| 摘要 |
<p>The present invention, generally speaking, provides a highly efficient RF power amplifier having a large output dynamic range. The amplifier avoid the large power dissipation that occurs in the LINC combiner at lower output levels. In general, this is achieved by using power-controlled switch-mode power amplifiers to vary output power at large power outputs, and reverting to LINC only at low output powers. Thus the present invention achieves the desirable combination of high efficiency at all output powers, while maintaining the fine output power control of the LINC method. More particularly, the power amplifier is based on a highly efficient structure in which amplitude modulation/power control of the out-put of an RF amplifier is achieved by operating the amplifier in switch mode an varying the power supply of the amplifier, as described more fully in U.S. Patent application 09/637,269 entitled High-Efficiency Modulating RF Amplifier, filed August 10, 2000 and incorporated herein by reference. Such an amplifier behaves quite linearly at high power but may exhibit non-linearity at lower output powers. Good linearity throughout a wide dynamic range, and particularly at low output power, may be achieved by phasing and combining the outputs of two (or more) such amplifiers. At high and medium power, the outputs are combined in-phase, allowing for low-loss, high-efficiency operation. At low power, the outputs are phased such that power subtraction occurs. In this manner, each amplifier may be operated at a power level that exhibits good linearity while producing an output signal of a lower level that would normally fall within a region of substantial non-linearity.</p> |
