Showing papers on "Coplanar waveguide published in 2017"

Application of Split Ring Resonator (SRR) Loaded Transmission Lines to the Design of Angular Displacement and Velocity Sensors for Space Applications

Abstract: The accurate measurement of the angular displacement and velocity of reaction wheels is necessary for attitude (orientation) control in space vehicles (satellites). In this paper, microwave, contactless, and low-cost (as compared to optical encoders) sensors useful for that purpose are analyzed in detail. The sensor consists of a rotor and a stator. The rotor is a disk (or a circular crown) of dielectric material, where one or several arrays of equidistant single-loop split ring resonators (SRRs) are etched along its edge, forming circular chains of hundreds of SRRs. The stator is a coplanar waveguide (CPW) also loaded with pairs of single-loop SRRs (etched in the back substrate side), with the centers located in the slot region. The sensing principle is based on the amplitude modulation of a harmonic (single-tone continuous wave) feeding signal, achieved when the chains of the rotor are displaced over the SRR pairs of the stator. Both sensor elements (rotor and stator) must be parallel oriented, with the SRR pairs of the CPW in close proximity to the SRR chains of the rotor (and rotated 180°), in order to favor their coupling. By this means, the transmission coefficient of the CPW is varied by the circular motion of the rotor, and significant amplitude modulation of the feeding signal is achieved. From the envelope function, the angular velocity can be accurately determined. With the proposed sensors, instantaneous and practically unlimited rotation speeds can be measured.

Ultrawideband (UWB) Planar Antenna with Single-, Dual-, and Triple-Band Notched Characteristic Based on Electric Ring Resonator

Abstract: The ultrawideband (UWB) planar antenna is designed as a circular metallic patch fed by a coplanar waveguide (CPW). This antenna provides the impedance bandwidth of the wideband response from 2.5 to 12 GHz. To achieve the notched characteristics at desirable frequencies, the electric ring resonator (ERR) incorporated into the CPW feedline is proposed for use in the planar configuration of the UWB antenna. The notched frequency band is controlled by dimensions of the ERR structure. The single-notched band can be obtained by placing a single ERR beneath the CPW structure. For implementation of the multinotch band, a modified multimode structure of the ERR is examined. Reconfigurability of the first notched band is provided by using a digital variable capacitor (DVC) instead of ERR's quasi-lumped capacitance. The results of simulations and measurements are in a good agreement.

Electron Spin Resonance at the Level of 1 0 4 Spins Using Low Impedance Superconducting Resonators

Abstract: We report on electron spin resonance measurements of phosphorus donors localized in a 200 μm^{2} area below the inductive wire of a lumped element superconducting resonator. By combining quantum limited parametric amplification with a low impedance microwave resonator design, we are able to detect around 2×10^{4} spins with a signal-to-noise ratio of 1 in a single shot. The 150 Hz coupling strength between the resonator field and individual spins is significantly larger than the 1-10 Hz coupling rates obtained with typical coplanar waveguide resonator designs. Because of the larger coupling rate, we find that spin relaxation is dominated by radiative decay into the resonator and dependent upon the spin-resonator detuning, as predicted by Purcell.

Compact CPW-fed UWB MIMO antenna with a novel modified Minkowski fractal defected ground structure (DGS) for high isolation and triple band-notch characteristic

Abstract: A compact printed ultra-wideband (UWB) multiple input multiple output (MIMO) antenna with coplanar waveguide feed for portable UWB applications is presented. The radiator and ground plane of the antenna are etched with an overall size of 26.75 mm × 41.5 mm. The UWB MIMO antenna consists of two planar identical monopole antenna elements and a novel modified Minkowski fractal defect is introduced in the ground plane for enhancing the isolation of the MIMO system. The proposed antenna has an impedance bandwidth (for │S11│ < −10 dB) ranging from 3.1 to 11.5 GHz (VSWR ≤ 2) and an isolation of more than 15 dB is achieved between the adjacent planar monopoles. The band rejection phenomenon in wireless local area network band is achieved by etching rotated C-shaped slots from the respective patches. Also, two identical rectangular slots are etched on the respective ground planes which enhances the lower UWB bandwidth and cause interference suppression at Wi-Max and C-band (3.3–3.7 and 3.7–4.2 GHz), respec...

Coupling ultracold atoms to a superconducting coplanar waveguide resonator.

Abstract: Ensembles of trapped atoms interacting with on-chip microwave resonators are considered as promising systems for the realization of quantum memories, novel quantum gates, and interfaces between the microwave and optical regime. Here, we demonstrate coupling of magnetically trapped ultracold Rb ground-state atoms to a coherently driven superconducting coplanar resonator on an integrated atom chip. When the cavity is driven off-resonance from the atomic transition, the microwave field strength in the cavity can be measured through observation of the AC shift of the atomic hyperfine transition frequency. When driving the cavity in resonance with the atoms, we observe Rabi oscillations between hyperfine states, demonstrating coherent control of the atomic states through the cavity field. These observations enable the preparation of coherent atomic superposition states, which are required for the implementation of an atomic quantum memory.

Microwave Encoders for Chipless RFID and Angular Velocity Sensors Based on S-Shaped Split Ring Resonators

Abstract: In this paper, it is demonstrated that a chain of S-shaped split ring resonators (S-SRRs) etched on a dielectric substrate can modulate the amplitude of a carrier signal injected to a transmission line (a coplanar waveguide (CPW). To this end, the S-SRR chain must be transversally displaced above the CPW, in close proximity to it. By this means, the transmission coefficient of the line is modulated by the time-varying electromagnetic (inductive) coupling between the line and the S-SRRs of the chain, related to their relative motion. Based on this principle, two different applications can be envisaged: 1) angular velocity sensors and 2) near-field chipless radiofrequency identification (chipless-RFID) tags. In the former application, the S-SRR chain is circularly shaped and the S-SRRs are distributed uniformly along the perimeter of the rotor, at equidistant positions. By this means, the amplitude-modulated signal generated by rotor motion exhibits envelope peaks, whose distance is related to the angular velocity of the rotor. In the use of S-SRRs as microwave encoders for chipless RFID tags, not all the S-SRRs of the chain are present. Their presence or absence at the predefined (equidistant) positions is related to the logic state “1” or “0.” Tag reading is sequential, and it is achieved through tag motion (at constant velocity) above the reader, a CPW transmission line fed by a carrier signal. The ID code is contained in the envelope function of the resulting amplitude modulated signal, which can be obtained by means of an envelope detector. With the proposed approach, a high number of pulses in angular velocity sensors can be achieved (with direct impact on angle resolution and sensitivity to changes in instantaneous rotation speed). Moreover, chipless-RFID tags with unprecedented number of bits can be obtained. The proposed angular velocity sensors can be useful in space environments, whereas the chipless-RFID systems based on the proposed tags are useful in applications where reading range can be sacrificed in favor of high data capacity (large number of bits), e.g., security and authentication.

Analysis and mitigation of interface losses in trenched superconducting coplanar waveguide resonators

Abstract: Improving the performance of superconducting qubits and resonators generally results from a combination of materials and fabrication process improvements and design modifications that reduce device sensitivity to residual losses. One instance of this approach is to use trenching into the device substrate in combination with superconductors and dielectrics with low intrinsic losses to improve quality factors and coherence times. Here we demonstrate titanium nitride coplanar waveguide resonators with mean quality factors exceeding two million and controlled trenching reaching 2.2 $\mu$m into the silicon substrate. Additionally, we measure sets of resonators with a range of sizes and trench depths and compare these results with finite-element simulations to demonstrate quantitative agreement with a model of interface dielectric loss. We then apply this analysis to determine the extent to which trenching can improve resonator performance.

Characterization and Reduction of Capacitive Loss Induced by Sub-Micron Josephson Junction Fabrication in Superconducting Qubits

Abstract: Josephson junctions form the essential non-linearity for almost all superconducting qubits. The junction is formed when two superconducting electrodes come within $\sim$1 nm of each other. Although the capacitance of these electrodes is a small fraction of the total qubit capacitance, the nearby electric fields are more concentrated in dielectric surfaces and can contribute substantially to the total dissipation. We have developed a technique to experimentally investigate the effect of these electrodes on the quality of superconducting devices. We use $\lambda$/4 coplanar waveguide resonators to emulate lumped qubit capacitors. We add a variable number of these electrodes to the capacitive end of these resonators and measure how the additional loss scales with number of electrodes. We then reduce this loss with fabrication techniques that limit the amount of lossy dielectrics. We then apply these techniques to the fabrication of Xmon qubits on a silicon substrate to improve their energy relaxation times by a factor of 5.

Coplanar Waveguide Transmission Line Loaded With Electric-LC Resonator for Determination of Glucose Concentration Sensing

Abstract: In this paper, a compact glucose concentration sensor is designed based on an electric-LC (ELC) resonator coupled with a coplanar waveguide (CPW) transmission line, and the ELC resonator is no longer aligned with the CPW transmission line axis. The principle of the sensor is based on the notch depth in the transmission coefficient ( $S_{21}$ ) depending on the glucose concentration, and it is applied using a micropipette into a cylindrical plastic sample chamber that covers the gap in the middle branch of the ELC resonator. The notch magnitude in the transmission coefficient response behavior was measured and analyzed in the range of 2.5–6 GHz with air, deionized water, phosphate buffered saline (PBS), and different glucose concentrations in deionized water and PBS in the range of 0%–20% (w/V). The experimental results showed that the proposed sensor has good detection of the glucose concentration with high linearity and wide dynamic range. A prototype of the sensor provides an opportunity for the development of a biological and chemical sensing application in the future.

Aluminium-oxide wires for superconducting high kinetic inductance circuits

Abstract: We investigate thin films of conducting aluminium-oxide, also known as granular aluminium, as a material for superconducting high quality, high kinetic inductance circuits. The films are deposited by an optimised reactive DC magnetron sputter process and characterised using microwave measurement techniques at milli-Kelvin temperatures. We show that, by precise control of the reactive sputter conditions, a high room temperature sheet resistance and therefore high kinetic inductance at low temperatures can be obtained. For a coplanar waveguide resonator with 1.5 kΩ sheet resistance and a kinetic inductance fraction close to unity, we measure a quality factor in the order of 700 000 at 20 mK. Furthermore, we observe a sheet resistance reduction by gentle heat treatment in air. This behaviour is exploited to study the kinetic inductance change using the microwave response of a coplanar wave guide resonator. We find the correlation between the kinetic inductance and the sheet resistance to be in good agreement with theoretical expectations.

Wideband CPW-Fed Flexible Bow-Tie Slot Antenna for WLAN/WiMax Systems

Abstract: A bow-tie antenna based on a slot configuration in a single metal sheet on top of a very thin flexible substrate is introduced The antenna is constructed from two slotted right-angle triangles fed by a coplanar waveguide transmission line The topology is very simple and extremely easy to tune in order to reach the proper characteristics after mounting on a supporting structure A prototype is designed, fabricated, and characterized experimentally The tunability is proven by considering both the version in free space and the version for use on a brick wall Measurements demonstrate good agreement with simulations Both versions cover the wireless local area network (24 and 365 GHz) and WiMax (23, 25, and 35 GHz) spectra, with an overall impedance bandwidth of 179 GHz (577%) and 146 GHz (497%), respectively The radiation of the antenna is bidirectional with maximum gains of 630 and 509 dBi for the free space and brick wall versions, respectively

A Miniature Ultrawideband Electric Field Probe Based on Coax-Thru-Hole via Array for Near-Field Measurement

Abstract: In this paper, a miniature electric field probe with an ultrawideband of 9 kHz–20 GHz is proposed, fabricated, and tested. The electric field probe is fabricated on a four-layer printed circuit board using high-performance and low-loss Rogers material ( $\varepsilon _{\mathrm{r}}= 3.48$ and tan $\delta = 0.0037$ ). Coax-thru-hole via array is used to control the signal via impedance to achieve impedance $50~\Omega $ match over the whole working band, reducing the harmful influence on the probe’s characteristic. The ground vias, called via fence, are utilized to suppress the resonance caused by the parallel-plate mode of conductor-backed coplanar waveguide (CB-CPW), expanding the working frequency band. Experimental result shows $\vert S_{21}\vert $ rather smooth in operation band, demonstrating the working frequency band is up to 9 kHz–20 GHz. The electric field probe has a 2–3 mm spatial resolution, which has a good ability to locate the interference source.

A new wideband planar antenna with band-notch functionality at GPS, Bluetooth and WiFi bands for integration in portable wireless systems

Abstract: Empirical results are presented for a novel miniature planar antenna that operates over a wide bandwidth (500 MHz to 3.05G Hz). The antenna consists of dual-square radiating patches separated by two narrow vertical stubs to reject interferences from GPS, Bluetooth and WiFi bands. Radiating patches and stubs are surrounded by a ground-plane conductor, and the antenna is fed through a common coplanar waveguide transmission line (CPW-TL). The two vertical stubs generate pass-band resonances enabling wideband operation across the following communications standards: cellular, APMS, JCDMA, GSM, DCS, PCS, KPCS, IMT-2000, WCDMA, UMTS and WiMAX. Embedded in the ground-plane conductor is an H-shaped dielectric slit, which has been rotated by 90°, whose function is to reject interferences from GPS, Bluetooth and WiFi bands. Measurements results confirm the antenna exhibits notched characteristics at frequency bands of GPS (1574.4–1576.4 MHz), Bluetooth (2402–2480 MHz) and WiFi (2412–2483.5 MHz). The impedance bandwidth of the antenna is 2.55G Hz for VSWR 3 .

Theory of multiwave mixing within the superconducting kinetic-inductance traveling-wave amplifier

Abstract: Traveling-wave parametric amplifiers may be fabricated from superconducting films that exhibit highly nonlinear kinetic inductance. The coplanar waveguide of such a microwave device, extending to a meter or more in length but compacted to reside on a chip of the order of a square centimeter, is engineered with periodic variations in its width. These width variations, or loadings, alter the dispersion characteristics of a nonlinear current propagating along the waveguide, changing its group velocity and modulation behavior. A strong pump and a small signal injected into one end of the waveguide mix parametrically in the presence of the nonlinear kinetic inductance. Engineered dispersion induces the favorable conditions of overall phase matching, leading to generation of idler products as well as signal amplification of wide bandwidth, high dynamic range, and low noise, making the device of particular use in quantum computing and photon detection. The authors present a theoretical framework in which signal gain may be calculated solely from loading design. This involves construction of a metamaterial band theory of the engineered dispersion, which is used as a basis to describe the mixing of nonlinear traveling waves.

A 185-215-GHz Subharmonic Resistive Graphene FET Integrated Mixer on Silicon

Abstract: A 200-GHz integrated resistive subharmonic mixer based on a single chemical vapor deposition graphene field-effect transistor (G-FET) is demonstrated experimentally. This device has a gate length of 0.5 μm and a gate width of 2x40 μm. The G-FET channel is patterned into an array of bow-tie-shaped nanoconstrictions, resulting in the device impedance levels of ~50 Ω and the ON-OFF ratios of ≥4. The integrated mixer circuit is implemented in coplanar waveguide technology and realized on a 100-μm-thick highly resistive silicon substrate. The mixer conversion loss is measured to be 29 ± 2 dB across the 185-210-GHz band with 12.5-11.5 dBm of local oscillator (LO) pump power and >15-dB LO-RF isolation. The estimated 3-dB IF bandwidth is 15 GHz.

Low Loss Multi-Layer Wiring for Superconducting Microwave Devices

Abstract: Complex integrated circuits require multiple wiring layers. In complementary metal-oxide-semiconductor (CMOS) processing, these layers are robustly separated by amorphous dielectrics. These dielectrics would dominate energy loss in superconducting integrated circuits. Here we demonstrate a procedure that capitalizes on the structural benefits of inter-layer dielectrics during fabrication and mitigates the added loss. We separate and support multiple wiring layers throughout fabrication using SiO$_2$ scaffolding, then remove it post-fabrication. This technique is compatible with foundry level processing and the can be generalized to make many different forms of low-loss multi-layer wiring. We use this technique to create freestanding aluminum vacuum gap crossovers (airbridges). We characterize the added capacitive loss of these airbridges by connecting ground planes over microwave frequency $\lambda/4$ coplanar waveguide resonators and measuring resonator loss. We measure a low power resonator loss of $\sim 3.9 \times 10^{-8}$ per bridge, which is 100 times lower than dielectric supported bridges. We further characterize these airbridges as crossovers, control line jumpers, and as part of a coupling network in gmon and fuxmon qubits. We measure qubit characteristic lifetimes ($T_1$'s) in excess of 30 $\mu$s in gmon devices.

Novel Tunable Bandstop Resonators in SIW Technology and Their Application to a Dual-Bandstop Filter with One Tunable Stopband

Abstract: Two novel tunable bandstop resonators in substrate integrated waveguide (SIW) technology are presented: a ridged SIW resonator and an open-ended coplanar waveguide (CPW) resonator that is etched into the SIW’s top metallization. The ridged SIW resonator shows a tuning range of 200 MHz at 5.54 GHz. The CPW resonator has a tuning range of 600 MHz at 3.8 GHz. The two bandstop resonators are combined to design a dual-band bandstop filter with one tunable stopband. Measured results confirm that the tunable bandstop circuits presented in this letter can be effectively used in reconfigurable SIW systems.

Characterization and Modeling of K-Band Coplanar Waveguides Digitally Manufactured Using Pulsed Picosecond Laser Machining of Thick-Film Conductive Paste

Abstract: Microdispensing of thick-film conductive paste has been demonstrated as a viable approach for manufacturing microwave planar transmission lines. However, the performance and upper frequency range of these lines is limited by the cross-sectional shape and electrical conductivity of the printed paste, as well as the achievable minimum feature size which is typically around $100~\mu \text{m}$ . In this paper, a picosecond Nd:YAG laser is used to machine slots in a 20–25- $\mu \text{m}$ -thick layer of silver paste (Dupont CB028) that is microdispensed on a Rogers RT5870 substrate, producing coplanar waveguide (CPW) transmission lines with 16– $20~\mu \text{m}$ -wide slots. It is shown that the laser solidifies an about 2- $\mu \text{m}$ -wide region of the edges of the slots, thus significantly increasing the effective conductivity of the film and improving the attenuation constant of the lines. The extracted attenuation constant at 20 GHz for laser machined CB028 is 0.74 dB/cm. CPW resonators and filters show that the effective conductivity is in the range from 10 to 30 MS/m, which represents a $100\times $ improvement when compared to the values obtained with the exclusive use of microdispensing. This paper demonstrates that a hybrid approach of additive manufacturing and laser machining enables the fabrication of higher frequency circuits (up to at least 40 GHz) with improved performance.

CPW-fed octagonal super-wideband fractal antenna with defected ground structure

Abstract: A coplanar waveguide (CPW)-fed octagonal super-wideband fractal antenna is presented. It comprises four iterations of an octagonal slot-loaded octagonal radiating patch, CPW feedline, and modified ground plane loaded with a pair of rectangular notches. An impedance bandwidth of 3.8–68 GHz (179%) – i.e. a17.89:1 ratio bandwidth – is achieved. Desirable radiation performance characteristics, including relatively stable and omnidirectional radiation patterns, are obtained over this range. The experimental and simulation results are found to be in good agreement. The designed antenna has the advantages of wider bandwidth and miniaturised size over the previously reported structures.

Circulator based on spoof surface plasmon polaritons

Abstract: In the letter, we propose the design of circulators based on spoof surface plasmon polaritons (SSPP). Rather than striplines, the center conductor is replaced with a blade structure that supports the SSPP mode and exhibits a shorter wavelength and larger wave vector. To enhance the efficiency, a matching transition is employed between the coplanar waveguide and the blade structure. With biased ferrites attached on both the top and bottom sides, the blade structure shows good nonreciprocal properties. The simulation results indicate that in the 5.0-6.6 GHz frequency range, the isolation and return loss reaches 15 dB and the insertion loss is less than 0.5 dB. Since the circulator utilizes the SSPP mode, which exhibits a shorter wavelength than its analogous stripline mode, the size of ferrites, and thus the size of the circulator, can be reduced. Our work provides an effective route to the design of compact, broadband circulators.

Compact Bandpass Filter With High Selectivity Using Quarter-Mode Substrate Integrated Waveguide and Coplanar Waveguide

Abstract: This letter presents a bandpass filter (BPF) based on a hybrid structure of quarter-mode substrate integrated waveguide (QMSIW) and coplanar waveguide (CPW). By incorporating two CPW resonators into two QMSIW resonators, the proposed filter obtains a high selectivity as the coupling between two CPW resonators is electric coupling, which helps to generate two transmission zeros. It also achieves compact layout as the embedded CPW resonators do not occupy extra area. In order to verify the design, a BPF with a center frequency of 8.7 GHz is fabricated and measured. The measured results show good agreement with the simulation results.

A Ka-Band Waveguide Magic-T With Coplanar Arms Using Ridge-Waveguide Transition

Abstract: A Ka-band waveguide magic-T with coplanar arms is presented in this letter. By using an E-plane power divider and a ridge-waveguide transition, the four arms of the magic-T are placed in the same plane, which greatly simplifies the assembly. Compared to the previous method utilizing a microstrip-to-waveguide transition, the structure proposed in this letter achieved a higher power-handling capability because of all-metal elements. Over the frequency band of 28 to 36 GHz, the measured return loss of the input port and the isolation between the opposite ports are greater than 20 dB, indicating good characteristics of the proposed structure.

Graphene-Flakes Printed Wideband Elliptical Dipole Antenna for Low-Cost Wireless Communications Applications

Abstract: This letter presents the design, manufacturing, and operational performance of a graphene-flakes-based screen-printed wideband elliptical dipole antenna operating from 2 up to 5 GHz for low-cost wireless communications applications. To investigate radio frequency (RF) conductivity of the printed graphene, a coplanar waveguide (CPW) test structure was designed, fabricated, and tested in the frequency range from 1 to 20 GHz. Antenna and CPW were screen-printed on Kapton substrates using a graphene paste formulated with a graphene-to-binder ratio of 1:2. A combination of thermal treatment and subsequent compression rolling is utilized to further decrease the sheet resistance for printed graphene structures, ultimately reaching 4 Ω/□ at 10- μ m thicknesses. For the graphene-flakes printed antenna, an antenna efficiency of 60% is obtained. The measured maximum antenna gain is 2.3 dBi at 4.8 GHz. Thus, the graphene-flakes printed antenna adds a total loss of only 3.1 dB to an RF link when compared to the same structure screen-printed for reference with a commercial silver ink. This shows that the electrical performance of screen-printed graphene flakes, which also does not degrade after repeated bending, is suitable for realizing low-cost wearable RF wireless communication devices.

A 300 GHz low-noise amplifier S-MMIC for use in next-generation imaging and communication applications

Abstract: A WR-3 (220–330 GHz) low-noise amplifier (LNA) circuit has been developed for use in next-generation high resolution imaging applications and ultra-high capacity communication links. The submillimeter-wave monolithic integrated circuit (S-MMIC) was realized by using a 35 nm InAlAs/InGaAs based metamorphic high electron mobility transistor (mHEMT) technology in combination with grounded coplanar waveguide topology (GCPW) and cascode transistors, thus leading to a very low noise figure in combination with high gain and large operational bandwidth. The packaged LNA circuit achieved a maximum gain of 29 dB at 314 GHz and more than 26 dB in the frequency range from 252 to 330 GHz. An average room temperature (T = 293 K) noise figure of 6.5 dB was measured between 280 and 330 GHz. Furthermore, the LNA circuit has been used to realize a very compact WR-3 single-chip receiver module, demonstrating an average conversion gain of 6.5 dB and a noise figure of 8.6 dB at the frequency of operation.

Near-field chipless RFID encoders with sequential bit reading and high data capacity

Abstract: This paper presents a novel and unconventional approach for the implementation of chipless RFID systems with high data capacity, suitable for authentication and security applications. Contrarily to previous time-domain or frequency-domain chipless RFID tags, where encoding is achieved either by generating defects (reflectors) in a transmission line (producing echoes in an input pulsed signal), or by etching multiple resonators (each tuned to a different frequency) in a dielectric substrate (providing a unique spectral signature), respectively, the chipless tags proposed in this paper consist of a set of identical resonators conveniently aligned and etched (or printed) on a dielectric layer (e.g., liquid crystal polymer, paper, etc). The resonators are located at predefined equidistant positions in such a way that the presence or absence of resonators in such positions corresponds to the ‘1’ or ‘0’ logic states, respectively. The reader is simply a coplanar waveguide (CPW) transmission line fed by a harmonic signal tuned to the frequency of the resonant elements. In a reading operation, the tag must be mechanically guided and transversally displaced over the CPW, so that the resonant elements modulate the amplitude of the feeding harmonic signal (through electromagnetic coupling) as they cross the axis of the CPW transmission line. This sequential bit reading alleviates the spectral bandwidth limitations of previous multi-resonator chipless RFID tags since the resonators are all identical in the proposed encoders. Therefore, the data capacity (number of bits) can be substantially enhanced since it is only limited by the area occupied by the resonant elements. The necessary close proximity between the tag and the reader is not an issue in certain applications such as authentication and security (e.g., secure paper), where the reading distances can be sacrificed in favor of a high number of bits. The design of 10-bit encoders based on this approach, and implemented by means of S-shaped split ring resonators (S-SRRs) etched on a flexible microwave substrate, is reported. The area of the encoders is as small as 1.35 cm2. The number of bits can be significantly increased by simply adding further S-SRRs to the codes. Thus, high data capacity can be achieved without penalizing the complexity of the reader.

Two-Dimensional Displacement Sensor Based on CPW Line Loaded by Defected Ground Structure With Two Separated Transmission Zeroes

Abstract: In this paper, application of a defected ground structure in realization of 1-D and 2-D microwave displacement sensors is presented. A coplanar waveguide (CPW) line with two slots along the line that generate a transmission zero (TZ) in the transmission response is printed on a fixed substrate. A metallic patch is also printed on the bottom face of a movable substrate located on the fixed substrate. By moving the upper substrate, the length of the etched slots on the fixed underneath substrate changes, and hence, the TZ shifts proportionally. The displacement can be measured based on the frequency shift of the TZ. The 2-D displacement sensor has a similar structure with two additional slots perpendicular to the CPW line on the signal trace. The parallel and perpendicular slots generate two separated TZs in two different frequency bands. The proposed 2-D displacement sensor uses the frequency range of 2.8–4.2 GHz to measure the horizontal displacement with the high sensitivity of 0.41 GHz/1 mm and the frequency range of 5.7–8.8 GHz to measure the vertical displacement with the high sensitivity of 1.2 GHz/1 mm. In comparison with the previous works, the displacement measurement in each direction is independent of the other one. Furthermore, since TZs show narrow notch-frequency bands with high and fixed rejection levels (high $Q$ -factor resonator), independent of the measured displacement, the measurement error is minimized. Also, the dynamic range of the sensor is wide and almost has no intrinsic geometrical limitation. The 2-D sensor is fabricated and tested. The measured results show good agreement with the simulated results.

Superconducting Grid-Bus Surface Code Architecture for Hole-Spin Qubits.

Abstract: We present a scalable hybrid architecture for the 2D surface code combining superconducting resonators and hole-spin qubits in nanowires with tunable direct Rashba spin-orbit coupling. The backbone of this architecture is a square lattice of capacitively coupled coplanar waveguide resonators each of which hosts a nanowire hole-spin qubit. Both the frequency of the qubits and their coupling to the microwave field are tunable by a static electric field applied via the resonator center pin. In the dispersive regime, an entangling two-qubit gate can be realized via a third order process, whereby a virtual photon in one resonator is created by a first qubit, coherently transferred to a neighboring resonator, and absorbed by a second qubit in that resonator. Numerical simulations with state-of-the-art coherence times yield gate fidelities approaching the 99% fault tolerance threshold.

Modeling electrical double-layer effects for microfluidic impedance spectroscopy from 100 kHz to 110 GHz.

Abstract: Broadband microfluidic-based impedance spectroscopy can be used to characterize complex fluids, with applications in medical diagnostics and in chemical and pharmacological manufacturing. Many relevant fluids are ionic; during impedance measurements ions migrate to the electrodes, forming an electrical double-layer. Effects from the electrical double-layer dominate over, and reduce sensitivity to, the intrinsic impedance of the fluid below a characteristic frequency. Here we use calibrated measurements of saline solution in microfluidic coplanar waveguide devices at frequencies between 100 kHz and 110 GHz to directly measure the double-layer admittance for solutions of varying ionic conductivity. We successfully model the double-layer admittance using a combination of a Cole–Cole response with a constant phase element contribution. Our analysis yields a double-layer relaxation time that decreases linearly with solution conductivity, and allows for double-layer effects to be separated from the intrinsic fluid response and quantified for a wide range of conducting fluids.

Excitation and tailoring of diffractive spin-wave beams in NiFe using nonuniform microwave antennas

Abstract: We experimentally demonstrate by time-resolved scanning magneto-optical Kerr microscopy the possibility to locally excite multiple spin-wave beams in the dipolar-dominated regime in metallic NiFe films. For this purpose we employ differently shaped nonuniform microwave antennas consisting of several coplanar waveguide sections different in size, thereby adapting an approach for the generation of spin-wave beams in the exchange-dominated regime suggested by Gruszecki et al. [Sci. Rep. 6, 22367 (2016)]. The occurring spin-wave beams are diffractive and we show that the width of the beam and its widening as it propagates can be tailored by the shape and the length of the nonuniformity. Moreover, the propagation direction of the diffractive beams can be manipulated by changing the bias field direction.