Measured Quality Factor Research Articles

Design and characterization of compact digital RF MEMS capacitors and phase shifters in CMOS 0.35 µm technology

This work reports on the design, fabrication and characterization of compact digital RF MEMS capacitors and phase shifters that are built in the back end of line (BEOL) of CMOS 0.35 µm technology. The devices are micromachined using a maskless post-processing sequence with cryogenic cooling on to control the out-of-plane warping of the metal-oxide structural layers. The implemented vertical electrostatic actuation in the developed post process allows the realization of highly compact designs of both devices, and an operating voltage of the devices is stay below 70 V. The 4-bit capacitors provide a measured tuning ratio close to 10:1 which corresponds to 0.15 pF to 1.2 pF over the frequency range 3–10 GHz. The overall footprint of the digital capacitor is 0.6 mm × 0.9 mm. The measured quality factor after de-embedding the losses due to the RF probing pads is up to 120. The measurement of the 4-bit phase shifters reveals low insertion loss <3 dB at 20 GHz along with low variation of the insertion loss <1 dB up to the same frequency. The measured phase shift is 150 at 20 GHz. The overall footprint of the 4-bit phase shifter is around 1 mm × 1 mm.

Ultra-high resolution sensing of glucose concentration based on amplified half-integer localized surface plasmons mode

Since the half-integer order localized surface plasmons mode is more sensitive to the change of the surrounding materials, an active spoof plasmonic microfluidic sensor using the mode for detecting minute change of glucose aqueous solutions has been proposed at microwave frequencies. By introducing an active coupling circuit near the slit of the spoof plasmonic resonator, the measured quality factor of the half integer order mode (n = 1.5) for the active spoof plasmonic resonator is increased from 148 to 40 000 and the dephasing time is increased to about 16.5 µs when the optimal bias voltage is applied, compared to the passive spoof plasmonic resonator. The resonance frequency changes from 2.45 GHz to 1.74 GHz, with a frequency shift of 710 MHz, when the microfluidic channel is filled with distilled water (about 12 µl). The experiments show that the resonance frequency increases almost linearly with the concentration of the glucose solution. The limit of detection of the active sensor is 9 mg dl−1. The figure of merit reaches 2236 MHz/(mg/dl). The high-resolution active spoof plasmonic sensor could find more potential applications for biological and chemical sensing.

A Label-Free, Non-Intrusive, and Rapid Monitoring of Bacterial Growth on Solid Medium Using Microwave Biosensor.

Microwave resonator sensors are attractive for their contactless and label-free capability of monitoring bacterial growth in liquid media. This paper outlines a new label-free microwave biosensor based on a pair of planar split ring resonators for non-invasive monitoring of bacterial growth on a solid agar media. The sensor is comprised of two split ring resonators with slightly different resonant frequencies for differential operation. The transmission coefficient (S21) of the sensor is considered as the sensor's response with a designed and measured quality factor above 200 to ensure a high-resolution operation of the biosensor. Two resonant frequencies of 1.95 and 2.11 GHz represent the sensing signal and the reference signal, respectively. The developed sensor demonstrates high performance in monitoring the growth dynamics of Escherichia coli (E. coli) on Luria-Bertani (LB) agar with 4 mm thickness. The sensor's resonant amplitude response demonstrated 0.5 dB variation corresponding to the bacterial growth over 48 hours when bacteria were spread on LB agar starting with initial OD600 = 1.5. Moreover, 0.6 dB change in the sensor's response was observed over 96 hours of bacterial growth starting with an initial OD600 = 1.17 spotted on LB agar. The measured results fit well to the curves created using Richards' bacterial growth model, showing the strength of the sensor as a potential candidate for use in predictive food microbiology systems.

Tuning of a tapered ridge-loaded waveguide coupler for a drift tube linac of the compact pulsed hadron source

This paper presents the tuning result of a tapered ridge-loaded waveguide coupler for the drift tube linac (DTL) of the compact pulsed hadron source (CPHS) at Tsinghua University. The coupler has been designed, manufactured, and mounted on the DTL cavity for the cold measurement and tuning. The iris diameter of the coupler which is related to the coupling coefficient needs to be determined in the tuning experiment, due to the difference between the designed and measured quality factors. Meanwhile, we found that the relationship between the coupling coefficient and iris diameter from the traditional analytical design method is not applicable when the iris diameter is relatively large. In this paper, the target coupling coefficient is analyzed, and the limit of the original analytical design is presented. The measurement method is introduced to improve the measurement efficiency and the tuning process of the coupling coefficient to the target value is described. After several iterations, the coupling coefficient is tuned to 1.54 which is close to the desired value of 1.56.

Design, development and power test of a spiral buncher RF cavity for the high current injector at IUAC

Abstract A 48.5 MHz spiral buncher cavity in the Medium Energy Beam Transport section (MEBT) of the High Current Injector (HCI) provides longitudinal beam matching at the entrance of the Drift Tube Linac (DTL). The spiral type cavity has been chosen for its high shunt impedance and mechanical stability. The cylindrical chamber was fabricated of copper plated stainless-steel, while OFHC copper was used for the inner components, leading to better results than previous similar cavities. The experimentally measured quality factor, shunt impedance, and resonance frequency fit very well with the design values. The bead-pull measurement technique has been used to validate the electric field profile. A fine tuner has been developed and installed to correct the frequency shift while the cavity is phase and amplitude locked. An air-cooled power coupler has been designed, developed, and installed. The cavity has been tested up to the full power of 1 kW to produce 27 kV across each gap. The X-ray energy spectroscopy technique has been used to measure the gap voltages across the drift tubes. The designed and measured value of the quality factor is 4000 and 3600, respectively. The details of the design, development, and power testing are discussed in this article.

New Activity for Instrumental Analysis: Laser Beam Profiling

Students built two laser beam profilers to measure several laser beam parameters in a university third-year instrumental chemistry laboratory using commercially available optical components used in modern optics research laboratories. While learning about practical properties of laser beams, students utilize laboratory grade optics and optomechanics for precise measurements of the laser beam quality factor, ellipticity, and diameter. Students build and troubleshoot beam profilers using two methods: the classic knife-edge technique as well as by employing a CMOS-based camera. Students recognize the sources of error associated with their constructed profiler, including background intensity, integration time, and lens alignment accuracy when measuring the beam parameters.

Measurements of radiation quality factor on Mars with the Mars Science Laboratory Radiation Assessment Detector

We report the first long-term measurements of the radiation quality factor of energetic charged particles on the surface of Mars. The Radiation Assessment Detector (RAD) aboard the Mars Science Laboratory rover, also known as Curiosity, has been operating on Mars since 2012. RAD contains thin silicon detectors that record the ionization energy loss of energetic charged particles. The particles are dominantly galactic cosmic rays (GCRs) and the products of their interactions in the Martian atmosphere, with occasional contributions from solar energetic particles (SEPs). The quality factor on the surface of Mars is influenced by two factors: variations in the shielding provided by the atmosphere, and changes in the spectrum of the incident energetic particle flux due to the 11-year solar cycle. The two cannot be easily disentangled using the data alone, but insights can be gained from calculations and Monte Carlo simulations.

Utilization of the superconducting transition for characterizing low-quality-factor superconducting resonators

Characterizing superconducting microwave resonators with highly dissipative elements is a technical challenge, but a requirement for implementing and understanding the operation of hybrid quantum devices involving dissipative elements, e.g., for thermal engineering and detection. We present experiments on λ/4 superconducting niobium coplanar waveguide resonators, terminating at the antinode by a dissipative copper microstrip via aluminum leads, such that the resonator response is difficult to measure in a typical microwave environment. By measuring the transmission both above and below the superconducting transition of aluminum, we are able to isolate the resonance. We then experimentally verify this method with copper microstrips of increasing thicknesses, from 50 nm to 150 nm, and measure quality factors in the range of 10–67 in a consistent way.

Stitching Stretchable Radiofrequency Coils for MRI: A Conductive Thread and Athletic Fabric Approach.

We propose a novel flexible and entirely stretchable radiofrequency coil for magnetic resonance imaging. This coil design aims at increasing patient comfort during joint imaging while maintaining or improving image quality. Conductive silver-coated thread was stitched in a zigzag pattern onto stretchable athletic fabric to create a single-loop receive coil. The stitched coil was mounted in a draped and stretched fashion and compared to a coil fabricated on flexible printed circuit board. Match/tune circuits, detuning circuits, and baluns were incorporated into the final setup for bench measurements and imaging on a 3T MR scanner. A fast spin echo sequence was used to obtain images for comparison. The fabricated coil presents multi-directional stretchability and flexibility while maintaining conductivity and stitch integrity. Quality factor measurements and SNR calculations show that this stretchable coil design is comparable to a flexible, standard PCB coil. Detailed human wrist images were successfully obtained in vivo using the stretched, stitched coil. The resulting MR images and SNR calculations support further experimentation into more complex coil geometries. This coil is uniquely stretchable in all direction and allows for joint imaging at various degrees of flexion. Additionally, this coil offers the closest proximity of placement to the skin with materials that provide a similar level of comfort to that of athletic wear and compression sleeves. This stitched design could be incorporated into coils for a variety of anatomies.

Rigorous broadband study of the intrinsic ferromagnetic linewidth of monocrystalline garnet spheres

This work demonstrates the first application of direct broadband (1 GHz–30 GHz) quality (Q) factor measurements of the uniform precession mode in magnetised garnet spheres for the accurate determination of the room-temperature intrinsic ferromagnetic linewidth (ΔH). The spheres were enclosed in a subwavelength cavity, so that the measured Q-factor depended mainly on their magnetic losses and the conduction losses of the cavity walls. The contribution of the latter is assessed by means of the recently proposed magnetic plasmon resonance model and has been found to be negligible. A total of 10 samples made from commercially available pure yttrium iron garnet (YIG) and gallium-substituted YIG have been measured, differing in diameter and/or saturation magnetisation Ms. The dependence of the intrinsic ΔH on the internal magnetic field is found to have near-perfect linear dependence, which cannot be said about the typically studied extrinsic ΔH even at high frequencies. It is found that the difference between the two linewidths, which becomes significant at low frequencies, can be attributed to a geometric effect. Due to its fundamental nature, this work is applicable not only to magnetic material characterization, but also to the study of the origins of losses in magnetic materials.

Measurement of Axially Inhomogeneous Permittivity Distributions in Resonant Microwave Cavities

The cavity perturbation method is a standard technique for material parameter estimation. It typically assumes that the sample consisting of the material under test (MUT) is small. This and other assumptions are violated in in-process measurement scenarios that involve big and inhomogeneous samples. We analyze the limitations of the classical perturbation method and present a new approach toward the measurement of spatially varying material parameters associated with a large sample in a rectangular or a circular cylindrical microwave cavity. The method is based on the measurement of multiple resonance frequencies and quality factors and is validated by numerical and laboratory experiments. It is demonstrated that relative permittivities and conductivities may be measured with typical accuracies on the order of 1%.

High $Q$ Coil Measurement for Inductive Power Transfer

A system for the measurement of quality factors, self-inductances, and interturn capacitances of inductive power transfer coils, in the frequency range of 1–20 MHz, is demonstrated. Coil quality factor in excess of 1000 is measured at megahertz frequencies, beyond the capabilities of commercial impedance analyzers. The method used is to measure the transmission bandwidth of the coil under test while under weak magnetic coupling, incorporating measures to reduce common-mode coupling. The measurement system is verified by comparison with electromagnetic simulation and by modeling. The system model shows robustness to system configuration and the potential to measure coils with $Q$ in excess of 10 000.

Fast measurement of the laser beam quality factor based on phase retrieval with a liquid lens.

In this paper, a new method for measuring the beam quality (M2) of lasers based on phase retrieval with a liquid lens is proposed. With intensity profiles obtained under different focal lengths in a certain position, a variable-focus iterative retrieval algorithm is established for the reconstruction of the complex amplitude. Then M2 can be calculated with the angular spectrum theory. Feasibility of the proposed method is demonstrated with single- and multimode lasers through both simulations and experiments. Compared with the traditional liquid lens method, the M2 of lasers can be measured faster with the proposed method.

Vacuum packaged electromagnetic 2D scanning micromirror

We herein present the design, fabrication, and wafer-level packaging of an electromagnetic biaxial scanning micromirror. The vacuum packaging of the micromirror was implemented by anodically bonding the glass cap wafer to both sides of the silicon substrate with the micromirror. The measured quality factor of the vacuum packaged micromirror is 1923.2 for the horizontal scan, whereas that of the device in the air is 649.6. The maximum optical scan angle of the vacuum packaged micromirror is 24.19° at 155 mApp and 11.9 kHz for the horizontal scan, and 7.1° at 204.7 mApp and 60 Hz for the vertical scan. The estimated vacuum level of the package is 1.65 ± 0.85 Torr.

Design and characterisation of single‐layer solenoid air‐core inductors

This study presents the design and experimental characterisation of single-layer solenoid air-core inductors. The analytical expressions for the winding inductance, self-capacitance, and winding resistance are derived. The inductor properties are analysed up to the first self-resonant frequency. The procedure to design air-core inductors for high-frequency (HF) applications is provided. Experimental validations of the analytical equations are given. A single-layer air-core 20 μ H inductor was designed, built, and measured. The bandwidth of the designed inductor obtained from theoretical predictions was about 100 MHz. The measured quality factor was 181 at 1 MHz. The results of this study are useful for engineers and designers in the areas of power supplies, datacentres, radio-frequency power amplifiers, radio-frequency transmitters, and HF filters.

Kinetic Inductance Detectors and readout electronics for the OLIMPO experiment

Kinetic Inductance Detectors (KIDs) are superconductive low–temperature detectors useful for astrophysics and particle physics. We have developed arrays of lumped elements KIDs (LEKIDs) sensitive to microwave photons, optimized for the four horn–coupled focal planes of the OLIMPO balloon–borne telescope, working in the spectral bands centered at 150 GHz, 250 GHz, 350 GHz, and 460 GHz. This is aimed at measuring the spectrum of the Sunyaev–Zel’dovich effect for a number of galaxy clusters, and will validate LEKIDs technology in a space–like environment. Our detectors are optimized for an intermediate background level, due to the presence of residual atmosphere and room–temperature optical system and they operate at a temperature of 0.3 K. The LEKID planar superconducting circuits are designed to resonate between 100 and 600 MHz, and to match the impedance of the feeding waveguides; the measured quality factors of the resonators are in the 104 – 105 range, and they have been tuned to obtain the needed dynamic range. The readout electronics is composed of a cold part, which includes a low noise amplifier, a dc–block, coaxial cables, and power attenuators; and a room–temperature part, FPGA–based, including up and down-conversion microwave components (IQ modulator, IQ demodulator, amplifiers, bias tees, attenuators). In this contribution, we describe the optimization, fabrication, characterization and validation of the OLIMPO detector system.

A method of determining microwave dissipation of Josephson junctions with non-linear frequency response

Based on Josephson junction (JJ), superconducting quantum bit (qubit) is operated at frequencies of several GHz. Dissipation of JJs in this frequency range can cause energy relaxation in qubits, and limit coherence time, therefore it is highly concerned and needs to be determined quantitatively. The dissipation of JJs can be quantified by microwave quality factor. It is usually done at very low temperature (~mK) to determine whether a JJ is suitable for qubit devices by measuring the quality factor. In this paper, a method based on nonlinear frequency response of JJs is proposed to determine the quality factor. This method can be used in thermal activation regime, which may bring great conveniences to experiments. To analyze high frequency properties of JJs, the dynamic equation of a current-biased JJ, which describes high frequency oscillation of the JJ, is introduced. A fourth-order potential approximation is used to obtain the analytical equation of non-linear response. The dependence on quality factor, as well as on amplitude, of difference between JJ’s plasma frequency and resonant frequency, is derived from the equation. The approximate treatment is quantitatively validated by our numerical simulations with practical JJ parameters including different environment influences. Thus, based on nonlinear frequency response of JJs, a reliable and simple method to determine quality factor of JJ is proposed, which is desirable for exploring JJ based microwave devices such as parametric amplifier, superconducting qubit. Being driven well into the nonlinear microwave response regime, due to frequency-amplitude interaction, the resonant frequency of a current bias JJ deviates from the JJ’s plasma frequency. The deviation is directly related to the microwave quality factor. Hence, the quality factor can be deducted from the experimental measurement of the resonant frequency deviation, with different microwave power values applied. In comparison with linear resonance experiment, the nonlinear resonance used by the proposed method produces stronger signal. Therefore it is more robust against external noise. When being conducted at high temperature, the proposed method is more reliable. The accuracy of the measured quality factor primarily depends on those of the JJ’s parameters such as critical current and capacitance, while those parameters can be experimentally determined with high precision.

2P2-15 Applying the Internet of things and quartz crystal microbalance oscillators to quality factor measurement

2P2-15 Applying the Internet of things and quartz crystal microbalance oscillators to quality factor measurement

0.04 degree-per-hour MEMS disk resonator gyroscope with high-quality factor (510\u2009k) and long decaying time constant (74.9\u2009s)

The disk resonator gyroscope is an attractive candidate for high-performance MEMS gyroscopes. This gyroscope consists of a sensor and readout electronics, and the characteristics of the sensor directly determine the performance. For the sensor, a high-quality factor and long decaying time constant are the most important characteristics required to achieve high performance. We report a disk resonator gyroscope with a measured quality factor of 510 k and decaying time constant of 74.9 s, which is a record for MEMS silicon disk resonator gyroscopes, to the best of our knowledge. To improve the quality factor of the DRG, the quality factor improvement mechanism is first analyzed, and based on this mechanism two stiffness-mass decoupled methods, i.e., spoke length distribution optimization and lumped mass configuration design, are proposed and demonstrated. A disk resonator gyroscope prototype is fabricated based on these design strategies, and the sensor itself shows an angle random walk as low as 0.001°/√h, demonstrating true potential to achieve navigation-grade performance. The gyroscope with readout electronics shows an angle random walk of 0.01°/√h and a bias instability of 0.04°/h at room temperature without compensation, revealing that the performance of the gyroscope is severely limited by the readout electronics, which should be further improved. We expect that the quality factor improvement methods can be used in the design of other MEMS gyroscopes and that the newly designed DRG can be further improved to achieve navigation-grade performances for high-end industrial, transportation, aerospace, and automotive applications.

Determination of particle distributions from sedimentation measurements using a piezoelectric tuning fork sensor

In this work, a resonant quartz tuning fork sensor based measurement system is employed to study the settlement of small particles in suspension as they pass the sensing element. The resonator features varying sensitivity to fluid parameter changes along its length, with the tip being most sensitive. The spatial averaging effect is analyzed theoretically and measured by passing the sensor through a fluid–fluid interface. Subsequently, the averaging function is used for particle distribution determination from recorded resonance frequency and quality factor measurements. The associated inverse problem is of Fredholm type and is solved numerically. Based on the system specifications, detection limits, required temperature stability and expected precision are assessed and particle distribution functions of defined test dispersions are measured.