Mitsubishi Denki Kabushiki Kaisha

Haruyasu Senda

Yukio Ikeda

Masatoshi Nakayama

Kenichi Horiguchi

Yuji Sakai

Tadashi Takagi

Satoshi Kunugi

Junichi Nagano

Kazuyuki Totani

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.

Feedforward amplifier

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.

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.

CDMA type multiple transmission apparatus and CDMA type multiple transmission method

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. This can solve a problem of a conventional feedforward amplifier in that the power level of the pilot signal must be increased to heighten the detection sensitivity of the pilot signal because the detection level of the pilot signal becomes minimum at an optimum operation point, and that the increasing power of the pilot signal degrades the communication quality of a system employing the conventional feedforward amplifier.

Feedforward amplifier with improved characteristics without using pilot

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). The comparator subjects the counter to the up or down counting operation when the detection voltage is less or larger than the reference voltage to provide an attenuation control signal to the alternator through the D/A convertor so that attenuation level is adjusted, whereby the detection voltage substantially coincides with the reference voltage. The control circuit controls the reference voltage source to vary the level of said reference voltage in accordance with the transmission signal and controls the clock generator to generate the clock having a high frequency during a transition period of the reference voltage and a low frequency during the reference voltage being kept substantially constant, whereby change of the transmission power level can be executed at a relatively high speed without interference for the adjacent channels.

Growing community of inventors

Tokyo, Japan

Haruyasu Senda