme, resulting in extremely sharp roll-off desirable for highly selective filters. The proposed structure is applied to design a PIN-diodes switch-controlled reconfigurable dual-band bandpass filter (BPF) with four-state filtering responses: both passbands ON, both passbands OFF, high-frequency passband ON, and low-frequency passband ON. Stepped-impedance open stubs and one-end-grounded coupled lines are studied and employed in the design to suppress unwanted responses. In addition, two filtering structures are placed symmetrically to design a dual-band balun BPF. Double-sided parallel-strip lines are added in the input port of the filter, and their inherent out-of-phase feature enables the balun filter to convert unbalanced signal to balanced signal at desired frequencies. The measured results of both fabricated devices agree well with the simulated results. The switchable BPF and balun BPF have two passbands (2.8 and 4.8 GHz) with high selectivity with the minimum roll-offs from −3 to −15 dB are 1.70 × 103 and 2.71 × 103 dB/decade, respectively. The insertion loss of the switchable BPF is 2.3/2.0 dB and the minimum signal suppressions level OFF state is measured as −18.2 dB. The insertion loss of the balun BPF is 1.8/1.4 dB, and the phase and magnitude imbalances are less than 0.3 dB and 5°, respectively. The excellent performances of the implemented filter and filtering balun successfully demonstrate the advantages and design efficacy of the proposed filtering structure for different applications.

Dual-band Band-pass Tunable Filter with Meander-Line Resonator

Radio frequency (RF) that can be tunable filters are band-pass filters (BPFs) with finely tunable passband frequencies. The passband frequency can be changed digitally, mechanically, or with a control voltage. Tunable BPF designs are increasing in importance as communication systems become more complex. In this study, a dual-band band-pass tunable filter with a meander-line resonator has been proposed. It aimed to create a tunable band-pass filter design in two different bands by using the SVM1413 varactor diode and gradually changing the capacitance value. SVM1413 varactor diode has been chosen in terms of applicability and capacitance value range width. The BPF operates in two different frequency ranges, from 2.5 to 3 GHz and from 4.2 to 4.6 GHz. BPF has been implemented and measured on a Rogers RO3003 substrate with a dielectric constant of 3 and a thickness of 1 mm. The substrate for the BPF has been chosen to be 30 × 30 mm^2 in size. The numerical calculation results have been simulated and optimized using computer simulation technology (CST). The insertion loss values are above -1 dB in both bandwidth ranges and all capacitance changes. Better results have been obtained when numerical calculation results have been compared with the outputs of the sources used.

Design of dual‐band balanced bandpass filter based on a single substrate integrated waveguide cavity

This paper proposes a dual-band balanced bandpass filter (BPF) based on a single interfered substrate integrated waveguide (SIW) cavity. The TE201, TE202, TE401, and TE402-modes are controlled by the metallic vias and divided into two groups. The first passband is made up of the affected TE201 and TE202-modes, while the second passband is made up of the disturbed TE401 and TE402-modes. In this balanced BPF design, it realizes the requested differential-mode (DM) transmission and common-mode (CM) suppression. Particularly, the bandwidths (BWs) of the two DM passbands can be efficiently controlled by only adjusting the locations of these metallic vias. A prototype dual-band balanced BPF operating at 16.71 and 22.23 GHz with BWs controllable is fabricated and measured for verification. Good accordance between simulation and measurement can be observed.

Wide‐stopband substrate‐integrated waveguide diplexers and dual‐band bandpass filter with large frequency ratios

Compact substrate-integrated waveguide (SIW) diplexers and dual-band bandpass filter (BPF) with widely separated passbands and wide-stopband are proposed for the first time based on half-mode substrate-integrated rectangular cavity (HMSIRC). Thanks to the dual-mode cavities and two respective channels, the frequencies and couplings of the two passbands can be flexibly controlled. To conquer the limitation of conventional full-mode cavity, the use of HMSIRC could intrinsically reject TE201 mode and many higher-order even modes, simultaneously realizing wide-stopband and widely separated passbands based on TE101 and TE102 modes. Moreover, the properly arranged internal coupling windows, which could intrinsically suppress the specific unwanted modes by sufficiently employing the existing design degrees of freedom, help further separate the two passbands and extend the stopband. The passband and stopband responses are systematically analyzed for different frequency ratios with the realizable frequency ratio and stopband bandwidth up to 1.91 and 2.65f1, respectively, which supplies the design guideline for SIW diplexers and dual-band BPFs with widely separated passbands and wide-stopband. Two SIW diplexers and an SIW dual-band BPF with frequency ratios of 1.72, 1.85, and 1.72 are synthesized and designed for demonstration, realizing the rejection levels and stopband bandwidths of 20 dB/2.34f1, 35 dB/2.36f1, and 20 dB/2.6f1, respectively.

Balanced Dual-Band BPF and FPD Using Quad-Mode RLR With Improved Selectivity

In this brief, a balanced dual-band bandpass filter (BPF) using quad-mode ring loaded resonator (RLR) is presented. The resonance characteristics of the proposed quad-mode RLR are analyzed and the design graphs of the electrical lengths and the four resonant modes are given. Based on the above analysis, four resonant modes are applied to achieve two differential-mode (DM) passbands. U-shaped microstrip lines and stepped impedance microstrip/slotline (MS) transition structures are employed to achieve good common-mode (CM) rejection without affecting DM ones. In addition, an additional transmission pole is realized in the lower passband due to the stepped impedance slotlines. Meanwhile, six transmission zeros (TZs) are generated due to the horizontal transmission interference of the resonator and new coupling path, which improves the selectivities of the passbands. Furthermore, based on the proposed filter, a balanced dual-band filtering power divider (FPD) is designed for miniaturization. By loading isolation resistors on the slotline, the output ports isolation is improved. To verify the theoretical design, two proposed designs have been manufactured and measured. The measured and simulated results are presented with a good agreement.