An analytical model for coplanar waveguide on silicon-on-insulator substrate with conformal mapping technique

In this paper, the authors present an analytical model for coplanar waveguide on silicon-on-insulator substrate. The four-element topological network and the conformal mapping technique are used to analyse the capacitance and the conductance of the sandwich substrate. The validity of the model is verified by the full-wave method and the experimental data. It is found that the inductance, the resistance, the capacitance and the conductance from the analytical model show they are in good agreement with the corresponding values extracted from experimental Sparameter until 10 GHz.

Tunable coplanar waveguide resonator with nanowires

A tunable superconducting half-wavelength coplanar waveguide resonator （CPWR） with Nb parallel nanowires - 300 nm in width embedded in the center conductor was designed, fabricated, and measured. The frequency shift and the amplitude attenuation of the resonance peak under irradiation of 404-nm pulse laser were observed with different light powers at 4.2 K. The RF power supplied to such a CPWR can serve as current bias, which will affect the light response of the resonator.

Superconducting tunable filter with constant bandwidth using coplanar waveguide resonators

In this paper we propose a two-pole varactor-tuned superconducting filter using coplanar waveguide （CPW） spiralin-spiral-out （SISO） resonators. Novel internal and external coupling structures are introduced to meet the requirements for a tunable filter with a constant absolute bandwidth. The fabricated device has a frequency tuning range of 14.4% at frequencies ranging from 274.1 MHz to 317.7 MHz, a 3-dB bandwidth of 5.14±0.06 MHz, and an insertion loss of 0.08 dB-0.70 dB. The simulated and measured results are in excellent agreement with each other.

Multi-Reconfigurable Band-Notched Coplanar Waveguide-Fed Slot Antenna

This paper proposes an antenna design concept to achieve a multi-reconfigurable band-notch antenna by using a set of microswitches. The proposed idea was proved by the design of the coplanar waveguide(CPW)-fed slot antenna. The sample design gives a wideband antenna the impedance bandwidth of which covers the frequency ranged from 1.9 GHz to 6.55 GHz.The antenna could be configured to work either in single-band mode or in one of the defined dual-band modes.

Fabrication of Al air-bridge on coplanar waveguide

Superconducting coplanar waveguide（CPW） can be widely used as two-dimensional（2 D） resonator, transmission line or feedline, providing an important component for superconducting quantum circuit which is a promising candidate for quantum information processing. Due to the discontinuities and asymmetries in the ground planes, CPW usually exhibits the spurious resonance, which is a common source of decoherence in circuit quantum electrodynamics experiments. To mitigate the spurious resonance, we fabricated superconducting aluminum air-bridges on Nb CPW. The fabricated airbridges are approximately 3 m high and up to 120 m long. Compared with other methods, the fabrication procedures of our air-bridges are simpler, and the air-bridge can withstand strong ultrasound.

A comparison study of on-chip short pulse generation circuits based on a coplanar waveguide

A few traditional pulse-forming circuits are implemented in a commercial 0.13 μm digital complementary-metal-oxide-semiconductor （CMOS） technology. These circuits, based on a coplanar waveguide, are analyzed and compared through CadenceTM Spectre simulations. The results show that these traditional pulse-forming-line （PFL） based circuits can be implemented in standard CMOS technology for short pulse generations. Further work is needed to explore the potential of the circuit techniques and to minimize parasitic effects.

A low-loss V-groove coplanar waveguide on an SOI substrate

A novel low-loss 50-Ω coplanar waveguide with V-groove on an SOI substrate is proposed.Through a CMOS-compatible process and anisotropic etching of silicon, surface silicon is removed from the SOI.The measured results show that the V-groove coplanar waveguide causes about 50% less loss than the conventional one at a high frequency of up to 40 GHz.

Distributed parameter circuit model for wideband photodiodes with inductive coplanar waveguide electrodes

An equivalent circuit model including multi-section distributed parameters is proposed to analyze wideband photodiodes(PDs)with coplanar waveguide(CPW)electrodes.The model helps extract CPW parameters as well as intrinsic bandwidth parameters so that the influence of theCPW structure can be investigated,making it valuable for the design of high-performance PDs.PDs with an inductive 115Ωimpedance CPW are fabricated,and the 3 dB bandwidth is improved from 28 GHz to 37.5 GHz compared with PDs with a conventional 50Ωimpedance CPW.

Electrically tunable liquid crystal coplanar waveguide

A tunable stepped-impedance resonator using liquid crystal is demonstrated.Two resonant frequencies at 3.367 and 7.198 GHz are realized and can be continuously tuned by external applied voltages.Continuous tunable ranges of 52 and 210 MHz have been achieved at a particularly low driving voltage of 14 V,which shows good agreement with the simulation results.The voltage-induced hysteresis phenomenon is also investigated.This device also has a low insertion loss of-2.9 and-4 dB for the two resonant frequencies and the return losses are less than-21.5 dB.This work provides a new protocol to realize a tunable frequency for communication systems.

Optimize Purcell filter design for reducing influence of fabrication variation

To protect superconducting qubits and enable rapid readout, optimally designed Purcell filters are essential. To suppress the off-resonant driving of untargeted readout resonators, individual Purcell filters are used for each readout resonator.However, achieving consistent frequency between a readout resonator and a Purcell filter is a significant challenge. A systematic computational analysis is conducted to investigate how fabrication variation affects filter performance, through focusing on the coupling capacitor structure and coplanar waveguide(CPW) transmission line specifications. The results indicate that the T-type enclosing capacitor(EC), which exhibits lower structural sensitivity, is more advantageous for achieving target capacitance than the C-type EC and the interdigital capacitor(IDC). By utilizing a large-sized CPW with the T-type EC structure, fluctuations in the effective coupling strength can be reduced to 10%, given typical micro-nanofabrication variances. The numerical simulations presented in this work minimize the influence of fabrication deviations, thereby significantly improving the reliability of Purcell filter designs.

A Fast and Accurate Method for the Analysis of Multi-conductor Coplanar Wave-Guide Transmission Lines

This paper introduces the complex image concept, and uses the method to analyze multi conductor coplanar waveguides. The method of spectral domain Green's function for modeling point charge and line charge structures is studied, in which Chebyshev polynomials are used as basis functions to solve the integral equation by the Galerkin's method. It is believed that the complex method has the features of accuracy and rapid convergence, and it is possible to make the technique useful as CAD tool for coplanar waveguide design.

Ultra-wideband printed antennas for communication applications

A new type of ultra-wideband （UWB） printed monopole antennas is presented, which is composed of a circular or armular patch and a trapeziform ground plane with a tapered CPW feeder in the middle. Both simulated and experimental results are presented, showing good agreement and therefore verifying validity of the design. The proposed antenna with a circular monopole patch achieves an 11.6： 1 measured ratio bandwidth of VSWR ≤2 （ from 0,79 GHz to 9.16 GHz）, while that with an annular patch obtains a measured ratio impedance bandwidth of 10.6：1 （from 0.87 GHz to 9.47 GHz）. In addition, these designs exhibit nearly omnidirectional radiation patterns with simple compact structures, which axe attractive in communications and others UWB applications.

Modeling of terahertz pulse generation from LT-GaAs ultrafast photoconductive switches

The technique of terahertz pulses generated from the photoconductive switches has been applied in the ultrafast electrical pulse metrology recently.A lumped-element theoretical model is established to describe the performance of the LT-GaAs ultrafast photoconductive switch used in the ultrafast pulse standard.The carrier transport processes of the photoexcited semiconductor,the attenuation and dispersion during terahertz pulse propagating are considered in the theoretical model.According to the experimental parameters,the waveforms of the generated terahertz pulses are calculated under optical excitations with different wavelengths of 840 nm and 450 nm,respectively.And comparisons between the theoretical results and the experimental results are carried out.

Quintuple Band Antenna for Wireless Applications with Small Form Factor

A coplanar waveguide-fed quintuple band antenna with a slotted circular-shaped radiator for wireless applications with a high isolation between adjacent bands is presented in this paper.The proposed antenna resonates at multiple frequencies with corresponding center frequencies of 2.35,4.92,5.75,6.52,and 8.46 GHz.The intended functionality is achieved by introducing a circular disc radiator with five slots and a U-shaped slot in the feed.The proposed antenna exhibits coverage of the maximum set of wireless applications,such as satellite communication,worldwide interoperability for microwave access,wireless local area network(WLAN),long-distance radio telecommunications,and X-band/Satcom wireless applications.The simulation and measurement results of the proposed fabricated antenna demonstrate the high isolation between adjacent bands.A stable realized gain with an advantageous radiation pattern is achieved at the operating frequency bands.The proposed simple design,compact structure,and simple feeding technique make this antenna suitable for integration in several wireless communication applications,where the portability of devices is a significant concern.The proposed antenna is anticipated to be an appropriate candidate for WLAN,long-term evolution,and fifth-generation mobile communication because of its multi-operational bands and compact size for handheld devices.

Frequency Reconfigurable Antenna for Portable Wireless Applications

In this paper,the design and experimental evaluation of a hexagonalshaped coplanar waveguide(CPW)-feed frequency reconfigurable antenna is presented using flame retardant(FR)-4 substrate with size of 37×35×1.6 mm3.The antenna is made tunable to three different modes through the status of two pin diodes to operate in four distinct frequency bands,i.e.,2.45 GHz wireless fidelity(Wi-Fi)in MODE 1,3.3 GHz(5G sub-6 GHz band)in MODE 2,2.1 GHz(3G Long Term Evolution(LTE)-advanced)and 3.50 GHz Worldwide Interoperability for Microwave Access(WiMAX)in MODE 3.The optimization through simulation modeling shows that the proposed antenna can provide adequate gain(1.44∼2.2 dB),sufficient bandwidth(200∼920 MHz)and high radiation efficiency(80%∼95%)in the four resonating frequency bands.Voltage standing wave ratio(VSWR)<1.5 is achieved for all bands with properly matched characteristics of the antenna.To validate the simulation results,fabrication of the proposed optimized design is performed,and experimental analysis is found to be in a considerable amount of agreement.Due to its reasonably small size and support of multiple frequency bands operation,the proposed antenna can support portable devices for handheld 5G and Wireless LAN(WLAN)applications.

CPW Circulators with Barium Ferrite Thin Films

A miniaturized circulator using barium ferrite films with a coplanar waveguide （CPW） structure is designed and optimized by high frequency electromagnetic field simulations based on finite element methods. The best circulation performance of the film circulator based on 10 pm thick barium ferrite thin films is obtained with an insertion loss of 0.13 dB and an isolation of 22.89 dB around 36.9 GHz. The microwave characteristics of film circulators with CPW and CPW with ground （CPWG） structures have been compared. The influences of the gap between the ground and the signal line, and the ferromagnetic resonance line width on the microwave properties are also studied.

Design of a 40-GHz LNA in 0.13-μm SiGe BiCMOS

A low-noise amplifier （LNA） operated at 40 GHz is designed. An improved cascode configuration is proposed and the design of matching networks is presented. Short-circuited coplanar waveguides （CPWs） were used as inductors to achieve a high Q-factor. The circuit was fabricated in a 0.13-μm SiGe BiCMOS technology with a transistor transit frequency fT of 103 GHz. The chip area is 0.21mm^2. The LNA has one cascode stage with a-3 dB bandwidth from 34 to 44 GHz. At 40 GHz, the measured gain is 8.6dB; the input return loss, S11, is -16.2dB; and the simulated noise figure is 5 dB. The circuit draws a current of only 3 mA from a 2.5 V supply.

Small signal modeling of AlGaN/GaN HEMTs with consideration of CPW capacitances

Given the coplanar waveguide （CPW） effect on A1GaN/GaN high electron mobility transistors at a high frequency, the traditional equivalent circuit model cannot accurately describe the electrical characteristics of the device. The admittance of CPW capacitances is large when the frequency is higher than 40 GHz; its impact on the device cannot be ignored. In this study, a small-signal equivalent circuit model considering CPW capacitance is provided. To verify the model, S-parameters are obtained from the modeling and measurements. A good agreement is observed between the simulation and measurement results, indicating the reliability of the model.

A W-band two-stage cascode amplifier with gain of 25.7 dB

AW-bandtwo-stageamplifierMMIChasbeendevelopedusingafullypassivated 2 × 20 μm gate-width and 0.15 μm gate-length InP-based high electron mobility transistor （HEMT） technology. The two-stage amplifier has been realized in combination with a coplanar waveguide technique and cascode topology, thus leading to a compact chip-size of 1.85 × 0.932 mm^2 and an excellent small-signal gain of 25.7 dB at 106 GHz. Additionally, an inter-digital coupling capacitor blocks low-frequency signal, thereby enhancing the stability of the amplifier. The successful design of the two-stage amplifier MMIC indicates that InP HEMT technology has a great potential for W-band applications.

UWB planar antenna technology

Recent developments of the ultra-wideband(UWB)planar antennas are reviewed,where the progress in UWB plate monopole antennas,UWB printed monopole antennas and the UWB printed slot antennas is introduced and compared.In addition,the UWB printed antennas with the band-notched functions are also presented.