| 摘要 |
PROBLEM TO BE SOLVED: To provide an automatic gain controller for an optical wireless transmission system that can respond to a received signal with a wide range of a signal level at high speed with a simple configuration so as to conduct level control with high accuracy and low power consumption. SOLUTION: Open loop high speed control by a high level control circuit Ah compresses and absorbs fluctuation in 20 dB of a high level component of a received signal resulting from applying photoelectric conversion to an optical signal from an opposite terminal by an APD 1, an intermediate level area control circuit Am absorbs the level fluctuation in 20 dB of an intermediate level component under the control of a current amplification factor of the APD 1, a low level control circuit Al absorbs the level fluctuation in 20 dB of a low level component under non oscillation negative feedback control, the level control of the received signal with a wide level range is conducted at high speed and a high response without causing oscillation even in the presence of scintillation with 1 millisecond period, the low level control circuit Al outputs a non distortion signal, a demodulator 17 demodulates it, and the demodulation with high quality can be properly conducted at low power consumption by absorbing the fluctuation in the signal level under a meteorological condition such as rain and mist scintillation or the like. |
