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With the advent of 5G, software-defined radios (SDRs), and ultra-wideband systems, there is a rapid rise in the demand for reconfigurable RF front ends. Conventional methods of using filter banks or cascading multiple devices to achieve wideband performance would result in bulky hardware. Devices that can change their characteristics and respond in a controlled manner to a desired input are suitable for such designs. In filtering applications, the most desirable adaptive features include band-switching capabilities, the use of a cutoff frequency and/or bandwidth tuning, and a change in filter response from passband to stopband. Periodic structures have demonstrated great potential in achieving these characteristics. Refereed/Peer-reviewed

Analysis and measurement validation of Marchand and Transformer baluns is presented in this brief that compares key performance metrics including amplitude and phase balance, circuit size, bandwidth and impedance match. Whilst novel variants of these circuits have been published in the open literature to improve their performance by direct compensation, there yet remains a fundamental comparison of the core coupled-line structures to reveal a systematic design procedure for baluns. Simple analytical equations are derived for both the baluns to reveal a deep analytical insight and a basis for performance comparison. It is then validated by measurement on the same gallium arsenide wafer, which is demonstrated for the first time. A systematic design approach is summarized that can be followed by other designers that has resulted in state-of-the-art performance for both balun types without the need for additional compensation and or tuning techniques at the output ports. The Marchand balun covers a frequency range of 30-65 GHz with a measured amplitude and phase imbalance less than 0.7 dB and 1.2° respectively. The transformer balun covers a frequency range of 30-45 GHz with a measured amplitude and phase imbalance less than 0.2 dB and 0.9° respectively.

An edge-coupled meandered three-coupled-line Marchand balun with a partial ground plane implemented in 0.13 $\mu \text{m}$ SiGe Bi-CMOS technology is presented in this brief. The balance performance of the designed balun is significantly improved by creating a ‘no ground plane’ beneath the coupled-line structure, which is demonstrated by simulating two baluns: one with a partial ground and the other with a solid ground underneath. The measured amplitude and phase imbalances are less than 0.4 dB and 2.5°, across the 3-dB bandwidth from 21.5 to 95 GHz, surpassing previously reported results of edge-coupled Marchand baluns. The balun occupies 230 $\mu \text{m}\,\,\times370\,\,\mu \text{m}$ .

In this paper, an eddy current loop coupled with the tunneling magneto resistor (EC-TMR) is used as a displacement sensor to detect the micromotion of an orthopaedic implant. The high sensitivity and signal to noise ratio of the TMR sensor are used to achieve high resolution at a large standoff distance. First, a small three-turn rectangular eddy current loop of dimension $2.5\,\,\text {mm} \times 10$ mm is designed and simulated inside the human body using a full-wave EM simulator. Then, it is fabricated and tested using vector network analyzer. The magnetic tunnel junction stack is optimized and a six-element TMR sensor is fabricated and characterized. The eddy current and tunnelling magneto resistive sensor are integrated and heterodyne detection technique is used to obtain the high-resolution micromotion detection at an extended standoff range. This technique can be used for in-vivo detection of the micromotion of the orthopaedic implant which will be useful in reducing the revision surgeries due to the mechanical failures of the implant.

A 1-D periodic structure having two shorted patches bearing dissimilar dimensions, in a unit cell, have been investigated for its application as a reconfigurable filter. To demonstrate the working mechanism, reactive loading to microstrip line is changed by periodically altering the patch connection to ground through presence/absence of shorting vias. Six filter structures with same unit cell dimensions and different switching patterns have been fabricated that represent different configurations of the filter. The proposed structure behaves as an all-pass filter in one state, and as a low pass filter and bandstop filter in other states with tunable cutoff frequencies. Refereed/Peer-reviewed

This paper presents the design and simulation of two single-stage power amplifiers (PAs) to determine the performance capabilities of WIN Semiconductors 0.15 μm Gallium Nitride (GaN)-on-SiC process. Subsequently a 28 GHz two-stage PA is presented for potential integration into 5G transceiver applications. A 2×100 gate-width device was used to develop a driving stage PA (MMIC1) which produced a simulated 12.8 dB small signal gain at the desired 28 GHz. A 4×100 gate-width device was used to characterize an output stage PA (MMIC2) producing 33 dBm power out, PAE of 41%, and a power gain of 11.2 dB. The subsequently designed two-stage PA, MMIC3, combines MMIC1 and MMIC2 and provides a peak small signal gain of 22.5 dB, peak power output of 33 dBm, peak PAE of 31% and peak power gain of 22.4 dB.

A wideband resistive mixer from 30 GHz to 56.5 GHz implemented in WIN Semiconductor's newly released 0.15μm GaN/SiC HEMT process is presented in this paper. The mixer exhibits a conversion loss of 10 dB at the midband for an optimum input LO power of 12 dBm. The LO-IF and RF-IF isolations are higher than 49 dB and 34 dB respectively. Mixer's input 1dB compression point is 18 dBm. The chip size including the pads is 1 mm2, and the circuit's active area is only 0.29 mm2.

A 0.13 SiGe upconverter circuit is presented that is suitable for use in broadband millimetre-wave transmitters and active phased arrays. The circuit accepts four differential IF inputs (I+, I−, Q+, Q−) in the frequency range of DC to 13 GHz. An off-chip X-band LO passes through an on-chip tripler before being used to drive the image rejection mixer. The resultant output may be placed anywhere in the frequency range of 25 to 42 GHz. When all four inputs are utilised the RF signals are combined passively at the mixer outputs to achieve an output referred P1dB compression point of +4.4 dBm without the need for additional amplifiers in the RF signal path. This paper highlights the measured bandwidth and single-tone compression characteristic of the circuit. Layout techniques are also briefly described.

In this paper, a 39 GHz power amplifier (PA) implemented in WIN Semiconductor's newly released 0.15 μm GaN HEMT process is presented. The load-pull simulation for power at 39 GHz for a 4×100 gate width transistor is also shown. The electromagnetic (EM) simulation of the designed two-stage PA shows a power gain of 17 dB at 39 GHz, 21% PAE and 31 dBm saturated output power.

© 2001-2012 IEEE. A highly accurate location estimation of a capsule endoscope in the gastrointestinal tract in the range of several millimeters is a challenging task, as radio-frequency signals encounter high power 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. To develop the path-loss model, electromagnetic simulations using the finite-difference time-domain method were carried out on three different anatomical human models from the Virtual Family. 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 real measurements are not completely practical for the capsule-endoscope subject. Based on the proposed path-loss model, the article also presents the 2-D location estimation of a capsule endoscope inside the small intestine using the trilateration method as well as the non-linear least squares algorithm. It is shown that with 90% probability, the location estimation error is less than 4 cm.

Measurement results performed on a GaN high-electron-mobility transistor that show the presence of a double-energy-level (DEL) trap center in the device are presented. A novel, yet simple, circuit implementation of a DEL trap center in an FET is presented that is immediately extendableto a trap centerwithmore than two energy levels. The model is based on the Shockley–Read–Hall statistics of the trapping process. The implementation is suitable for both time-domain and harmonic-balance simulations. Simulation results validate the proposed model.

The temperature response of field-effect transistors (FETs) to instantaneous power dissipation has been shown to be significant at high frequencies, even though the self-heating process has a very slow time constant. This affects intermodulation at high frequencies. A major difficulty in characterizing the self-heating process in microwave FETs is to differentiate between the self-heating and charge-trapping rates. An iso-trapping measurement technique is proposed by which it becomes possible to characterize the self-heating process in an FET in isolation from the effect of the charge-trapping process in the FET. The results of iso-trapping measurements performed on a GaN high-electron-mobility transistor are presented, and used to successfully characterize the self-heating process.

© 2016 IEEE. This paper presents a theoretical analysis for location estimation of a wireless capsule endoscope (WCE) in the small-intestine region. Under three different shadowing scenarios by assuming standard deviation of the shadowing with the constant variance, parameter-dependent variance, or correlated and parameter-dependent variance, analytical formulas are derived for the Cramér-Rao lower bound (CRLB) for capsule positioning when distance and azimuth angle measurements are employed to estimate the location of the capsule. The CRLB analysis can be employed to quantify the best achievable location estimation performance. We also present some numerical results to show the CRLB for three scenarios. The results show that in the most realistic scenario, when the shadowing is spatially correlated and distance dependent and the standard deviation of noise is 7 dB, the maximum square root of CRLB is 3.8 mm. Moreover, the square root of CRLB experiences its minimum value of 2 mm, when the capsule is away from its first location about half of the capsule length. Overall, the result of this paper suggests that it is possible to use received signal strength such as measured by a radar system for location estimation of a WCE.

A circuit implementation of a single-energy-level trap center in an FET is presented. When included in transistor models it explains the temperature-potential-dependent time constants seen in the circuit manifestations of charge trapping, being gate lag and drain overshoot. The implementation is suitable for both time-domain and harmonic-balance simulations. The proposed model is based on the Shockley-Read-Hall (SRH) statistics of the trapping process. The results of isothermal pulse measurements performed on a GaN HEMT are presented. These measurement allow characterizing charge trapping in isolation from the effect of self-heating. These results are used to obtain the parameters of the proposed model.

A self-biased balanced frequency doubler is presented in gallium arsenide (GaAs) with more than 38 dB fundamental suppression and broad bandwidth from 22 to 40 GHz at its output. The combination of both large bandwidth and excellent harmonic rejection was achieved by applying a transformer balun with a high degree of symmetry and minimal capacitive coupling. The balun alone has a gain and phase imbalance of less than 0.3 dB and 0.7° respectively from 2 to 25 GHz. The conversion gain of the doubler with the balun is -2 to -5 dB across the output frequency range. The highest output power is approximately 8 dBm between 18 and 20 GHz, with 10 dBm input. This work features the highest fundamental rejection across the band compared to the previously reported broadband GaAs doublers, enabled by the excellent balance of the balun.

A one-dimensional periodic structure comprising of eight unit cells each having two metallic patches sandwiched between microstrip line and ground plane has been investigated. Patches bearing dissimilar dimensions present distinct reactive loads, determined by their respective areas, to generate relatively wider bandgap. Patches can be selectively connected to ground or left floating through a combination of vias and externally controlled FET switches. Dispersion analysis of the structure has been carried out to determine the propagating modes of the line for all four possible states of the unit cell. A top-down, design guide approach has been adopted with the effect of parameters determining performance attributes captured. The proposed structure acts as an all pass filter from DC to 19.5 GHz with all patches floating and exhibits stopband characteristics from 6 to 19.5 GHz with different combinations of the switches offering an overall stop bandwidth greater than 100%. The proposed structure offers tunability from no bandgap to bandgap with added advantages of band switching capability with double the number of unique reconfigurable switch patterns as compared to conventional single patch structures.