Inverse class-E Power Amplifier Research Articles

An Inverse Class-E Power Amplifier for Ultrasound Transducer

An inverse Class-E power amplifier was designed for an ultrasound transducer. The proposed inverse Class-E power amplifier can be useful because of the low series inductance values used in the output matching network that helps to reduce signal distortions. Therefore, a newly designed Class-E power amplifier can obtain a proper echo signal quality. The measured output voltage, voltage gain, voltage gain difference, and power efficiency were 50.1 V, 22.871 dB, 0.932 dB, and 55.342%, respectively. This low voltage difference and relatively high efficiency could verify the capability of the ultrasound transducer. The pulse-echo response experiment using an ultrasound transducer was performed to verify the capability of the proposed inverse Class-E power amplifier. The obtained echo signal amplitude and pulse width were 6.01 mVp-p and 0.81 μs, respectively. The -6 dB bandwidth and center frequencies of the echo signal were 27.25 and 9.82 MHz, respectively. Consequently, the designed Class-E power amplifier did not significantly alter the performance of the center frequency of the ultrasound transducer; therefore, it could be employed particularly in certain ultrasound applications that require high linearity and reasonable power efficiency.

Outside Nominal Operation Analysis and Design Considerations of Inverse-Class-E Power Amplifier

In this paper, design and analysis using analytical expressions for the inverse class-E power amplifier (PA) operating at the outside nominal operation, i.e., class- $\text{E}_{\mathrm{n}}$ PA, is presented. This operation is defined as nonzero current switch (n-ZCS) and nonzero-derivative-current switch (n-ZDCS) conditions. The generalized design equations as a function of design specifications, load resistance, and a given dc-supply voltage are derived. Two degrees of the design freedom achieved thanks to n-ZCS and n-ZDCS that are utilized for the simultaneous satisfaction of design specifications, such as peak-switch-voltage and peak-switch-current along with a given load resistance. The output power capability is affected by n-ZCS and n-ZDCS conditions, which can be obtained in the desired value using the controlled adjustment of introduced deviation parameters. In order to prove the validity of the proposed design methodology, an inverse class-E PA operating in 2 GHz with output power of 23 dBm is implemented in 0.25- $\mu \text{m}$ AlGaAs–InGaAs pHEMT technology. There is a close agreement between the theoretical and simulation results and the measurements of the fabricated prototype PA, which proved the validity of the obtained design expressions.

Derivation of Closed-Form Design Equations for Idealized Operation of Inverse Class-E Power Amplifiers at Any Duty Ratio

Abstract Complementary to the conventional class-E topology, inverse class-E operation has several advantages over the class-E counterpart, such as lower peak switch voltage and smaller circuit inductance, which are attractive to high power RF design and MMIC implementation. This paper derives the closed-form design equations that can be used to synthesize the idealized operation of inverse class-E power amplifiers at any switch duty ratio. Calculation of the key design parameters, such as the maximum switch voltage and circuit components values, is elaborated and compared with the case of conventional class-E operation. Further, the theoretical analysis is confirmed and verified by numerical simulations performed on a 500 mW, 2.4 GHz idealized inverse class-E power amplifier.

Investigation of Inverse Class-E Power Amplifier at Sub-Nominal Condition for Any Duty Ratio

The performance of the inverse class-E power amplifier at sub-nominal condition for any duty ratio is investigated in this paper. Comparing with the inverse class-E power amplifier at nominal condition, which demands both zero-current-switching (ZCS) and zero-current-derivative-switching (ZCDS) conditions simultaneously, the presented inverse class-E power amplifier at sub-nominal condition is only restricted by the ZCS condition. The proposed power amplifier increases two design parameters because the ZCDS condition limitation is cancelled and the duty ratio can be arbitrarily set. The analytical results demonstrate that the theoretical drain efficiency is still 100% and that all the circuit elements can be adjusted by the two released parameters. Furthermore, the influences of the transistor's parasitic switch-on resistor and output capacitor are investigated and a simulation example is given to verify the proposed design methodology's accuracy. Although it is not sufficiently tolerant of the elements mismatches and the transistor's parasitic capacitor in practical design, the inverse class-E power amplifier at sub-nominal condition is still one of the promising candidates for high-efficiency power amplifier design if the two drawbacks are appropriately averted.

Analysis of Inverse Class-E Power Amplifier at Subnominal Condition With 50% Duty Ratio

In this brief, the performance of the inverse class-E power amplifier at subnominal condition with 50% duty ratio is studied. The inverse class-E power amplifier at subnominal condition means that it only requires the zero-current switching condition. Since the zero-current derivative switching condition is no longer demanded, the inverse class-E power amplifier at subnominal condition releases an extra design freedom. The theoretical drain efficiency of the inverse class-E power amplifier at subnominal condition is still 100%, and all the circuit element values can be adjusted by the new released parameter. Furthermore, the effect of the switch-on resistor on the practical drain efficiency and the effect of the parasitic inductor on the amplifier maximum operational frequency are investigated.

High-efficiency inverse class-E power amplifier with envelope tracking technique

This letter describes a highly efficient inverse class-E power amplifier (PA) with an envelope tracking (ET) technique.To enhance efficiency performances, the PA uses a harmonic control network with double composite right/left-handed transmission lines. The use of the ET technique also results in high efficiency for the modulated signals. For verifications, the inverse class-E PA is implemented with a 35-W GaN HEMT and tested using 3.5 GHz continuous wave (CW) and 802.16e WiMAX signals. With the CW signal, a peak drain efficiency of 79.0% with a power gain of 9.8 dB is achieved at a saturation output power of 45.6 dBm. With WiMAX signals, a drain efficiency of 37.8% with a power-added efficiency (PAE) of 33.6% is achieved at an average output power of 36 dBm, which is the 9.6 dB back-off power region, using the ET technique. After the DPD technique, the linearity significantly improved without decreasing efficiency. © 2012 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:866–869, 2013; View this article online at wileyonlinelibrary.com. DOI: 10.1002/mop.27420

A High-Efficiency GaN-Based Power Amplifier Employing Inverse Class-E Topology

A high efficiency, GaN based power amplifier (PA) employing the inverse class-E topology is reported. The parasitic inductance and large output capacitance of the packaged active device are used as the series inductance and compensated by a shunt inductor, respectively. The composite right/left-handed transmission line is used as a harmonic control network. For the experimental validation, an inverse class-E PA is designed using a GaN HEMT and tested with a continuous wave at 1 GHz. From the measured results, the drain efficiency and power-added efficiency (PAE) of 79.7% and 78.8% with a gain of 19.03 dB is achieved at an output power of 41.03 dBm. Also, the inverse class-E PA can deliver the output power and PAE of over 40.8 dBm and 65% through the bandwidth of 100 MHz.

The Effects of Limited Drain Current and On Resistance on the Performance of an LDMOS Inverse Class-E Power Amplifier

In this paper, the effects of limited drain current and transistor's on resistance on the performance of an LDMOS inverse class-E power amplifier (PA) are analyzed using a simplified transistor model of piecewise linear dc I-V curves. The minimal magnitude of driving signal, the maximal voltage gain, and the maximal output power of an inverse class-E PA can be defined with the maximal drain kept. The theoretical and simulated results of amplifier performance, such as drain efficiency and output voltage, are compared to verify the analysis, and the nonlinear relation among the drain dc supply voltage, input/output voltage, and phase of an inverse class-E PA caused by limited drain current are presented. The effects on the amplifier performance are further verified by the measured results of a 945-MHz transmission-line inverse class-E amplifier in comparison with the corresponding theoretical and simulated results.

Digital Baseband Predistortion Based Linearized Broadband Inverse Class-E Power Amplifier

A newly introduced inverse class-E power amplifier (PA) was designed, simulated, fabricated, and characterized. The PA operated at 2.26 GHz and delivered 20.4-dBm output power with peak drain efficiency (DE) of 65% and power gain of 12 dB. Broadband performance was achieved across a 300-MHz bandwidth with DE of better than 50% and 1-dB output-power flatness. The concept of enhanced injection predistortion with a capability to selectively suppress unwanted sub-frequency components and hence suitable for memory effects minimization is described coupled with a new technique that facilitates an accurate measurement of the phase of the third-order intermodulation (IM3) products. A robust iterative computational algorithm proposed in this paper dispenses with the need for manual tuning of amplitude and phase of the IM3 injected signals as commonly employed in the previous publications. The constructed inverse class-E PA was subjected to a nonconstant envelope 16 quadrature amplitude modulation signal and was linearized using combined lookup table (LUT) and enhanced injection technique from which superior properties from each technique can be simultaneously adopted. The proposed method resulted in 0.7% measured error vector magnitude (in rms) and 34-dB adjacent channel leakage power ratio improvement, which was 10 dB better than that achieved using the LUT predistortion alone.

Inverse Class-E Amplifier With Transmission-Line Harmonic Suppression

This paper reports on the design methodology and experimental characterization of the inverse class-E power amplifier. A demonstration amplifier with excellent second and third harmonic-suppression levels has been designed, constructed, and measured. The circuit fabricated using a 1.2-mm gate-width GaAs MESFET is shown to be able to deliver 22-dBm output power at 2.3 GHz. The amplifier achieve a peak power-added efficiency of 64% and drain efficiency of 69%, and exhibits 11.6 dB power gain when operated from a 3-V supply voltage. Comparisons of simulated and measured results are given with good agreement between them being obtained. Experimental results are presented for the amplifier's response to Gaussian minimum shift keying modulation, where a peak error vector modulation value of 0.6% is measured.