Part of a first signal path (100) for amplifying a signal includes circuits (33b, 34b) for detecting a signal, and a second signal path (200) connected to an input portion of the first signal path includes circuits (61b, 62b) for detecting the signal. A signal strength detector circuit (5) adds outputs from the respective detector circuits in the first and second signal paths. The first signal path has a function of expanding the dynamic range in a smaller signal region as compared with the second signal path, while the second signal path has a function of expanding the dynamic range in a larger signal region as compared with the first signal path. When a radio transmitted output is variably controlled in a radio transmitter section (TX) based on a field strength detection output for a received signal, the transmitted output is optimized, resulting in minimizing consumed power and unnecessary radiation of radio waves.