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Dielectric sensing based on capacitive measurement technology is a favourable measurement approach in many industries and fields of application. From an electrical point of view, a coupling capacitance must be measured in the presence of stray capacitances. Different receiver circuit structures have been proposed for the underlying displacement current measurement. Ideally, the sensor assembly is directly connected to the sensor circuitry to minimize the influence with respect to these parasitic capacitances. However, under harsh operating conditions, e.g., at high temperatures, the sensor and the receiver circuit must be separated in order to protect the electronics. Consequently, the receiver circuit and the sensor have to be connected by cables, e.g., coaxial cables. The measurement setup differs significantly from the ideal design with a direct connection. In this paper, we investigate the behaviour of three common measurement circuits for capacitive measurements in instrumentations with cables. We study the interaction between the sensor and the electronics and analyse the operating behaviour of the circuit, as well as the operating states of the amplifiers used. We also address cross-sensitivities in the sensor design due to stray capacitances. The analyses are carried out for different cable lengths and measuring frequencies, and conditions for the usability of the circuit are deduced. In addition to the operational behaviour, we also evaluate the circuits by means of a noise analyses. Based on this analysis, we show a direct comparison of the circuits. The analysis is based on simulation studies, as well as collaborative measurements on test circuits where all circuit parameters are provided. The test circuits are realized with dedicated state-of-the-art circuit elements and, together with the analysis approach and the results, thus provide a basis for future developments.

Dynamically-tunable impedance matching is a key feature in numerous radio-frequency (RF) applications at high frequencies (10 s of MHz) and power levels (100s–1000 s of Watts and above). This work develops techniques that enable the design of high power tunable matching networks (TMN) that can be tuned orders of magnitude faster than with conventional tunable impedance matching techniques, while realizing the high power levels required for many industrial applications. This is achieved by leveraging an emerging technique – known as phase-switched impedance modulation (PSIM), which involves switching passive elements at the rf operating frequency – that has previously been demonstrated at rf frequencies at up to a few hundred Watts. In this paper, we develop design approaches that enable it to be practically used at up to many kilowatts of power at frequencies in the 10 s of MHz. A detailed analysis of the factors affecting the losses as well as the tradeoffs of a basic PSIM-based element is provided. Furthermore, it is shown how incorporating additional stages to the PSIM-based element, including impedance scaling and / or the addition of series or shunt passive elements, influences the losses and enables the efficient processing of high power levels given the limitations of available switches. A PSIM-based TMN that matches load impedances to 50 $\,\Omega$ and delivers up to 1.5 kW of power at frequencies centered around 13.56 MHz is implemented and tested over a load impedance range suitable for various industrial plasma processes.

A novel design method of microstrip diplexer without extra matching circuit is proposed in this paper. Because of the synthesizable circuit parameters and controllable transmission zeros (TZs) in composite resonator (CR) cell, diplexer A based on CR cell is proposed. By allocating TZs at center frequency of the opposite channel, as well as the using of impedance transformations of J inverters, high isolation and good passband selectivity are realized in diplexer A without extra matching circuit. In order to improve the stopband performance, diplexer B based on coupled CR cells is proposed. Furthermore, diplexer B using the proposed design method is implemented by directly combining two bandpass filters (BPFs), which simplifies significantly the design process of diplexers. Diplexer A operated at 1/1.2 GHz and diplexer B operated at 1/1.5 GHz are designed and fabricated. The measured isolation characteristics in diplexer A and diplexer B are all higher than 40 dB. Good agreements between simulated and measured results are achieved, which successfully verifies the proposed design method of diplexers.

In this paper, the systematic design for a dual-band balun featuring impedance transformation and high output isolation is presented. A dual-band balun capable of conducting transformation between an unbalanced 50-$\Omega $ line and a balanced one of 300-$\Omega $ is proposed for its operations at 2.4/5.2 GHz with high output isolation. The combination of a dual-band $\lambda $ /4 stepped-impedance-stub line and a dual-band $3\lambda $ /4 T-junction coupled line produces an output phase difference of 180° at the two operating frequencies for the balun. An important feature of the proposed design is the 1:6 impedance transformation from an unbalanced source to a balanced load. High isolation can also be achieved by introducing an isolation circuit between the output ports. The measured isolation is better than -26 dB. The phase imbalance is under 3°, and the magnitude imbalance is less than 0.9 dB within the bandwidths.

Small-signal stability assessment of the three-phase system can be performed using the measured impedances of the load and source. To obtain the dc steady-state operation point, the impedances are measured in the rotating $\boldsymbol{dq}$ -frame, and the phase angle is needed for the coordinate transformation used in both the perturbation injection and the impedance calculation. However, the phase estimation may introduce additional dynamics, affecting the accuracy of impedance measurement. This paper investigates the impact of phase synchronization dynamics on the measured impedance results. It is revealed that the phase variations in the perturbation injection has little effect on the measured impedance, while the phase dynamics introduced in the impedance calculation may have a significant impact. Based on impedance transformation, a new impedance calculation method is proposed, which can reduce the errors caused by the phase dynamics. Finally, the simulation and experiment results verify the accuracy of the analytical results and the effectiveness of the proposed method.

This paper proposes a novel planar dual-band coupled-line balun with impedance transformation and high isolation. Closed-form design equations are obtained based on the classical even-odd mode equivalent approach. For convenience of designing and synthesizing such a novel dual-band balun, the practical ranges of the frequency ratio, terminated impedances, and two free variables are provided under the conventional microstrip fabrication constraints. By adopting four coupled-line sections, six transmission-line stubs, and an isolation resistor, a microstrip prototype balun working at 1.0/2.6 GHz is designed, fabricated, and measured. There is a good agreement between the simulated and measured results. The wide bandwidths of 290 MHz from 0.83 to 1.12 GHz and 270 MHz from 2.44 to 2.71 GHz are obtained with the measured return losses (|S11|, |S22|, |S33|) and the isolation (|S23|) better than 10 dB, which effectively confirm the proposed theoretical predictions.

The authors propose a method for computation of electrical parameters of single pole multi-throw (SPMT) switch, the input matching of which is provided by the transmission line transformer, located on its input. The influence of parameters of line segments, which connect the lines branching outputs and keys in each path, on the value of SPMT switch operating parameters are offered. Use of the proposed method is demonstrated by the way of example of design and simulation of SPDT and SP4T switches with different types of keys.

This research presents design techniques for a linear power amplifier with high efficiency in wireless handsets. The power amplifier operates with high efficiency at the saturated output power, maintains high linearity with enhanced efficiency at back-off power levels, and covers a broadband frequency response. The amplifier is thus able to operate in multiple modes (2G/2.5G/3G/4G). The design techniques provide contributions to current research in handset power amplifiers, especially to the converged power amplifier architecture, to reduce the number of power amplifiers within the handset while covering all standards and frequency bands around the globe. Three main areas of interest in power amplifier design are investigated: high power efficiency; high linearity; and broadband frequency response. Multiple techniques for improving the efficiency are investigated with the focus on maintaining linear operation. The research applies a new technique to the handset industry, class-J, to improve the power efficiency while avoiding the practical issues that hinder the typical techniques (class-AB and class-F). Class-J has been implemented using GaN FET in high power applications. To our knowledge, this work provides the first implementation of class-J using GaAs HBT in a handset power amplifier. The research investigates the linearity, and the nature and causes of nonlinearities. Multiple concepts for improving the linearity are presented, such as avoiding odd-degree harmonics, and linearizing the relationship between the output current and the input voltage of the amplifier at the fundamental frequency. The concept of bias depression in HBT transistors is introduced with a bias circuit that reduces the bias-offset effect to improve linearity at high output power. A design methodology is presented for broadband matching networks, including the component loss. The methodology offers a quick and accurate estimation of component values, giving more degrees of freedom to meet the design specifications. It enables a trade-off among high out-of-band attenuation, number/size of components, and power loss within the network. Although the main focus is handset power amplifiers, most of the developed techniques can be applied to a wide range of power amplifiers. Ph. D.

In this paper we introduce for the first time the concept of exploiting the rectifier part of passive RFID systems not only for sensor powering but also for remotely performing the sensor reading. This solution is proposed for harsh industrial environments where remote machineries parts need be simultaneously powered and monitored wirelessly. We demonstrate the co-existence of high wireless power transfer and NFC communication for temperature sensor read-out, with no need for extra electronics at the RFID tag side to control the sensor readout. In particular, we show that the behavior of the RF-to-DC rectifier of a passive RFID, loaded by the sensor, can be exploited for powering the sensor operations as well as for reading its activities.

In this paper the method for calculation of single pole multi-throw (SPMT) switches insertion loss and isolation which can be obtained at the assigned type of the switching elements and its connection circuit is offered. The formulas for determination of electrical parameters of elements of transforming four-poles circuits which are necessary to provide the SPMT switch mentioned parameters and input matching of it are resulted The method for compensation of effect of discontinuity of lines branching, which is part of such devices, is also offered.

Five chapters of this dissertation concentrate on the characterization and cancellation of high frequency parasitic parameters in EMI filters. One chapter addresses the interaction between the power interconnects and the parasitic parameters in EMI filters. The last chapter addresses the characterization, evaluation and design of noise separators. Both theoretical and experimental analyses are applied to each topic. This dissertation tries to explore several important issues related to EMI filters and noise separators. The author wishes to find some helpful approaches to benefit the understanding and design of EMI filters. The contributions of the dissertation can be summarized below: 1) Identification of mutual couplings and their effects on EMI filter performance 2) Extraction of mutual couplings using scattering parameters 3) Cancellation of mutual couplings to improve EMI filter performance 4) Cancellation of equivalent series inductance to improve capacitor performance 5) Analysis of mode transformations due to the imperfectly balanced parameters in EMI filters 6) Analysis of interaction between power interconnects and EMI filters on filter high-frequency performance 7) Modeling and design of high-performance noise separator for EMI diagnosis 8) Identification of the effects of parasitics in boost PFC inductor on DM noise Although all topics are supported by both theory and experiments, there may still be some mistakes in the dissertation. The author welcomes any advice and comments. Please send them via email to shuowang@ieee.org. Thanks Ph. D.