Half-wavelength Resonator Research Articles

Highly selective tri-wideband bandpass filter with adjustable passbands for high-performance space-based assets applications

A straightforward approach to designing a tri-wideband bandpass filter employing an E-shaped stepped impedance resonator loaded by an open-circuited tri-section stepped impedance stub (OSLTSIR) is explored in this paper. Upon analysis, it is ascertained that this resonator offers a distinct advantage by providing increased degrees of freedom for adjusting resonant frequencies, and the strength to generate transmission zeros at lower/upper stopbands. Capitalizing on these attributes, a tri-band bandpass filter is examined by combining this OSLTSIR with a half-wavelength resonator. The incorporation between the OSLTSIRs gives rise to creating a dual-wide band, while the introduced λ/2 resonators led to split the second passband into two, yielding in tri-band performance. The resultant filter operates at 8.25 GHz, 11.1 GHz, and 15.35 GHz with wide fractional bandwidths of 25.57 %, 18.45 %, and 24.6 %, respectively. Resonant frequencies and bandwidth can be controlled with substantial flexibility. The Experimental assessments confirm the existence of seven transmission zeros, showcasing high selectivity and good isolation. Besides, the fabricated structure maintains a compact size of (6.2 × 8.4) mm, about 0.12 λg2. The close agreement between the simulated and measured findings verifies its applicability for space-based asset applications.

Polarization-insensitive cross-polarization converter with high frequency selectivity based on an antenna-resonator-antenna module

In this paper, a novel transmission-type polarization-insensitive frequency selective polarization converter (PIFSPC) is proposed. The overall structural scheme of the proposed PIFSPC is based on an antenna-resonator-antenna (ARA) module, which is composed of a receiving patch antenna, double “S-shaped” half-wavelength resonators, and a transmitting patch antenna. By adopting cross-coupling, high frequency selectivity is achieved, and through the utilization of a staggered rotationally symmetric structure, polarization insensitivity is attained. The prototype possesses four transmission poles and two zeros on the polarization conversion spectrum, and it shows insensitivity to the polarization direction of incident electromagnetic waves. The frequency selectivity of the prototype at the lower and upper band edges is 425 dB/GHz and 283 dB/GHz respectively. The cross-polarization conversion rate (PCR) is over 95% within the passband from 4.93 GHz to 5.09 GHz for arbitrarily polarized azimuth incident waves, and its thickness is merely 0.052λ0. The operation bandwidth and frequency selectivity of the prototype can be readily altered. A prototype is fabricated and measured, with excellent consistency between simulations and experiments. It indicates the feasibility of integrating frequency selection and polarization conversion. The proposed PIFSPC has extensive application prospects in enhancing the anti-interference ability and electromagnetic compatibility in the fields of communication, measurement, and microwave detection.

Multimode physics of the unimon circuit

We consider a superconducting half-wavelength resonator that is grounded at its both ends and contains a single Josephson junction. Previously this circuit was considered as a unimon qubit in the single-mode approximation where dc-phase-biasing the junction to π leads to increased anharmonicity and 99.9% experimentally observed single-qubit gate fidelity. Inspired by the promising first experimental results, we develop here a theoretical and numerical model for the detailed understanding of the multimode physics of the unimon circuit. To this end, first, we consider the high-frequency modes of the unimon circuit and find that even though these modes are at their ground state, they imply a significant renormalization to the Josephson energy. We introduce an efficient method to fully account for the relevant modes and show that unexcited high-lying modes lead to corrections in the qubit energy and anharmonicity. Interestingly, provided that the junction is offset from the middle of the circuit, we find strong cross-Kerr coupling strengths between a few low-lying modes. This observation paves the way for the utilization of the multimode structure, for example, as several qubits embedded into a single unimon circuit. Published by the American Physical Society 2024

A continuous-wave and pulsed X-band electron spin resonance spectrometer operating in ultra-high vacuum for the study of low dimensional spin ensembles.

We report the development of a continuous-wave and pulsed X-band electron spin resonance (ESR) spectrometer for the study of spins on ordered surfaces down to cryogenic temperatures. The spectrometer operates in ultra-high vacuum and utilizes a half-wavelength microstrip line resonator realized using epitaxially grown copper films on single crystal Al2O3 substrates. The one-dimensional microstrip line resonator exhibits a quality factor of more than 200 at room temperature, close to the upper limit determined by radiation losses. The surface characterizations of the copper strip of the resonator by atomic force microscopy, low-energy electron diffraction, and scanning tunneling microscopy show that the surface is atomically clean, flat, and single crystalline. Measuring the ESR spectrum at 15K from a few nm thick molecular film of YPc2, we find a continuous-wave ESR sensitivity of 2.6 × 1011spins/G · Hz1/2, indicating that a signal-to-noise ratio of 3.9G · Hz1/2 is expected from a monolayer of YPc2 molecules. Advanced pulsed ESR experimental capabilities, including dynamical decoupling and electron-nuclear double resonance, are demonstrated using free radicals diluted in a glassy matrix.

Bandpass filter with multiple selective absorptive stopbands for 28 GHz transmitters

Abstract This manuscript presents a novel design for an absorptive bandpass filter for mm-wave applications, specifically the commercial FR2 spectrum. Three bands have been selected to be properly input matched with only one of them being the passband, where the insertion loss is minimized. The proposed approach relies on a multiplexer topology implemented through microstrip lines and on thin-film manufacturing process on alumina to shrink the footprint. Cascades of half-wavelength C-shape open-ended resonators are exploited to create the matched bands and define the filter’s selectivity. The selected passband spans from 26.5 to 28.5 GHz, with a measured maximum insertion loss of 3.05 dB for a −3 dB fractional bandwidth of 7.3%. Two absorptive bands are realized to match signals at 24 and 32.25 GHz. The alumina die footprint is 5500 × 3440 µm2, compatible with immediate integration within a mm-wave lineup.

Design of highly selective balanced bandpass filter with wide differential-mode stopband and high common-mode suppression

A highly selective and wide stopband bandpass filter (BPF) with multiple transmission poles (TPs) and transmission zeros (TZs) has been proposed. The BPF employs a box-like coupling structure consisting of two half-wavelength resonators and a dual-mode open stub loaded resonator, enabling the generation of two TZs and four TPs. Three controllable TZs are obtained by adding an annular spiral open stub to the terminal of the input and output coupling lines, which significantly improves the selectivity of the BPF. To achieve a wide stopband characteristic, a wide stopband unit with three additional TZs is cascaded within the structure. A balanced BPF is realized by introducing a microstrip-slotline-microstrip balun structure to the input and output ports of the proposed BPF. Experimental results validate the feasibility of the proposed BPF and balanced BPF applied in 2.45 GHz ISM band. The introduction of eight TZs gives the BPF a 20 dB rectangular coefficient of 1.3 with an upper stopband exceeding than 12 GHz. The balanced BPF can achieve 40 dB of high common-mode(CM) suppression in the passband, while differential-mode (DM) transmission is close to the performance of the proposed BPF. The minimum insertion loss for BPF and balanced BPF is 0.8 dB and 1.3 dB, respectively.

Compact Hybrid Bandpass Filters Using Substrate-Integrated Waveguide and Stripline Resonators

This article presents a novel class of compact hybrid bandpass filters (BPFs) using substrate-integrated waveguide (SIW) and stripline resonators. As the stripline resonators are inserted between two SIW cavities, they are able to increase the filtering order without occupying any additional area. This is beneficial for circuit miniaturization. To verify the concept, several third-order hybrid filters with various responses are designed by combining a half-wavelength stripline resonator (HWSLR) or a full-wavelength stripline resonator (FWSLR) and two SIW resonators. Their sizes are reduced by more than 33% compared with standard third-order SIW filters. In addition, a class of fourth-order box-like hybrid filters with two flexible transmission zeros (TZs) is also proposed by using the HWSLR and FWSLR simultaneously. Compared with previously reported box-like SIW filters, a size reduction of more than 65% is obtained. Three filter prototypes are fabricated and measured for validation.

Wavelength sensitivity reconfigurable SPR photodetector with a blazed grating profile.

Surface plasmonic detectors based on one-dimensional half-wavelength gratings have attracted attention due to their wavelength- or polarization-specific photodetection. Although the effect of a grating period and a grating depth on the photoelectric conversion of 1D half-wavelength grating-based surface plasmon resonance (SPR) detectors has been discussed thoroughly in recent years, the effect of different grating profiles on device performance is still limited to the rectangular shape. In this article, we proposed a wavelength sensitivity reconfigurable photodetector enhanced by SPR with a blazed grating profile. The gold layer was fabricated on a silicon-based blazed grating to form a Schottky barrier and act as an SPR coupler. By measuring the photocurrent in the range of -58° to -48°of an incident angle, the peak shifts of a photocurrent signal waveform are found to depend on the wavelength over 800-1000 nm.

Quasi-Elliptic Lossy Filter With Reconfigurable Bandwidth

This letter proposed a quasi-elliptic lossy filter with a wide tunable bandwidth and enhanced passband flatness. For adapting the limited circuit sizes, a new type of lossy technique named center-loaded resistive-cross-couplings (CLRCCs) is proposed. By loading resistor coupling at the centers of half-wavelength resonators, additional mid-passband losses can be introduced to flatten the passband. A bandwidth reconfigurable five-pole filter with a hybrid structure is developed for the examination. The measured promising results showed the superiority of the proposed novel lossy method for wideband tunable filters.

A Balanced BPF with Wide Bandwidth and Steep Selectivity Based on Slotline Stub Loaded Resonators (SSLRs)

A balanced bandpass filter (BPF) with a wide differential mode (DM) bandwidth and steep DM passband selectivity and high common-mode (CM) block based on slotline stub-loaded resonators (SSLRs) is designed in this brief. The proposed SSLR, which is composed of a half-wavelength slotline resonator and a shorted slot stub loaded at the symmetrical plane, is applied to achieve a broad DM passband with a center frequency at 5.1 GHz and a 3 dB bandwidth of 92%. Meanwhile, two transmission zeros (TZs) are introduced to realize a steep DM passband selectivity. The center frequency and bandwidth of the DM passband can be adjusted by changing the dimensions of SSLRs and the gaps between them. Meanwhile, one narrow notched band with a 3 dB bandwidth of 4.9% is realized by employing one coupled quarter-wavelength short-circuited stub at the input ports. In addition, the DM stopband with a rejection level of 10 dB can be extended to 20 GHz. The designed balanced broadband filter is stimulated by a U-shaped microstrip line to slotline transition structure, which can realize wideband a CM block with a high suppression level without influencing the DM one, and this can reduce the design complexity. In order to prove the idea, a balanced broadband filter is designed and measured. The predicted results of S parameters are compared with the measured ones, and a good agreement is achieved.

Hybrid Quantum Systems for Higher Temperature Quantum Information Processing

The ability to operate superconducting quantum computers at higher temperatures would greatly expand their utility and range of applications. This could be achieved by increasing resonance frequencies and/or utilizing collective modes that are less noisy and more robust against decoherence. We discuss several nonlinear resonator concepts in which the roles of linear and nonlinear elements are reversed vs. the transmon. The simplest version is a nonlinear <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">LC</i> resonator with a linear superconducting inductor and a nonlinear capacitor employing a nonlinear dielectric material. Due to progress in tunable dielectrics for 6G, some ferroelectric composites may enable operation of a nonlinear dielectric – superconductor qubit at hundreds of gigahertz. Other nonlinear dielectric materials include quantum paraelectrics and charge density wave materials. These are of interest due to robust collective modes resulting from macroscopically occupied states. Other proposed nonlinear resonators employing nonlinear dielectrics include quarter- and half-wavelength resonators. Voltage tunability is a potential feature of the proposed concepts.

Fabrication Development for SPT-SLIM, a Superconducting Spectrometer for Line Intensity Mapping

Line Intensity Mapping (LIM) is a new observational technique that uses low-resolution observations of line emission to efficiently trace the large-scale structure of the Universe out to high redshift. Common mm/sub-mm emission lines are accessible from ground-based observatories, and the requirements on the detectors for LIM at mm-wavelengths are well matched to the capabilities of large-format arrays of superconducting sensors. We describe the development of an <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$R$</tex-math></inline-formula> = <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\lambda / \Delta \lambda = 300$</tex-math></inline-formula> on-chip superconducting filter-bank spectrometer covering the 120–180 GHz band for future mm-LIM experiments, focusing on SPT-SLIM, a pathfinder LIM instrument for the South Pole Telescope. Radiation is coupled from the telescope optical system to the spectrometer chip via an array of feedhorn-coupled orthomode transducers. Superconducting microstrip transmission lines then carry the signal to an array of channelizing half-wavelength resonators, and the output of each spectral channel is sensed by a lumped element kinetic inductance detector (leKID). Key areas of development include incorporating new low-loss dielectrics to improve both the achievable spectral resolution and optical efficiency and development of a robust fabrication process to create a galvanic connection between ultra-pure superconducting thin-films to realize multi-material (hybrid) leKIDs. We provide an overview of the spectrometer design, fabrication process, and prototype devices.

Advancing Raman spectroscopy of erythrocytes with 3D-printed acoustofluidic devices

Acoustofluidics is a technique that utilizes the forces produced by ultrasonic waves and fluid flows to manipulate cells or nano-/microparticles within microfluidic systems. In this study, we demonstrate the feasibility of performing the Raman analysis of living human erythrocytes (Erys) within a 3D-printed acoustofluidic device designed as a half-wavelength multilayer resonator. Experiments show that a stable and orderly Ery aggregate can be formed in the pressure nodal plane at the resonator's mid-height. This has a significant potential for improving the applicability of Raman spectroscopy in single Ery analysis, as evidenced by the acquisition of the spectrum of healthy and pre-heated Erys without substrate interference. Moreover, principal component analysis applied on the obtained spectra confirms the correct Ery group identification. Our study demonstrates that 3D-printed acoustofluidic devices can improve the accuracy and sensitivity of Raman spectroscopy in blood investigations, with potential clinical applications for noninvasive disease diagnosis and treatment monitoring.

A Compact Wideband Quasi-Yagi Antenna for Millimeter-Wave Communication

A millimeter-wave (mm-Wave) quasi-Yagi antenna utilizing a pair of back-to-back U-shaped full-wavelength dipoles and a folded shorted stub-loaded half-wavelength strip resonator is proposed. The high impedance of the U-shaped full-wavelength dipole overcomes the mismatching problem when it is close to the reflector, enabling compact size in the endfire direction. Three reflection zeros can be obtained from the full-wavelength dipole, the half-wavelength strip resonator, and the equivalent inductor and capacitor derived from the folded shorted stub. The three reflection zeros and appropriate impedance make the proposed antenna have wide bandwidth. For demonstration, a prototype of 1 × 4 array is designed with the antenna element planar size (without ground) of 0.57 λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> × 0.18 λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> (λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> is the wavelength in the free space at center frequency), the 10-dB impedance matching bandwidth of 49.7% (24.2 - 40.2 GHz), and the average gain of 9.12 dBi. The proposed compact wideband antenna array can be a good candidate for 5G mm-Wave wireless application.

Design of High Order HTS Duplexer Based on SIR Structure

A folded half-wavelength micro-strip resonator with a stepped impedance structure (FSIR) is designed to extend the second harmonic and affect the strength of the external electromagnetic coupling. The FSIRs of electromagnetic mutual cancellation structure and strong electric coupling structures are designed to realize the design of narrowband and broadband filters with extended second harmonic, respectively. A T- junction is designed to cascade the two high-order filters to achieve high isolation between two channels. The duplexer is fabricated on a single piece of 2-in double-sided YBCO (YBa <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> Cu <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">7</sub> ) thin film on a MgO substrate with a dimension of 34.86×26.30×0.50 mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> , a thickness of 0.5 mm, and a dielectric constant of 9.8. At 77K, the measured central frequency of the duplexer are 910 MHz and 1100MHz, the fractional bandwidths (FBW) are 2.19% and 18.18%, the out-of-band rejections are greater than 60 dB, the two second harmonic are located at 2.4 GHz and 2.5 GHz, the insertion loss is less than 0.20 dB, and the return losses are better than 16.1 dB and 17.2 dB. The test results of the duplexer are in good agreement with the simulated ones.

CPW fed shovel shaped super wideband MIMO antenna for 5G applications

A shovel shaped antenna operating from 4.1 to >60 GHz to cover C/X/Ku/K/Ka/Q/U bands along with 5G bands n257/n258/n259/n260/n261/n79/60 GHz is presented in this paper. It consists of a modified square patch, tapered feed line and modified defected coplanar waveguide ground planes. A half-wavelength split ring resonator (SRR) is used to achieve X-band satellite downlink (6.8–7.8) GHz band notch. It has dimensions of 20 × 14 mm2, quasi-stable radiation patterns, a maximum peak realized gain of 9 dBi, fidelity factor > 50%, |S21| > 32 dB and linear S21 phase response. It’s two element spatial diversity configuration has footprint of 20 × 36 mm2, operating bandwidth of 4.3 to >60 GHz with notch band characteristics and isolation >15 dB due to hybrid decoupling structure. The pattern diversity configuration has footprint of 20 × 41.5 mm2, impedance bandwidth of 4.3 to >60 GHz for Port 1 & 3.9 to >60 for Port 2 and isolation >21 dB due to hybrid decoupling structure. Both MIMO antennas have ECC≤0.01, DG≅10, TARC < -10 dB, ηmux > -3.5 dB and CCL≤0.3 b/sec/Hz and channel capacity of ∼11.34b/sec/Hz. The proposed antenna geometries are dominating previously reported structures in terms of superwide bandwidth, compact dimensions, high BDR ∼3335, high peak gain and good diversity performance with less intra element spacing.

Optimization and Design of Balanced BPF Based on Mixed Electric and Magnetic Couplings

A balanced bandpass filter (BPF) with an improved frequency selectivity for differential-mode (DM) excitation and high rejection for common-mode (CM) excitation is proposed in this paper. Two half-wavelength stepped impedance resonators (SIRs) are employed based on mixed electric and magnetic couplings to realize a DM passband centered at 2.48 GHz. The center frequency and bandwidth can be easily controlled by optimizing the dimensions of SIRs and the coupling between them, respectively. Meanwhile, two transmission zeros (TZs) are generated based on the mixed electric and magnetic couplings and are independently controlled by tuning the coupling strength. Moreover, a wide DM stopband can be realized by optimizing the SIRs. The proposed balanced BPF is fed by balanced U-type microstrip–slotline transition structures, which can achieve high wideband CM rejection without influencing the DM responses, and the design complexity can be clearly reduced. Finally, a balanced BPF is fabricated, and a good agreement between the simulation and the measurement is observed, which verifies the design method.

Channel Selectivity of Satellite Transponders with the Antenna Combined with a Size-Reduced Metallic Waveguide Bandpass Filter Having Thin Metamaterial Resonators.

Global and intercontinental networking relies on satellite communication. Its wireless communication system always has antennas and their feed assembly comprising waveguides. This makes the satellite payload heavy and costly. In this paper, a novel method is proposed to effectively reduce the size of a waveguide bandpass filter (BPF). Because the metallic cavities make the conventional waveguide end up with a large geometry, especially for high-order BPFs, very compact waveguide-type resonators having metamaterial zeroth-order resonance (WG-ZOR) are designed on the cross-section of the waveguide and substituted for the cavities. While the cavities are half-wavelength resonators, the WG-ZOR is shorter than one eighth of a wavelength. A substantial reduction in size and weight of the waveguide filter is observed as the resonators are cascaded in series through coupling elements in the X-band much longer than K- or Ka-band. An X-band of 7.25~7.75 GHz is chosen to verify the method as the passband with attenuation of 40 dB at 7.00 GHz and 8.00 GHz as the roll-off in the stopband. The BPF is manufactured using the CNC milling technique. The design is carried out with geometrical parameters, not of the level of 10 μm, but the level of 100 μm, which is good for manufacturers but a big challenge for component designers. The measurement of the manufactured metal waveguide filter reveals that the passband has about ≤1 dB and ≤-15 dB as insertion loss and reflection coefficient and the stopband has ≤-40 dB as attenuation, which are in good agreement with the results of the circuit and simulation. The proposed filter has a length of 3.5 λg as the eighth-order BPF, but the conventional waveguide is 5 λg as the seventh-order BPF for the same area of the cross-section. This metamaterial BPF is combined with a horn antenna. The filter enables the wide-band antenna to distinguish the band of transmission from that of noise suppression. This channel selectivity is obviously observed by the filter integrated antenna test.

Inline Waveguide Filter With Transmission Zeros Using a Modified-T-Shaped-Post Coupling Inverter

This letter reports the design techniques for a class of inline waveguide bandpass filters with sharp-rejection capabilities at the lower stopband based on a novel nonlinear-frequency-variant-coupling (NFVC) structure. The proposed NFVC consists of a modified-T-shaped metallic post (MTP) that is placed at the center of the waveguide broad wall with its open arms lying along the waveguide width. The engineered NFVC structure produces a first-order bandpass filtering transfer function with a pair of transmission zeros (TZs) located below the passband range. To demonstrate the usefulness of the proposed NFVC inverter, a 9.9-GHz third-order inline waveguide bandpass filter prototype with two TZs is developed and tested. It consists of two half-wavelength cavity resonators coupled together via the conceived MTP coupling structure. The measured results are in close agreement with the electromagnetic (EM) simulated ones, thus validating the devised waveguide filter design principle.

Effective Size Reduction of the Metallic Waveguide Bandpass Filter with Metamaterial Resonators and Its 3D-Printed Version.

In this paper, a novel method is proposed to effectively reduce the size of a waveguide bandpass filter (BPF). Because the metallic cavities make the conventional waveguide end up with a large geometry, especially for high-order BPFs, very compact waveguide-type resonators having metamaterial zeroth-order resonance (WG ZOR) are designed on the cross section of the waveguide and substituted for the cavities. While the cavities are half-wavelength resonators, the WG ZOR is shorter than one-eighth of a wavelength. A substantial reduction in the size and weight of the waveguide filter is observed as the resonators are cascaded in series through coupling elements in the X-band that is much longer than that in K- or Ka-bands. The proposed metamaterial filter is realized as a 3D-printed structure to be lighter and thus more suitable for low earth orbit (LEO) satellites. An X-band of 7.25-7.75 GHz is chosen to verify the method as the passband with an attenuation of 40 dB at 7.00 GHz and 8.00 GHz as the roll-off in the stopband. The BPF is manufactured in two ways, namely the CNC-milling technique and metal coating-added 3D printing. The design is carried out with a geometrical parameter of not 10-2 mm but rather 10-1 mm, which is good for manufacturers but challenging for component designers. The measurement of the manufactured metal waveguide filters reveals that the passband has about ≤1 dB and ≤-15 dB as the insertion loss and the reflection coefficient, respectively, and the stopband has an attenuation of ≤-40 dB, which are in good agreement with the results of the circuit and the simulation. The proposed filter has a length of 14 cm as the eighth-order BPF, but the conventional waveguide is 20 cm as the seventh-order BPF for the same area of the cross section.