TRANSMITTER AND DATA TRANSMISSION METHOD

摘要

PROBLEM TO BE SOLVED: To provide a transmitter-receiver where no AGC circuit of a voice wireless unit is malfunctioned and no error is caused in transmission information even when data are transmitted by the modulation system including amplitude modulation through the use of the voice wireless unit and to provide a transmission system employing the transmitter-receiver. SOLUTION: A level detector 7 detects a level of an output SB of a modulation circuit 1 and an LPF 8 extracts its low frequency component. Then a level inverting circuit 9 inverts its level. This signal SG is used to apply amplitude modulation to a carrier C from a carrier circuit 10 to generate a modulation wave SC whose frequency band is not overlapped with that of the modulation wave SB and whose amplitude is in proportion to an amplitude change of the modulation wave SB. The modulation wave SB to which the modulation wave SC is added is transmitted. A filter 11 eliminates the modulation wave SC from an output of a receiver 3 and the resulting signal is demodulated.