| 摘要 |
PCT No. PCT/EP90/01889 Sec. 371 Date Jun. 19, 1991 Sec. 102(e) Date Jun. 19, 1991 PCT Filed Nov. 12, 1990 PCT Pub. No. WO91/07817 PCT Pub. Date May 30, 1991.A r.f. wideband high power amplifier (1) receives an input signal at its input via a coupler (7) whenever a signal for amplification is applied to an input port (15). The output of the amplifier (1) is tapped by a coupler (8) and fed to an input of a comparator (3). The input signal applied at the input port (15) is fed to a second input of the comparator (3) via a delay line (5), arranged to introduce a delay substantially equal to that of the power amplifier (1). The comparator (3) produces at its output an error signal representative of the difference between the input signal fed via the amplified and the delayed path. A combiner (16) serves to introduce the amplified error signal to the amplifier output signal such that the error signal is in anti-phase therewith. Thus, the resultant signal produced at an output port (4) has had feed forward distortion cancellation. In accordance with the present invention the arrangement further includes an amplitude compensating network (8) in the form of a PIN-diode attenuator, controlled by a signal from a comparator (14). The comparator (14) provides a control signal to the attenuator (8) in accordance with the respective levels of signal from a first detector (17) and a second detector (18). The feedback control loops are arranged to function with a fast response time with respect to the period of the highest frequency of the input signal.
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