Abstract: A feedforward amplifier combines an input signal combined by a first error rejection loop with an error component and a first pilot signal detected by a second error detection loop, thereby canceling out the error component and the first pilot signal residual in the input signal.

Abstract: A feedforward amplifier combines an input signal delayed by a delay circuit with an output signal by a combiner; down-converts the output of the combiner to a low frequency by a frequency converter; extracts a distortion component from the output of the frequency converter; measures the distortion component by a power detector; and controls a second vector regulator of a distortion canceling loop by a controller such that the distortion component measured becomes minimum.

Abstract: Pieces of transmission data of channels are multiplexed with each other in a multiplexing unit to produce a base band signal, and the base band signal is orthogonally modulated in an orthogonal modulating unit to produce a transmission signal. The transmission signal is orthogonally demodulated in an orthogonal demodulating unit, the base band signal produced in the multiplexing unit is compared in a comparing unit (or a comparing and correcting unit) with the demodulated base band signal, and the base band signal is corrected in a vector adjusting unit (or the comparing and correcting unit) according to a compared result. Therefore, an electric power of the transmission signal can be precisely corrected without using an electric power table fitted to an electric power ratio of the pieces of transmission data, and the interference between channels can be prevented.

Abstract: A feedforward amplifier combines an input signal combined by a first error rejection loop with an error component and a first pilot signal detected by a second error detection loop, thereby canceling out the error component and the first pilot signal residual in the input signal.

Abstract: A feedforward amplifier combines an input signal delayed by a delay circuit with an output signal by a combiner; down-converts the output of the combiner to a low frequency by a frequency converter; extracts a distortion component from the output of-the frequency converter; measures the distortion component by a power detector; and controls a second vector regulator of a distortion canceling loop by a controller such that the distortion component measured becomes minimum.

Abstract: A feedforward amplifier which includes a distortion detector, a distortion eliminator, an error power extractor, a first level detector and a first controller. The error power extractor extracts output error power due to variations in the distortion eliminator by combining the output signal from the distortion eliminator with the signal from a first linear signal path in the distortion detector in opposite phases. The first level detector detects the output error power extracted by the error power extractor, and the first controller controls a first variable attenuator and a first phase shifter which are interposed in the distortion eliminator such that the output error power is maintained at zero.

Abstract: A transmission power control circuit for controlling a power level of a transmission signal is provided which comprises a variable attenuator (2) for adjusting the amplitude level of an input signal, a detection circuit for detecting an amplitude of the transmission signal via a branch circuit (5), a reference voltage source (7) for generating a reference voltage associated to a predetermined level of the transmission signal to be transmitted, a comparator (11) for comparing the reference and detection voltages, a clock generator (13), an up/down counter (12) for up or down counting pluses of a clock output from the clock generator, a D/A converter (14) for converting the count value of the counter, and a control circuit (10).