High-Efficiency Amplifiers with Discretely Variable Output Power

"The proposal is focused on development of microwave power amplifier techniques to reduce the power consumption of phased array radiating elements. Elements are spaced by l/2 at the center frequency of the array. At L/S-band frequencies this correspondsto 200mm and only 4mm at 40 GHz. The output power of the transmitter ranges from few tenths of watts at millimeter wave frequencies to tens of watts in L/S-band frequencies, and power consumption in amplifiers becomes a practical limit to the outputcapabilities of the transmitter. To minimize the prime power consumption, the power-added efficiency (PAE) of the amplifier must be maximized. While the amplifier PAE is normally at its maximum at saturation, many of the elements in an array are notalways operated at maximum power output. To maintain the maximum efficiency of the amplifier at all operating power levels, it is necessary to develop circuit techniques for adaptive and/or programmed control of amplifier efficiency at all power levels.Those circuit techniques include a method of adjusting the bias level proportionately with the operating power and a method of power output compensation using an auxiliary amplifier. This proposal addresses the need to develop MMIC based amplifier designapproaches for efficiency enhancement of power amplifiers over a wide dynamic range. The Phase 1 effort will be focused on development of specific circuits for application in selected radar app