Alexander S. Jurkov

Design of Single-Switch Inverters for Variable Resistance/Load Modulation Operation

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 Φ2 inverters for variable-resistance operation. The proposed methodology is demonstrated and experimentally validated at 27.12 MHz in a Class E and Φ2 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.

Lossless multi-way power combining and outphasing for high-frequency resonant inverters

A lossless multi-way power combining and outphasing system has recently been proposed for high-frequency inverters and power amplifiers which offers major performance advantages over traditional approaches. This paper presents a new outphasing control strategy for the proposed system that enables output power control through effective load modulation of the inverters while minimizing loading admittance phase. Moreover, we present 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 combiners characteristics and evaluate the effectiveness of the proposed outphasing law to control output power over a 10:1 range.

Multi-Way Lossless Outphasing System Based on an All-Transmission-Line Combiner

A lossless power-combining network comprising cascaded transmission-line segments in a tree structure is introduced for a multi-way outphasing architecture. This architecture addresses the suboptimal loading conditions in Chireix outphasing transmitters while offering a compact and microwave-friendly implementation compared to previous techniques. In the proposed system, four saturated power amplifiers (PAs) interact through an all-TL power-combining network to produce nearly ideal resistive load modulation of the branch PAs over a 10:1 range of output powers. This work focuses on the operation of the combining network, deriving analytical expressions for input-port admittance characteristics and an outphasing control strategy to modulate output power while minimizing reactive loading of the saturated branch amplifiers. A methodology for combiner design is given, along with a combiner design example for compact layout. An experimental four-way outphasing amplifier system operating at 2.14 GHz demonstrates the technique with greater than 60% drain efficiency for an output power range of 6.2 dB. The system demonstrates a W-CDMA modulated signal with a 9.15-dB peak-to-average power ratio with 54.5% average modulated efficiency at 41.1-dBm average output power.

Lossless Multiway Power Combining and Outphasing for High-Frequency Resonant Inverters

A lossless multi-way power combining and outphasing system have recently been proposed for high-frequency 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 study 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 combiners characteristics. The proposed outphasing law is shown to be effective in controlling the output power over a 10-100 W (10:1) power range.

Design and control of lossless multi-way power combining and outphasing systems

A lossless multi-way power combining and outphasing system has been recently proposed which offers major performance advantages over conventional approaches such as Chireix power combining. This paper presents a new outphasing control strategy for the proposed system that enables output power control through effective load modulation of the power amplifiers while minimizing susceptive variations in loading. Moreover, a simple methodology for designing the combiner is introduced.

Transmission-line-based multi-way lossless power combining and outphasing system

This paper presents a non-isolating multi-way outphasing and power combining system that achieves nearly resistive loading of branch amplifiers over the entire output power range through a combiner network comprising only transmission line sections. We derive a design methodology and describe an outphasing control law that selects control angles to minimize the peak susceptive loading of the branch PAs over a specified output power range. The approach is demonstrated in a 2.14-GHz, four-way outphasing amplifier system that achieves >60% drain efficiency over a 6.2-dB output power range.

Dynamic Matching System for Radio-Frequency Plasma Generation

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 O2, C4F8, and SF6 gases at 13.56 MHz and over the entire plasma operating range of up to 250 W.

Tunable impedance matching networks based on phase-switched impedance modulation

The ability to provide accurate, rapid and dynamically-controlled impedance matching offers significant advantages to a wide range of present and emerging radio-frequency (RF) power applications. This work develops a new type of tunable impedance matching networks (TMN) that enables a combination of much faster and more accurate impedance matching than is available with conventional techniques. This implementation is based on a narrow-band technique, termed here phase-switched impedance modulation (PSIM), which entails the switching of passive elements at the RF operating frequency, effectively modulating their impedances. The proposed approach provides absorption of device parasitics and zero-voltage switching (ZVS) of the active devices, and we introduce control techniques that enable ZVS operation to be maintained across operating conditions. A prototype PSIM-based TMN is developed that provides a 50 Ohms match over a load impedance range suitable for inductively-coupled plasma processes. The prototype TMN operates at frequencies centered around 13.56 MHz at input RF power levels of up to 150 W.