Microstrip Line Resonator Research Articles

Exploration of room temperature magnetodielectric behavior in Nd0.5Dy0.5FeO3 thin films and transmission line resonators in GHz frequency range

This study explores the room-temperature magnetodielectric (MD) and magnetoresistance (MR) properties of Nd0.5Dy0.5FeO3 thin films on n-type silicon substrates from 4 Hz to 2 MHz. The observed MD effect registers a change of ∼23 %, and the MR effect manifests a change of ∼11 % when subjected to an applied magnetic field of 2.5 T at a frequency of 177 Hz. Interestingly, the MD effect was absent at 1 T across all frequencies. However, we observed an MR of 6 % at 1 T, implying the possibility of an intrinsic MD effect or the co-existence of both intrinsic and extrinsic contributions to the MD effect. To comprehensively gauge the dielectric properties of the thin film at higher frequencies, a 5-GHz microstripline resonator was fabricated. Coupled with experimental data and simulations, this study reveals a dielectric constant of ∼56 for the Nd0.5Dy0.5FeO3 thin film at 5 GHz and 300 K.

Compact linear‐phase bandpass filters with notched frequency response employing eighth‐mode substrate integrated waveguide and dual‐mode microstrip line structure

AbstractA series of fourth‐order bandpass filters (BPFs) with compact footprints, broad bandwidth, high selectivity, linear phase and notched response are proposed. The sketch of these BPFs is in accordance with the combination of the eighth‐mode substrate integrated waveguide (EMSIW) and dual‐mode microstrip line (DMML) resonators. The DMML resonator is constructed by means of metallic via‐holes and pad in the double‐layered structures. Among them, the DMML resonator can provide two transmission poles. Besides, the cross coupling is introduced through the vertical slot or fan‐shaped aperture in the dual‐layered substrates. The coupling schemes of the proposed BPFs can introduce two transmission zeros in the vicinity of operating passband, and the coupled scheme also exhibits a relatively flat in‐band group delay. Notched frequency responses have been obtained by exploiting the U‐shaped resonator and folded‐ring resonator embedded with the mixed EMSIW and DMML BPFs. To validate the conceptual design, the proposed BPFs are simulated, fabricated and measured. Both the simulation and measurement have reached to a satisfactory agreement.

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.

Improvement of rejection band with Defected Microstrip Line and Ground plane Resonators

In this paper first a dual band bandstop filter is proposed using a unique spiral defect at the signal plane for Wi-Fi communication and remote sensing applications. The spiral defects is studied, simulated and measured. Next proposed spiral defect is combined with the hexagonal head defected resonators at ground plane to improve the rejection band. In addition a study is also done to observe the effects of the proposed defects at both signal plane and ground plane. A comparison is done among the response of individual defects filters and combined defect filter. It is observed that later shows improved overall bandwidth with compactness. The proposed combined defect filter with improved stopband displays 92.6% FBW and 112.5 dB/GHz sharpness factor with very compact in size as 0.26 λ0 × 0.25 λ0. All measurement results are in good agreement with the simulated results.

Review of scientific instruments: Evaluation of adulteration in honey using a microwave planar resonator sensor.

A microwave microstrip line resonator sensor is developed as an alternative tool for detecting adulteration in honey. A honey-filled tube is placed at the position with the maximum electric field intensity. When the honey is adulterated, its permittivity is changed, leading to a distinct resonance frequency shift and enabling detection. Compared with the existing microwave sensors, this sensor offers the advantages of low cost, compact size, and easy fabrication. Moreover, quantitative analysis of the adulteration could be achieved. Electromagnetic simulation is performed using a co-simulation with CST and MATLAB. The simulation results reveal that the resonance frequency of the resonator decreases as the added water content increases, following a quadratic polynomial relationship. In the experiments, the results demonstrate a successive decrease in the resonance frequency from the empty tube, honey-filled tube to water-filled tube cases. Furthermore, honey samples with varying water contents (up to 70%) are tested, and the resonance frequency decreases with increasing added water content, which agrees well with the simulation results. In addition, there is a quadratic relationship between the two parameters. Principal component analysis is conducted on the transmission coefficients, and the first principal component decreases with increasing water content. With the addition of the second principal component, the cases of different water contents in honey can be well classified.

Compact hybrid eighth‐mode substrate integrated waveguide and microstrip line filters with mixed electric and magnetic coupling

AbstractThis paper proposes a new type of hybrid eighth‐mode substrate integrated waveguide (EMSIW) and microstrip line (MSL) bandpass filter (BPF) with mixed electric and magnetic coupling. Firstly, two second‐order EMSIW BPFs with mixed coupling and wide stopband performance are investigated. Then, in order to realise high‐order BPF with decent performance, half‐wavelength (λ/2) open‐circuited MSL resonators are employed in the hybrid BPFs design. In the end, two third‐order BPFs and a fourth‐order BPF are developed by combining the EMSIW and MSL resonators together. Extra transmission zeros can be introduced due to the cross couplings in the trisection and quadruplet topologies. For demonstration, the proposed prototypes are designed, fabricated and measured. Reasonable agreements can be achieved between the measurement and simulation. The proposed third‐order BPFs compete against the state of the art, exhibiting the competitive characteristics of the operating bandwidth, physical footprint and upper‐stopband rejection with less order. The proposed fourth‐order BPF features a compact size of 0.34 × 0.34λ0, a low insertion loss of 1 dB, a broad 3‐dB fractional bandwidth of 22.9% and an excellent lower‐stopband suppression.

High Sensitivity Detection Method for Liquid Concentrations Based on Coupled Microwave Resonators

This paper presents a new measurement method for liquid concentrations based on two inductively coupled resonators with enhanced sensitivity compared with traditional methods in microwave frequency ranges. The equivalent circuit of the coupled resonators is proposed with its eigenequation having three eigenfrequencies derived. We demonstrate that, compared to a single resonator, the sensitivity of the center eigenfrequency shift to the changed capacitance increases by an order of magnitude if the product of the coupling coefficient and Q-factor of the second resonator is close to unity. In addition, that the reflection magnitude changes with the varied capacitance is also giant under impedance matching condition at the down and up eigenfrequencies. Based on the proposed method, a sensor composed of an open quarter-wavelength microstrip-line resonator (OQMR) and a split ring resonator (SRR) for detecting concentrations of water-glucose solutions is designed. By adjusting the sample volume and the distance between two resonators, different coupling coefficients and Q-factors can be attained, enabling marked increases in the sensitivity. Experimental and simulated results show that the sensitivity of the center eigenfrequency shift and of the reflection magnitude change to the concentration are as high as 9.4 MHz/(mg/mL) and 5.41 dB/(mg/mL), respectively, both of which are excellent compared to other sensors.

Compact single‐ and dual‐band band‐pass filters employing mixed eighth‐mode substrate‐integrated waveguide and microstrip line resonators

In this study, single- and dual-band band-pass filters (BPFs) employing mixed eighth-mode substrate-integrated waveguide (EMSIW) and microstrip line (MSL) resonators are proposed and investigated. The mixed resonators feature compact circuit size, moderate quality factor and flexible design topology. By exploiting the mixed resonators to implement the BPF designs, a single-band BPF is developed, exhibiting four-order broadband band-pass filtering responses in a single-layered substrate. Several transmission zeros are introduced near the working passband to enhance the frequency selectivity. Moreover, the proposed BPF has the capability to suppress the harmonics superior to 20 dB rejection level up to 2.36 f0. Meanwhile, two dual-band BPFs are designed in double-layered substrates with magnetic and electric coupling schemes. Both dual-band BPFs exhibit compact circuit size and low insertion loss. To the best of the authors' knowledge, it is the first time to develop single- and dual-band BPFs based on mixed EMSIW and MSL resonators in this study. For demonstration, a series of single- and dual-band BPFs with mixed SIW/MSL resonators are developed and fabricated. The simulated, measured and synthesised results have reached satisfactory agreements.

A low-cost photonic band gap (PBG) microstrip line resonator for dielectric characterization of liquids

Abstract In this paper, hybrid integration of planar microstrip line and Photonic Band Gap (PBG) structure is proposed for the dielectric characterization of liquids. To implement the PBG structure of the microstrip line, a microfluidic channel with periodic form is introduced into the substrate and filled with different liquids. Based on this configuration, the operation principle of the sensor is based on a frequency shift due to the variation in the center of the bandgap, which in turn changes with the variation of the permittivity of LUT filled in the microfluidic channel. The proposed sensor exploits the behavior of the bandgap as a reflector to construct a resonant structure sensitive to the variation in LUT permittivity. The dimensions of the planar structure are optimized to achieve high precision and discrimination capability. The different empirical expressions describing the complex permittivity with the measured parameters were carried out. To validate the proposed concept, the sensor prototype is designed, fabricated, and tested. The frequency shift related to a change of 3.2 in LUT permittivity corresponds to 180 MHz around 6 GHz. The resonant-mode sensor spans a permittivity range from 1 to 80 with a precision better than 7.2%. The proposed sensor is simple in design and low cost, which may be applied in different applications at the industrial.

Multi-layer approach of polarization agile oscillating-type active integrated array antennas for RFtransmitter front-end

AbstractThis paper presents a polarization switchable self-oscillating active integrated array antenna (AIAA) using a multi-layer approach. The antenna comprises two antenna elements, four PIN diodes, and a Gunn oscillator employing a microstrip line resonator. Reconfiguring the feed network of the array antenna realizes slant polarization (± 45°) switching. The multi-layer structure allows the patch spacing to be adjusted, thereby helping to minimize the antenna's sidelobe level. The Gunn oscillator, which employs a λ/2 microstrip–line resonator, is placed at the bottom layer. The proposed AIAA has an effective isotopic radiated power (EIRP) of + 18.25 dBm at the oscillation frequency of 9.47 GHz. EIRP is improved by better than 8.45 dB compared to the single-layer structure. The proposed AIAA features a transmitted power of + 8.45 dBm, DC-to-RF efficiency of 1.0%, and a low phase noise of −101.8 dBc/Hz at 1-MHz offset frequency with better than 12-dB cross-polarization suppression.

A Compact, Hybrid SIW Filter With Controllable Transmission Zeros and High Selectivity

A novel, highly selective, and compact filter with controllable transmission zeros (TZs) is proposed in this brief. The hybrid structure of the proposed filter is based on the substrate integrated waveguide (SIW) and microstrip line resonators. The negative magnetic coupling was introduced through a full-wavelength microstrip line resonator, and the additional TZ was added by the cross-coupling of indirectly connected resonators in the traditional box-like topology. Consequently, high selectivity is achieved with TZs located at both sides of the passband. The independent control of the left and right TZs can be realized by controlling the cross-coupling and external coupling. The proposed work achieves good performance, including sharp skirt characteristics, compact size, and low loss. As a validation of the concept and performance, a filter prototype designed following the procedure is fabricated and measured.

A Filtering Balun Utilizing Multi-Ring Loaded Vertical Transition Structure With 161% Fractional Bandwidth and >5.8f₀ Stopband

An ultra-broadband filtering balun with microstrip line-slotline (ML-SL) vertical transition structure and multi-ring slotline termination is proposed in this brief. The proposed multi-ring structure consisting of three closed slotline loops connecting in series with each other is stretched beyond ML-SL transitions as a termination load and helps introduce five transmission poles (TPs). Furthermore, a hybrid structure integrating backside coplanar waveguide (CPW) and topside microstrip-line stepped-impedance resonators (SIRs) are employed to achieve a high harmonic rejection within a wide frequency range. In addition, a low insertion loss can be obtained owing to the reduced radiation loss brought by the fully symmetry of the ring loops. The fabricated balun filter demonstrates a 161% fractional bandwidth (FBW) centering around f <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> of 3.3 GHz, a minimum in-band insertion loss of 0.37 dB, and a wide harmonic rejection band up to 20 GHz (5.8f <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> ) with a minimum rejection level of 18.9 dB. To the best of the authors’ knowledge, the achieved fractional bandwidth and stopband are among the best.

Tunable wideband THz graphene-based artificial magnetic conductors

Graphene-based artificial magnetic conductor (AMC) structures featuring wideband and tunable responses at terahertz frequencies are presented. The unit cells of the proposed structures comprise curved coupled microstrip line (CCML) resonators, in which small graphene patches are added for electrical tuning. An advantage of the present structure is that the full range of graphene chemical potential, from 0 to about 1 eV, can be used to tune the center frequency; therefore the AMC is tunable in a larger frequency range, for which the return loss remains near 0 dB. This feature is missing in the previous tunable graphene-based AMC structures. A typical design in the present work yields a fractional bandwidth of 45% and an electrically tunable center frequency in a range from 3.7 to 4.4 THz.

Compact Wideband BPF With Wide Stopband Using Substrate Integrated Defected Ground Structure

In this letter, a compact wideband bandpass filter (BPF) with a wide stopband is proposed based on the substrate integrated defected ground structure (SIDGS) and folded stepped-impedance resonator (FSIR). Such a SIDGS resonator can not only allocate a specific resonance with compact size but also introduce the different harmonic positions compared with a traditional microstrip line resonator. Meanwhile, due to the discrepant harmonic positions of proposed SIDGS and FSIR, a wide stopband response can be achieved using a compact stacked-coupled scheme. To verify the mechanism, a miniaturized wideband BPF operating at 1.69 GHz (i.e., f <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> ) is implemented and fabricated. A measured wide stopband up to 11.8 f <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> with a 20-dB rejection level is achieved.

Compact, Wide Stopband, Shielded Hybrid Filter Based on Quarter-Mode Substrate Integrated Waveguide and Microstrip Line Resonators

A novel miniaturized bandpass filter (BPF) with high stopband rejection based on a hybrid structure is proposed with shielded quarter-mode substrate integrated waveguide (QMSIW) and microstrip technologies. The shielded QMSIW cavity provides a high-quality ( $Q$ ) factor with substantial size reduction. This filter exhibits flexible response with four poles and two controllable transmission zeros (TZs) by incorporating two quarter-wavelength microstrip resonators into two back-to-back QMSIW resonators. The working principles for higher order mode suppression and filter coupling topology are carefully illustrated by eigen-mode simulation, coupling matrix, and field distribution analysis, respectively. Compared with the reported works, the proposed four-order BPF demonstrates advantageous features in terms of a compact size of $0.62\,\,\lambda _{0}\times 0.62 \,\,\lambda _{0}$ , a low insertion loss of 1.2 dB, a wide passband (22.7%), and a high stopband rejection (better than 36 dB).

Complex Permittivity Extraction of Planar Dielectrics Using a Noninvasive Microwave Transmission Line Resonant Technique

This article presents a novel planar resonant method for complex permittivity measurement of planar dielectric substrates. Conventional planar dielectric sensors are composed of resonant structures, such as metamaterials, annular rings, and patch coupled to transmission lines to generate resonance. Here, we demonstrate a simple microstrip line resonator for complex permittivity measurement, and the generated resonant modes in the microstrip line are much like in 3-D conventional microwave cavities. The proposed prototype is distinguished from regular planar resonators due to the presence of a number of distinct electric and magnetic perturbable resonant modes and the absence of additional resonating structures in the design. The use of test samples in the commercially available thickness eliminates extensive sample preparation and possible air gaps or errors introduced due to the stacking of multiple dielectric layers. The microstrip line resonator fabricated on the FR4 substrate shows good agreement in measured permittivity and loss tangent values compared with the manufacturer’s datasheets. The proposed technique is a simple, fast, compact, and cost-effective measurement method for dielectric characterization, and it could be extended for other microwave transmission lines also.

Compact four-port vertically polarized UWB monopole antenna for MIMO communications

PurposeThis paper aims to present the design of a compact vertically polarized four-element UWB antenna suitable for MIMO communications.Design/methodology/approachThe unit cell antenna is constructed using a square ring radiator excited through a stepped impedance feed. The proposed antenna covers the Ultra-wideband (UWB) spectrum ranging from 2.2 to 12.3 GHz. The isolation between the unit cell antennas in the array is enhanced using a simple microstrip line resonator. The decoupling element is connected to the ground through a via.FindingsThe proposed scheme offers at least 16 dB improvement in the port-to-port coupling. Furthermore, the four-element antenna array is constructed using a specific interlocking scheme. The proposed antenna array’s Multiple Input Multiple Output (MIMO) performance metrics are analyzed.Originality/valueBy suitably selecting the excitation port, directional radiation patterns can be realized. The combined radiation pattern covers 360 degrees. A prototype antenna array is fabricated, and the simulation results are verified using real-time experiments. The proposed antenna is a suitable candidate for shark fin housing in automotive communications.

Design of Dual Band and Tri-band Bandpass Filter (BPF) with Improved Inter-band Isolation Using DGS Integrated Coupled Microstrip Lines Structures

A novel approach to design dual-band as well as a triple-band BPF with improved isolation is ventured in this paper. In dual-band filter, dual mode property of coupled line filters is utilized to obtain resonant frequencies at 2.4 GHz and 7.4 GHz suitable for WLAN and WiMAX application respectively. Additionally a rectangular-ring DGS element is introduced within the coupled line filter to obtain a separate mid-band resonance at 5.2 GHz. The frequency shifting property of the pass bands due to cross-coupling between the microstrip line resonators and the DGS element is mostly eliminated by implementing stepped impedance open stub (SIOS) technique. All filter configurations are fabricated, measured and compared with the simulated models to validate the practical effectiveness. Stop band isolation > 40 dB and insertion loss (IL) < 0.8 dB is attained in all the filter configurations.

Publisher’s Note: “Microstrip-line resonator with broadband, circularly polarized, uniform microwave field for nitrogen vacancy center ensembles in diamond” [AIP Advances 9, 075213 (2019)

Publisher’s Note: “Microstrip-line resonator with broadband, circularly polarized, uniform microwave field for nitrogen vacancy center ensembles in diamond” [AIP Advances 9, 075213 (2019)

Differentially Fed Wideband Filtering Slot Antenna With Endfire Radiation Under Multi-Resonant Modes

In this communication, a differentially fed wideband slot antenna on a single layer with endfire radiation and filtering response under multi-resonant modes is proposed. By using the $\lambda $ /4 slot radiator with its opened terminal at one side, the endfire-radiated fields of the slot antenna is initially formed with compact dimension and endfire radiation. After that, the $\lambda $ /4 slot radiator with two distinctive portions of different slot widths is presented and investigated. The results demonstrate that the resonant frequencies of the first two odd-order modes could be progressively reallocated in proximity to each other as the length and width ratios of these two portions are properly selected. Thus, the bandwidth in input impedance of the entire differentially fed slot antenna could be significantly improved under operation of dual-resonant modes. Next, an extra microstrip-line resonator is introduced in the feeding part so as to produce a third resonant mode and improve its frequency selectivity in the wide operating band. To validate these predicted performances, a filtering slot antenna operating from 3.33 to 4.50 GHz is in final fabricated and tested. The measured results exhibit good impedance matching property, flat radiation gain of about 5 dBi, and improved endfire radiation characteristic with the front-to-back ratio (FBR) better than 9.0 dB in the operating band. Both the simulated and measured results are provided with good agreement.