To reduce the dispersion of function due to the difference in transmitting direction of signal for a fixed receiver by a method wherein original signals are modulated to form signals having different frequencies, which signals are oscillated, transmitted and received and received signals are demodulated to have the original signals.
A switch 18 of a key operation part 20 of a remote controller 12 is operated to read corresponding codes and the codes are outputted as code signals from a code generating part 22 to a modulation oscillating circuit 24. Further, fundamental waves and higher harmonics modulated in synchronization with code signals as original signals are oscillated to transmit signals to a fixed receiver 14 through a transmission antenna 26, and the signals, after being received, are passed through first and second RF filters 30, 32, connected in parallel. At that moment, when a receiving antenna 28 receives two kinds of signals, signals, in which fundamental waves are modulated, only are outputted from the filter 30 and signals, in which secondary higher harmonics are modulated, only are outputted from the filter 32. Thus noises such as radio waves can be removed and hence number of parts can be reduced in comparison with a case in which signals are generated from a plurality of fundamental waves.
SHIBAGAKI YUJI
NODA TAKAHISA
