High-efficiency Operating Modes Research Articles

Design Approach for Implementation of Class-J Broadband Power Amplifiers Using Synthesized Band-Pass and Low-Pass Matching Topology

A new synthesis method for the design of broadband impedance matching network has been introduced to match the transistor input. The proposed matching network would be a realistic alternative to those that are frequently designed in low-pass structure. Easy-to-use design equations are given for this filter-based matching network. The required impedance of the stubs and the connecting lines can be directly calculated from the equations. This synthesis method simplifies the implementation of the network in the distributed form as compared with the LC low-pass matching network where equivalences are necessarily required in the rough conversion from lumped-to-distributed elements. The high-efficiency mode of operation is guaranteed by the constructed output low-pass matching network, since the LC low-pass network can provide the prescribed load terminations at fundamental frequencies and at harmonics. A commercially available 10-W GaN HEMT device (CGH40010) was used in this investigation. The proposed broadband power amplifier exhibits band-pass Chebyshev response in S-parameter measurements, and yields good gain flatness (±0.5 dB) and input return loss (>13 dB). Power-added efficiency of 58%-72% has been measured in large-signal measurements. After digital predistortion, the measured adjacent channel leakage power ratio is below -50 dBc at ±5- and ±10-MHz offset, when driven by 5- and 10-MHz WCDMA signals at 7-dB power back off.

Efficient, Linear Amplification of Varying-Envelope Signals Using FET's with Parabolic Transfer Characteristics

A linear, high-efficiency mode of operation is described for FET power amplifiers of varying envelope signals (e.g., single-sideband, quadrature-amplitude-modulation, and multicarrier signals). It makes use of FET's having parabolic transfer characteristics (PTC). It is shown theoretically and experimentally that the efficiency of the PTC mode is about 2 dB higher than that of the standard class-A mode. For example, two-tone, 4-GHz measurements on a Western Electric FET model 131-L showed that, for an output power of about 1.5 W and for a relative third-order intermodulation level of -35 dB, the power-added efficiency of the PTC mode was 20 percent, while that of the class-A mode was 13 percent. Comparisons are also made with other high-efficiency modes of operation proposed elsewhere.

Power-Frequency Characteristics of the TRAPATT Diode Mode of High Efficiency Power Generation in Germanium and Silicon Avalanche Diodes

We calculate in this paper the output power obtainable, versus frequency, for TRAPATT diodes. This high efficiency mode of operation is analyzed by means of a simplified model for both germanium and silicon avalanche diodes. The model evolved from a study of detailed computer simulations of experimental diode-circuit systems. The simplified analysis assumes: (i) The avalanche zone transit, plus the recovery time to the swept-out state, occurs in a half period of the TRAPATT frequency. (ii) The ratio of IMPATT frequency to TRAPATT frequency is 3:1. (iii) The diode area is chosen to provide 10 ohms negative resistance, a reasonable value for microwave circuits. The calculated electrical characteristics agree well with experimental observations. Consideration of circuit and thermal limitations results in a design for maximum power output for a millimeter wave silicon oscillator. Power output in excess of 1 watt CW, with an efficiency of 40 percent, is predicted at a frequency of 50 GHz.