Balanced Dual-band Bandpass Filter Research Articles

Compact dual-band balanced bandpass filter using CRLH resonator with intrinsic common-mode suppression and multiple transmission zeros

In this paper, a newly composite right-/left-handed (CRLH) resonator is presented and applied to constitute a compact dual-band balanced bandpass filter (BPF). The proposed CRLH resonator contains two spiral coupled line segments. By imposing the differential-mode (DM) and common-mode (CM) excitation, the DM and CM equivalent circuits of the presented resonator and their lumped-element circuit models are built for investigating the resonant property. The CRLH resonator has two DM resonances and are adopted to design two DM passbands. Also, the CM resonances are all far away from DM resonances, achieved intrinsic desirable CM rejection within DM frequency range without any auxiliary elements. Attributing to the mixed electric and magnetic coupling between two coupled resonators and the introduced source-loaded coupling, multiple transmission zeros are obtained and therefore enhance the selectivity and attenuation in stopband. Finally, a well-designed dual-band balanced BPF is fabricated. Verification of the presented structure and design method’s validity is evidenced by the measured results, which are in agreement with the simulations.

Multilayer packaging dual‐band balanced bandpass filter based on dual‐mode substrate integrated waveguide cavities with split‐type topology

A new design method of the dual-band balanced bandpass filter (BPF) using multilayer packaging dual-mode substrate integrated waveguide (SIW) cavities is proposed. Split-type coupling topology based on dual-mode resonators is developed for the design. Firstly, a single-band balanced filter with perturbed metal vias is designed. The TE201 mode and the TE202 mode perturbed by the metal vias can form a passband. Secondly, an additional metal vias perturbed SIW cavity with the same dual-mode is placed in the lower layer for the bandstop function. A dual-band balanced BPF with split-type coupling topology is successfully realised. Compared with the traditional cascaded single-mode form, the proposed dual-mode split-type design has more compact size and can be more easily extended to multi-passbands. To verify the proposed method, a dual-band balanced filter operating at 13.3 and 14.2 GHz is designed, fabricated and measured. The designed dual-band balanced filter has good filtering performance including differential mode passband transmission and common mode rejection. Measured results show good agreements with simulated ones.

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.

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.

A balanced dual-band BPF with quasi-independently tunable center frequency and bandwidth

Abstract By introducing an open stub loaded resonator (OSLR) and a uniform impedance resonator (UIR) into balanced stepped-impedance microstrip-slotline transition structures, a balanced dual-band bandpass filter (BPF) with high selectivity and low insertion loss performance is presented in this paper. The balanced microstrip-slotline transition structures can achieve a wideband common-mode (CM) suppression. Meanwhile, the differential-mode (DM) passbands are independent from the CM responses, which greatly simplifies the design procedure. In addition, four varactors are loaded into OSLR and UIR to achieve the electrical reconfiguration. The proposed balanced dual-band BPF can realize quasi-independently tunable center frequencies and bandwidths. In order to verify the feasibility of the proposed design method, a prototype circuit of the proposed reconfigurable balanced dual-band BPF is simulated, fabricated and measured. A good agreement between the simulation and measurement results is observed.

A Reconfigurable Balanced Dual-Band Bandpass Filter With Constant Absolute Bandwidth and High Selectivity

A reconfigurable balanced dual-band bandpass filter (BPF) with constant differential-mode (DM) absolute bandwidth (ABW) and high selectivity is designed in this article. The proposed BPF is composed of a set of asymmetric short stub-loaded resonators (A-SSLRs) and balanced microstrip-to-slotline transition structures (MSTSs). Four varactor diodes are employed to achieve the reconfigurable characteristics with small insertion losses. By changing the coupling distances and selecting the positions of the loaded varactor diodes on A-SSLRs, the DM coupling coefficients <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$K_{i}$ </tex-math></inline-formula> and quality factors <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$Q_{i}$ </tex-math></inline-formula> of the proposed BPF can be easily controlled to keep a constant DM ABW. In the overall tuning range, a superior common-mode (CM) suppression is achieved intrinsically, and the DM responses are independent of the CM ones. Furthermore, five DM transmission zeros (TZs) are generated by the mixed-coupling and source–load coupling, which can improve the selectivity obviously. Compared with the published reconfigurable balanced BPFs, the proposed one has the advantages of constant DM ABW, smaller insertion losses, and more independent control on the two DM passbands. In order to validate the design strategies, a prototype circuit is designed, fabricated, and measured. The simulated and measured results are presented with a good agreement to verify the theory and design.

Design of a Multilayer Dual-Band Balanced Bandpass Filter on a Circular Patch Resonator

This letter presents a novel multilayer dual-band balanced bandpass filter (BPF) design by using two perturbed circular patch resonators. The TM11 mode and TM21 mode of the resonator with odd-symmetric field distributions are explored to realize the desired differential-mode (DM) transmission and common-mode (CM) suppression. Two circular patches are properly coupled in the back-to-back form to realize a dual-passband balanced response by virtue of coupling apertures etched on the ground. In addition to the internal coupling, the above apertures are also further utilized for the undesired degenerate mode harmonic suppression. Besides, slot perturbations on the patch are introduced to perturb the TM21 resonant mode to independently adjust the center frequency of the higher passband, while the lower passband remains almost unchanged. Thus, two passbands can be flexibly controlled by simultaneously tuning the above slots and size of the patch. For validation, a dual-band balanced BPF prototype is implemented. The results indicate 18 and 26% wide fractional bandwidths centered at 5.5 and 7.5 GHz with return loss higher than 20 dB under DM operation and CM suppression higher than 40 dB over an ultra-wide frequency band.

Compact dual-band balanced bandpass filter based on circular SIW cavity

Abstract A compact dual-band balanced bandpass filter with high frequency selectivity and adjustable passband based on the perturbed circular substrate integrated waveguide cavity is firstly proposed in this paper. Two pairs of metallic vias are located at 45°direction of cavities to separate a pair of degenerate modes (TM110 modes) to achieve the differential-mode (DM) dual-band response. Moreover, the perturbation vias can also be used to control the center frequency of the second DM passband while the first one still stays unaffected. The introduction of source-load coupling makes the filter exhibit excellent selectivity. And four controllable transmission zeros appear near two DM passbands. Finally, good common-mode suppression has been got owing to the proposed balanced structure. The measured results are in accordance with the simulated ones well.

Compact Tunable Balanced Dual-band Bandpass Filter Using Tri-Stub Loaded Resonator

This letter proposes a tunable balanced dual-band bandpass filter (BPF) with high common-mode (CM) suppression based on tri-stub loaded resonator (TSLR). Two TSLRs terminated with varactor diodes are employed to obtain the tunable second differential-mode (DM) passband, which is independent of the first one. For validation, a tunable balanced dual-band BPF is designed, fabricated and measured that achieve the continuous frequency-tuning range of the second DM passband from 5.968 to 6.368 GHz with constant 3dB fractional bandwidth (FBW) of 6.8% ± 0.17% and CM rejection levels of over 30 dB. The measured results agree well with the simulated ones.

Compact Dual-Band Dual-Mode SIW Balanced BPF With Intrinsic Common-Mode Suppression

In this letter, a compact dual-band dual-mode substrate integrated waveguide (SIW) balanced band-pass filter (BPF) with intrinsic common-mode (CM) suppression is designed by using a single perturbed SIW circular cavity. The vias and slot perturbations are introduced to tune the resonant modes TE <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">010</sub> , TE <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">110</sub> (a pair of degenerate modes), and TE <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">210</sub> of a circular cavity. Thus, they can be used to form two differential-mode (DM) passbands with independently adjustable center frequencies and bandwidths. The SIW can be seen as a natural balun with intrinsic CM suppression. Furthermore, the planar differential excitation structure is designed to excite the perturbed SIW cavity. The CM noise cannot excite SIW cavity due to the characteristics of hybrid electromagnetic boundary. Finally, a compact dual-band dual-mode SIW balanced BPF at 8 and 10 GHz is designed and fabricated, and the measured results show good agreement with the simulated ones.

Balanced dual-band superconducting filter using square ring loaded resonators with ultra-low insertion loss and common-mode noise suppression

In this paper, a multi-mode square ring loaded resonator (SRLR) comprising a full-wavelength ring resonator and six open stubs is introduced. The resonant characteristics are discussed and analyzed using differential-mode (DM) and common-mode (CM) equivalent circuits. Compared to the conventional design, the proposed SRLR involves two advantageous modifications for high-order balanced structure. First, two pairs of open stubs on the four corners of the ring resonator provide more flexible control of the internal coupling between two SRLR units under DM excitation. In addition, the shorted H-shaped resonator is compact, which makes proposed structure suitable for high-order filter design with desired operating frequency and bandwidth. Second, one pair of open stubs is added to the ring resonator along the horizontally symmetric plane. We found that the proposed SRLR provides more design freedom for CM noise suppression without extra components or defected ground structure. In addition, the proposed SRLR topology structure is folded to avoid large circuit occupation. Based on our analyses, a fourth-order balanced dual-band bandpass filter was designed with two passbands operating at 2.2 GHz and 3.5 GHz with corresponding in-band insertion loss of 0.1 dB and 0.12 dB, respectively. The filter was fabricated using high-temperature superconductor (HTS) YBCO thin films on an MgO substrate. Good agreement between simulated and measured frequency responses was observed, which verifies the proposed structure and design method.

A tunable balanced dual‐band BPF with quasi‐independently controlled center frequency and bandwidth

In this paper, a balanced dual-band bandpass filter (BPF) with high selectivity and low insertion loss performance is presented by employing stub loaded resonators (SLRs) and stepped impedance resonators (SIRs) into balanced microstrip-slotline (MS) transition structures. The balanced MS transition structures can achieve a wideband common-mode (CM) suppression which is independent of the differential-mode (DM) response, significantly simplifying the design procedure. Six varactors are loaded into the resonators to achieve the electrical reconfiguration. The proposed balanced dual-band BPF can realize quasi-independently tunable center frequencies and bandwidths. A tuning center frequency from 2.48 to 2.85 GHz and a fractional bandwidth (20.16%-7.02%) with more than 15 dB return loss and less than 2.36 dB insertion loss are achieved in the first passband. The second passband can realize a tuning center frequency from 3.6 to 3.95 GHz with more than 12 dB return loss and less than 2.38 dB insertion loss. A good agreement between the simulated and measured results is observed.

Dual-Band Balanced Bandpass Filter Using Slotlines Loaded Patch Resonators With Independently Controllable Bandwidths

A novel dual-band balanced bandpass filter structure is constructed by utilizing patch resonators and meandered slotlines (MSLs). The center frequencies and passband bandwidths of two differential-mode (DM) passbands can be controlled independently. Specifically, the fractional bandwidth (FBW) in a lower band with the level of ${S}_{11}$ better than 15 dB ranges from 2.9% to 19.1%, and the FBW in an upper band with the level of ${S}_{11}$ better than 15 dB is from 2.0% to 13.9%. Furthermore, isolation resistors are added in the middle of the patch resonators to improve the common-mode (CM) suppression across the given frequency range. To verify the proposed filter concept, two dual-band balanced filters with different bandwidths are designed, fabricated, and measured.

Balanced Dual-Band Superconducting Filter Using Stepped-Impedance Resonators With High Band-to-Band Isolation and Wide Stopband

A balanced dual-band and wide-stopband high-temperature superconducting (HTS) bandpass filter (BPF) with deep stopband rejection is designed using modified stepped impedance resonators (SIRs) in this brief. The center frequencies of the two differential-mode (DM) passbands can be controlled by adjusting two electrical length ratios of the proposed SIR, while keeping the third spurious frequency far away for wide-stopband design. An inherent common-mode (CM) suppression can also be obtained due to the discriminating CM resonant frequencies different from the DM ones. Multiple transmission zeros (TZs) are achieved to realize high passband selectivity and enhanced DM stopband by multipath coupling and shunt stubs loaded on the I/O ports. The proposed balanced dual-band filter operating at 1.78/4.0 GHz is eventually fabricated using HTS YBCO thin films on a MgO substrate, which can significantly lower the insertion losses. The circuit was measured at the temperature of 77 K, which shows maximum insertion losses of 0.42/0.37 dB and a DM stopband of 5.0f <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1</sub> <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">d</sup> with 40-dB attenuation, respectively.

Multilayered Balanced Dual-Band Bandpass Filter Based on Magnetically Coupled Open-Loop Resonators with Intrinsic Common-Mode Rejection

A new dual-band balanced bandpass filter based on magnetically coupled open-loop resonators in multilayer technology is proposed in this paper. The lower differential passband, centered at the Global Positioning System (GPS) L1 frequency, 1.575 GHz, was created by means of two coupled resonators etched in the middle layer of the structure, while the upper differential passband, centered at a Wi-Fi frequency of 2.4 GHz, was generated by coupling two resonators on the top layer. Magnetic coupling was used to design both passbands, leading to an intrinsic common-mode rejection of 39 dB within the lower passband and 33 dB within the upper passband. Simulation and measurement results are provided to verify the usefulness of the proposed dual-band differential bandpass filter.

A balanced dual‐band bandpass filter with a wide stopband and controllable differential‐mode frequencies and fractional bandwidths

In this article, a balanced microstrip dual-band bandpass filter (BPF) is designed. The proposed filter is achieved by employing a microstrip U-shape half-wavelength resonator, a folded stub-loaded resonator and balanced microstrip/slotline transition structures. The center frequencies and the fractional bandwidths of the two differential-mode (DM) passbands can be controlled independently by changing the physical lengths of the two resonators and the gaps between each resonator, respectively. The balanced microstrip/slotline transition structures can achieve a wideband common-mode (CM) suppression. Meanwhile, the DM passbands are independent from the CM responses, which significantly simplify the design procedure. In addition, a wide DM stopband is also realized. In order to validate the design strategies, a balanced dual-band BPF centered at 2.57 and 3.41 GHz was fabricated and a good agreement between the simulated and measured results is observed.

A Balanced Dual-Band BPF with High CM Suppression and Improved Selectivity

Abstract In this paper, a balanced dual-band bandpass filter (BPF) is designed based on microstrip folded stepped impedance split ring resonators (SISRRs) and balanced microstrip/slotline transition structures. The center frequencies and the fractional bandwidths (FBWs) of the two differential-mode (DM) passbands can be tuned by changing the physical lengths of two SISRRs and the gaps between the two resonators, respectively. The balanced microstrip/slotline transition structures can achieve a wideband common-mode (CM) suppression. Moreover, the DM passbands are independent from the CM responses, which significantly simplifies the design procedure. In addition, due to 0-degree feed structure and cross coupling structure, more transmission zeros can be realized, which can improve the passbands selectivity greatly. In order to validate the design strategies, a balanced dual-band BPF centered at 2.47 GHz and 5.21 GHz was fabricated and a good agreement between the simulated and measured results is observed.

A Balanced Dual-Band BPF Based on C-CSRR with Improved Passband Selectivity

Abstract A balanced dual-band bandpass filter (BPF) is proposed by embedding two nested coupled complementary split-ring resonators (C-CSRRs) into a H-type balanced stepped-impedance slotline resonator in this paper. C-CSRR is composed of a complementary split-ring resonator (CSRR) with a pair of coupling slotlines in the open end, which can generate a bandpass response. In order to improve the passband selectivity further, source-load-coupled structure is employed. Moreover, it can be found that the proposed BPF has a wideband common-mode (CM) suppression, which is independent from the differential-mode (DM) passbands. Therefore, the design procedure can be significantly simplified. In order to validate its practicalbility, one balanced dual-band BPF is fabricated. The predicted results on S parameters are compared with the measured ones and a good agreement is found.

A balanced dual‐band BPF with independently controllable frequencies and bandwidths

A balanced second-order dual-band bandpass filter (BPF) with independently controllable center frequencies and bandwidths based on coupled stepped-impedance resonators (SIRs) is designed in this article. To obtain a dual-band differential-mode (DM) response, two pairs of SIRs with different resonant frequencies are employed in the design. The bandwidths of the two DM passbands can be independently tuned by adjusting the coupling gaps and coupling lengths of the corresponding resonators. In addition, three transmission zeros are realized to enhance the selectivity of the DM passbands. The microstrip-slotline transition structure is utilized to achieve a wideband common-mode (CM) suppression. Moreover, the DM responses are independent of the CM ones, which significantly simplify the design procedure. Finally, a balanced dual-band BPF is designed to validate the design method and a good agreement between the simulated and measured results is observed.

Compact Balanced Dual-Band Bandpass Filter With High Common-Mode Suppression Using Planar Via-Free CRLH Resonator

A novel planar via-free composite right-/left-handed resonator with an interdigital capacitor and meander microstrip line is proposed in this letter. Under differential-mode (DM) excitation, the quasi-lumped resonator is virtually connected to ground, and it exhibits dual-mode characteristics. Moreover, two DMs can be tuned independently in an appropriate way. Under common-mode (CM) excitation, CM resonant modes are away from DM resonant modes, which contributes to the excellent CM suppression without additional circuits. Based on this resonator with compact size, CM suppression ability, and dual-mode DM characters, a balanced dual-band bandpass filter is analyzed and fabricated. Finally, simulated and measured results verify this design method.