Communication system capable of performing FDMA transmission

摘要

A communication apparatus is disclosed which is capable of measuring levels of carrier signals used in adjacent zones during telecommunication with a small circuit scale, and capable of simultaneously transmitting/receiving to FDMA-system signals through a plurality of communication channels. All of transmission signals received through the communication channels under use are wholly converted into an intermediate signal by a mixer. The intermediate signal is quadrature-detected and then A/D-converted into digital I/Q-channel signals by A/D-converters. Thereafter, the digital I/Q-channel signals are frequency-converted by frequency converting circuits in such a manner that center frequencies of these I/Q-channel signals become zero, two sets of I/Q-channel signals may be demodulated by two sets of demodulating circuits. Otherwise, one of these I/Q-channel signals is demodulated by a single demodulating circuit, and the other is level-detected by a level detecting circuit.