To realize a time division multiple access transmitter-receiver that ensures high-speed convergence of a demodulator input level in the inside of a demodulator and low noise performance and stability of a receiver even under a tight external propagation environment where a received electric field is changed at a high-speed over a wide dynamic range.

An RF switch 12 is connected to a reception section 2 in reception timing, an RF signal received by an antenna 11 is given to an amplifier section 5 via an isolator 3 and an RF filter 4, where the signal is subjected to automatic gain amplification and the resulting signal is fed to a demodulator section 6. An RSSI 61 detects a reception signal level and when the level exceeds a threshold value, a demodulator 62 switches the RF switch to a position of a transmission section 7 having no transmission output to provide a high attenuation to the input to the reception section so as to realize an automatic gain control function of an amplifier section with a simple circuit configuration. The isolator maintains matching of the input impedance of the amplifier section independently of the switching state of a changeover switch to ensure low noise performance and stability.