Abstract-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  2 inverters for variable-resistance operation.The proposed methodology is demonstrated and experimentally validated at 27.12 MHz in a class E and  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.

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Functional neural gastrointestinal electrical stimulation (NGES) is a methodology of gastric electrical stimulation that can be applied as a possible treatment for disorders such as obesity and gastroparesis. NGES is capable of generating strong lumen-occluding local contractions that can produce retrograde or antegrade movement of gastric content. A feedback-controlled implantable NGES system has been designed, implemented and tested both in laboratory conditions and in an acute animal setting. The feedback system, based on gastric tissue impedance change, is aimed at reducing battery energy requirements and managing the phenomenon of gastric tissue accommodation. Acute animal testing was undertaken in four mongrel dogs (2 M, 2 F, weight 25.53 ± 7.3 kg) that underwent subserosal two-channel electrode implantation. Three force transducers sutured serosally along the gastric axis and a wireless signal acquisition system were utilized to record stimulation-generated contractions and tissue impedance variations respectively. Mechanically induced contractions in the stomach were utilized to indirectly generate a tissue impedance change that was detected by the feedback system. Results showed that increasing or decreasing impedance changes were detected by the implantable stimulator and that therapy can be triggered as a result. The implantable feedback system brings NGES one step closer to long term treatment of burdening gastric motility disorders in humans.

Abstract-A lossless multi-way power combining and outphasing system has recently been proposed for highfrequency inverters and power amplifiers that offers major performance advantages over traditional approaches. This paper presents outphasing control strategies for the proposed power combining system that enable output power control through effective load modulation of the inverters. It describes a straightforward power combiner design methodology and enumerates various possible topological combiner implementations. Moreover, this work presents the first-ever experimental demonstration of the proposed outphasing system. The design of a 27.12 MHz, four-way power combining and outphasing system is described and used to experimentally verify the power combiner's characteristics. The proposed outphasing law is shown to be effective in controlling the output power over a 10 W to 100 W (10:1) power range.Index Terms-Outphasing, phase-shift control, LINC, power combining, Chireix combiner, RF power amplifier (RF PA).

Neural gastric electrical stimulation (NGES) is a new method for invoking gastric contractions under microprocessor control. However, optimization of this technique using feedback mechanisms to minimize power consumption and maximize effectiveness has been lacking. The present pilot study proposes a prototype feedback-controlled neural gastric electric stimulator for the treatment of obesity. Both force-based and inter-electrode impedance-based feedback neurostimulators were implemented and tested. Four mongrel dogs (2 M, 2 F, weight 14.9 +/- 2.3 kg) underwent subserosal implantation of two-channel, 1 cm, bipolar electrode leads and two force transducers in the distal antrum. Two of the dogs were stimulated with a force feedback system utilizing the force transducers, and the other two animals were stimulated utilizing an inter-electrode impedance-based feedback system utilizing the proximal electrode leads. Both feedback systems were able to recognize erythromycin-driven contractions of the stomach and were capable of overriding them with NGES-invoked retrograde contractions which exceeded the magnitudes of the erythromycin-driven contractions by an average of 100.6 +/- 33.5% in all animals. The NGES-invoked contractions blocked the erythromycin-driven contractions past the proximal electrode pair and induced temporary gastroparesis in the vicinity of the distal force transducer despite the continuing erythromycin infusion. The amplitudes of the erythromycin-invoked contractions in the vicinity of the proximal force transducer decreased abruptly by an average of 47.9 +/- 6.3% in all four dogs after triggering-invoked retrograde contractions, regardless of the specific feedback-controlled mechanism. The proposed technique could be helpful for retaining food longer in the stomach, thus inducing early satiety and diminishing food intake.