GHz For Measurements Research Articles

Stacked lightweight metasurfaces for wider stopband in X-K band

Frequency selective surfaces printed on optically transparent, large-area, flexible plastic sheets are studied for their passband and stopband characteristics when present as single-layer, two-layer and three-layer stacks. The unit cell design, its size, spacing and thickness on the substrate enable the single layer metasurface to yield a stopband width of 4.46 GHz (corresponding to 34.80%), when the center frequency is at 12.83 GHz in simulation and 12.86 GHz in measurement. On stacking identical surfaces as two-layer and three-layer configurations with suitable displacements both within the surface plane and perpendicular to the surface plane, the structural geometry of the unit cell gets varied leading to an ultra-wide stopband of 8.96 GHz in the range from 12.16 GHz to 21.11 GHz which covers X to K band. This leads to a wider stopband width of 43.60% for two-layer stack and 48.10% for three-layer stack with no in-plane shift. This is further enhanced to 65.50% with suitable shift within the plane of the stacked design. The three-layer stacked structure is ultra-thin with a thickness of 0.012 λ0. The single layer as well as all the three stacked structures have stopband characteristics that are invariant to incidence angle variation up to 750.

Low noise amplifier design with enhanced noise and gain performance using transformer boosting method for millimeter‐wave applications

AbstractIn low noise amplifier (LNA) design, achieving minimum noise figure (NF) and enhanced gain is equally important in the field of communication. The major aim of this design with previous methods are those having implemented in the topology of design like metal oxide semiconductor field effect transistor at common source connection topology, pole‐based transformer boosting, and dual feedback technique. However, these methods fail to reach the desired performance due to their low NF and low gain. In order to overcome these failures and their causes, this article presented a topology in LNA design using a transformer as boosting component to improve the performance of NF and gain for millimeter‐wave applications. It has three common gate stages connected in cascode form, and three transformers are acquired to link the drain to the input signal. Transformers permit radio frequency feeding signal from drain to source, and output from the previous stage is connected to the input of the next stage. This connection increases the gain of the circuit and an enlarged coupling coefficient of value “1,” which minimizes noise. The unilateral coefficient remains to be 1, to make the circuit stable throughout execution. NF value can be minimized by properly selecting conductance coefficient and S‐parameter values. Since the transformer is used to provide feedback in this circuit, stability condition has to be analyzed carefully. Output load value is selected optimum as it creates an impact on the stability of LNA. This topology implemented in LNA design helps to increase the gain by boosting the signal input, and hence, in turn, it increases overall gain performance. Similarly, while executing this optimal LNA design using transformer boosting technique in CADENCE software, this LNA exhibits a minimum NF of 3 dB at 30 GHz and power gain of 12.2 dB at 50 GHz in measurement. Comparatively, the proposed LNA design overruns conventional methods and consumes a power supply of 1.1 V.

MTM- and SIW-Inspired Bowtie Antenna Loaded with AMC for 5G mm-Wave Applications

This paper investigates a feasible configuration of slotted bowtie antenna based on MTM and SIW properties for 5G millimeter-wave applications. To realize the proposed slotted bowtie antenna in a compact dimension with high performances, the MTM and SIW concepts are implemented by applying the trapezoidal slots on the top surface of the antenna and metallic via holes through the substrate layer connecting the top surface to the ground plane. The antenna has been fed with a simple microstip-line which is connected to a waveguide-port. It is shown that the slotted bowtie antenna with a small dimension of 30 × 16 × 0.8 mm3 operates over a measured wideband of 32–34.6 GHz with the fractional bandwidth, average gain, and radiation efficiency of 7.8%, 3.2 dBi, and 50%, respectively. To improve the antenna's performance, the artificial magnetic conductor (AMC) properties have been employed on the ground plane by loading vertical and linear slots with various lengths. The AMC slots are aligned under the trapezoidal slots on the top surface to transfer the maximum electromagnetic signals to them for optimum radiation. The proposed method enlarges the antenna’s effective aperture area, keeping constant its physical dimensions. The proposed AMC-loaded antenna covers wider frequency range of 30–37 GHz in measurement, which corresponds to 21% fractional bandwidth. The average experimental gain and radiation efficiency have been increased to 5.5 dBi and 66.5%, respectively, which illustrate the effectiveness of the proposed AMC-loaded antenna. The results confirm that the proposed slotted bowtie antenna with advantages of compact dimension, wide bandwidth, high gain and efficiency, low profile, being cost-effective, simple design, and easy fabrication process, which makes it applicable for mass production, can be a good candidate for 5G millimeter-wave applications.

Polarization Insensitive and Transparent Frequency Selective Surface for Dual Band GSM Shielding

This article proposes a single-layer, dual-band, optically transparent frequency-selective surface (FSS) for GSM shielding. The design evolves from a fractal cross dipole to achieve dual-band response, polarization insensitivity, and wide angle of incidence stability with a miniaturized size. A two-axis symmetric structure helps to provide a stable frequency response for incident waves with different polarization angles up to 60°. Capacitive loading further reduces the unit size and extends the maximum stable incident angle. The working mechanism of the design has been explained through an equivalent lumped element circuit model (ECM), which provides a generic approach to retune or optimize the design for another frequency band. Both the full-wave EM and circuit simulations are in good agreement. A prototype has been realized by screen printing a custom silver nanowire (Ag NW)-based transparent ink on a flexible polymer substrate. A decent reflection performance has been achieved from 0.71 to 1.25 GHz and from 1.73 to 2.16 GHz in measurements, which are consistent with the simulations. Optical measurements reveal a transparency of 81.6%. Printed FSS is completely flexible, and the performance does not deteriorate after bent or rolled up conditions. Field testing on a glass box demonstrates decent shielding from the incoming GSM signals. The highly transparent and flexible nature of the FSS structure makes it suitable for mounting on glass windows of cars or home environments for EM shielding purposes.

A compact wideband antenna with detailed time domain analysis for wireless applications

In this research paper, a compact wideband monopole antenna of the dimensions 20 � 20 � 1:6 mm3ði:e: total volume ¼ 640 mm3Þ is presented. The proposed antenna configuration has simplified design in which the ground plane, as well as the radiating patch, are on the same plane. This design renders one side of the substrate consummately empty resulting in an overall design which is more facile to fabricate. It is excited by Coplanar Waveguide (CPW) feeding technique. The proposed structure has a fractional bandwidth of 40.56% (4.3–6.45 GHz) in simulation and 34.41% (4.4– 6.38 GHz) in measurements for S11 < �10 dB criteria. It has linearly increasing gain over its entire oper�ational bandwidth and has a maximum peak realized gain of 4.7 dB at 6.4 GHz in simulation and about 3.8 dBi at 6.3 GHz in measurement. The designed antenna is suitable for WLAN and WiMAX of the range corresponding to 4.70–6.19, 5.5–5.7 and 5–6 GHz. To overcome the major drawback of narrow band�width in printed patch antenna, the uniquely designed split patch technique is used to achieve wide bandwidth. The antenna time-domain analysis is detailed by keeping it in side-to-side and face-to-face orientations. This analysis resulted in a stable performance which is very much required from a wideband antenna. All the necessary antenna simulations are done using HFSS and are validated by fabricating a model of it

Compact UWB flexible elliptical CPW‐fed antenna with triple notch bands for wireless communications

A coplanar waveguide (CPW)-fed flexible elliptical antenna with triple band notched characteristics is presented in this article. The designed antenna consists of an elliptical patch and slots incorporated CPW feed line to cover the bandwidth requirements for ultra-wideband (UWB) applications. The designed UWB antenna has a fractional bandwidth of about 166.19% (1.20-13 GHz) with a center frequency of 7.1 GHz in simulation and about 170.10% (1.05-13 GHz) with a center frequency of 7.025 GHz in measurement. The overall dimension of the proposed flexible antenna is 45 × 35 × 0.6 mm3. The triple notched bands are realized by designing with circular shaped split-ring-resonators (SRRs) and defected ground structure (DGS). According to the measurement, first notched band (2.0−2.70 GHz) is generated for rejecting 2.4 GHz WLAN by introducing a single circular ST-SRR on the radiating patch. The second notch (3.45-3.80 GHz) is obtained by embedding another circular ST-SRR on the patch to mitigate the interference of 3.5 GHz Wi-MAX system. Finally, due to presence of DGS, third notch (5.15-6.20 GHz) is produced which suppresses the interference from 5.5 GHz Wi-MAX and 5.2/5.8 GHz WLAN systems. The proposed antenna offers excellent performance in different flexible conditions that confirm its applicability on curved surfaces for UWB systems.

A 3-D-Printed &lt;italic&gt;W&lt;/italic&gt;-Band Slotted Waveguide Array Antenna Optimized Using Machine Learning

A three-dimensional (3-D) printed W -band slotted waveguide array antenna (SWAA) is proposed. The proposed SWAA consists of three different sections (two horizontal ones and a vertical one) such as a radiating waveguide array with 10 × 10 slots array with an aperture size of 31 mm × 31.4 mm, a coupling waveguide to feed the radiating waveguide array, and a vertical waveguide to feed the coupling waveguide. Machine learning technique based on artificial neural network algorithm is used to optimize the design. The optimized SWAA is fabricated using stereolithography apparatus (SLA) 3-D printing and then is metallized with silver on the inner and outer surfaces by jet metal spraying method. To metallize the inner and outer surfaces of the monolithic structure, nonradiating slots are added on the surface of the designed SWAA. The surface roughness is taken into account by employing the Huray-model methodology in simulation. The SWAA has a 22.5 dBi far-field gain, a −13.5 dB sidelobe level, and 10° half-power beamwidth (HPBW) at 78.7 GHz in measurement.

An inward directed antenna for gastro‐intestinal radio pill tracking at 2.45 GHz

AbstractThe accurate location of an ingested transmitter requires an array of surface electric field sensors worn on the body for more than 24 h. The small antenna (33 mm × 33 mm × 11 mm) consisting of a conductive box with a small slot (28 mm × 7 mm) pressed against the body with a centrally located feed probe was optimized to match the body impedance when located on the torso. The antenna properties when placed on different locations of the torso were calculated using computer modeling and verified using reflection measurements on 6 participants with body‐mass index between 17 and 27 kg/m2. Small center frequency shifts because of placing the antenna on different bodies and locations were within the 2.45 GHz bandwidth in all cases. The −10 dB bandwidth takes values between 0.75 and 0.97 GHz in simulations and between 0.51 and 1.15 GHz in measurements. The antenna design shows front‐to‐back isolation higher than 15 dB. The experimental results were not related to the body‐mass index of the participants.

Corporate-Feed Slotted Waveguide Array Antenna in the 350-GHz Band by Silicon Process

A corporate-feed slotted waveguide array antenna with broadband characteristics in terms of gain and reflection in the 350-GHz band is proposed. To improve the etching accuracy of the thin laminated plates with the conventional diffusion bonding process, a new fabrication process has been developed, where the etching accuracy is lower than $\pm 5~\mu \text{m}$ . In this process, the laminated plates are made with silicon wafers and etched by deep reactive ion etcher process. These are gold plated then bonded with the diffusion bonding process. The estimated effective conductivity of the gold plated wafer is $1.6 \times 10^{7}$ S/m. The loss per unit length is 1.1 dB/cm. A $16 \times 16$ element array antenna has been designed and fabricated in the 350-GHz band with the proposed process. The broadband characteristic in terms of the antenna gain is demonstrated for the first time by measurement in this frequency band. The 3-dB down gain bandwidth is 50.8 GHz in simulation and is 44.6 GHz in measurement.

A Transformer Feedback &lt;inline-formula&gt; &lt;tex-math notation="LaTeX"&gt;${G}_{m}$ &lt;/tex-math&gt; &lt;/inline-formula&gt;-Boosting Technique for Gain Improvement and Noise Reduction in mm-Wave Cascode LNAs

This paper presents the analysis and design of a novel topology of a low-noise amplifier (LNA) with gain improvement and noise reduction simultaneously. A transformer feedback ${ g}_{ m}$ -boosting technique is proposed in a single-ended cascode topology to increase the gain and reduce the noise. The proposed technique is theoretically formulated and detailed analyses are presented. Two V-band single-ended cascode LNAs, with a transformer and transmission line for impedance matching, respectively, are demonstrated to verify this technique. Fabricated in a 65-nm CMOS process, the transformer-based (TF-based) LNA exhibits a minimum noise figure (NF) of 3.6 dB at 53.5 GHz and a highest power gain of 28.2 dB at 54 GHz in measurement. To our best knowledge, this LNA has the best NF and power gain among all the published V-band LNAs in 65-nm CMOS up to date. The transmission-line-based (TL-based) LNA exhibits a minimum NF of 3.8 dB at 53.9 GHz and a highest power gain of 25.4 dB at 54.2 GHz in measurement. Both the LNAs consume 18 mA from a power supply of 1.1 V.

A New Broadband Common-Mode Noise Absorption Circuit for High-Speed Differential Digital Systems

A novel concept of the absorptive common-mode filter (A-CMF) is proposed for solving electromagnetic interference and RF interference problems in high-speed differential digital systems. The A-CMF is realized by a balanced four-port circuit with both horizontal and vertical symmetry. The common-mode (CM) noise can be terminated (or absorbed) by the resistors in the A-CMF and is thus transferred to heat. In addition, the signal integrity of differential signals can be well preserved by the A-CMF. Theory and design procedures are developed to determine corresponding element values of the A-CMF. A design sample is realized by an integrated passive device process on glass substrate. The circuit size is only 1 mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> . Results of measurement and full-wave simulation have good consistency. It will be found that the CM power loss (or absorption) ratio is over 80% from 4 to 14 GHz in measurement, and the differential-mode cutoff frequency can maintain up to 9 GHz with insertion loss, which is good enough for high-speed digital system applications. Finally, the eye diagram at the A-CMF output does not degrade significantly even when the differential data rate is up to 5 Gb/s.

Wide stopband compact microstrip lowpass filter using circular ring resonator and split ring resonators

In this contribution, a microstrip low-pass filter with a wide stop-band using split ring resonators and a circular ring resonator is introduced. The passband ripple of proposed filter was measured 0.6 dB and minimum insertion loss of passband is about 0.75 dB at 0.5 GHz frequency. Moreover, the 1.0 dB cut off frequency of proposed filter is 1.45 GHz in measurement. Designing this type of low-pass filter requires a high impedance transmission-line. However, the microstrip line width cannot be taken less than 0.2 mm in practical implementation. This causes to a small mismatch in passband. Furthermore, these results show wide stop-band up to 9.0 GHz with more than 30 dB rejection. The dimensions of proposed compact filter are about 12.5×30 mm2 (excluding extra substrate width). The proposed filter is a microstrip filter and can compete with defected ground structure (DGS) or defected microstrip structures lowpass filters in miniaturizing and wide stopband. However, the DGS or DGS filters have some problems in manufacturing applications such as radiation fields from defected structures and requiring a specific box. In addition, a distributed equivalent circuit model based on geometrical filer parameters is introduced, and good agreement can be seen between EM simulation and distributed equivalent circuit model up to 6.0 GHz frequency. © 2011 Wiley Periodicals, Inc. Microwave Opt Technol Lett, 2011; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.26203

A New Compact Ultra Wide Band (UWB) Planar Antenna using Glass as Substrate

In this paper, we present a new planar waveguide-fed ultra wideband (UWB) antenna. This antenna is designed for 50 Ω feed on a loss less glass as a substrate. The impedance bandwidth with VSWR < 2 is from about 4.4 GHz to more than 12 GHz in simulation results but from 3.8 GHz to about 11.5 GHz in measurement. This Antenna also has a directional gain pattern. Other important features of this antenna are its high gain and directivity as well as its easy shape to design. The reliable full wave simulation analysis by HFSS and CST Microwave Studio show that this novel structure can easily realize a good linear variation for the sweep gain as well as high directivity within a controllable bandwidth.

Frequency‐Dependent Dielectric Permittivity from 0 to 1 GHz: Time Domain Reflectometry Measurements Compared with Frequency Domain Network Analyzer Measurements

Measurements on a seven‐wire coaxial probe carried out with a cable tester in the time domain are compared with measurements carried out with a network analyzer in the frequency domain. Results are compared in the frequency domain and in the time domain. The frequency domain results of the time domain measurements are less smooth than the direct frequency domain measurements, but similar trends can be observed. The measurements carried out with the cable tester (Tektronix 1502B) clearly have a frequency content well above 3 GHz for measurements in air but with a very low signal‐to‐noise ratio for the higher frequencies. The useful frequency band for measurements carried out with a seven‐wire probe depends on the dielectric properties of the material being measured. The higher the complex dielectric permittivity, the lower the useful frequency band. Methods are presented for calibrating seven‐wire coaxial probes and measuring the frequency‐dependent dielectric properties of soil samples using a combination of frequency and time domain analyses. The approach does not depend on a choice of frequency bandwidth. A Debye relaxation curve is capable of describing the frequency domain dielectric permittivity of sandy soils containing a soil solution with an electrical conductivity of approximately 0.4 S m−1. Results indicate an effective bandwidth of at least 0–1 GHz for sandy soils.