Grounded Coplanar Waveguide Research Articles

On-chip sub-terahertz surface plasmon polariton transmission lines with mode converter in CMOS.

An on-chip low-loss and high conversion efficiency plasmonic waveguide converter is demonstrated at sub-THz in CMOS. By introducing a subwavelength periodic corrugated structure onto the transmission line (T-line) implemented by a top-layer metal, surface plasmon polaritons (SPP) are established to propagate signals with strongly localized surface-wave. To match both impedance and momentum of other on-chip components with TEM-wave propagation, a mode converter structure featured by a smooth bridge between the Ground coplanar waveguide (GCPW) with 50 Ω impedance and SPP T-line is proposed. To further reduce area, the converter is ultimately simplified to a gradual increment of groove with smooth gradient. The proposed SPP T-lines with the converter is designed and fabricated in the standard 65 nm CMOS process. Both near-field simulation and measurement results show excellent conversion efficiency from quasi-TEM to SPP modes in a broadband frequency range. The converter achieves wideband impedance matching (<−9 dB) with excellent transmission efficiency (averagely −1.9 dB) from 110 GHz–325 GHz. The demonstrated compact and wideband SPP T-lines with mode converter have shown great potentials to replace existing waveguides as future on-chip THz interconnects. To the best of the author’s knowledge, this is the first time to demonstrate the (sub)-THz surface mode conversion on-chip in CMOS technology.

Center-Fed Patch Antenna Array Excited by an Inset Dielectric Waveguide for 60-GHz Applications

A patch antenna array proximity-coupled fed by the inset dielectric waveguide (IDW) is proposed in 60-GHz frequency band. The antenna array consists of four series-fed subarrays each having eight pairs of circular patch elements, four substrate integrated IDWs, and a compact four-way power divider transmitting the signal from the grounded coplanar waveguide (GCPW) to the IDWs. The IDW is realized by metallized via-hole arrays in a printed circuit board (PCB). The parallel center-fed configuration is applied to suppress the frequency-dependent beam squinting of the series-fed subarray. Measured results show that the proposed antenna exhibits a gain variation between 15.8 and 19.2 dBi, fixed main beam in the direction of $\theta= 0^\circ$ , and the reflection coefficient $\vert S_{11}\vert \le-10 {\text{ dB}}$ over the frequency band from 58 to 64 GHz.

Asymmetrically CPW-fed octagonal sierpinski UWB fractal antenna

An asymmetrically CPW-fed octagonal Sierpinski fractal antenna is designed for ultrawideband applications. It comprises of a second iterative fractal radiating patch, microstrip feedline and asymmetrical coplanar waveguide ground planes. An impedance bandwidth of 3.73 GHz to more than 20 GHz is achieved. Stable radiation patterns and desirable gain characteristics are observed. The simulated and experimental results are found to be in good agreement. The designed antenna structure has advantages of wide bandwidth and miniaturized dimensions over already reported UWB antenna structures. © 2016 Wiley Periodicals, Inc. Microwave Opt Technol Lett 58:1738–1745, 2016

A broadband ferromagnetic resonance dipper probe for magnetic damping measurements from 4.2 K to 300 K.

A dipper probe for broadband Ferromagnetic Resonance (FMR) operating from 4.2 K to room temperature is described. The apparatus is based on a 2-port transmitted microwave signal measurement with a grounded coplanar waveguide. The waveguide generates a microwave field and records the sample response. A 3-stage dipper design is adopted for fast and stable temperature control. The temperature variation due to FMR is in the milli-Kelvin range at liquid helium temperature. We also designed a novel FMR probe head with a spring-loaded sample holder. Improved signal-to-noise ratio and stability compared to a common FMR head are achieved. Using a superconducting vector magnet we demonstrate Gilbert damping measurements on two thin film samples using a vector network analyzer with frequency up to 26 GHz: (1) A Permalloy film of 5 nm thickness and (2) a CoFeB film of 1.5 nm thickness. Experiments were performed with the applied magnetic field parallel and perpendicular to the film plane.

Gap Waveguide PMC Packaging for a SIW-GCPW-Based Filter

In addition to microstrip line and basic grounded coplanar waveguide (GCPW) line circuits with perfect magnetic conductor (PMC) package, we further study the PMC package for a real component—a fifth order bandpass filter designed based on substrate integrated waveguide (SIW) with transitions to GCPWs. In particular, a simplified design of the PMC package is proposed for such a hybrid circuit. A fabricated SIW-GCPW filter was characterized without a lid, and with a traditional smooth lid, a modified smooth lid, a complete PMC lid and a simplified PMC lid. Both simulated and measured S-parameters show that the filter outband rejection using the proposed simplified PMC lid is better than the traditional and existing lids.

Impact of Ground via Placement in Grounded Coplanar Waveguide Interconnects

Methods for higher order parallel plate mode suppression in grounded coplanar waveguides (GCPW) using unique ground via structures are presented in this paper. Suppression of these higher order modes can increase GCPW bandwidth. The ground via fence parameters that affect the bandwidth of the GCPWs are also discussed. Two new structures using staggered ground via fences and with defected side ground planes, for improving GCPW performances while meeting fabrication and routing requirements, are discussed. These two methods improve the interconnect bandwidth by 62.2% and 27.8%, respectively. The measured and simulated results of a test GCPW structure are in close agreement.

Millimeter-Wave Broadband Mode Transition between Grounded Coplanar Waveguide and Post-Wall Waveguide

Millimeter-Wave Broadband Mode Transition between Grounded Coplanar Waveguide and Post-Wall Waveguide

A high performance ultra-wideband low cost SMA-to-GCPW transition

This letter presents a novel low cost through-the-wall SMA connector and the transition structures from the SMA to a grounded coplanar waveguide (GCPW). The SMA connector has two short metal legs extended from the outer conductor used to reduce the discontinuity of the transition. The parameters of the GCPW are designed to match the geometry of the coaxial. A matching stub is introduced in the center conductor line to further improve the performance of the transition. A prototype device is developed and measured. The measurement results show the return loss of the proposed transition is better than 20dB up to 26.5GHz.

Planar E-Band (71-76 GHz) Platforms for Integrating Millimeter Wave Photodiodes with WR-12 Waveguides

A planar 71-76 GHz integration platform is designed and fabricated for high-power radio-over-fiber (RoF) wireless photonic transmitters (PTs). The platform enables the integration of high-electron-mobility-transistor RF amplifiers and millimeter wave photodiodes (PDs), e.g., the waveguide triple transit region PD. An efficient electrical coupling between the PD chip and the rectangular waveguide (WR-12) output is attained through a low-loss grounded coplanar waveguide to a rectangular waveguide transition. The integration platform features a novel planar bias-tee design making use of a single quarter-wave coupled-lines (SCLs) section and slotted split-ring resonators (SRRs). The bias-tee network enables proper biasing for the PD chip and protects the hybrid integrated RF amplifier from being damaged by the DC bias voltage. The introduced design together with the WR-12 output enables the development of high-power (>17 dBm) PTs for mobile backhaul links and radar applications. Experimental characterization of the designed platform is introduced and compared to numerical results.

Flexible Uniplanar Electrically Small Directive Antenna Empowered by a Modified CPW-Feed

A flexible printed near-field resonant parasitic (NFRP) GPS L1 antenna that is a compact, efficient, directive radiator is demonstrated. The simple uniplanar design incorporates a capacitively loaded loop (CLL) resonator, which acts as the NFRP element, and a coplanar waveguide (CPW)-fed semi-loop antenna. A set of slots is introduced into the CPW feedline ground strips. The resulting meander-line-shaped CPW ground strips act as a driven dipole element that is capacitively coupled to the NFRP element in such a manner that when they are properly tuned, nearly complete matching to the 50-Ω source is achieved with no matching circuit, and the pair acts as a two-element endfire array. Parameter studies are reported to illustrate the nuances of the design and its operating mechanisms. The experimental results are in good agreement with their simulated values. The endfire realized gain is 3.57 dBi with a 13.44-dB front-to-back-ratio (FTBR) at its resonance frequency: 1.574 GHz (GPS L1), where the electrical size ka = 0.97. The flexibility of the proposed antenna is demonstrated both numerically and experimentally by mounting it on several cylindrical structures whose curvatures vary over a large range and by confirming that there is little impact on its operational frequency, impedance matching, bandwidth, and radiation characteristics.

CPW-Fed 8-Shaped Monopole Antenna for Ultra Wideband Applications

AbstractA CPW-fed 8-shaped monopole antenna for ultra wideband applications is presented. It consists of a 8-shaped monopole and two quarter elliptical coplanar waveguide ground planes. An impedance bandwidth from 5.4 GHz to 23.83 GHz is achieved. The radiation patterns are observed to be omnidirectional and bidirectional in E-and H-plane respectively at lower resonances. At higher frequencies, the radiation patterns are found to be nearly omnidirectional in both planes. The group delay variation is also observed to be constant in the operating frequency range. A good agreement is found between the simulation and experimental results. The designed antenna structure has miniaturized dimensions and wider bandwidth as compared to other already reported monopole structures.

A Compact 2.45-GHz Broadband Rectenna Using Grounded Coplanar Waveguide

This letter presents a compact 2.45 GHz broadband rectenna using the grounded coplanar waveguide (GCPW). A new broadband slot antenna fed by GCPW with a high gain of 10 dBi and a wide half-power beamwidth of 60 $^{\circ}$ is designed as the receiving antenna. By designing an input and an output impedance match network, a compact GCPW rectifying circuit based on the voltage doubler principle is proposed, which has broadband performance and is easy to be integrated with the novel GCPW antenna. The receiving antenna and the rectifying circuit are simulated and measured. The measured results of the rectenna agree well with those of the rectifying circuit, which validate the effectiveness of the design. The microwave-direct current (mw-dc) conversion efficiencies of the rectenna keep higher than 50% within the band from 2.2 to 2.6 GHz at 13 dBm received power on a $900\Omega $ load, and the highest efficiency is 72.5%. This rectenna has good performances of broadband, high mw-dc efficiency and compact structure.

Impact of Metallization Layer Structure on the Performance of G-Band Branch-Line Couplers

Five different versions of grounded coplanar waveguide (GCPW) branch-line couplers on GaAs were EM simulated, processed and investigated for operation in G-band (140–220 GHz), based on different layer structures (including 2 or 3 metallization layers) and layouts. The best results have been obtained with the structures based on a continuous galvanic metal in the central conductor line and ohmic connections between top ground planes, reducing the insertion losses by 0.8 dB. A measured amplitude imbalance less than 0.5 dB from 160 to 200 GHz (22%), with a coupler insertion loss lower than 1.3 dB was achieved for a 3 metallization layer branch-line coupler.

A Wide-Band, 5-Tap Transversal Filter With Improved Testability for Equalization up to 84 Gb/s

A millimeter wave integrated transversal filter operating at up to 84 Gb/s is presented. The implemented topology offers improved testability, which allows for filter characterization in both the time and frequency domain. The filter has an input and output return loss better than 10 dB up to 67 GHz. Using this filter, frequency equalization of an NRZ input to either an NRZ or a duobinary output is demonstrated at 84 Gb/s across a channel consisting of a 5 cm differential grounded coplanar waveguide trace and a pair of 80 cm coaxial cables. The filter is implemented in 130 nm SiGe BiCMOS process, has a die area of 2.5 mm $\,\times \,$ 1.4 mm and consumes 210 mW from a 2.5 V power supply.

Fabrication of metal strip waveguides for optical and microwave data transmission

Metal strip waveguides and devices suitable for high-speed digital signal transmission at both microwave and optical frequencies are fabricated and demonstrated in this work. The waveguide structure consists of three metal strips forming a coplanar waveguide (CPW) to support a microwave mode. In the proposed structure, the signal line consists of a copper strip sandwiched between two thin gold layers. The CPW ground planes are thin gold strips supporting long-range surface plasmon polaritons (LRSPPs) at optical frequencies. Thus, the proposed structure can simultaneously support LRSPPs at optical frequencies and microwave signals up to at least 40 GHz. The metalizations are patterned using bilayer photolithography followed by thermal evaporation. Then, to create the signal waveguide, an O2 plasma etch of the cladding and copper E-beam evaporation are used. The fabrication process steps are verified through experimental characterization. Microwave and optical transmission through the fabricated devices is demonstrated using radio frequency probes applied to the top of the device and optical fibers in an end-fire coupling configuration, respectively.

An ultra-wideband dielectric material characterization method using grounded coplanar waveguide and genetic algorithm optimization

An ultra-wideband complex permittivity extraction method is reported here using numerical fitting of scattering parameters to measured results. A grounded coplanar waveguide transmission line is realized on an unknown dielectric material, whose dielectric constant and loss tangent are extracted by the best fitting of the simulated magnitude, |S21|, and phase, ϕ21, of forward scattering parameter using an electromagnetic full-wave simulator (high frequency structure simulator) to the measured results. The genetic algorithm is employed for optimum rapid extraction, where errors between the numerically simulated and measured S21 (|S21| and ϕ21) are minimized in an iterative manner. As long as the convergence criterion is not satisfied, modifications to dielectric properties are made with this genetic algorithm implemented in Matlab. Feasibility of this extraction technique is validated on benzocyclobutane polymer from 10 MHz to 40 GHz.

Compact Wideband SIW Horn Antenna Fed by Elevated-CPW Structure

This communication presents a compact substrate-integrated waveguide (SIW) H-plane horn antenna fed by a novel elevated coplanar waveguide (ECPW) structure. First, the wideband characteristic of the SIW horn antenna is achieved through loading a dielectric slab with gradually decreasing dielectric constants, which can be realized through simply perforating different air vias on the extended slab. Second, in order to sustain an efficient feeding for the relatively thick substrate ( $0.27 {\lambda}_{0}$ ), an additional metal ground is inserted in the middle of the grounded coplanar waveguide (GCPW). Moreover, a triangular-shaped transition structure is placed at the end of the ECPW to smoothly transmit the energy from the thin ECPW to the thick SIW horn antenna. Finally, a prototype is fabricated to validate the proposed concept. Measured results indicate that the proposed horn antenna operates from 17.4 to 24 GHz. Stable radiation patterns can be observed in the whole operating band. The measured results show good accordance with the simulated ones. Above all, the proposed antenna occupies an area of $22 \times 56.5 \times 4\;{\text{mm}}^{3}$ ( $1.47{\lambda}_{0} \times 3.77 {\lambda}_{0} \times 0.27{\lambda}_{0}$ ), which is much more compact than the previous rectangular waveguide-fed horn antenna ( $2.33{\lambda}_{0} \times 9.21{\lambda}_{0} \times 0.31{\lambda}_{0}$ ) (where ${\lambda}_{0}$ is the wavelength at 20 GHz in the free space).

Modified approach for high frequency dielectric characterization of thinly metallized soft polymer film using grounded coplanar waveguide

In this paper, we introduce the dielectric characterization of soft polymer, polyurethane (PU), between 1 and 31 GHz frequency band using Grounded CoPlanar Waveguide (GCPW) lines with a modified analytical method. The unavoidable thin metallization (1 μm) of GCPW lines on polyurethane yields high conductor losses, which contribute to the extracted global losses up to 58% at 4 GHz. In order to get more precisely the dielectric losses, a modification of an already existing analytical model by coupling it with 3D electromagnetic simulations is proposed, which allows to estimate and subtract quickly the conductor losses. The measurements indicated that polyurethane relative permittivity ranges from 3.49 to 2.65 and the loss tangent was about 0.08, which is in agreement with the state of the art on this grade of PU as well as the Metal-Insulator-Metal capacitors characterizations (from 10−1 to 107 Hz and from 2 × 108 to 5 × 109 Hz). The proposed approach may open a fast and simple way for precisely determining the microwave dielectric properties of (ultra) soft polymers in a large bandwidth.

Modified theta‐shaped monopole antenna with defected ground structure for UWB applications

ABSTRACTA compact modified theta‐shaped monopole antenna for ultrawideband communication is presented. It consists of a modified theta‐shaped radiator fed with a modified microstrip feedline and rectangular notch‐loaded quarter elliptical coplanar waveguide ground plane. An impedance bandwidth of 4.35–20.75 GHz (131%) below −10 dB reflection coefficient line is achieved. The designed antenna structure has nearly omnidirectional radiation pattern in H‐plane and bidirectional pattern in E‐plane. The cross polarization level is also 20 dB lesser than copolarization level in every direction at lower frequencies. The performance of the designed antenna structure for three substrate materials, that is, FR‐4 epoxy, carbon nanotubes, and Ni0.2Co0.2Zn0.6Fe2O4, are also studied. The experimental and simulation results are found to be in good agreement. The designed antenna structure has advantage of wider bandwidth along with smaller dimensions as compared to previously reported monopole structures. © 2015 Wiley Periodicals, Inc. Microwave Opt Technol Lett 57:1625–1632, 2015

An Insertion Thermoelectric RF MEMS Power Sensor for GaAs MMIC-Compatible Applications

Design, fabrication and measurement of an X-band inline insertion thermoelectric radio frequency (RF) microelectro- mechanical systems power sensor are proposed in this letter. It is based on sensing a portion of the RF power dissipated by a gradient coplanar waveguide (CPW) due to the intrinsic ohmic losses and converted into thermovoltages by thermopiles, where the thermopiles are inserted below suspended ground planes of the CPW. In the thermopiles' design, cold junctions are covered with the CPW ground planes to reduce the reflection loss by depressing the electromagnetic coupling and serve as hot sink, while hot junctions are covered with the CPW signal plane to increase the sensitivity by improving the temperature of the end. This power sensor is fabricated by the GaAs MESFET process. Measured reflection losses are less than ${-}16.1$ dB and insertion losses are better than 0.4 dB at 8–12 GHz. Experiments show that this improved insertion power sensor has good linearity of the output response, and results in average sensitivities of about 49.3, 35.1, and 47.9 $\mu$ V $\cdot$ mW $^{-1}$ at 8, 10, and 12 GHz, respectively.