| 摘要 |
<p>An RF power amplifier for mobile telecommunications including an unequal power divider (4) coupled between an RF power amplifier input (2) and inputs of first, second and third amplifying paths (12,14, 16), the outputs of the amplifying paths being coupled through an impedance network (24) to an RF power amplifier output (28), each amplifying path having respectively different first, second and third power output levels, for example in the ratio 1: 0.25: 0.1, and switching means for selectively switching said amplifying paths, so that in operation, one of the amplifying paths is operative at any one time, and the others are inoperative. The amplifying paths include transistor power amplifiers (20), with a bias switching arrangement (64) for switching off the transistor and associated amplifying path. The impedance network includes phase offset transmission line lengths (26, 30, 32) coupled to the outputs of the transistor amplifiers for phase adjustment, and a chain of transmission line stubs (34, 36, 38) for coupling the outputs to ground via an open circuit impedance, for stability.</p> |
