Yun Zeng

An Extended Topology of Parallel-Circuit Class-E Power Amplifier Using Transmission-Line Compensation

This paper presents a parallel-circuit Class-E amplifier that maintains it operating characteristics even when the output capacitance of the transistor is greater than the optimum shunt capacitance. The finite dc feed inductor in the parallel circuit topology is replaced by a transmission-line compensation circuit to eliminate the limitations on the operating frequency imposed by the output capacitance. Theoretical formulas for the circuit elements of the proposed network are derived in detail, and the analysis is validated by simulation and measurement. The measured maximum output power of 40.1 dBm, drain efficiency of 77.5%, and power-added efficiency of 70.8% were obtained at 2.8 GHz with a 29.4-dBm input power. These measurements show a similar or better level of efficiency and output power that is reported for other amplifiers at lower frequencies using the same transistor.

First-principles study on La-doped ZnO used as transparent electrode for optoelectronic device

A systematic study on electronic and optical properties of wurtzite zinc oxide (ZnO) with different Ladoping concentrations has been performed. The calculations are based on the first principles planewave pseudopotential method with the density functional theory (DFT) and the generalized gradient approximation (GGA). According to the results, the band gap of ZnO is broadened due to the increase of La-doping concentrations. By La-doping, the decrease of absorption coefficient and the blueshift of absorption edge are obtained. In addition, there is a strong interaction between the La atom and the surrounding atoms, because the high electron density overlaps. By Mulliken population analysis, we found out that the metallization effect appears due to the increase of La-doping concentration, which demonstrates that the La-doped ZnO is a potential material as a low absorption coefficient semiconductor material. The simulation and calculation results are in good agreement with the existing experimental data and the study can provide a theoretical basis for future applications of La-doped ZnO as a semi-transparent electrode.

Design of inverse class-E amplifier with finite D.C. feed inductance

This paper reports on a design of inverse class-E amplifier with finite D.C. feed inductance. The finite D.C. feed inductance is resonated by the parallel capacitance at the fundamental frequency. The direct design equations required to determine the optimum operations are derived in detail. Comparing with the classic inverse class-E amplifier, numerical results show that improvements in minimizing size, cost, and complexity of the circuit can be obtained by the inverse class-E topology with finite D.C. feed inductance. Comparing with the sub-harmonic and parallel-circuit class-E amplifiers, the inverse class-E topology with finite D.C. feed offers advantages for MMIC realization. Theoretical analysis is validated by numerical simulation and measurement. Excellent agreement between theory and simulation results is achieved. Comparison between simulations and measurements of an experimental circuit validate the feasibility of the design. A measured output power of 40.01dBm, with a drain efficiency of 80.16% and power-added efficiency of 78.93% were obtained at 250MHz with a 22-dBm input power.

Modeling and Electrical Simulations of Thin-Film Gated SOI Lateral PIN Photodetectors for High Sensitivity and Speed Performances

Thin-film gated SOI lateral PIN (LPIN) photodetectors was proposed, with ITO deposited on topside as transparent gate electrode. This paper investigates performances of the photodetectors versus the P-doping level in the intrinsic region (I-region), with gate voltage applied. We present analytical model and two-dimensional Atlas simulations of the current characteristics, sensitivity and speed performance. At a 400 nm wavelength, the output photocurrent approximately reaches the available photocurrent, the internal quantum efficiencies yield over 90%, even nearly 100% with various dopings. In terms of speed performances, the total -3dB frequencies of the photodetectors are up to a few tens of MHz with the intrinsic length of 8 um. And dark currents as low as 10− 14 A can give a high ratio of more than 107 between illuminated to dark currents under low-voltage operation. With such advantageous electrical characteristics, thin-film gated SOI LPIN photodetectros appear highly suitable for optical storage systems and blue DVD applications.

Analysis and Simulation of Temperature Characteristic of Sensitivity for SOI Lateral PIN Photodiode Gated by Transparent Electrode

This paper performs the structure and principle of SOI Lateral PIN photodiode Gated by Transparent Electrode. The temperature models of photocurrent and dark current are presented and validated by 2D ATLAS simulation. The variation of temperature on sensitivity is addressed when the LPIN PD-GTE is fully depleted. In contrast, the same work is presented on SOI Lateral PIN photo diode. The simulated results indicate the internal quantum efficiency of SOI LPIN PD-GTE remains about (95 %) with illumination of 400 nm wavelength as the temperature rises while the signal-noise-ratio decreases. SNR achieves (10^7) at 300 K and decreases to (10^3) at 473 K. FHWM is almost unchanged varing the temperatures. Thus, the sensitivity decreases when the temperature rises. Still, considering the fact that the operating temperature of the device generally cannot be 473 K or higher, SOI Lateral PD-GTE can be used at high temperature with good sensitivity.

Design of Octave Bandwidth Balanced Power Amplifier in GaN HEMT Technology

In this paper, the design and implementation of a broadband balanced power amplifier using a GaN HEMT transistor are presented. Two Lange couplers are used for a balanced PA configuration, and two multi-section matching networks are used to improve the bandwidth of PA. In order to simplify the matching network, the output impedance is matched to an intermediate impedance. By biasing the amplifier at =28 V, =110 mA, the measurement results show 12-13 dB linear gain and 56%-65% drain efficiency in the 1.5-3.5 GHz frequency range. Moreover, an output power higher than 8 W is maintained over the band. For a 3.1 GHz pulse wave signal with 10% duty cycle and 300µs pulse width, we obtain an output power of 39.4 dBm(8.7 W) and a peak drain efficiency of 60%.

Wide-Band Low-Noise Quadrature VCO Design

A 2.9 GHz quadrature VCO designed in a 0.18 um CMOS process achieves a very wide tuning range of 77% when the supply voltage equals 1.8 V. The phase noise is -120 dB/Hz at 1MHz offset for the oscillation frequency of 2 GHz, and -104 dB/Hz at 1MHz offset for the oscillation frequency of 4 GHz. The coupled oscillator architecture is adopted to widen tuning range and to minimum phase noise. Accurate quadrature outputs are maintained throughout the entire frequency range, as needed in all modern transceiver architectures.