Broadband Coplanar Waveguide Research Articles

Design and optimization of broadband CPW rectenna for RF energy harvesting

ABSTRACT Wireless sensor networks (WSNs) are widely used in a variety of sectors, including the surveillance, healthcare, and military, and so on. The high cost and short lifespan of wireless sensor networks prohibit emerging and low-income nations for using their benefits. This article proposes a compact, low cost, and broadband coplanar waveguide rectenna with a simple novel ground plane operate in band range of 4.8–5.5 GHz (700 MHz) for an effective solution to radio frequency (RF) energy harvesting applications in WSNs. A parametric study of distinct antennas is also conducted to strengthen the attributes of the proposed antenna. The defected ground structure created on the co-plane offers 105° measured half power beamwidth (HPBW) in the H-plane for wide angular coverage. As a result, design alignment does not need to be extremely perfect in order to make conversion efficiency constant. The rectifying circuit is made compact by using a two-stub impedance matching network. At load resistance of 1k Ω, the power conversion efficiency of the proposed rectenna for a low input power level of −10 dBm is 27.2% (simulated) and 20.1% (measured) while its maximum value is 52.5% (simulated) and 50.1% (measured) for input power level of 10 dBm.

A new design of a printed reconfigurable coplanar multiband antenna

The demand for multi-functional components has increased enormously in recent years. Advances in integrated technology have enabled researchers to adapt diverse applications operating at different frequencies in a single wireless device. A compact broadband coplanar waveguide (CPW)-fed square aperture monopole antenna with inverted-L grounded strips is first described. The proposed antenna has a small size of 60×60×0.74 mm3 and has excellent performances which include a good input impedance matching with a much wider operating bandwidth, an excitation of the circular polarization at 2.45 GHz, and a stable omnidirectional radiation pattern. Then, a multiband reconfigurable antenna design is developed from this structure. The frequency reconfigurable approach is obtained using a varactor diode. In this work, it is observed that frequency diversity can be obtained by varying the value of the capacity by leaving the dimensions antenna unchanged. The results are given using CST microwave studio and show good performances in terms of return loss, bandwidth, gain and radiation pattern and demonstrate that the proposed antenna offers a reconfigurable solution for multi-standard wireless communication applications.

Broadband CPW fed butterfly shape printed slot antenna

AbstractA broadband coplanar waveguide fed butterfly shape slot antenna is presented in this paper. The designed antenna operates in the frequency range from 1.89 to 5.21 GHz (93.5%) for S11 ≤ −10 dB with a broadside gain of 5 ± 1 dBi over the bandwidth of 1.97–5.19 GHz (90.3%). The designed antenna is uniplanar having the size of 0.5 λ0 × 0.28 λ0 × 0.005 λ0 (λ0 is the wavelength at the lowest operating frequency in free space). The proposed configuration has a stable radiation pattern over the operating frequency band. The designed antenna is fabricated and simulated results are validated with measured results.

A Transmission Line Sensor With Sensitivity Improved for Detection of Ionic Concentration in Microfluidic Channel

Microwave measurements of minute dielectric property variations have many advantages such as noninvasive test, rapid sensing capability, and being label-free. Several researches including concentration detection are promoted by measuring the minute dielectric property variations of samples. Highly sensitive and accurate device is required for measurement of electrolyte concentration in biological fluids, especially when measuring samples in nanoliter or less scale. In this paper, a miniaturized broadband coplanar waveguide (CPW) transmission-line (TL) sensor with enhanced sensitivity is proposed. The sensitive device is realized by introducing interdigital capacitance (IDC) at the central conduction band of the CPW TL. The sensor is fabricated using print circuit board (PCB) technology with a microfluidic channel designed on it. A calibration based on microwave network theory is used to obtain the characteristic impedance and propagation constant of the sensing part. And accordingly, variations in magnitude and phase of S-parameters are employed to express the changes in concentration of the sample. Furthermore, an extracted equation between S-parameters and electrolyte concentration of the sample is first proposed. Experiments show the proposed sensor can detect the minimum concentration of 0.05 g/l for the three electrolytes (NaCl, KCl, and GaCl2 in deionized (DI) water)). Compared with a corrugator coplanar transmission line and a split ring resonator senor, the proposed sensor has a much higher sensitivity. Moreover, the device is robust in front of cross sensitivity caused by external factors (such as temperature variations, moisture, etc.). Thus, the proposed sensor is well suited for low-cost, real-tine, and CMOS compatibles sensing technologies.

Observing Spin Resonance in Two-Dimensional Conductivity Electrons in Contactless Geometry

Two fundamentally different non-contact techniques are used to observe electronic paramagnetic resonance (EPR) in a two-dimensional system based on the ZnO/MgZnO heterotransition. Spin resonance is detected in the first geometry for the transmission signal in a broadband coplanar waveguide applied to the surface of a sample. In the second, EPR manifests in a change of the power of a radio wave signal passing through a pair of T-shaped emitter/detector antennas having capacitive coupling with a two-dimensional channel. Results are compared to data measured using standard means of transport EPR detection.

A compact broadband coplanar waveguide fed circularly polarized printed monopole antenna with asymmetric modified ground plane

In this communication, a broadband circularly polarized (CP) monopole antenna with coplanar waveguide (CPW) feeding is proposed. It consists of a modified rectangular monopole, an asymmetric ground plane, a two-linked inverted L-shaped strips on the left CPW ground, and two rectangular horizontal slots in asymmetric CPW ground plane. The overall dimension is only 0.47λ o × 0.47λ o. The antenna prototype has been fabricated. The measured results indicate that a broad −10 dB impedance bandwidth (IBW) of 107.5% (4.3 GHz, 1.85-6.15 GHz) and a broad 3 dB axial ratio ARBW of 104.3% (4 GHz, 1.855-5.9 GHz) can be achieved; the average realized gain is 2.3 dBi for the entire CP band. The proposed antenna is an attractive candidate for several wireless communication systems.

Design of a Broadband Coplanar Waveguide-Fed Antenna Incorporating Organic Solar Cells with 100% Insolation for Ku Band Satellite Communication.

A broadband coplanar waveguide (CPW)-fed monopole antenna based on conventional CPW-fed integration with an organic solar cell (OSC) of 100% insolation is suggested for Ku band satellite communication. The proposed configuration was designed to allow for 100% insolation of the OSC, thereby improving the performance of the antenna. The device structure was fabricated using a Leiterplatten-Kopierfrasen (LPKF) prototyping Printed circuit board (PCB) machine, while a vector network analyzer was utilized to measure the return loss. The simulated results demonstrated that the proposed antenna was able to cover an interesting operating frequency band from 11.7 to 12.22 GHz, which is in compliance with the International Telecommunication Union (ITU). Consequently, a 3 GHz broadband in the Ku band was achieved, along with an enhancement in the realized gain of about 6.30 dB. The simulation and experimental results showed good agreement, whereby the proposed structure could be specifically useful for fixed-satellite-services (FSS) operating over the frequency range from the 11.7 to 12.22 GHz (downlink) band.

Contactless measurements of microwave-induced resistance oscillations in a ZnO/MgZnO heterojunction

The high-frequency conductivity of the two dimensional electron system formed at a ZnO/MgZnO heterojunction was investigated in the 4--18 GHz frequency range at high Landau level fillings and in the regime of both integer quantum Hall effect. The conductivity was probed by measuring the transmission of the broadband coplanar waveguide deposited on the sample surface. At low magnetic fields in case the sample was additionally subjected to the exciting radiation of the 60--140 GHz frequencies, the high-frequency conductivity exhibited well developed microwave-induced oscillations. Remarkably, these oscillations were detected in the whole range of probe frequencies studied---up to 18 GHz---in contrast to GaAs/AlGaAs heterostructures, where microwave-induced oscillations were reported to smear out at probe frequencies around 1 GHz. Furthermore, for each exciting frequency the phase and the period of the microwave-induced oscillations revealed no dependence on the probe frequency and coincided with the period and phase of the microwave-induced resistance oscillations studied independently by dc transport measurements in the same sample. The characteristic probe frequency at which the oscillations start to degrade corresponds to the characteristic scattering time in the region between quantum scattering rates deduced from the cyclotron resonance linewidth and that extracted from the magnetic field dependence of the microwave-induced resistance oscillations.

Substrate Integrated Waveguide (SIW)-Based Wireless Temperature Sensor for Harsh Environments

This paper presents a new wireless sensor structure based on a substrate integrated circular waveguide (SICW) for the temperature test in harsh environments. The sensor substrate material is 99% alumina ceramic, and the SICW structure is composed of upper and lower metal plates and a series of metal cylindrical sidewall vias. A rectangular aperture antenna integrated on the surface of the SICW resonator is used for electromagnetic wave transmission between the sensor and the external antenna. The resonant frequency of the temperature sensor decreases when the temperature increases, because the relative permittivity of the alumina ceramic increases with temperature. The temperature sensor presented in this paper was tested four times at a range of 30–1200 °C, and a broad band coplanar waveguide (CPW)-fed antenna was used as an interrogation antenna during the test process. The resonant frequency changed from 2.371 to 2.141 GHz as the temperature varied from 30 to 1200 °C, leading to a sensitivity of 0.197 MHz/°C. The quality factor of the sensor changed from 3444.6 to 35.028 when the temperature varied from 30 to 1000 °C.

Broadband compact CPW-fed metasurface antenna for SAR-based portable imaging system

A broadband and compact coplanar waveguide (CPW) coupled-fed metasurface (MS)-based antenna for C-band synthetic aperture radar (SAR) imaging application is proposed in this article, which is consisted of 16 uniform periodic square patches performed as radiators. The CPW feeding structure gives two following functions: (1) It excites an aperture coupling slot structure underneath the center of MS patch array. (2) It acts as a ground plane for the metasurface patch units. Different slots were investigated and eventually an hourglass-shaped slot is applied to enhance bandwidth for imaging applications. A prototype with a dimension of 60 × 60 × 1.524 mm3 (1.1λ0 × 1.1λ0 × 0.03λ0) operating at the center frequency 5.5 GHz (f0) has been fabricated and measured to verify the design principle. This antenna has a measured impedance bandwidth of 12.4% from 5.14 to 5.82 GHz, a peak gain of 9.2 dBi and averaged gain of 7.2 dBi at broadside radiation. Microwave imaging experiments using the proposed antenna have been carried out and a good performance is achieved.

Coplanar waveguide wideband band-stop filter based on localized spoof surface plasmons.

In this work, a wideband band-stop plasmonic filter based on localized spoof surface plasmons is reported, which consists of a coplanar waveguide (CPW) and an ultra-thin periodic corrugated metallic strip with defect units at the back of the substrate. Defect units are used to localize the transmission energy along the CPW. Each defect unit can introduce a narrow stop band, and a series of defect units is judiciously designed to form a broadband CPW band-stop filter. The center frequency and bandwidth of the filter can be tuned by the heights and numbers of the defect units. In addition, a T-shaped unit is designed to increase the equivalent height of the lateral branch so as to realize the miniaturization of the vertical geometric dimension. Theoretical analysis of the filter has been conducted, and a sample at microwave frequency has been fabricated and measured to validate our design. This simple band-stop plasmonic filter can find potential applications in plasmonic circuits and antennas at microwave and terahertz frequencies.

Strongly Confined Spoof Surface Plasmon Polaritons Waveguiding Enabled by Planar Staggered Plasmonic Waveguides.

We demonstrate a novel route to achieving highly efficient and strongly confined spoof surface plasmon polaritons (SPPs) waveguides at subwavelength scale enabled by planar staggered plasmonic waveguides (PSPWs). The structure of these new waveguides consists of an ultrathin metallic strip with periodic subwavelength staggered double groove arrays supported by a flexible dielectric substrate, leading to unique staggered EM coupling and waveguiding phenomenon. The spoof SPP propagation properties, including dispersion relations and near field distributions, are numerically investigated. Furthermore, broadband coplanar waveguide (CPW) to planar staggered plasmonic waveguide (PSPW) transitions are designed to achieve smooth momentum matching and highly efficient spoof SPP mode conversion. By applying these transitions, a CPW-PSPW-CPW structure is designed, fabricated and measured to verify the PSPW’s propagation performance at microwave frequencies. The investigation results show the proposed PSPWs have excellent performance of deep subwavelength spoof SPPs confinement, long propagation length and low bend loss, as well as great design flexibility to engineer the propagation properties by adjusting their geometry dimensions and material parameters. Our work opens up a new avenue for development of various advanced planar integrated plasmonic devices and circuits in microwave and terahertz regimes.

Compact and Broadband CPW-to-RWG Transition Using Stub Resonators

This paper proposes a broadband coplanar waveguide (CPW)-to-rectangular waveguide (RWG) transition using stub resonators. The reflection coefficient of the proposed transition is less than −20 dB in the frequency band ranging from 8.6 to 12.6 GHz, which almost covers the whole X-band (8.2–12.4 GHz). As compared with the miniaturized CPW-to-RWG transition using the inductance-compensated slotline, the reflection coefficient is reduced from −15 to −20 dB and the size is maintained at 8.6 mm. In order to reduce the circuit size, a compact CPW-to-RWG transition using right-angled stub resonators is proposed. The circuit size is reduced from 8.6 to 7.8 mm while the broadband response of the −20-dB reflection coefficient is maintained. In order to verify the simulation results, three back-to-back CPW-to-RWG transitions are fabricated and measured by which the measurement results agree with the simulation results.

CPW‐fed flower‐shaped patch antenna for broadband applications

ABSTRACTIn this article, the simulation and experimental studies on a novel compact and broadband coplanar waveguide (CPW)‐fed flower‐shaped microstrip patch antenna are reported. The proposed flower‐shaped patch is a modified version of circular patch. Although the proposed antenna has largest radius (= 12.5 mm) equal to the radius of a circular patch, it provides much wider impedance bandwidth and lower first resonant frequency as compared with the CPW‐fed circular patch antenna. The flower‐shaped patch itself is capable of providing good impedance match with the CPW feed without any modification of feed line and ground plane. The simulated input and radiation characteristics of the proposed antenna are compared with the corresponding experimental characteristics over the operating frequency range. The simulated and experimental input VSWR bandwidth (VSWR ≤ 2) of antenna are found to be 4.59:1 (2.2–10.1 GHz) and 4.81:1 (2.2–10.6 GHz), respectively. The antenna provides bidirectional and omnidirectional patterns in E‐ and H‐planes, respectively, along with average gain value of 3.89 dB and good radiation efficiency (more than 75%) over whole operating frequency range. Time domain behavior of the antenna is also analyzed along with system fidelity factor and group delay. © 2015 Wiley Periodicals, Inc. Microwave Opt Technol Lett 57:2908–2913, 2015

A broadband coplanar waveguide to rectangular waveguide power divider using a slot

In this article, a broadband coplanar waveguide (CPW) to rectangular waveguide power divider using the dipole slot is proposed. The power divider consists of an input CPW port and two output rectangular waveguide ports. The CPW to rectangular waveguide power divider using the dipole slot has a return loss larger than 15 dB and an insertion loss equal to 3.08–3.27 dB in the whole X-band (8.2–12.4 GHz). Furthermore, to broaden the bandwidth, the dipole slot is replaced by the bow-tie slot. The CPW to rectangular waveguide power divider using the bow-tie slot yields a return loss larger than 16 dB and an insertion loss equal to 3.05–3.29 dB from 8 to 13 GHz, which exceeds the X-band. To verify our design, power dividers that use the dipole slot or the bow-tie slot are fabricated and measured. The measurement results of both power dividers are in good agreement with the simulation results. © 2012 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2013.

Broad-band CPWG to stripline feed-through transition and de-embedding method for millimeter wave measurement

A broadband coplanar waveguide with ground to stripline transition with high performance is designed and implemented, which can work at DC or a frequency up to 40 GHz. The ground-signal-ground probe test is a widely used method for accurate measurement of millimeter wave device. Because the probe pitch is smaller than the best dimension of the transition, a 50Ω connector fabricated by Gallium-Arsenic technology was introduced as the bridge between the transition and the probes. In order to acquire accurate measurement result, de-embedding method is adopted. The measurement results show that the insertion loss of the entire transition path is less than 0.5 dB and the return loss is better than −14.5 dB at a frequency up to 40 GHz. Besides, an equivalent circuit model of the transition is also proposed.

BROADBAND CPW-FED ANTENNA WITH BAND-REJECTED CHARACTERISTIC FOR WLAN/ WIMAX OPERATION

A novel single-layer broadband coplanar waveguide- fed antenna with band-rejected characteristic is proposed for WLAN/WiMAX operation. First, the broadband characteristic (2.43{ 5.97GHz) is achieved by a CPW-fed patch antenna with a dual-Y slot. Then, a single slit is inserted on the radiating patch or ground plane to introduce a notched band. The proposed antenna has a compact size of 40 £ 25mm 2 . The broadband characteristic and band-rejected functions of the proposed antennas are implemented and measured. Two types of antennas were studied. Measured notched- band impedance bandwidths (return loss < 10dB) are 370MHz and 1050MHz, respectively, which satisfles the requirements for WLAN and WiMAX applications. Detailed design steps and experimental results for the designs are studied and investigated in this paper.

Ferromagnetic resonance study of polycrystalline Fe1−xVx alloy thin films

Ferromagnetic resonance has been used to study the magnetic properties and magnetization dynamics of polycrystalline Fe1−xVx alloy films with 0⩽x&amp;lt;0.7. Films were produced by cosputtering from separate Fe and V targets, leading to a composition gradient across a Si substrate. Ferromagnetic resonance studies were conducted at room temperature with a broadband coplanar waveguide at frequencies up to 50GHz using the flip-chip method. The effective demagnetization field 4πMeff and the Gilbert damping parameter α have been determined as a function of V concentration. The results are compared to those of epitaxial FeV films.

A 0–55-GHz Coplanar Waveguide to Coplanar Strip Transition

A broadband coplanar waveguide (CPW) to coplanar strip (CPS) transmission line transition directly integrated with an RF microelectromechanical systems reconfigurable multiband antenna is presented in this paper. This transition design exhibits very good performance up to 55 GHz, and uses a minimum number of dissimilar transmission line sections and wire bonds, achieving a low-loss and low-cost balancing solution to feed planar antenna designs. The transition design methodology that was followed is described and measurement results are presented.

Effect of measurement geometry on permeability extracted by a broadband method

AbstractA broadband coplanar waveguide method, recognized as a simple and effective broadband permeability measurement tool, was used to measure the frequency dependent permeability of various magnetic thin films. It was revealed that measured permeability was strongly dependent on the dimension of the films and the geometry of the waveguide. This dependency was proven to result from the confinement of magnetic fields in the films by LLG equation. (© 2008 WILEY‐VCH Verlag GmbH &amp; Co. KGaA, Weinheim)