| 摘要 |
PURPOSE:To attain normal reception and transmission even if a frequency of a noise signal is overlapped on a frequency of a carrier signal by applying frequency modulation linearly to a carrier pulse to transmit a transmission code, retarding each frequency component of the carrier pulse at the reception side and compressing and synthesizing the component on a time axis to decode the transmitted code. CONSTITUTION:A transmission wave forming circuit 33 uses a code C as a modulation signal and applies pulse modulation to a carrier signal Sc given from a carrier signal generating circuit 34 as a pulse train. Each pulse Pc of the carrier signal Sc is a sinusoidal wave SW whose frequency is changed linearly between pulse width W as shown in a figure. Then a signal received by a photodiode 41 is given to a matched filter 44 via a preamplifier 42 and a limiter 43. Each frequency component in each carrier pulse Pc is delayed by a different delay time and compressed and synthesized on time axis. The compressed output is converted into a pulse by a Schmitt trigger circuit 45 and given to a tuning circuit 45 of the center frequency fc. |
