Microstrip Line Resonator Research Articles

Linear arrays of stable atmospheric pressure microplasmas

Microdischarges produce cold atmospheric plasma when the discharge current is limited by the quenching of a microwave resonator. A quarter-wavelength microstripline resonator is shown to support stable atmospheric microplasma in pure argon. Electrical characterization of the microplasma shows that its impedance is resistive and capacitive (Zp=500−j900 Ω). An array of these linear resonators generates a stable, line-shaped microplasma operating from a single power source due to close-coupling among adjacent resonators. Both simulations and experiments confirm that coupled-mode theory describes the collective behavior of linear microplasma arrays.

Ultra-wideband bandpass filters with improved out-of-band behaviour via embedded electromagnetic-bandgap multimode resonators

A class of ultra-wideband microstrip-line bandpass filters with improved out-of-band behaviours is presented by using an electromagnetic (EM) bandgap embedded multimode resonator. At first, the two EM bandgap structures are constructed by periodically loading uniform or non-uniform open-circuited stubs. Their performances are numerically characterised, aiming at exhibiting the existence of a bandstop in a frequency range of 15.0–30.0 GHz. These bandgap structures are then internally embedded in the middle part of an open-ended microstrip line resonator, constituting a modified type of multimode resonator. In the design, the dimensions of this resonator need to be properly adjusted towards allocating the first three resonant modes in the 3.1–10.6 GHz ultra-wide passband. To achieve a preferably wide upper stopband, the transmission zero of parallel-coupled lines is used to cancel the spurious fourth-order resonant mode. Also, higher-order modes in the upper band are inhibited by the employed bandgap structures. Two bandpass filters using the non-uniform stub-loaded resonator are finally designed, fabricated and tested. Predicted insertion/return losses and group delays are experimentally confirmed in a wide frequency range of 1.0–30.0 GHz.

Detection of micro-cracks on metal surfaces using near-field microwave dual-behavior resonator filters

This paper demonstrates how micro-cracks at the surface of metals can be detected and imaged by near-field microwave techniques from the crack-induced variations of the resonance frequency and of the resonant circuit quality factor. It deals with two resonant sensors: a quarter wavelength microstrip line resonator terminated by an electric dipole and an original dual-behavior resonator (DBR) band-pass filter probe. The detection principle is developed, at first, from the use of the electric dipole probe. The low sensitivity of the electric dipole resonator led us to investigate whether first-order band-pass filters based on dual behavior resonators were able to detect a 200 µm wide and 3 mm deep rectangular EDM notch at the surface of a steel plate used to validate our method. Simulation data and measurements results carried out on a stainless steel mock-up with several 200 µm wide EDM rectangular notches showed that the DBR sensor is more sensitive than the electric dipole probe, and highlighted the link between the spatial resolution and the width of the high-frequency stub of the DBR filter. Moreover, we demonstrate the notch detection for any orientation of the defect in relation to the DBR sensor and the ability to differentiate between notches of different depths. Simulation data and measurement results are presented and discussed.

High-frequency microstrip cross resonators for circular polarization electron paramagnetic resonance spectroscopy

In this article we discuss the design and implementation of a novel microstrip resonator which allows absolute control of the microwaves polarization degree for frequencies up to 30 GHz. The sensor is composed of two half-wavelength microstrip line resonators, designed to match the 50 Omega impedance of the lines on a high dielectric constant GaAs substrate. The line resonators cross each other perpendicularly through their centers, forming a cross. Microstrip feed lines are coupled through small gaps to three arms of the cross to connect the resonator to the excitation ports. The control of the relative magnitude and phase between the two microwave stimuli at the input ports of each line allows for tuning the degree and type of polarization of the microwave excitation at the center of the cross resonator. The third (output) port is used to measure the transmitted signal, which is crucial to work at low temperatures, where reflections along lengthy coaxial lines mask the signal reflected by the resonator. Electron paramagnetic resonance spectra recorded at low temperature in an S=5/2 molecular magnet system show that 82% fidelity circular polarization of the microwaves is achieved over the central area of the resonator.

Power handling capability improvement of HTS filter with sliced microstrip line resonators

We investigated the third-order intermodulation distortion (IMD3) properties of high- temperature superconducting (HTS) filters with sliced microstrip line resonators. Electromagnetic simulations indicated that the current concentration along the outer edges of a sliced microstrip line was lower than that of a conventional microstrip line. We fabricated a 3-pole filter with a sliced microstrip line resonator using HTS YBCO thin films and measured the IMD3. Until the input power increase to 7 W, the filter has proper operation from 50 to 77.3 K. The third-order intercept point value of 64 dBm was observed at 70 K. The ΔIMD3 was less than −55 dBc at 1 W input power when the temperature was 50–77.3 K. The sliced microstrip line indicated low ΔIMD3 to the fundamental two-tone sinusoidal waves, which had a difference of 1 MHz, when the input power was 1 W. The results showed that HTS filters with sliced microstrip line resonators have better power handling capability and can feasibly be used in transmitters.

마이크로스트립 사각 개방 루프 공진기와 가변 부성 저항을 이용한 저위상 잡음 Push-Push 전압 제어 발진기

본 논문에서는 마이크로스트립 사각 개방 루프 공진기와 가변 부성 저항을 이용한 향상된 push-push 전압제어 발진기를 제시하였다. 마이크로스트립 사각 개방 루프 공진기는 큰 결합 계수 값을 갖는데, 이는 Q값을 크게 만들고, 전압 제어 발진기의 위상 잡음을 줄인다. 1.8V의 공급 전압을 사용한 전압 제어 발진기는 <TEX>$5.744{\sim}5.859GHz$</TEX>의 주파수 조절 범위에서 <TEX>$-124.67{\sim}-122.67dBc/Hz\;@\;100 kHz$</TEX>의 위상 잡음 특성을 갖는다. 이 전압 제어 발진기의 FOM은 같은 주파수 조절 범위에서 <TEX>$-202.83{\sim}-201dBc/Hz\;@\;100 kHz$</TEX>의 값을 갖는다. 마이크로 스트립 사각 개방 루프 공진기를 이용한 단일 종단 전압 제어 발진기와 마이크로스트립 공진기를 이용한 push-push 발진기와 비교했을 때 개선된 위상 잡음 특성은 각각 -8.51 dB와 -33.67 dB이다. In this paper, a novel push-push voltage-controlled oscillator(VCO) using microstrip square open loop resonator and tunable negative resistance is presented. The microstrip square open loop resonator has the large coupling coefficient value, which makes a high Q value, and has reduced phase noise of VCO. The VCO with 1.8V power supply has phase noise of <TEX>$-124.67{\sim}-122.67dBc/Hz\;@\;100 kHz$</TEX> in the tuning range, <TEX>$5.744{\sim}5.859 GHz$</TEX>. The FOM of this VCO is <TEX>$-202.83{\sim}-201dBc/Hz\;@\;100 kHz$</TEX> in the same tuning range. When it has been compared with single-ended VCO using microstrip square open loop resonator, and push-push oscillator using microstrip line resonator, the reduced phase noise has been -8.51dB, and -33.67dB, respectively.

Self-consistent numerical method to study nonlinearity in high- Tc superconductors using complex conductivity

The determination of the origin of the nonlinear response in high- T c superconductors is yet to be well understood. The microwave surface impedance and current density mutually depend on one another. For this reason, we developed a self-consistent numerical method to determine the RF magnetic field, which is related to the microwave input power. To take the nonlinearity into consideration, we added quadratic nonlinear terms to the real and imaginary parts of the complex conductivity. The surface current density distribution, derived from the critical state model, along the width of the studied microstrip line resonator has been used in our calculations. This numerical method has been validated through three different reported experimental data. Then, the corresponding physical quantities like surface impedance, resonance frequency and critical current density as function of power have been calculated. Subsequently, the averages of the surface resistance ( R Sur) as well as that of the surface reactance ( X Sur) as function of the microwave input power are calculated. Moreover, two geometrical factors g and g 1/ I 2 are shown to be dependent of input power rather than considered constant as used to be reported in literature.

Noncontact Evanescent Microwave Magnetic Dipole Probe Imaging of Ferromagnets

We describe a 2-GHz evanescent microwave magnetic dipole probe and its applications in imaging high-frequency electromagnetic properties of metallic magnetic samples. The probe offers the advantages of low cost and ease of implementation. It consists of a small inductive metallic loop fed by a microstripline resonator that is scanned over ferromagnetic samples. In contrast to the electric dipole probe reported previously, the magnetic dipole probe has higher input admittance, making it more suitable for quantitative imaging of high-conductivity metallic samples. When calibrated with a Gauss probe, the magnetic dipole probe was insensitive to electric field while it detected the magnetic field above the magnetized ferromagnetic sample with 1% accuracy and 0.06% resolution at 2 GHz. Using a simplified circuit model of the resonator, we were able to interpret the probe's output and predict the magnitude of the reflected wave and relate it to the magnetic properties of the samples under investigation.

Influence of split ring resonators on the properties of propagating structures

The study of a 50 V microstrip line and microstrip resonators loaded with resonant elements called split-ring resonators (SRRs) is presented. The two different filtering phenomena observed lead to make an analogy with those observed when waveguides are loaded with these elements. So, in order to make this analogy, the different results obtained with the SRRs loaded in a propagating and an under cut-off waveguide are shown. Then, another technique to achieve and even improve these results is presented. The technique consists of using, respectively, a 50 V microstrip line and capacitive-gap-coupled microstrip resonators instead of the propagating and under cut-off waveguides. The numerical and experimental results obtained with the two structures (waveguides and microstrip lines) are compared and discussed. This study shows that the combination of SRRs with guiding structures helps in the design of compact structures, but an enhancement of the performances needs a better fabrication accuracy.

V-Band GaAs pHEMT Cross-Coupled Sub-Harmonic Oscillator

A V-band cross-coupled sub-harmonic injection-locked oscillator has been designed and fabricated using 0.15-mum GaAs pHMET technology. Based on the known harmonic injecting circuit topology, this oscillator was designed by a differential output approach, a low-Q microstrip-line resonator, and a current mirror, which has a free-running oscillation frequency around 60GHz with a tuning range of 2.5GHz (from 57.8GHz to 60.3GHz). The maximum single-end output power is 3.8dBm with a dc dissipation of 225mW under a -3V supply voltage. Within the input matching network for second (30GHz) and fourth (15GHz) sub-harmonic signals injection, it demonstrates the maximum locking ranges close to 120MHz and 30MHz, respectively

Dependence of the surface resistance and critical current density in HTS thin films on an angle of applied magnetic field

We investigated the relation between the surface resistance (Rs) and the critical current density (Jc) of YBCO thin films as a function of an angle of the applied dc magnetic field. The Rs of YBCO thin film deposited on a MgO (100) substrate was measured using a microstrip line resonator (MSLR) method. After the MSLR in a closed-type Cu cavity was cooled at 4K under a zero dc field, dc magnetic field strengths up to 5.0T were applied. The Rs measured when the field was parallel to the film was less than that measured when the field was perpendicular to the film. The dependence of the Jc on angle of the applied magnetic field was measured using a vibrating sample magnetometer. The Jc decreased with increasing angle of the applied magnetic field. We could qualitatively explain the relation between the Rs and the Jc for magnetic fields applied parallel or perpendicular to the film.

Design of microstrip resonators using balanced and unbalanced composite right/left-handed transmission lines

Balanced and unbalanced composite right/left-handed transmission lines are used in the design of resonators. The balanced resonator is designed by changing the nonlinear phase response in order to control the spacing between modes and the Q factor. Two balanced ring resonators are measured and one demonstrates increased mode spacing/decreased Q factor and the other demonstrates decreased mode spacing/increased loaded Q factor. The unbalanced resonator is designed by changing the nonlinear phase response and magnitude response. A measured unbalanced ring resonator shows increased mode spacing with a reasonable Q factor. A microstrip line resonator is measured to demonstrate higher frequency capabilities.

The effects of component Q distribution on microwave filters

The effects of lossy components on the passband response of a bandpass filter are studied in this paper. It is found that the resonator Q has pronounced effects on the insertion losses, while its effects on the group delays are rather minor. The first-order approximation is used to estimate the deviations of insertion loss and group delay from the ideal. The effects of a lossy resonator in each stage are individually analyzed to evaluate which components are more critical and should be paid more attention. Filters designed by the predistortion technique are also discussed with emphasis on the effects of component Q distribution on the transmission level. When resonators with different Q are used in a filter, a bell-shaped Q distribution is proposed to achieve the optimal passband response. Finally, three filters with different component Q distributions were designed by combining the dielectric and microstrip-line resonators, and the measured results agreed well with the theoretical predictions.

Out‐of‐band improvement by BPFs with multiple attenuation poles using a condition of variable coupling length of a parallel partially coupled‐line section

AbstractA combination of two microstrip‐line resonators, which are partially coupled, are considered in a parallel partially coupled‐line bandpass filter (BPF), where one resonator is one half‐wavelength (λ/2) long, and the other (whose one end is grounded) is only one quarter‐wavelength (λ/4) long. Therefore, the length of a coupled‐line section can be varied based on the position of the grounded end. Five conditions of the movable coupling length are simulated, which greatly influences the spurious responses of the BPF. This property is numerically investigated in this paper. The analysis shows that, based on the grounding position, this method is capable of realizing improved out‐of‐band characteristics by locating the multiple attenuation poles in the stopband and improved spurious responses up to five times of the passband frequency (5f0) of a parallel partially coupled‐line BPF. An empirical model of the BPF is fabricated, and the numerical results are verified via comparison with the experiment. © 2005 Wiley Periodicals, Inc. Microwave Opt Technol Lett 47: 4–9, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.21064

An Iterative Method for Computing the Surface Resistance of YBCO Thin Films in the Nonlinear Regime of RF Power

A numerical method to find, in the nonlinear regime, the quality factor, the surface resistance, and the resonance frequency of YBCO microstrip line resonator, deposited on both sides of an MgO substrate, is presented. The numerical method is based on an iterative self-consistent technique used to find the RF magnetic field in the nonlinear regime of the dissipation mechanisms. The determination of the RF magnetic field yields to the corresponding surface resistance and resonance frequency. The dependence of the geometrical factor of the film on the RF magnetic field is discussed. This latter is usually used as constant in the literature. However, in our calculation this factor has a maximum at a certain RF input power.

Out-of-Band Improvement by Microstrip Line BPFs with Multiple Attenuation Poles in Stopband Using Various Conditions of Coupling Length of Partially Coupled-Line Section

In a partially coupled-line bandpass filter (BPF), a combination of two microstrip line resonators which are partially coupled, are considered, where one resonator is half-wavelength (λ/2)-long, and another whose one end is grounded, is only quarter-wavelength (λ/4)-long. Therefore, the length of a coupled-line section can be varied based on the position of the grounding end, and five conditions of the movable coupling length have been simulated which will greatly influence the spurious responses of a BPF. This property is numerically investigated in this paper. The analysis shows that, based on the grounding position, this method is capable of realizing the improved out-of-band characteristics by locating the multiple attenuation poles in the stopband and improved spurious responses up to five times of the center frequency (5 f0). A few empirical models of BPF are fabricated, and the numerical results are ensured by comparing with the experimental results.

Guided-Wave Electro-Optic Modulators Using Novel Electrode Structure of Coupled Microstrip Line Resonator

A novel structure of guided-wave electro-optic modulators is proposed and their operation of the optical intensity modulation is successfully confirmed. The modulators use a newly developed modulation electrode consisting of coupled microstrip lines. A high voltage can be induced by the resonance of the odd propagation mode to realize efficient electro-optic modulation in spite of the microstrip-line configuration. The properties of the coupled microstrip lines were analytically evaluated by using the method of conformal transformations and the effectiveness as a modulation electrode was presented. The modulation electrodes of the half-wavelength coupled microstrip line resonator were designed at 10 GHz and 26 GHz, where the electrode lengths were 3 mm and 1.2 mm, respectively. The modulators using these electrodes with the Mach-Zehnder interferometer of LiTaO 3 waveguides were fabricated. The measured modulation coefficient of the 26 GHz modulator normalized at 100 mW signal input was 0.13 rad.

Characterization and analysis of high temperature superconducting microstrip andcoplanar resonators using a spectral domain method

Microwave characteristics of planar high temperature superconducting microstrip lineresonator (MSR) and coplanar waveguide (CPW) resonators have been estimated using afull wave spectral domain technique in conjunction with the complex resistive boundarycondition. The computer aided design method developed is applied to simulate thecharacteristics of planar resonators. The proposed method has been validated withexperimental results after taking into account the practical operating conditions. A reasonableagreement for the theoretically computed and measured resonant frequency and unloadedQ-value with experimental data of Porch et al (1995 IEEE Microw. Theory Technol. 2306–14) has been observed for the MSR operated at 5 GHz as well as for the CPWresonator at 7.95 GHz.

Deduction of the Experimental Surface Impedance of YBCO Thin Films Using a Self-Consistent Calculation

Measurement of surface impedance of double sided microstrip line resonator patterned out of thin film YBCO has been carried out as a function of temperature and power (restricted to linear regime). New model of the current density distribution has been used in order to extract the real and imaginary parts of the surface impedance. This model is based on a sound physical theory rather than a phenomenological one. The introduction of the critical current density in this model has a great influence on the determination of the microwave loss mechanisms along the transmission lines. Several propagation quantities have been extracted using the above mentioned model. Using this model and an iteration method to determine the RF magnetic field, we were able to reproduce our experimental results of the quality factor and then determine the corresponding surface impedance as well as the kinetic inductance and the shift in the effective dielectric constant as a function of temperature.

Compact microstrip bandpass filter with two transmission zeros

A novel compact microstrip bandpass filter is proposed using a half-wavelength (/spl lambda//2) microstrip line resonator and an end-coupling resonator. The filter has two transmission zeros at both low and high rejection bands, as well as low insertion loss and compact design by giving two paths to the input signals. A demonstration filter has been designed and tested. Theoretical and experimental results are presented.