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A compact balanced frequency doubler with more than 35 dB odd-harmonic rejection and fractional bandwidth of 73% is presented in this letter. Wide bandwidth and high odd-harmonic suppression is achieved by adopting a new technique for the transformer balun design, resulting in a very low magnitude imbalance of 0.13 dB and a phase imbalance of 0.4° over 7–15 GHz. The balun performance is improved by offsetting the radius of the primary and secondary coils, which reduces the parasitic coupling capacitance. The input and output frequency ranges for the doubler are 7–15 GHz and 14–30 GHz respectively. The circuit was fabricated in 0.13- $\mu \text{m}$ SiGe technology. The chip size is 0.6 mm $\times \, 0.4$ mm.

The results of measurements performed on a GaN high electron-mobility transistor (HEMT) by two different pulse-measurement techniques are presented. By performing two-stage pulse measurements, two distinct current-injection mechanisms responsible for triggering the trapping process are identified. By performing three-stage pulse measurements, the trap center at which the trapping process occurs is identified to be a double-energy-level trap center, which is a trap center with two distinct energy levels between which there is an interaction. This result has a significant impact on the design of more accurate large signal models for GaN HEMTs.

Conventional and additive manufacturing (three-dimensional [3D] printing) techniques for a dual-ridged horn antenna (DRHA) are presented. The different aspects of the conventional manufacturing of a DRHA and the limitations incurred during additive manufacturing are discussed in detail. The antenna design was further optimized for fused deposition modeling and was 3D printed using acrylonitrile butadiene styrene (ABS). The polymer-based print was painted with nickel-based aerosol spray. The coaxial transition is also included in the 3D printed prototype. The antenna was manufactured with the intention of improving the learning and education of electromagnetism and antennas of undergraduate students using a low-cost personal desktop 3D printer. The painted DRHA has a 10 dB return-loss bandwidth of 6621 MHz (1905–8526 MHz) with a peak gain of 11 dBi. The average cross-polarization isolation achieved was more than 25 dB. Rapid prototyping was possible with additive manufacturing, and limitations were addressed with conventional machining processes whenever required. This prototype is the first known ABS-based horn antenna with the coaxial transition embedded into it. © 2016 Wiley Periodicals, Inc. Microwave Opt Technol Lett 58:2110–2117, 2016.

An on-chip resonator is designed and fabricated using a standard 0.13- $\mu \text{m}$ SiGe technology for millimeter-wave applications. The designed resonator is based on a unique structure, which consists of two broadside-coupled meander lines with opposite orientation. The equivalent $LC$ circuit of the resonator is given, while the impact of the structure on the resonance frequencies is investigated. Using this structure along with capacitors, a compact bandpass filter (BPF) is also designed and fabricated. The measured results show that the resonator can generate a resonance at 57 GHz with the attenuation better than 13.7 dB, while the BPF has a center frequency at 31 GHz and a insertion loss of 2.4 dB. The chip size of both the resonator and the BPF, excluding the pads, is only 0.024 mm2 ( $0.09 \times 0.27$ mm $^{2})$ .

A 3D printed dual-ridged horn antenna (DRHA) is presented. The antenna design is optimized for additive manufacturing and is 3D printed using acrylonitrile butadiene styrene (ABS) and then painted with nickel based aerosol spray. The coaxial transition is also included in the 3D printed prototype. The antenna was manufactured with the intention of improving learning and education of electromagnetism and antennas for undergraduate students using a low-cost personal desktop 3D printer. The painted DRHA has a 10 dB return-loss bandwidth of 6621 MHz (1905 MHz–8526 MHz) with a peak gain of 11 dBi. This prototype is the first known ABS-based horn antenna with the coaxial transition embedded into it.

A higher frequency, over 2 GHz, is suggested for current 4G or 5G wideband applications. By adopting a unique gain control method, an analog-controlled variable-gain amplifier (VGA) with an accurate dB-linear characteristic is presented. The designed VGA not only features large bandwidth, but also has accurate gain adjustment with a relatively wide control voltage range. The VGA has a measured gain range of 24 dB, of which 17.3 dB is dB-linear with less than $\pm$ 0.3-dB gain error. The $-$ 3-dB bandwidth is relatively constant from 2 to 2.2 GHz for the entire dB-linear range. An output 1-dB compression point of 1.8 dBm and a noise figure of 24 dB are measured. Due to the simple structure, the current consumption of the VGA core is only 2.9 mA from a 1.2-V supply, and the size is only ${\hbox{225}}\ \mu{\hbox{m}}\times {\hbox{45}}\ \mu{\hbox{m}}$ , excluding pads. Moreover, the robustness of the designed VGA is verified by means of Monte Carlo simulation.

Transient gate resistance thermometry is employed to characterise the time domain response of a GaAs pHEMT under pulsed conditions. Self heating is observed from hundreds of nanoseconds to hundreds of milliseconds. A TFR-heated test structure is used to develop a 3-D finite-element thermal model that scales with power density and gate periphery. Thermal coupling between gate fingers in a multi-finger device is measured, and then further investigated via simulation. The model's application to thermal optimisation of devices and circuits is discussed.

A folded edge-coupled transformer balun is presented with excellent balance and 3-dB bandwidth from 9 to 20 GHz. Three structures were simulated; straight, folded, spiralled; to study the trade-off between the circuit size and balance performance. A simplified lumped equivalent circuit model of the transformer balun is also shown. The transformer balun was implemented with two-port characterization structures to accurately measure the balance. The measured magnitude and phase imbalances are less than 0.3 dB and 0.7° from 2 to 25 G Hz, surpassing previously reported results for GaAs baluns. The balun was fabricated in a $0.1\ \mu \mathrm{m}$ GaAs pHEMT technology and occupies 0.24 mm2. This paper also highlights that the edge-coupling is preferred for GaAs technology baluns due to restrictions in metal fabrication.

International audience; —The strongest-cell criterion has been extensively used for handover algorithms during the last cellular-network generations. When network topologies become multi-layered, it results in abrupt behaviors such as the ping-pong effect as a consequence of the power gap between tiers and their irregular deployment. This effect not only affects users' quality of experience but also introduces a significant network overhead. Therefore, we propose an original handover algorithm based on predicted incomplete channel states from a Radio Environment Map to reduce this effect. The proposed algorithm is user triggered, network assisted, and fully backward compatible with LTE-A. Moreover, we evaluate the performance of our proposed algorithm against LTE-A in a two-tier cellular network for different user speeds following the guidelines outlined by the 3GPP on diverse matters (channel, mobility, wrapping, etc.). When applying realistic timing, our results reveal a highly substantial improvement in the number of ping-pong handovers regardless of the handover policy adopted in comparison to LTE-A without sacrificing users' experience; for instance, we obtain at least an order of magnitude decrease in the ping-pong rate at the expense of losing less than 9 percent in spectral efficiency.

Every year millions of people around the world undergo orthopaedic surgeries with partial or complete joint replacements. However, according to the various arthroplasty registers around the world, about 10 % of the implants require re-surgery at some point in their lifetime [1]. About 80–90% of implant failures occur due to mechanical reasons [1–2]. It is proposed in [2], that micromotion of the orthopaedic implants during the limb movement can provide insights on the possible implant failure in the future. For this purpose, it is necessary to monitor the motion of metallic orthopaedic implants with the resolution of the order of tens of microns when the person moves a limb. In this paper, it is proposed to use a small sensor embedded inside the bone at a distance from the orthopaedic implant. The space available for such a sensor is limited to the cylindrical hole of dimensions 3 mm × 10 mm.

A 0.1 Watt GaAs pre-amplifier has been developed with broadband match, gain, and power compression characteristics spanning 28 to 47 GHz. Flat gain was achieved by choosing a balanced topology and selectively mismatching the input and inter-stage networks at the low end of the band. The gain is 15.7 dB with 1.4 dB ripple. Input and output matches are −17 dB and −22 dB respectively. The Psat is +22.0 dBm, P1 +19.4 dBm and the DC current is 160 mA from a 4 V supply. The amplifer is suitable for cascading to multiple-stages to achieve a low ripple, high gain frequency response for broadband electronic warfare applications.

In this paper we report an investigation into the low-frequency noise characterisation of electronic devices. Low-frequency noise measurements are complex with several noise sources present in the full measurement set-up. The different noise sources make measurement of the noise signal from the device complicated as noise from sources other than the device need to be suppressed or eliminated. We present a clear quantitative understanding of the noise signals from the various critical components in a typical noise measurement set-up. The quantitative analysis presented here can serve as a guide for accurate noise measurements of electronic devices.

The design of two transformer baluns is presented using different process technologies. Gallium Arsenside (GaAs) has been widely used for microwave circuits over the past few decades for its high performance. Silicon Germanium (SiGe) is an emerging technology that offers performance similar to GaAs and digital circuit integration. The differences between the metal and insulator layers are presented in the context of the balun design and its requirement for tight coupling between primary and secondary coils. A comparable performance was achieved between the two processes using electromagnetic simulation. The magnitude and phase imbalances were (0.05 dB, 0.5o) for GaAs and (0.05 dB, 0.2o) for SiGe between 10 and 20 GHz.

An eddy current sensor can be deployed near an orthopaedic implant for detecting its micro motion as the person moves. A numerical investigation by using a finite element solver is done to investigate the feasibility of such sensor head. A two-turn loop is modelled inside a tibial bone surrounded by the muscle phantom. The inductance, resistance and Q factor of the sensor are evaluated over different standoff distances and frequencies for 10μm motion of the tibial implant. From this data, the sensitivity and the range of the sensor at different sensitivity levels are calculated. It is found that while the range of sensor increases with frequency, the tissue losses also increase. The sensor is experimentally tested using a cow bone and the results are explained.

The temperature-dependent thermal conductivities of a GaAs pseudomorphic high-electron mobility transistor’s (pHEMT) substrate and epilayer regions are extracted to develop a 3-D finite-element-method thermal model. The thermal characterization is based on electrical gate-metal-finger temperature measurements of a customized GaAs pHEMT test structure. Heat flow from an integrated thin-film resistor is shown to be sensitive to the device’s substrate thermal conductivity, while heat flow from the device’s channel is most significantly affected by the epilayer region thermal conductivity. These observations are used in the formulation of the thermal parameter extraction technique, which serves as a useful and convenient device modeling tool that can be integrated into an engineering design flow. Specific knowledge about the semiconductor material fabrication process, which may be unavailable to the design engineer, is not required for accurate thermal characterization; this is the overriding advantage of the technique presented.

International audience; The advent of 5G networks, where a plethora of spectrum-sharing schemes are expected to be adopted as an answer to the ever-growing users' need for data traffic, will require addressing mobility ubiquitously. The trend initiated with the deployment of heterogeneous networks and past standards will give way to a multi-tiered network where different services will coexist, such as device-to-device, vehicle-to-vehicle or massive-machine communications. Because of the high variability in the cell sizes given the different transmit powers, the classical handover process, which relies solely on measurements, will lead to an unbearable network overhead as a consequence of the high number of handovers. The use of spatial databases, also known as radio environment maps (REM), was first introduced as a tool to detect opportunistic spectrum access opportunities in cognitive radio applications. Since then, REM usage has been widely expanded to cover deployment optimization, interference management or resource allocation to name a few. In this paper, we introduce a handover algorithm that can predict the best network connection for the current user's trajectory from a radio environment map. We consider a geometric approach to derive the handover and handover-failure regions and compare the current handover algorithm used in Long-Term Evolution with our proposed one. Results show a drastic reduction in the number of handovers while maintaining a trade-off between the ping-pong handover and the handover-failure probabilities.

Characterization of a wide-band transformer balun with low magnitude and phase imbalance is presented in this paper. Excellent balance over a large bandwidth is achieved by adopting two new techniques for the transformer balun design, resulting in a very low magnitude imbalance of 0.12 dB and phase imbalance of less than 1° over 30 to 60 GHz. The tradeoff between the insertion loss and the balance of the balun is investigated. First, the appropriate width of the primary and the secondary coils is selected for a reasonable insertion loss. Secondly, the radii of the primary and secondary coils were offset to reduce the parasitic coupling capacitance, thereby improving the balance of the differential signal. The balun is fabricated in 0.13 μιη SiGe technology. The balun is very compact with chip size of 0.2 mm × 0.145 mm.

There is a lack of comprehensive and generally accepted secondary spectrum analysis methods for evaluating short timescale whitespace opportunities. High resolution time and frequency measurements generate enormous amounts of multidimensional data, posing a significant challenge in visualising the dataset. This work presents the construction of a novel ‘Whitespace Opportunity Distribution’ for quantifying the availability of spectrum resources within an observed secondary spectrum environment. Two different spectrum use cases are examined and measured to contrast whitespace availability based on incumbent spectrum usage. The dimensionality of spectrum measurement data is reduced by applying a known NP-Hard partitioning problem to successfully capture discrete whitespace opportunities at millisecond timescales and sub kilohertz resolutions, enabling the available spectrum resources to be quantified.

In this paper, we present a spiral loop type antenna, implanted in the tibial bone. The antenna has been designed for fabrication on commercially available RT Duroid 6010 (ɛr=10.2) substrate and encapsulated in biologically compatible Polydimethylsiloxane (PDMS) material (ɛr=2.6). The antenna has a footprint of 2.6 mm × 2.6 mm and a height of 1.94 mm. The antenna operates at the 2.4 GHz ISM band with the peak gain of -36.2 dBi.

High data rate implantable wireless systems come with many challenges, chief among them being low power operation and high linearity. A low noise amplifier (LNA) designed for this application must include high gain, low noise figure (NF) and better linearity at low power consumption within the required frequency band. The down converter also requires a passive mixer to achieve low power and better linearity. In this paper, design is based on an Impulse Response (IR) Ultra-wideband (UWB) receiver operating at (3.1-5) GHz implemented in 0.25 μm CMOS Silicon on Sapphire (SOS). This paper reports the design and measurement of a UWB receiver with a designed and measured linearity of 17 dBm, a gain of 30.5 dB and a minimum NF of 4.5 dB, which make it suitable for implantable radio applications. © 2014 Published by Elsevier Ltd.

The thermal impact of device bias-state and structures (such as source connected field plates, gate-pitch, back-vias, and number of gate fingers) in AlGaN/GaN-on-Si high electron mobility transistors (HEMTs) are measured using gate metal resistance thermometry (GMRT). The technique characterizes the thermal response of device gate metallization to determine the gate-epilayer junction temperature (Tj), which is directly influenced by the channel heat source due to its close proximity. It is found that low gate leakage levels in GaN HEMTs make them favorable candidates for GMRT. Bias-dependent self-heating, independent of power dissipation, is observed in the devices. Therefore, Tj of different device configurations are compared at constant bias state, as well as constant power density (3.75 W/mm) to improve accuracy. Tj reduction is observed at high drain bias due to the migration of the channel heat source toward the gate field plate edge. This provides independent experimental validation for a reported electrothermal model [7]. A 3-D thermal finite element method model is presented, which simulates measured Tj rise to within ~6% across a range of device configurations and operating conditions. This is ultimately made possible upon implementation of a thermal boundary resistance layer and extraction of its temperature response using GMRT data.

Gate junction temperature is presented as the crucial parameter for modeling thermal degradation in GaAs device reliability studies, and sufficient for modeling the impact of temperature on device terminal characteristics. Gate metal resistance thermometry (GMRT) is applied to a GaAs pseudomorphic high-electron mobility transistor to measure its gate junction temperature. It is found that gate leakage current due to impact ionization can interfere with dc GMRT measurements. To the best of our knowledge, for the first time it is demonstrated that this can be largely avoided by instead applying an ac version of GMRT. However, the dynamic resistance of the gate leakage current path can interfere with ac GMRT. Measurements and thermal finite element method simulations of devices at constant power dissipation conclude that the bias dependence of the channel heat source profile affects the gate junction temperature. A parameter extraction technique is presented and used in device lifetime calculations to demonstrate MTTF variations of more than an order of magnitude (despite fixed power) due to bias-dependent self-heating.

Carbon nanotube (CNT) yarns are novel CNT-based materials that extend the advantages of CNT from the nanoscale to macroscale applications. In this study, we have modeled CNT yarns as potential data transmission lines. Test structures have been designed to measure electrical properties of CNT yarns, which are attached to these test structures using gold paste. DC testing and microwave S-parameter measurements have been conducted for characterization. The observed frequency independent resistive behavior of the CNT yarn is a very promising indicator that this material, with its added values of mechanical resilience and thermal conductivity, could be invaluable for a range of applications such as body area networks. A model is developed for the CNT yarn, which fits the measured data collected and agrees in general with similar data for non-yarn CNTs.

The frequency range 25–45 GHz contains point-to-point bands at 28, 32, 38 and 42 GHz, potential implementation of 5G at 28 and 39 GHz and various military applications. Traditionally, short gate length GaAs pHEMT technology has been used to develop products for these frequencies. Alternatively, SiGe HBT technology may offer lower cost solutions for systems that can tolerate lower performance. This paper presents the design and measurements of a broadband SiGe receiver with a noise figure of 6 ± 1 dB over the entire 25 to 45 GHz bandwidth. The measured gain exceeds 20 dB from 26 to 43 GHz and, with gain control, is sufficiently linear to support 1024 QAM in the 35 to 45 GHz range. To the authors' knowledge, this the broadest bandwidth achieved to date with a SiGe receiver at these Ka or low millimetre-wave frequencies.

150 GHz amplifiers fabricated on a commercial GaAs process with an f T of 135 GHz are presented. The core design achieves a gain of 10 dB or more from 105 to 150 GHz and the balanced variant has a bandwidth of 100 to 150 GHz and output power above 8 dBm at 140 GHz. Significantly, this coplanar design was carried out with a model extracted from biased S-parameters up to only 50 GHz taken on a microstrip device with different gate width. The measured S-parameters and output power of the amplifiers agree remarkably well with that predicted by the model.

An accurate scalable 3-D thermal finite-element-method (FEM) model is developed and verified for a GaAs pHEMT process using gate resistance thermometry (GRT) as the basis. The measurement technique is suited to scalable model development, since the gate metal is in intimate proximity to the heat source in the device channel. The FEM model is demonstrated to scale with channel power dissipation and gate periphery, simultaneously. Agreement to within 6% of all measured configurations/operating conditions is demonstrated. The model is suitable for inclusion in semiconductor foundry design kits to determine thermal resistance values for nonlinear device models, and also for thermal analyses of power amplifier layouts.

Modern microwave circuit performance is susceptible to dispersion of the characteristics of microwave FETs. This is because the complex signals used in communication systems invoke charge trapping and self-heating mechanisms. These mechanisms are sensitive to bias, temperature, and frequency variations. A major difficulty in characterizing charge trapping in microwave FETs is to differentiate between the self-heating and charge trapping rates. In this paper, the trapping behavior in a GaN HEMT is characterized by performing isothermal three-stage pulse measurements.

A 3D printed dual ridged horn antenna (DRHA) is presented. The antenna design is optimized for additive manufacturing and is 3D printed using acrylonitrile butadiene styrene (ABS) and then painted with nickel based aerosol spray. The coaxial transition is also included in the 3D printed prototype. The antenna was manufactured with the intention of improving learning and education of electromagnetism and antennas for undergraduate students using a low cost personal desktop 3D printer. The painted DRHA has a 10 dB return-loss bandwidth of 6621 MHz (1905 MHz–8526 MHz) with a peak gain of 11 dBi. This prototype is the first known ABS based horn antenna with the coaxial transition embedded into it.

© 2016 IEEE. Personnel detection embedded in foliage is extremely important to border patrol, perimeter protection and search-and-rescue operations. In this paper, we explore the utility of radio-sensor network (RSN) to distinguish between humans and animals. We explore the phenomenon that signals are always affected by the presence of obstacles and identify human based on the received signals by transceivers, which leads to a potential low-cost way for personnel detection without specific sensors. In our study, the impulse radio ultra-wideband (IR-UWB) technology is selected for the RF transceiver due to the fact that it is not only energy efficient, but also robust against interferences. The principle component analysis (PCA) is applied to extract the feature vector, and a support vector machine is used as the target classifier. Experiment result with an average accuracy of 97.5% based on actual data collected in a cornfield indicates that this approach has a good capability to distinguish between human and animals in a foliage environment.

A compact slotted planar inverted-F antenna (PIFA) with a superstrate is presented in this paper. The proposed antenna covers 28 GHz millimeter wave frequency bands and can be useful for future 5G hand held devices. The antenna has been designed to be integrated to a mobile phone substrate of dimensions 110 mm × 60 mm, while reserving 70 mm × 35 mm area for a battery, and occupies a small volume of 4 mm × 4 mm × 1.34 mm. It has a wide operating bandwidth (|S11| < − 10dB) of 3.18 GHz (27.57–30.75 GHz) and a peak gain of 8.8 dBi with a gain variation of less than 0.83 dB within the operating bandwidth. The proposed antenna has stable broadside radiation in yz and xz planes with low side lobe levels. It features wide half power beamwidths of 65.90 in the xz plane and 61.10 in the yz plane at 28 GHz. Radiation efficiency and total efficiency of the antenna vary between 97.9%–98.8% and 69.3%–97.3%, respectively.

© 2016 IEEE. An ultra-compact integrated resonator and bandpass filters (BPF), in silicon-based technology, are presented for millimetre-wave applications. The resonator consists of two broadside-coupled lines in opposite orientations. Using this resonator, a first-order and a second-order BPFs were also designed. To prove the concept, three prototypes of each of the resonator and the first-order BPF were fabricated using a standard 0.13-μm SiGe process. The measured results show that the resonator has an attenuation of 13.7 dB at the resonance frequency of 57 GHz, while the BPF has a centre frequency of 31 GHz and an insertion loss of only 2.4 dB. Excluding the pads, the chip size of both the resonator and the BPF is extremely compact, only 0.024 mm2 that is equivalent to 0.001 λg2. The unloaded Q factor of the filter is higher than other state-of-the-art designs.

The development of transient gate resistance thermometry (T-GRT) is reported. It is a technique used to measure the transient self-heating of a FET's gate metal. Demonstrations of T-GRT are presented at the wafer level on a GaAs pHEMT and an AlGaN/GaN-on-SiC HEMT. Dynamic self heating is monitored from hundreds of nanoseconds to hundreds of milliseconds. Preliminary finite-element simulations across a range of power dissipation levels agree closely with T-GRT at, and beyond, 1 µs after the applied drain pulse. Characterization of dynamic self heating and its application to pulsed applications such as radar are discussed.

This paper reports the investigation of RF GaN HEMTs as integrated power switches in high frequency, high efficiency switching topologies. GaN HEMTs suffer from trap phenomena which degrades the performance of the HEMT when used as power switches. Pulsed IV characterisation revealed upto 50% reduction in the theoretically available output power, at pulse frequency of 500 KHz and quiescent switch voltage of 60V. Transient measurements done a MMIC switching circuit with integrated drivers fabricated in the same process delivered an output power of 5.8 W at a switching frequency of 100 MHz and drain voltage of 30V.

Novel and realistic application of hot-via interconnects to millimeter-wave active and power MMICs is demonstrated for the first time. Power amplifier MMICs in the 80- and 100-GHz range were successfully designed, assembled, and characterized for wire-bond free chip interconnect technology. With hot-via RF transitions, compact E-band power amplifier MMICs directly soldered onto evaluation boards demonstrate 22-dB gain and over 28-dBm output power in the ETSI band of 81–86 GHz, with little performance degradation compared to reference circuits probed with traditional front-side RF pads. Similarly, a broadband amplifier, when interconnected to its matching PCB, delivers 13-dB of gain in the W-band, and 21-dBm P1dB. To the author's knowledge, this work represents the highest frequency demonstration of any soldered millimeter-wave hot-via active circuits onto standard PCBs, with remarkable measured power performance, closely equaling that of ideally front-side RF probed PA MMICs.

© 2015 IEEE. Sensitivity analysis plays an important role in a variety of statistical methodologies, design procedures and model selection. For development of in-body wireless communications, it is essential to evaluate the designed system performance prior to conducting any practical procedures. Localization of a capsule endoscope inside the gastrointestinal tract is one of the areas that needs to be precisely addressed in wireless body area networks. Since practical experiments on the real human body are quite infeasible, various human phantom models have been developed for this purpose. This study provides a detailed sensitivity analysis for two different anatomical human phantom models. The study shows that the adjustment of best possible grid and the number of cells have a significant impact on the simulation results to obtain a precise path loss and consequently to estimate an accurate location of capsule. This all aid us to improve the system performance.

A compact planar inverted-F antenna (PIFA) with single layer dielectric load is presented in this paper. The proposed antenna covers 28 GHz millimeter wave frequency bands and can be useful for future 5G hand held devices. The antenna is placed on a mobile phone substrate of dimensions 110 mm × 60 mm reserving 70 mm × 35 mm for a battery, and occupies a small volume of 4 mm × 4 mm × 1.34 mm. The antenna has a wide operating bandwidth (|S11| < −10dB) of 980 MHz (27.47 – 28.45 GHz) and a peak gain of 8.80 dBi with a gain variation of less than 0.55 dB within the antenna bandwidth. The proposed antenna has stable broadside radiation in yz and xz planes with low side lobe levels of −13.3 dB, −14.4 dB, and wide beamwidths of 66.6°, 64.5°, respectively. Radiation efficiency and total efficiency of the antenna vary between 97% – 99% and 88% – 96%, respectively. Antennas impedance bandwidth, gain, radiation, and total efficiency are assessed with and without a battery.

A difficulty concerning characterization of charge trapping in microwave FETs by performing pulse measurements is the possible overlap between the trapping and self-heating rates. Another difficulty is that the potential introduced by charge trapping modulates the drain-source current differently at bias points with different values of drain-source conductance, gm, and drain transconductance, g d . Measurement of true-DC values for g m and g d at all bias points will then be required for estimating the potential introduced by charge trapping. For devices such as GaN HEMTs, true-DC values for gm and g d at each bias point can be obtained only after thousands or tens of thousands of seconds after pulsing the device. A new pulse-measurement technique is proposed that overcomes these difficulties. The results of measurements performed on a GaN HEMT using the proposed pulse-measurement technique is presented, and the observed trapping behavior is characterized.

© 2016 IEEE. A compact transformer balun with less than 0.13 dB magnitude imbalance and 0.4° phase imbalance from 7 to 15 GHz is presented. The balun is suitable for use with frequency doublers using a balanced circuit architecture. Measured data for the balun is used to predict the harmonic rejection of the frequency doubler. The fundamental rejection is 29 dB and third harmonic rejection is better than 35 dB. The balun is 420 μm by 320 μm.

Recent developments in capsule endoscopy have highlighted the need for accurate techniques to estimate the location of a capsule endoscope. A highly accurate location estimation of a capsule endoscope in the gastrointestinal (GI) tract in the range of several millimeters is a challenging task. This is mainly because the radio-frequency signals encounter high loss and a highly dynamic channel propagation environment. Therefore, an accurate path-loss model is required for the development of accurate localization algorithms. This paper presents an in-body path-loss model for the human abdomen region at 2.4 GHz frequency. To develop the path-loss model, electromagnetic simulations using the Finite-Difference Time-Domain (FDTD) method were carried out on two different anatomical human models. A mathematical expression for the path-loss model was proposed based on analysis of the measured loss at different capsule locations inside the small intestine. The proposed path-loss model is a good approximation to model in-body RF propagation, since the real measurements are quite infeasible for the capsule endoscopy subject.

A 1.5 V 4.5 mW 3-5 GHz low-noise amplifier (LNA) suitable for power-constraint application is implemented in a 0.25-μm silicon-on-insulator CMOS process.The designed LNA with good input and output impedance matching exhibits gain of 10.3 dB and 2-2.9 dB noise figure within the 3-5 GHz band. Moreover, the -3 dB bandwidth of the presented LNA is insensitive to process corner variations. A third-order input intercept point of -5 dBm is also achieved for the LNA at 3.6 GHz. © 2012 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:89-93, 2013; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.27262 Copyright © 2012 Wiley Periodicals, Inc.

The integrated design flow that links simulation, layout, and electromagnetic (EM) analysis is the foundation for modern RF/microwave integrated circuit (IC) design. The inclusion of thermal simulation in this flow is now possible with modern thermal solvers linked into RF/microwave integrated design tools. Silicon germanium (SiGe) heterojunction bipolar transistor (HBT) power amplifier (PA) design is used as an example where such a flow is most beneficial due to numerous issues such as array sizing and thermal runaway. An electrothermal flow is discussed relative to some overall metrics for design flows and that incorporates the availability of an integrated thermal solver into the earliest parts of, and potentially throughout, the entire design flow. The result is a flow that potentially reduces iterations during the design process and boosts design performance by freeing up margin.

This paper presents a low power, low drop-out (LDO) voltage regulator, designed and implemented using 0.18 micron CMOS process. With a supply voltage of 1.8V, 50mA current and with a single compensation capacitor of 1pF. A constant transconductance current reference is used as a bias circuit for the Error Amplifier. The maximum output load current is 50mA at a regulated output voltage of 1.68V.The voltage regulator delivers a full load transient response of 5.5mV overshoot and 3.4mV undershoot. Furthermore, the LDO PSRR rating is −73dB @ 16.7MHz, and a relatively low power of 90mW.

In summary, nonlinear modeling is not a trivial exercise: it is our version of rocket science. Compact models have served us well for many years, but there are several shortcomings that behavioral models can address. The industry is experiencing some very heady times for measurement-based models and the test and measurement systems needed to gener ate them. Great progress has been made, but more experience will be needed with measurement-based models before the caveat emptor-let the buyer beware-is completely understood. For this to be accelerated, measurement-based model use and mis use needs to be communicated in a timely manner in a format and within a forum where the collective effort can be freely, openly, and easily discussed with minimal ambiguity. The OWF is working to address this. Like S-parameters before, there will be an adoption period, but if measurement-based mod els live up to their promise, there are very exciting days ahead indeed.

Different placement strategies for Field-Effect-Transistor (FET) active switching devices in an electromagnetic band gap (EBG) periodic structure are investigated. Two possible placements for the switches are considered: (a) switches on top of a substrate and (b) switches at the ground-plane level. Their advantages and drawbacks are analyzed and discussed in relation to fabrication, extension to 2-D and ground plane design. The transmission results and band gaps of the EBG structure are presented for both switch placements. When determining the transmission of the structure, the FET switches are modeled in two different ways, first as an ideal conductor and then using a more accurate model consisting of embedded scattering parameters. Significant differences have been observed between the results predicted using simple and accurate models. Experimental characterization of the switch reveals technological issues related to their biasing.

A digitally controlled half-width microstrip leaky-wave antenna (LWA) is presented for fixed-frequency beam scanning. The free edge of a half-width microstrip line is loaded with a number of periodic interdigital capacitors. Each capacitor is connected to the ground plane by a digital switch. By dynamically changing the reactance profile at the free edge of the microstrip the beam direction is changed at a fixed frequency. Full-wave numerical simulations show that the antenna has the ability to scan the main beam from 35° to 56 ° at 5.75 GHz. Refereed/Peer-reviewed

This paper reports on the development of high frequency, high efficiency integrated supply modulators for airborne and space based high power amplifier modules. The power switches within the integrated modulators were RF HEMTs optimized for power amplifier applications. The modulators were fabricated in commercial foundry GaN process and delivered 10W of output power with an efficiency of 83.5% while switching at a frequency of 100 MHz. Development of high frequency supply modulators paves the way for integration of the HPA and modulators onto the MMIC die and on-chip drain bias modulation for efficiency enhancement of the HPA.

A transformer-coupled frequency quadrupler with 50% bandwidth is designed in a 0.25μm SiGe process. The quadrupler covers an output frequency range from 36GHz to 60 GHz with a total power consumption of 38.5mW for a supply voltage of 2.5V. To fulfil the requirement of harmonic suppression, a novel on-chip asymmetrical Marchand balun structure is adopted to compensate the phase and amplitude errors across a wide bandwidth, so that the 3rd- and 5th harmonic suppressions of more than 30-dB can be achieved. The transformer-coupled approach along with a common-base configuration is adopted to enlarge the bandwidth of the multiplier.

Carbon Nanotubes (CNTs) have emerged as potential candidates for replacement of conventional metals due to their significant mechanical, electrical, thermal properties and non-oxidizing abilities [1, 2]. The density of CNT composites is about five times lower than copper and around half that of aluminium. Moreover, their thermal conductivity is about ten times that of copper. With the above mentioned distinguishing features, CNTs have been of interest in medical, electronics and antenna applications [3]. CNTs are drawn into yarns by pulling and twisting them from CNT forests. Previously we have presented microwave characterization of CNT yarns [4]. Our results have shown that the CNT yarns exhibits frequency independent resistive behavior and is beneficial for wideband applications such as ultra-wideband (UWB) and wireless body area networks [4]. Electrical conductivity of a CNT yarn depends on the properties, loading and aspect ratio of the CNTs. It also depends upon the twist angle and the characteristics of the conductive network. By doping or adding materials, such as gold, silver or NiCr, electrical conductivity of CNTs can by varied. In [5], highly conductive carbon nanotube-graphene hybrid yarns are reported. They are obtained by drawing vertically aligned multi-walled carbon nanotubes (MWCNT) into long MWCNT sheets. Then graphene flakes are deposited onto the MWCNT sheet to form a composite hybrid structure that is transformed into yarns by twisting. The electrical conductivity of these composite MWCNT-graphene hybrid yarns is over 900 S/cm. In this work, we have modeled this hybrid material as a potential data transmission line and compared it with a transmission line made out of copper on the same substrate. The results are tabulated in Table-I. They show a good agreement between copper based and composite MWCNT-graphene hybrid material based transmission lines. The hybrid material is high conductive, flexible and stretchable. This makes it suitable to use as transmission lines and connecting wires in systems that require stretching and flexibility, such as wearable systems.

One of the important components of a receiver is the low noise amplifier (LNA). The challenges of LNA design include ability to achieve high gain, low noise figure, and better linearity at low power consumption within the required frequency. In this article, our design is based on Impulse Response (IR) Ultra Wide-Band (UWB) transceiver operating at 3.1–4.6 GHz. Hence, the LNA designed has been optimized for low noise figure, considerably high gain and better linearity at low power consumption, which make it suitable for implantable radio application. The process technology used here is 0.25 μm CMOS Silanna process. © 2013 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:1399–1401, 2013; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.27588

Electromagnetic Bandgap (EBG) structures exhibit large continuous operational regions as a function of frequency over which they will not allow a signal to propagate. A subclass of bandstop filters, EBG structures stop a signal from passing through by having signals not propagate (vs. some other means of signal rejection, like reflection) in abeyance of Maxwell's Equations. Typically, EBG performance is achieved by modulating the geometric properties of an electromagnetic-guided or radiating structure so as to create a periodicity which induces the EBG and as such is not tuneable [1] if implemented as integrated circuits (IC) or printed circuit boards (PCB).