Abstract: A radio transmitter apparatus performing an ALC operation by selecting either of a high power mode and a low power mode and capable of further increasing a level difference of transmission power levels in the modes while supplying a stable detection voltage to an ALC circuit without destruction of a detection diode, including a transmission power generating stage, a detection unit, an ALC circuit performing automatic level control, and an ATPC unit performing automatic power control for operation in either of the high power mode or the low power mode, the detection unit configured by a first detection unit which becomes effective in the low power mode and a second detection unit which becomes effective in the high power mode.

Abstract: Simple and low-cost linearizing circuit for compensating for amplitude and phase distortion produced in a power amplification stage of a radio transmitter apparatus that is required to have a high linearity. Amplitude distortion compensation means, disposed in an intermediate frequency amplifier, has a field-effect transistor whose gate bias voltage is set near to its pinchoff voltage and compensates for amplitude distortion produced in a radio frequency amplifier. On the other hand, phase distortion compensation means having a varactor diode and a branch-line hybrid is disposed in the radio frequency amplifier so as to compensate for phase distortion produced in the radio frequency amplifier. The phase distortion compensation means can be disposed in a local frequency oscillation circuit, alternatively.