Dual-mode Filter Research Articles

Low-Cost W-Band Dual-Mode SIW Bandpass Filters Using Commercially Available Printed-Circuit-Board Technology

W-band filters play a crucial role in modern millimeter-wave communication and radar systems, finding applications in 5G/6G networks, automotive radar, and passive imaging. With the growing demand for higher data rates and efficient wireless communication, W-band filter development has gained significant attention in recent years. Various design techniques and fabrication technologies have been explored for improved performance and integration possibilities. This paper presents a planar substrate-integrated waveguide (SIW) dual-mode cavity filter as a solution to the challenges faced by previous designs in terms of integration, size, and cost. The dual-mode cavity coupling principle and design parameters are analyzed to optimize the filter’s performance. A W-band 4th-order dual-mode filter prototype is designed and fabricated on a 0.127-mm-thick RO5880 substrate, and a finline waveguide-to-microstrip transition structure is employed for compatibility with the test instrument. Simulation and experimental results demonstrate that the proposed filter exhibits low insertion loss, good in-band standing wave performance, and improved out-of-band suppression. Moreover, a visible high-frequency out-of-band transmission zero is implemented to enhance the steep roll-off characteristics in the high-frequency out-of-band region.

A High-Temperature Superconducting Bandpass Dual-Mode Filter with Tunable Relative Bandwidth and Center Frequency.

This study proposes a high-temperature superconducting (HTS) bandpass filter with a continuously tunable bandwidth and center frequency. The proposed filter combines several gallium arsenide varactors and a dual-mode resonator (DMR). The even and odd modes of the DMR can be tuned simultaneously using a single bias voltage. The capacitive value of varactors in the circuit is tuned continuously under continuous voltage and frequency tunability. External couplings and the interstage can be realized using an interdigital coupling structure; a fixed capacitor is added to the feeder to improve its coupling strength. A low-insertion loss within the band is obtained using HTS technology. Additionally, the proposed filter is etched on a 0.5 mm-thick MgO substrate and combined with YBCO thin films for demonstration. For the as-fabricated device, the tuning frequency range of 1.22~1.34 GHz was 9.4%; the 3-dB fractional bandwidth was 12.95~17.39%, and the insertion loss was 2.28~3.59 dB. The simulation and experimental measurement results were highly consistent.

Improved TM Dual-Mode Filters With Reduced Fabrication Complexity

This work presents an alternate and improved approach for the design of dual-mode filters that utilize transverse magnetic (TM) and nonresonating modes. The method that is proposed in this work allows for an improvement of the typical TM dual-mode filter design through the reformation of the coupling irises that connect the TM dual-mode cavity to the source/load waveguide ports, where the new interconnection means takes the form of resonate slot-irises. In this manner, a fourth-order quasi-elliptic response can be achieved within a very limited physical geometry and able to cover more than double the usable fractional bandwidth than previously reported. Furthermore, the selectivity and insertion loss of the filter response is significantly improved when compared to the typical single-cavity TM dual-mode filter response that uses coupling irises, while on the comparison of equal-order structures, a reduction in fabrication complexity and improved insertion loss is achieved. A characterization of the dimensional variations and effects of altering one of the source/load port positions in the proposed filter design is investigated in order to demonstrate notable effects on the rejection characteristics and positions of transmission zeros. A presentation on the design theory is given and formulations of various filter responses are examined. The fabrication of an experimental prototype with approximately 7.3% fractional bandwidth (FBW), centered at 90 GHz is conducted using high-precision computer numerical control (CNC) milling in order to demonstrate that the unique simplicity and overall compaction of this method can be easily applied at millimetre-wave frequencies without the need of tuning means. The results which are presented demonstrate highly accurate measurements throughout the W-band range, while an additional Q-factor analysis is provided in order to compare the improved filter scheme with other known design methodologies.

A Circular Waveguide Dual-Mode Filter With Improved Out-of-Band Performance for Satellite Communication Systems

This letter presents a novel design for a 3-D-printed circular waveguide dual-mode (CWDM) filter with a modified cavity shape. The modification leads to a wide spurious-free stopband, which is highly desirable for channel separation in waveguide contiguous output multiplexers (OMUXs) in satellite communication systems. The new resonant cavity design is a result of applying shape deformation to a basic circular cavity in order to move away and suppress parasitic modes. A fourth-order Ku-band channel filter with two transmission zeros (TZs) is designed, fabricated by additive manufacturing (AM) in one piece and measured. In comparison with the state-of-the-art design of a stepped CWDM filter, an improvement of approximately 35% wider spurious-free range is achieved.

Description of Microwave Circuits via the Reduced-Basis Method Giving Physical Insight

A description of electromagnetics by means of the reduced-basis method (RBM), which gives physical insight, is detailed. Contrary to what has been previously done to get further insights from the electromagnetic behavior, a reliable reduced-order model completely describing a microwave circuit in a frequency band of interest is carried out. Following a theoretical analysis starting from time-harmonic Maxwell’s equations, we identify the dominant contributions to electromagnetics in a band of analysis. Making use of the reliable reduced-order model, we present the electromagnetic information in that reduced-order model in a more insightful manner, using a specific dynamical system representation of electromagnetics. As a result, a full-wave coupling matrix completely describing electromagnetics in the band of analysis is identified, where no narrowband approximation is considered, such as it is the case in classical coupling matrix circuit theory. No approximation is taken into account other than carrying out the analysis in a given frequency band, which can be arbitrarily large. The proposed approach provides a way to understand electromagnetics, where a full-wave coupling matrix allows the description of electromagnetics in a band of interest as a simple physically insightful circuit, and not the other way around. Finally, several real-life microwave circuits, such as a dual-mode filter and diplexer, will illustrate the capabilities and efficiency of the proposed approach.

Ceramic Additive Manufactured Monolithic X-Shaped TM Dual-Mode Filter

This paper presents a monolithic 3D-printed ceramic X-shaped dual-mode microwave filter. The filter is manufactured utilizing a lithography-based ceramic manufacturing (LCM) process, allowing the realization of the resonator as well as the housing in one single piece. Therefore, contact as well as alignment problems, usually arising between a ceramic in <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$TM$</tex-math></inline-formula> mode operation and a metallic enclosure, can conveniently be avoided. A fourth order dual-mode filter with a designed center frequency of 6 GHz and a bandwidth of 279 MHz is realized in alumina material. Practical design rules to be considered in the filter layout process as well as limitations imposed by the LCM approach are discussed. The outer surface of the ceramic cavity is subsequently metallized using a silver spray-coating. Advantageously, the metallization is only a few micrometers thick, wherefore the weight of the component can be reduced. The measurement results are compared to the simulation and reveal good agreement. A temperature stability measurement shows a center frequency downward shift of 0.22%.

A Narrowband 3-D Printed Invar Spherical Dual-Mode Filter With High Thermal Stability for OMUXs

A 3-D printed narrowband bandpass filter based on spherical dual-mode resonators is presented in this article. It is designed for output multiplexers (OMUXs) using high-<inline-formula> <tex-math notation="LaTeX">$Q$ </tex-math></inline-formula> spherical dual-mode resonators. Realization is by laser powder bed fusion (L-PBF) technology of Invar alloy chosen for its low coefficient of thermal expansion (CTE). Using PBF circumvents the alloy&#x2019;s manufacturability issues associated with its hardness in machining and free forming. Compared with polymer-based vat photopolymerization technology, PBF allows for direct metal manufacture of complex monolithic microwave components with better thermal-mechanical properties and higher power-handling capability. Using Invar can further help achieve high temperature stability of the filter in high-power operation. To demonstrate the proposed solution, detailed thermal-RF test at different temperatures was carried out. The experimental results of a 0.47&#x0025; fourth-order silver-plated Invar filter with two transmission zeros verify the design and manufacturing. An insertion loss of 1 dB and an effective temperature coefficient of less than 2 ppm/K were achieved.

3D-Printed Dielectric Resonators for Quasi-TE112 Mode Singlets, Doublets and Dual-Mode Filters

This paper demonstrates the use of a ceramic-based stereolithography additive manufacturing process in the fabrication of higher-order mode dielectric resonators. In this work, dielectric resonators with concentric disks around a combline rod structure are 3D-printed using alumina. The integration of the concentric disks for use of the TE <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">112</sub> mode allows for a more compact cavity structure and a higher unloaded quality factor when compared to a simple dielectric combline resonator with a similar S-parameter response. The achievable improvements in quality factor for the TE <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">112</sub> -mode resonators utilising concentric disks are compared through simulations and experimental results. The measured results demonstrate an increased average in the unloaded quality factor of Q <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><i>u</i></sub> ≈ 2172 which is approximately 44%. Additionally, the application of the 3D-printed resonators is further demonstrated in a TE <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">112</sub> singlet, doublet, and dual-mode filter configuration.

Compact dual-mode microstrip bandpass filter based on slotted square patch resonator

PurposeThe purpose of this paper is to present the design of a compact microstrip bandpass filter (BPF) in dual-mode configuration loaded with cross-loop and square ring slots on a square patch resonator for C-band applications.Design/methodology/approachIn the proposed design, the dual-mode response for the filter is realized with two transmission zeros (TZs) by the insertion of a perturbation element at the diagonal corner of the square patch resonator with orthogonal feed lines. Such TZs at the edges of the passband result in better selectivity for the proposed BPF. Moreover, the cross-loop and square ring slots are etched on a square patch resonator to obtain a miniaturized BPF.FindingsThe proposed dual-mode microstrip filter fabricated in RT/duroid 6010 substrate using PCB technology has a measured minimum insertion loss of 1.8 dB and return loss better than 24.5 dB with a fractional bandwidth (FBW) of 6.9%. A compact size of 7.35 × 7.35 mm2 is achieved for the slotted patch resonator-based dual-mode BPF at the center frequency of 4.76 GHz. As compared with the conventional square patch resonator, a size reduction of 61% is achieved with the proposed slotted design. The feasibility of the filter design is confirmed by the good agreement between the measured and simulated responses. The performance of the proposed filter structure is compared with other dual-mode filter works.Originality/valueIn the proposed work, a compact dual-mode BPF is reported with slotted structures. The conventional square patch resonator is deployed with cross-loop and square ring slots to design a dual-mode filter with a square perturbation element at its diagonal corner. The proposed filter exhibits compact size and favorable performance compared to other dual-mode filter works reported in literature. The aforementioned design of the dual-mode BPF at 4.76 GHz is suitable for applications in the lower part of the C-band.

Dual-Band Dual-Mode Filter-Enhanced Linearity Measurement

This letter presents, for the first time, a new filter-enhanced linearity measurement technique using a dual-band and dual-mode filter. While traditional two-tone linearity tests are simple and effective, their ultimate performance is determined by the quality (dynamic range and noise floor) and cost of the employed equipment. On the other hand, the proposed method consists of a simple conventional single-tone test facilitated by a low-cost appropriately designed bandstop filter (BSF). In particular, the employed dual-band/dual-mode absorptive BSF suppresses the fundamental frequency by over 35 dB (absorptive notch) and the second harmonic by over 25 dB (reflective notch), allowing for accurate measurement of the third harmonic, and hence, IP3. The proof-of-concept system is demonstrated at 2 GHz. The filter absorbs with better than 20 dB of reflection the excitation signal at f <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> =2 GHz and reflects the signal at 2f <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> =4 GHz. With just the insertion of the presented filter and without improving the measurement equipment, we demonstrate an improvement of over 12.7 dB in the IP3 characterization to a maximum of 81 dBm. We also demonstrate the ability to conduct this test with just a low-cost power detector in lieu of a spectrum analyzer leading to a simple scalable measurement technique.

A Dual-Mode Dielectric Filter for 5G System

Based on 5G system, a cylindrical dual-mode resonator and filter are designed. The electric field distribution characteristics of each mode of the dual-mode resonator are analyzed by using high-frequency electromagnetic field simulation software. Based on the designed dual-mode resonator, through theoretical calculation and analysis, a 5G system dielectric dual-mode filter is designed by using the RF / microwave simulation software ADS/HFSS. The coupling between modes is realized by setting metal screw perturbation on surfaces. The effect of two coupled degenerate modes is equivalent to that of two coupled resonators, so that the number of resonators can be reduced while the resonant circuit remains unchanged. For example, two modes of a resonator can be used in a traditional n-section filter, the same physical space realizes the characteristic of 2n section filter, which greatly reduces the size of the filter. A 5G system dielectric filter is designed based on dual-mode resonator. The results show that in the pass-band (3.4 ∼ 3.5GHz), the return loss is more than 18db, the insertion loss is less than 0.3dB, the zero on the left side of the pass-band is 3.1716GHz, the zero on the right side of the pass-band is 3.8537GHz, the VSWR is less than 1.28. Transmission zeros are introduced on both sides of the pass-band, which improves the suppression ability out of pass-band. The 5G system dielectric filter has the advantages of low insertion loss, small size and good suppression performance out of pass-band. When applied to 5G wireless communication system, the anti-interference ability and stability of the system can be improved.

Dual-Mode Dielectric Waveguide Filters With Controllable Transmission Zeros

A novel dual-mode (DM) dielectric waveguide (DW) filter with controllable transmission zeros (TZs) is presented. The DM filter is based on a cascaded implementation, utilizing individual DM DW cavities. The filter is practically realized by embedding three circular blind holes at different positions in the surface of a dielectric silver-coated square cavity. By changing the relative position of the blind holes or rotating the direction of the proposed DW cavity, the filter's TZs' frequency locations can be flexibly adjusted. The zero points can be set in frequency at the low end of the passband, at the high end of the passband, or they can be generated at both the low and high ends of the passband in order to improve the selectivity of the filter. In this study, the two-cavity fourth-order filter is taken as an example, and the experimental results validate the feasibility of the presented theoretical design.

Compact Dual-Mode Balun Bandpass Filter with Improved Out-of-Band Performance

A compact dual-mode balun bandpass filter with improved out-of-band performance is proposed based on a ring resonator. In order to excite the two degenerate modes and obtain filtering balun performance, three parallel-coupled lines are placed at three excitation ports along the ring resonator. By properly arranging the angles between the excitation arms, four transmission zeros can be realized to improve stopband performance. Finally, a prototype of the designed balun bandpass filter is implemented and fabricated. The measured results show a good agreement with those obtained from the simulation, thus verifying our proposal with good in-band filtering and out-of-band performance.

Dual mode filter with tunable cross Iris

ABSTRACT The aim of this work is to analyze the effect of tuning screws located at the cross iris of a dual-mode vacuum filled cylindrical waveguide filter. Dual-mode waveguide filters with and without cross iris screws are designed and manufactured. Their simulation and measurement results are compared. It is clear that the bandwidth of the filter (and also Finite Transmission Zero (FTZ) locations) can be adjusted with cross iris screws. So, design and mechanical production tolerances can be easily compensated depending on the technical requirements.

Compact dual‐mode wideband MIMO filtering antenna array with high selectivity and improved isolation

A novel compact MIMO dual-mode filtering antenna array with wide bandwidth, high selectivity and good isolation is proposed. The filtering antenna unit consists of a patch radiator at the top layer coupled with a high-order dual-mode filter at the bottom layer through a rectangular slot in the middle ground layer. The fourth-order filter adopts two E-shape dual-mode resonators to achieve wide bandwidth and high selectivity. A pair of filtering antenna units form a MIMO array with a distance of 0.2λg by using three interdigital lines in the middle to enhance the port isolation. Finally, a 1 × 2 MIMO filtering antenna array operating at 2.45 GHz is designed and fabricated, which shows wide fractional bandwidth of 24.5%, sharp skirt slope with a pair of radiation nulls, smooth realized gain of 4.5 dBi as well as high isolation more than 20 dB.

Single VDGA-Based Dual-Mode Multifunction Biquadratic Filter and Quadrature Sinusoidal Oscillator

This article relates to the realization of voltage-mode and/or current-mode multifunction biquadratic filter and quadrature oscillator circuits each using one voltage differencing gain amplifier (VDGA), two resistors and two grounded capacitors. The proposed dual-mode filter having one output and three inputs can provide the three standard biquadratic transfer functions with both voltage and current output filter responses simultaneously. It also has the independent tuning of the angular resonance frequency and the quality factor . With a slight modification of the proposed filter, a new dual-mode quadrature sinusoidal oscillator can be obtained. The proposed quadrature oscillator provides orthogonal resistive/electronic control of both oscillation condition and oscillation frequency. Non-ideal and parasitic conditions are also examined and their effects on the circuit performance are discussed. In order to confirm the theory, several computer simulation results with PSPICE program are given .

A Compact Dual-Mode Bandpass Filter with High Out-of-Band Suppression Using a Stub-Loaded Resonator Based on the GaAs IPD Process

In this letter, a compact dual-mode bandpass filter (BPF) with an ultra-wide stopband that employs two folded open-loop resonators (FOLRs) and stub-loaded resonators (SLRs) is proposed. The dual-mode resonators are optimized by loading two SLRs onto the folded open-loop resonators, and this process is analyzed using the dual-mode theory. To miniaturize the device size and increase chip performance, the proposed BPF is fabricated by a III–V compound semiconductor-fabrication process using a high-performance GaAs substrate based on the integration passivation device (IPD) fabrication process. A compact dual-mode BPF with low insertion loss and high return loss is designed and fabricated. Two extra transmission zeros (TZs) located in the high-frequency range increase the wide stopband, and the two TZs near the passband result in a higher selectivity. A resonant frequency centered at 7.45 GHz with an insertion loss of −1.21 dB and a measured return loss of higher than −23.53 dB and 3 dB fractional bandwidths of 5.8% are achieved. The stopband can be suppressed up to 20 GHz owing to the two tunable TZs resulting in higher selectivity and wideband rejection. The size of the filter was drastically optimized using a simplified architecture of two FOLRs and SLRs.

Improvement of Passband Flatness for a Compact, Narrowband, and Highly Selective TM Dual-Mode Filter

This article presents a compact, narrowband and highly selective filter with flattened passband response using TM dual-mode cavities. Indispensable passband flatness as well as very high selectivity was achieved using TM dual-mode resonator filter and equalizer. The design of an eighth-order filter is presented with the experimental results at 10.97 GHz and to satisfy the passband flatness requirements, an external equalizer is devised. Comparisons between the filter and equalized-filter results proves the improvement in the amplitude and group-delay flatness simultaneously in the passband.

Miniaturised dual‐mode dielectric resonator filter with controllable passband

A miniaturised dual-mode filter based on dielectric resonator (DR) with a controllable passband is proposed in this Letter. The filter is a combination of a traditional rectangular DR and a planar metallic loop with the dual-mode feature. The loop decreases the frequencies of the dominant modes inside the DR, thus the circuit size is greatly reduced compared with the traditional DR devices. By using commonly used tuning disk, the passband of the proposed filter can be altered freely. A demonstration example is designed and fabricated, and the simulated and measured results verify the design method with good agreement.

Compact, Low Loss, and High Power Handling HTS Dual-Mode Double-Strip Resonator Filter With New Feeding Structure

A compact, low loss and high power handling high temperature superconducting filter using dual-mode double-strip resonators (DSRs) was developed. We proposed new superconducting feeding structure, which was replaced from the previously reported brass center pin feeding structure, to improve insertion loss. A four-pole elliptic function dual-mode DSR filter was designed by the electromagnetic simulator based on the moment method. The center frequency and bandwidth of the filter are a 5.0-GHz and an 80-MHz. The compact filter was fabricated using YB2Cu3Oy thin films on r-Al2O3 substrates (25 mm × 25 mm). The measured frequency responses of the filter were in reasonable agreement with the simulated ones. The measured insertion loss was 0.08 dB. The measured power handling capability of the proposed filter was more than 40 W at 60 K.