Non-adjacent Resonators Research Articles

High-Performance monolithic ceramic waveguide filter with isosceles Right-Angled triangular resonator for base station applications

This paper presents a high-performance integrated monolithic ceramic dielectric waveguide (DW) filter featuring isosceles right-angled triangular (IRAT) resonators. The fabrication process of the filter involves embedding a specific number of blind holes (BHs) or through holes/slots (THs/TSs) in a hexagonal ceramic dielectric block, fully metallizing the dielectric surface, and forming a monolithic ceramic DW filter. To achieve magnetic coupling, four THs and a BH are introduced in the oblique edges of two IRAT resonators; alternatively, a TS and BH are introduced in their right-angled edges. Electrical coupling is realized through a deep BH on the right-angle side of the resonators. Two non-adjacent resonators initiate weak cross-coupling by cascading a T-shaped rectangular TS, shallow BHs, and deep BH, creating two transmission zeros (TZs) outside the band. The filter was fabricated to ensure theoretical correctness and process reliability. The measured results show an insertion loss between 0.5 – 1 dB and a return loss greater than 18 dB at a bandwidth of 3.4 – 3.6 GHz. Two steep out-of-band TZs occur at 3.26 GHz and 3.72 GHz, aligning with simulation results. Therefore, the filter not only exhibits excellent performance but is also convenient for mass production and manufacturing, offering significant potential for future applications in 5G / 6G communication base stations.

A Simultaneous Power and Data Transfer Technology Using Dual-Resonance-Band Circuits for Domino-Resonator WPT Systems

The integrated transmission of power and data is a promising technology in various wireless power transfer (WPT) application scenarios. In this work, a novel simultaneous power and data transfer (SPDT) technology for domino-resonator WPT systems is proposed. The frequency shift keying (FSK) power modulation method is adopted in dual-resonance-band circuits to maintain high system transfer efficiency at two different frequencies. Considering the cross-coupling between nonadjacent resonators, the system operating frequencies shift slightly away from the circuit resonant frequencies, and the same constant output voltage (CV) characteristics can be always guaranteed with different data sequences. Subsequently, a compact coil structure is developed to accommodate the tight space constraint inside the insulator. Finally, aiming at the 35-kV suspension composite insulator with five embedded domino resonators, a 15W experimental prototype is built to realize simultaneous power and data transfer and constant voltage output. The experimental results show that the fluctuation of output voltage is less than 5%, and the overall system transfer efficiency is higher than 75%.

Balanced single/dual band trisection filters

ABSTRACT This work presents balanced microstrip filters with asymmetrical frequency response based on a balanced trisection topology. The proposed balanced trisection topology has the feature of being used in single and multiband microwave filters. In this work, in order to test the topology flexibility, we address two applications, one for a single-band filter and the other for a dual-band filter. This topology introduces TZs on either side of the passband edges, improving the selectivity on one side of the passband. The non-adjacent resonators of the single-band trisection balanced filter are based on a Pi-network balanced resonator which is composed by six transmission lines (TLs) and two inductors (Ls). The differential-mode (DM) and common-mode (CM) resonances can be chosen independently with a proper selection of the impedances and the electrical lengths of TLs in order to have high DM stopband and intrinsic high common mode rejection (CMR). The Pi-network was modified and analyzed under the even and odd mode technique to have a dual-band behavior. Good agreement between simulation and measurement was achieved.

Селективные свойства двухрезонаторных структур и высокоизбирательные фильтры на их основе

An increase in the frequency selectivity of microstrip filters is traditionally achieved by forming transient response zeros at final frequencies. In this case, the specified requirements for the selectivity of filters are provided with a smaller number of resonators, and, consequently, lower loss es in the passband are achieved in more compact structures. Thus, the effectiveness of this approach to the synthesis of microstrip filters is determined by the number of transient response zeros that can potentially be formed in various structures. One way to form damping transient response zeros is to introduce additional cross-couplings between non-adjacent resonators. However, when synthesizing highly selective filters based on such widely used N-resonator structures, a limited number of transient response zeros equal to N-2 is formed. At the same time, two-resonator structures are known in which a much larger number of transient response zeros is formed, which is several times greater than the number of resonators in them. However, each of these structures has its own specific frequency-selective properties, which limits the scope of their wide application as universal links. The aim of this work is the synthesis of highly selective two-cavity structures with various types of frequency characteristics, which expands the scope of such structures. The frequency properties of microstrip two-resonator structures of a new type, which have broad functionality and increased frequency selectivity, are studied. It is shown that in multistage structures on two half-wave hairpin resonators, under certain conditions, a significant number of transient response zeros is formed, which is two to three times greater than the number of resonators in the filter, and parasitic transmission bands also degenerate. Depending on the ratio of the coefficients of electromagnetic interaction in different sections of the length of the coupled resonators, they acquire the properties of both single-band and multi-band bandpass filters, as well as low-pass filters. The noted features predetermine the possibility of wide application of these structures as both independent compact filters and basic units as part of higher-order filters with a significantly limited number of resonators. The results of electrodynamic 3D modeling and experimental studies of the proposed structures are presented, which are in good agreement.

Высокоселективный волноводный полосно-пропускающий фильтр с уровнем подавления помех более 120 dB

The design of a 10th-order waveguide bandpass filter with an additional inductive cross-coupling between non-adjacent resonators has been proposed and studied. An inductive coupling is formed by a U-shaped conductor structure with grounded ends that is formed in the filter cover. This method of cross-coupling organization ensures not only the temperature stability of the characteristics, but also the manufacturability of the structure. The high selectivity of the device is achieved by both the attenuation poles located near the passband, as well as the level of suppression in the stopbands, exceeding 120 dB. The passband loss of the fabricated filter is ~0.8 dB at its central frequency f0 = 18.2 GHz and relative bandwidth Δf / f0 = 1.5%. The small dimensions (135×30×10 mm3) and the weight of about 200 g of the device, with simultaneously high electrical characteristics show the promise of its use, for example, in on-board and ground-based space communication systems.

A high-selectivity waveguide bandpass filter with interference suppression by more than 120 dB in rejection band

The design of a 10th-order waveguide bandpass filter with an additional inductive cross-coupling between non-adjacent resonators has been proposed and studied. An inductive coupling is formed by a U-shaped conductor structure with grounded ends that is formed in the filter cover. This method of cross-coupling organization ensures not only the temperature stability of the characteristics, but also the manufacturability of the structure. The high selectivity of the device is achieved by both the attenuation poles located near the passband, as well as the level of suppression in the stopbands, exceeding 120 dB. The passband loss of the fabricated filter is ~ 0.8 dB at its central frequency f0=18.2 GHz and relative bandwidth Delta f/f0=1.5%. The small dimensions (135x 30x 10 mm) and the weight of about 200 g of the device, with simultaneously high electrical characteristics show the promise of its use, for example, in on-board and ground-based space communication systems Keywords: bandpass filter, waveguide, resonator, cross-coupling.

A Transmission Zero Position Control for 28 GHz Rectangular Waveguide Cavity Bandpass Filter

This paper presents a method to control on single real-frequency transmission zeros (TZs) position in the reject band for third-order waveguide band pass filter (BPF). The external couplings are achieved by using a coaxial probes while the internal couplings are achieved by using short-circuit metallic posts. The TZs appear are generated by forming a triplet, i.e., multipath cancellation between non-adjacent resonators. The dimensions of the metal post between non-adjacent resonators are adjusted to control the position of TZs in the rejection band. A third order waveguide generalized Chebyshev BPF is simulated with HFSS at a center frequency of 28 GHz to validate the design method. The simulated insertion loss is 0.05 dB and the bandwidth (BW) is 500MHz. The simulation demonstrates the compatibility of the presented filtering structure with 5G applications.

Compact Microstrip Wideband Cross-Coupled Inline Bandpass Filters With Miniaturized Stepped-Impedance Resonators (SIRs)

This paper presents a class of reduced footprint inline microstrip bandpass filters capable of covering bandwidth up to 20% as well as good flexibility in establishing various cross-couplings for creating transmission zeros. The resonating elements are quarter-wave stepped-impedance resonators (SIRs), which have a wide upper stopband in nature. To achieve size miniaturization, the low-impedance segment of each SIR is implemented as a thick-trace ring and configured in a spiral form, and the high-impedance section is deformed to accommodate the low-impedance section. An interlaced coupling structure is proposed to enhance the coupling limited by the downsized coupled segments of adjacent resonators. In addition, by properly routing the associated shorted stubs, the structure can easily establish cross-coupling between nonadjacent resonators. Thus, compact SIR filters in an inline arrangement can be achieved to have either narrow or wide passbands with multiple transmission zeros. Two such circuits with sharp transition bands and upper stopband extension are synthesized, fabricated, and tested. The measured results show good agreement with simulated data. The circuit areas together with the performances of the experimental filters are compared with those in existing literature.

Microstrip Quazi-Elliptic Bandpass Filter With Two Pairs of Antiparallel Mixed-Coupled SIRs

An analysis of the second-order mixed-coupled bandpass filter (BPF) of a general form is carried out. The resonators in this BPF are presented by a resonant frequency $f_{0}$ and a susceptance slope parameter $b$ . The position of the transmission zero (TZ) generated by the mixed coupling is determined. A correspondence is established between the mixed coupling representation as the sum of magnetic $K_{\mathrm{ m}}$ and electric $K_{\mathrm{ e}}$ components and the linear representation form $m (\Omega) = m_{0} {-} a \,\,\Omega $ . It is shown that the slope of the frequency dependence $m(\Omega $ ) is negative. The conditions for equidistant arrangement of two TZs in BPF with mixed couplings between adjacent resonators are formulated. A fourth-order microstrip quazi-elliptic BPF with two pairs of antiparallel mixed-coupled stepped-impedance resonators (SIRs) is proposed. It reduces the parasitic interaction between nonadjacent resonators and makes it possible to obtain the required frequency responses more accurately. The results of the measurements and simulation are presented.

A Varactor-Based Very Compact Tunable Filter with Wide Tuning Range for 4G and Sub-6 GHz 5G Communications.

A very compact microstrip reconfigurable filter for fourth-generation (4G) and sub-6 GHz fifth-generation (5G) systems using a new hybrid co-simulation method is presented in this manuscript. The basic microstrip design uses three coupled line resonators with λ/4 open-circuited stubs. The coupling coefficients between the adjacent and non-adjacent resonators are used to tune the filter at the required center frequency to cover the frequency range from 2.5 to 3.8 GHz. The coupling coefficient factors between the adjacent resonators are adjusted to control and achieve the required bandwidth, while the input and output external quality factors are adjusted to ensure maximum power transfer between the input and output ports. Two varactor diodes and biasing circuit components are selected and designed to meet the targeted performance for the tunable filter. The impedance bandwidth is maintained between 95 and 115 MHz with measured return losses of more than 17 dB and measured insertion loss of less than 1 dB. Computer simulation technology (CST) is utilized to design and optimize the presented reconfigurable filter, with hybrid co-simulation technique, using both CST microwave studio (MWS) and CST design studio (DS), is applied to build the model by considering the SPICE representation for the varactor switches and all electronic elements of the biasing circuit. The introduced reconfigurable microstrip filter is also fabricated using a Rogers RO3010 material with a relative dielectric constant of 10.1 and it is printed on a very compact size of 13 × 8 × 0.81 mm3. An excellent agreement is obtained between the simulation and measurement performance.

Design of High-Selective Printed-Ridge Gap Waveguide Filter Using Source–Load and Cross Couplings

In this letter, high-selective bandpass filters, in the printed ridge gap waveguide technology, are presented. The filters are designed to perform 4.68% fractional bandwidth at center frequency $f_{0}$ = 24.78 GHz. In the proposed filters, to obtain high selectivity, a cross-coupling between the nonadjacent resonators and also a coupling between the input and output ports to create an extra pair of transmission zeros in the transfer function of the filters are used. Finally, the filters are fabricated, and their scattering parameters are measured to verify the simulation results.

High-Selectivity Microstrip Filters Based on Structures With a Limited Number of Hairpin Resonators [Application Notes

Microstrip filters on half-wave hairpin resonators are widely used in different microwave applications because they are very compact structures and do not contain short circuit elements, characteristics that make them relatively easy to manufacture and use over a wide frequency range. In this class of microstrip filters, three basic structures can be defined: one based on hairpin resonators with alternating orientations [Figure 1(a)], another based on codirectional hairpin resonators [Figure 1(b)], and a third based on filters using hairpin resonators with supplementary electromagnetic couplings between nonadjacent resonators [Figure 1(c)]. These structures are fundamentally different both in their operating principles and in their achievable characteristics despite layouts that, for two of them, seem similar.

Filter design for folded canonical topologies based on equivalent circuit segmentation

This paper presents a methodology to design filters with folded canonical topologies, which implement cross couplings between non-adjacent resonators. The technique is based on segmenting the traditional coupling matrix in a step-by-step fashion. At each step, a subset of the whole physical structure is optimized to match the response of the corresponding segment of the coupling matrix. In the context of this design technique, in this paper we propose an efficient segmentation methodology of the coupling matrix based on multiport networks. The use of multiport networks allows to generate at each step several goal functions, which are simultaneously used during the optimization of the corresponding physical segment. These multiport networks allow to efficiently monitor the different paths of the signal, present in folded canonical topologies. It is shown that this strategy leads to a fast convergence of the step-by-step segmentation technique for the design of this type of coupling topologies. We apply the proposed methodology to the design of two filters using the quartet topology. The first filter has two transmission zeros placed at the real frequency axis, and the second one has two complex transmission zeros intended for group delay equalization. The results indicate that the proposed methodology is effective for the design of this type of coupling topologies, leading to initial dimensions for the filters that typically have less than 1% of error when they are compared with those obtained from a final global optimization.

A Novel Configuration for Compact HTS CQ Structure Linear Phase Filter Design

In this paper, a novel trapezoidal meander-line resonator (TMLR) is proposed to design compact high-order high-temperature superconducting (HTS) linear phase bandpass filters with cascaded quadruplet (CQ) structures. By changing the conventional rectangle half-wavelength meander-line microstrip resonator into a trapezoidal resonator, unnecessary cross coupling between nonadjacent resonators in the CQ units can be avoided. And using the proposed TMLR to design the CQ unit, electric field cross coupling or magnetic field cross coupling can be easily achieved and tuned without the cross-coupling line. To further demonstrate the feasibility of using this configuration for miniaturized circuit design, an 8-order HTS linear phase filter with one pair of transmission zeros was designed. The measured responses agree very well with the simulated results. The physical HTS filter has a center frequency of 1935 MHz and bandwidth of 70 MHz. The out-of-band rejection is greater than 50 dB, and the effective bandwidth of group delay fluctuation less than ±3 ns takes up more than 65% in the whole passband.

Implementing Quasi-Elliptic Microstrip Filters Using Terminating Half Sections

This letter presents a technique for the introduction of transmission zeros (TZs) using half section matched terminations for implementing high selectivity filters in planar technology. The proposed technique does not require any cross coupling between nonadjacent resonators or multiple signal paths, and it can be easily incorporated on any planar filter using lumped, quasi-lumped, and/or distributed elements depending on the desired response. Two different bandpass filter topologies are employed for applying the proposed technique. Both prototypes are designed, manufactured, and measured. The measured results show that the TZs can be independently located very close to the passband edges, without degrading the original filter response.

Filtering Antenna With High Selectivity Using Multiple Coupling Paths From Source/Load to Resonators

This communication presents a filtering antenna with high selectivity using multiple coupling path from source/load to resonators. The high selectivity of the filtering antenna’s boresight gain response is achieved by a novel coupling scheme, which induces additional coupling between source/load and nonadjacent resonators to construct cross coupling paths. Thanks to the extra cross-coupling paths, the filtering antenna can generate a maximum of N radiation nulls with N resonators. Besides, a resonator using a combination of open-ended stub and short-ended stub is adopted to construct this novel coupling scheme more easily. For demonstration, a three-order filtering stacked patch antenna with a center frequency of 2.3 GHz and a fractional bandwidth of 15.2% is fabricated. Two independently controllable radiation nulls are located at 1.97 and 2.61 GHz. Unidirectional radiation patterns have been achieved with cross polarization lower than −20 dB and back lobes lower than −18 dB.

Microstrip Bandpass Filter with Left Transmission Zero Controlled by Parasitic Cross Coupling

A third-order microstrip filter is proposed and studied. It is characterized by a left-handed transmission zero fz, caused by the parasitic cross-coupling between non-adjacent resonators. The filter contains a half-wave middle resonator and two quarter-wave resonators located from different sides, near the open ends of the middle resonator. The coupling between all resonators has magnetic character, and the zero of the filter transfer function fz is located to the left of the center frequency of the passband f0. Such filter is described by a modified coupling matrix, where one of the main coupling coefficients is artificially assigned a minus sign. In the proposed filter design, for a given value of the main coupling coefficients, it is possible to provide different values of the cross-coupling coefficient by appropriately selecting the design parameters. This allows adjusting the zero position of the transmission fz for a given bandwidth of the filter, thereby changing the left slope of the amplitude-frequency characteristic. A sequence of steps is proposed for constructing such a filter. The measured and simulated frequency characteristics of the experimental filter are given.

Analysis and optimization of the unpredictable transmission zero in X-band filter design

This article focuses on the common problem of uncontrollable transmission zero (TZ) in X-band filter design. Using uniform impedance rectangular resonator (UIRR) to design an X-band filter always results in an unpredictable TZ on the low-frequency side of the passband, which greatly deteriorates the frequency selectivity of the filter performance. Electromagnetic coupling polarity analysis of the UIRR shows that the magnetic crosscoupling between nonadjacent resonators which is opposite to the main coupling plays a major role in the unpredictable TZ. By optimizing the UIRR from the loop structure with a small opening to the folded one, weak couplings between resonators are obtained. A high-temperature superconducting filter at X-band using folded UIRR resonator was designed and fabricated with a center frequency of 10.01 GHz and a bandwidth of 58 MHz, and the uncontrollable TZ has been removed successfully from the low-frequency side of passband. The measured insertion loss is less than 0.4 dB and the return loss is greater than 15 dB.

小型化交指型LTCC带通滤波器设计

本文提出了一种基于LTCC技术的小型化交指型带通滤波器的设计方法，通过在交指线末端加载对地电容，压缩了谐振器尺寸，将对地电容布置在分立的空间中，避免了电容间的耦合干扰，引入非相邻谐振器间交叉耦合，在通带两端各产生一个零点，提高了边带抑制。设计了一款中心频率2.3 GHz，带宽200 M交指型带通滤波器，插损小于2.5 dB，通带波动优于0.5 dB，利用三维仿真软件HFSS建模及优化，并利用LTCC工艺加工制造，尺寸仅为3 mm × 2 mm × 1.5 mm，经测试，实际测试曲线与仿真曲线符合较好，验证了设计的有效性。 A method of designing miniaturized interdigital bandpass filter based on LTCC technology was proposed, through loading ground capacitance at the end of interdigital transmission line, com-pressed the volume of resonator, to arrange the ground capacitance in discrete space, avoided the coupling interference between themselves, then cross-coupling was introduced between nonad-jacent resonator, generated two transmission zeros on both sides of the passband and improved the sideband suppression. A interdigital bandpass filter with center frequency 2.3 GHz and bandwidth 200 M was designed, the insertion loss was less than 2.5 dB, passband fluctuation was better than 0.5 dB, HFSS was used to construct the 3D model and optimize the simulated results, then fa-bricated the filter with LTCC technology, the size was only 3 mm × 2 mm × 1.5 mm, the measured curves confirmed well with the simulated curves, verified the validity of the design.

Design and Multiphysics Analysis of Direct and Cross-Coupled SIW Combline Filters Using Electric and Magnetic Couplings

In this paper, combline substrate integrated waveguide (SIW) filters using electric and magnetic couplings are thoroughly studied. Thus, a negative coupling scheme consisting on an open-ended coplanar probe is proposed and analyzed in detail. Several in-line 3-pole filters at C-band are designed, manufactured and measured showing how the presented approach can be used for implementing direct couplings while enabling an important size reduction and improved spurious-free band compared to conventional magnetic irises. A fully-packaged quasi-elliptic 4-pole filter is also designed at 5.75 GHz showing how the negative coupling structure can be used for introducing transmission zeros by means of cross-couplings between non-adjacent resonators. Finally, average and peak power handling capabilities of these filters have been also analyzed from a multiphysics point of view. Measured results validate the theoretical predictions confirming that combline SIW filters can handle significant levels of continuous and peak power, providing at the same time easy integration, compact size and advanced filtering responses.