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This paper proposes a new design method of impedance matching networks for wireless power transfer systems. In wireless power transfer systems, the input impedance of resonator varies over a wide range rather than having a fixed value due to coupling variation. In conventional systems, tunable matching networks have been commonly used to match the variable impedance to a fixed impedance. Three-port impedance compression networks have also been proposed to eliminate the mechanical tuning processes. In this paper, a two-port impedance compressing matching network is proposed that addresses the load variations without the need for any mechanical tuning. In impedance matching, a two-port network can have a low design degree-of-freedom for load variation. In order to overcome this limitation, this paper analyzes the general model of a two-port network and proposes a systematic design procedure. The effectiveness of the proposed method is verified with a design example that constructs a Impedance Compressing Matching Network (ICMN).

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.

Applications such as plasma generation require the generation and delivery of radio-frequency (rf) power into widely-varying loads while simultaneously demanding high accuracy and speed in controlling the output power across a wide range of power levels. Attaining high efficiency and performance across all operating conditions while meeting these system requirements is challenging, especially at high frequencies (10s of MHz) and power levels (1000s of Watts and above). This paper evaluates different architectures that directly address these challenges and enable efficient high-frequency operation over a wide range of output power levels and load impedances with the capability of fast output power control (e.g., within a few microseconds). We review techniques for achieving fast output power control and evaluate their suitability in efficient rf systems demanding accurate and fast control of output power. Two dc-to-rf system architectures utilizing the discussed power control techniques are presented to illustrate both the achievable performance benefits as well as their robustness to load impedance variation, and are compared using time-domain simulations. The results indicate the ability of the proposed architectures to maintain high efficiency (> 90%) across a very wide range of output power levels (e.g., over a factor of up to 85x) while being robust to load impedance variations.

Industrial radio frequency (rf) power applications, such as plasma generation, require high-frequency rf power over a wide dynamic power range and across variable load impedances. It is desired in these applications to maintain high efficiency and fast dynamic response. This paper introduces a scalable power amplifier (PA) architecture and control approach suitable for such applications. This approach, which we refer to as Multi-Inverter Discrete Backoff (MIDB), losslessly combines the outputs of paralleled switched-mode PAs, and modulates the number of active PAs to provide discrete steps in rf output voltage. It further employs outphasing among sub-groups of PAs for rapid and continuous output power control over a wide range. In doing so, the architecture can maintain high efficiency and fast rf power control across a very wide backoff range. A device selection and loss optimization method for MIDB architectures is discussed for plasma generation applications. We address the use of GaN FET-based, ZVS class-D PA units, and consider dynamic R[subscript ds],on effects and C[subscript oss] losses typical of GaN FETs.

Plasma generation systems represent a particularly challenging load for radio-frequency power amplifiers owing to the combination of high operating frequency (e.g., 13.56 MHz) and highly variable load parameters. We introduce a dynamic matching system for inductively coupled plasma (ICP) generation that losslessly maintains near-constant driving point impedance (for low reflected power) across the entire plasma operating range. This new system utilizes a resistance compression network (RCN), an impedance transformation stage, and a specially configured set of plasma drive coils to achieve rapid adjustment to plasma load variations. As compared to conventional matching techniques for plasma systems, the proposed approach has the benefit of relatively low cost and fast response, and does not require any moving components. We describe suitable coil geometries for the proposed system, and treat the design of the RCN and matching stages, including design options and tradeoffs. A prototype system is implemented and its operation is demonstrated with low pressure ICP discharges with O $_{2}$ , C $_{4}$ F $_{8}$ , and SF $_{{6}}$ gases at 13.56 MHz and over the entire plasma operating range of up to 250 W.

Single-Switch inverters such as the conventional Class-E inverter are often highly load sensitive, and maintain zero-voltage switching over only a narrow range of load resistances. This paper introduces a design methodology that enables rapid synthesis of Class E and related single-switch inverters that maintain ZVS operation over a wide range of resistive loads. We treat the design of Class-E inverters for variable resistance operation and show how the proposed methodology relates to circuit transformations on traditional Class-E designs. We also illustrate the use of this transformation approach to realize Φ[subscript 2] inverters for variable-resistance operation. The proposed methodology is demonstrated and experimentally validated at 27.12 MHz in a Class E and Φ[subscript 2] inverter designs that operate efficiently over 12:1 load resistance range for an 8:1 and 10:1 variation in output power, respectively, and a 25-W peak output power., Massachusetts Institute of Technology. Center for Integrated Circuits and Systems, MIT Energy Initiative, Skolkovo Institute of Science and Technology, Warsaw University of Science and Technology (Poland). Center for Advanced Studies

Plasma generation systems represent a particularly challenging load for radio-frequency power amplifiers owing to the combination of high operating frequency (e.g., 13.56 MHz) and highly variable load parameters. We introduce a dynamic matching system for Inductively Coupled Plasma (ICP) generation that losslessly maintains near-constant driving point impedance (minimal reflected power) across the entire plasma operating range. This new system utilizes a Resistance Compression Network (RCN), an impedance transformation stage, and a specially-configured set of plasma drive coils to achieve rapid adjustment to plasma load variations. As compared to conventional matching techniques for plasma systems, the proposed approach has the benefit of relatively low cost and fast response, and does not require any moving components. We describe suitable coil geometries for the proposed system, and treat the design of the RCN and matching stages, including design options and tradeoffs. A prototype system is implemented and its operation is demonstrated with low pressure ICP discharges with O 2 , C 4 F 8 , and SF 6 gases at 13.56 MHz and over the entire plasma operating range of up to 250 W.

Analytical solutions to the (3 + 1)-dimensional Gross-Pitaevskii equation in the presence of chirp and for different diffraction and potential functions are found. We utilize a method we formulated to solve the Riccati equation for the chirp function that arises when the F-expansion technique and the homogeneous balance principle are applied to the Gross-Pitaevskii equation. Three specific examples of physical interest are considered in some detail.

We determine analytical extended traveling-wave and spatiotemporal solitary solutions to the generalized (3$+$1)-dimensional Gross-Pitaevskii equation with time-dependent coefficients, for the sinusoidally time-varying diffraction and quadratic potential strength. A number of periodic and localized solutions are obtained whose intensity does not decrease in time in the absence of externally induced gain or loss. Stability analysis of our solitary solutions is carried out, to display their modulational stability.

Chronic stress is a leading risk factor for heart diseases, diabetes, asthma and depression. However, physicians find it difficult to continuously track a person's stress levels throughout the day, as current techniques of electrocardiogram and blood pressure monitoring are not practical. There is thus a critical need for a non-invasive, ambulatory device to track physiological stress over extended periods of time. Such information would allow physicians to assess precisely the affect of stress and determine the most appropriate interventions. The primary objective of this study was to investigate the relationship between non-invasive, physiological signal parameters and the stress level as perceived by the subject. The mapping of physiological parameters onto stress levels to accurately monitor the stress levels in a subject under various conditions will assist the diagnosis of subjects at risk of various stress related disorders. An ambulatory, wireless device was developed with respiratory rate, galvanic skin response and heart rate sensors, which the subjects can wear comfortably while performing their everyday tasks. An experiment involving 13 activities with different stress levels was conducted on 22 subjects during which physiological data was collected using the developed device. While participating in the experiment, subjects had to record the stress level of each activity on a scale of 1 and 7. The data collected was processed in MATLAB, appropriate signal parameters extracted and then correlated with the subject's perceived stress levels. Analysis of the data showed that the stress levels varied as the subjects progressed into different activities due to their varying current mental states. The perceived nature of stress varied considerably amongst the individuals with certain activities able to induce a stronger variation in stress compared to others. The derived features were shown to be effective in tracking the variation in stress induced in the subjects. Results of the experiment showed that the developed device was effective in recording non-invasive physiological for use in tracking the stress levels and mental state of the subjects. Further work is being done to develop an effective model that accurately predicts stress levels based on the physiological data collected.