Dual-mode Cavity Research Articles

A D-band extracted pole waveguide bandpass filter based on TE202 and TE301 resonator

This paper presents a D-band waveguide bandpass filter (BPF) with high selectivity based on extracted pole technology. Unlike a single transmission zero (TZ) in the traditional design, the basic structure of the proposed extracted pole resonator is the novel TE202 and TE301 resonator, which provides two TZs. In which, each TZ position can be independently controlled by adjusting the dimensions of the resonant cavity. As an illustrative example, a pseudo-elliptic waveguide filter with two pairs of TZs generated on both sides of the passband using the extracted pole resonator and two dual-mode cavities. The filter is fabricated using high-precision computer numerical control (CNC) milling technology. The strong agreement between measured and simulated results validates the enhanced selectivity of the filter achieved by this novel extracted pole resonator.

Low-Loss 3D-Printed Waveguide Filters Based on Deformed Dual-Mode Cavity Resonators

Low-Loss 3D-Printed Waveguide Filters Based on Deformed Dual-Mode Cavity Resonators

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.

DGS Loaded Substrate Integrated Waveguide Dual Mode Cavity Filter

DGS Loaded Substrate Integrated Waveguide Dual Mode Cavity Filter

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 D-Band Manifold Triplexer With High Isolation Utilizing Novel Waveguide Dual-Mode Filters

This letter presents our design of a wideband manifold-coupled triplexer with high isolation in <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">D</i> -band. The basic structure of channel filters is the novel TM <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">120</sub> and TE <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">101</sub> dual-mode cavity, which provide two reflection zeros and one transmission zero. To achieve good computational efficiency and design accuracy, the space-mapping technique, consists of a coarse distribute model and a fine full-wave electromagnetic model, is adopted in the development of the triplexer. The proposed triplexer is fabricated by high-precision computer numerical control milling technology. The measured results are all in good agreement with the simulated ones. The measured lowest in-band insertion loss is 0.54/0.62/0.55 dB for three channels, respectively. The return loss of each channel is better than 14 dB and the isolation between each channel is better than 45 dB.

New Triple-Resonance Configuration Using Stubbed Waveguide Dual-Mode Cavities

This letter presents new configurations of stubbed waveguide cavities for the realization of pseudo-elliptic and self-equalized filters. The basic structure consists of a main TE <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">102</sub> /TE <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">201</sub> dual-mode cavity that is loaded with a pair of waveguide stubs. The two stubs are located at the top and bottom walls of the cavity while always being parallel and in-line to each other. Such a two-stub arrangement can be seen as a TM <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">110</sub> mode cavity, which is embedded into the main dual-mode cavity. By properly setting the polarization of the stubs with respect to the main cavity as well as finely adjusting the difference between the lengths of the stubs, triple-resonance structures with selected topologies and controllable coupling mechanisms can be implemented. The resulting third-order filtering functions comprise three poles and two zeros, the latter being either group delay equalization zeros or finite frequency transmission zeros depending on the polarization of the stubs. The experimental results of a fifth-order filter with two finite frequency transmission zeros using one stubbed waveguide cavity between two standard cavities validate the new configuration.

Artificial neural networks assisting the design of a dual-mode photonic crystal nanobeam cavity for simultaneous sensing of the refractive index and temperature.

We put forward a dual-mode photonic crystal nanobeam cavity for simultaneous sensing of the refractive index (RI) and temperature (T) designed with the assistance of artificial neural networks (ANNs). We choose the structure of quadratically tapered elliptical holes with a slot to improve the sensitivities of the two modes. To reduce the time consumption of the design, the ANNs are trained to predict the band structure and to inverse design the geometric structure. For the forward prediction and the inverse design neural networks, low mean square errors of 5.1×10-4 and 1.4×10-2 are achieved, respectively. Through a specific design of band properties by the well-trained neural networks, a dual-mode nanobeam sensor with high quality factors of 9.34×104 and 1.55×105 and a small footprint of 23.8×0.7µm2 are designed. The RI and T sensitivities of the air mode are 405 nm/RIU and 40 pm/K, respectively, whereas those of the dielectric mode are 531 nm/RIU and 27 pm/K, respectively. The present work shows significance in further research on the design and applications for dual-mode cavities.

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.

A sixth‐order SIW bandpass filter based on combining single‐ and dual‐mode cavities with high selectivity at Ka‐band

In this paper, a novel substrate integrated waveguide quasi-elliptic bandpass filter is proposed by combining single- and dual-mode cavities. Two single-mode cavities with TE101 mode are directly coupled to the dual-mode resonance cavity which employs a pair of disturbing metallic via-holes to make the resonant points of TE101 and TE102 mode in one passband. Based on the conventional box-like topology, two additional single cavities are used to achieve wider bandwidth and simplify the design difficulty. In addition to two transmission zeros (TZs) realized by the cross-coupling technology, nonreasoning node will generate an additional TZ at a higher frequency to improve the upper stopband performance. Finally, a sixth-order filter, having the passband frequency of 24.25–27.5 GHz for 5G application, with three TZs, is simulated, fabricated and measured to demonstrate and verify the proposed structure. The test results show the insertion loss is 1.7 and 3 dB bandwidth is 3.37 GHz. The three TZs improve out of band rejection of the filter.

Tri-Layered Stacked Substrate Integrated Waveguide Bandpass Filter Using Non-Resonant Nodes Excitation

Tri-layer stacked substrate integrated waveguide (SIW) bandpass filters (BPFs) using non-resonant nodes based on single-and dual-mode cavities are presented. Two identical single-mode (TM110) cavities in the top and bottom layer are independently coupled to a dual-mode (TM120/TM210) cavity in the middle layer by two slots. Based on carefully designed coupling topology, we can realize SIW BPFs with one or two flexible finite transmission zeros (FTZs). TM110 and TM220 modes in the dual-mode cavity are further used to excite non-resonant nodes by changing the position of slots, and additional FTZs in the upper and lower stopband can be obtained. In order to verify the proposed strategy, two samples with a center frequency of 10 GHz have been designed and manufactured.

Design Considerations of a Dual Mode X-Band EPR Resonator for Rapid In-Situ Microwave Heating

This paper describes the design considerations for a dual mode X-band continuous wave (CW) Electron Paramagnetic Resonance (EPR) cavity, for simultaneous EPR measurement and microwave heating of the same sample. An elliptical cavity geometry is chosen to split the degeneracy of the TM110 mode, allowing for a well resolved EPR signal with the TM110,a and TM110,b modes resonating at around 10 GHz and 9.5 GHz, respectively, the latter of which is used for EPR measurements. This geometry has the benefit that the TM010 mode used for microwave heating resonates at 6.1 GHz, below the cut off frequency of the X-band waveguide used for the EPR channel, providing effective isolation between the heating and EPR channels. The use of a pair of 9 µm thick copper clad laminates as the flat cavity walls allows for sufficient penetration of the modulation field (Bmod) into the cavity, as well as maintaining a high cavity Q factor (> 5700) for sensitive EPR measurements. Locating the heating port at an angle of 135° to the EPR port provides additional space for easier coupling adjustment and for larger sample access to be accommodated. The associated decrease of EPR signal strength is fully compensated for by using a 7.2 GHz low pass filter on the heating port. EPR spectra using 1.6 mm and 4.0 mm sample tubes are shown at room temperature (298 K) and 318 K for a standard Cu(acac)2 solution, demonstrating the effectiveness of this dual-mode EPR cavity for microwave heating during EPR detection.

Multilayer metallic filters for Q/V band IMUX

AbstractCurrent designs of space IMUX filters are based on dual-mode circular waveguide cavities, on dielectric resonators or, at the lower end of the frequency spectrum, on coaxial resonators. This paper presents a new kind of IMUX filter aimed at high operating frequencies (Ka, Q, and V bands) which was developed in the frame of an ESA funded study named KALOS-DEVAQ. The new filter implements a quasi-elliptic frequency response and is characterized by simple geometry. The mechanical structure is composed of stacked metallic plates and it is well suited to be manufactured, at a low cost, with high accuracy. Despite the lower unloaded Q factor, the new configuration allows achieving a comparable flatness of insertion loss and group delay, thanks to the application of the pre-distortion technique. The increased insertion loss does not affect the system performances because it can be compensated by the amplification stages in the RF chain.

Dual-mode cavity design for advanced continuous-wave electron injector

The Advanced Continuous-wave Electron (ACE) injector group at the Coherence and Quantum Technology (CQT) group of the Eindhoven University of Technology is developing a GHz repetition-rate electron injector where a low emittance and high repetition-rate are simultaneously required. The injector is based on a high-quality DC thermionic gun and two normal conducting RF cavities utilizing dual-mode resonance frequencies in the 1.5–3 GHz range. In the first phase, the installation and commissioning of ACE’s electron gun were completed. In this next phase, two dual modes RF cavities are designed for chopping and compressing of a DC electron beam. This paper focuses on the RF design and measurements of these cavities, demonstrating the claimed quality and performance.

Wideband SIW Filtering Antenna With Controllable Radiation Nulls Using Dual-Mode Cavities

A wideband fourth-order filtering antenna consists of two substrate integrated waveguide (SIW) dual-mode cavities is presented in this letter. The first SIW cavity creates two resonant nodes and one radiation null (RN) located on the upper stopband. The second SIW cavity integrated with a slot cannot only achieve radiation function but also realize dual-mode resonance, which can produce another lower out-of-band RN. These two RNs can be controlled to improve frequency selectivity and design flexibility. The coupling matrix theory is adopted to guide the design of the filtering antenna, and the generation principle of these two RNs can be explained by cross coupling. Finally, such a filtering antenna operating at the center frequency of 5.4 GHz with a fractional bandwidth of 7.64% and a maximum gain of 5.3 dBi is fabricated and measured.

Filtering Antenna With Quasi-Elliptic Response Based on SIW H-Plane Horn

A filtering antenna with a quasi-elliptic response based on the substrate-integrated waveguide(SIW) H-plane horn is presented. It is mainly composed of two symmetrical horn elements embedded with the trapezoidal dual-mode cavity. By exploiting the cross couplings of the dual-mode cavity, two radiation nulls are introduced on the gain curve showing a quasi-elliptic filtering response without the increase of horn size. Then, a modified transition is printed in front of the horn aperture on both sides of the substrate, which acquires wider impedance bandwidth and maintains a low backlobe radiation throughout the bandwidth. Besides, the proposed antenna is designed, fabricated, and measured at Ku-band. Two measured radiation nulls can be observed at 14.02 and 17.98 GHz, where the gain drops significantly to below -28 and -38 dBi, leading to high frequency selectivity. A wide measured impedance bandwidth of 12.2% and a large front-to-back ratio of more than 20 dB are achieved. To the author's best knowledge, it is the first time that the filtering horn antenna with radiation nulls, wide bandwidth, and excellent radiation is designed.

Compact In-Band Full Duplexing Antenna for Sub-6 GHz 5G Applications

A novel compact in-band full duplexing antenna using a cavity-like structure for sub-6 GHz fifth-generation (5G) applications is proposed. By exploring a shared aperture cavity-like structure with two highly orthogonal modes (quarter-wavelength slot mode and half-mode cavity mode), high isolation between Tx and Rx ports is achieved. Two quarter-wavelength slots are etched on both sides of the cavity, so a shared aperture dual-mode cavity is implemented. When this cavity is fed by a pair of even–odd mode feeding structures, two orthogonal polarization modes are excited at the same frequency band. To validate the proposed concepts, a high isolation duplexing antenna with a compact size of 0.45 λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> × 0.20 λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> × 0.04 λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> is fabricated. A measured isolation greater than 43 dB is achieved over the working band from 3.4 to 3.8 GHz (LTE B42/B43 band) and its peak radiation efficiency is larger than 87%. It shows a compact size, low cost, high isolation, good bandwidth, and efficiency, which is well situated for in-band duplexing systems and 5G indoor application.

Planar Circularly Polarized Antenna With Bandpass Filtering Response Based on Dual-Mode SIW Cavity

In this study, a novel single-fed low-profile circularly polarized (CP) antenna with a bandpass filtering response is proposed. It is based on a planar substrate integrated waveguide (SIW) dual-mode (TE102/TE201) cavity. When the vias on the edge become sparse, the electromagnetic wave leaks out while maintaining a good dual-mode filtering response. The antenna is folded in order to reduce the aperture size to form an un-splitted radiation beam with small side lobes. Owing to a rotated dual-mode operation, the fields escaping from four sets of sparse vias are approximately of equal amplitude with a progressive phase difference of 90° in sequence. CP radiation is thus achieved when the four orthogonal half-mode radiation patches are excited by the leaking field. By adopting a single feeding with two pairs of asymmetrical shorting pins, the peak gain is improved significantly and a 3 dB axial ratio (AR) response with two minima is obtained simultaneously. Long metal walls and rectangular slots are introduced to fold the current flow and change the wave direction. Consequently, sidelobe level is significantly reduced and the antenna directivity is enhanced. To verify this novel design idea, an antenna prototype with a height of $0.036\lambda _{0}$ has been fabricated using the multilayer PCB process and measured in a near-field microwave chamber. Measured results are well consistent with the simulation, demonstrating CP radiation with a flat/high gain and good filtering performance.

Analytical Synthesis of Fully Canonical Cascaded-Doublet Prototype Filters

This letter presents an analytical procedure for the synthesis of a low-pass prototype filter constituted by the cascade of doublet blocks coupled by inverters or shunt reactances. The considered doublet is a second-order resonating structure composed of two resonant and two nonresonant nodes which allow the placement of two finite transmission zeros (TZs) in the frequency response. The considered configuration allows realizing compact fully canonical filters with the maximum number of TZs (the doublets are typically implemented through dual-mode cavities). The proposed procedure introduces for the first time an analytical procedure for synthesizing the low-pass prototype of the cascaded-block topology, overcoming the time consuming and inaccurate procedures currently based on numerical optimization. Two synthesis examples are presented to validate the novel synthesis procedure.

Compact, Tunable and Narrowband Waveguide Filters Using TM Dual-Mode Cavities for Satellite Communication Applications

Compact, Tunable and Narrowband Waveguide Filters Using TM Dual-Mode Cavities for Satellite Communication Applications