| 摘要 |
PURPOSE:To perform loop-back transmission by fixing the gain of an opposite station reception part by transmitting and receiving a specific patten, varying the level of a carrier signal, and detecting that on the opposite station side. CONSTITUTION:For the loop-back transmission of the transmission system in the figure, a specific pattern from a pattern generator 7 is inputted to a modulator 3 through a DA converter 1 and an LPF2. The modulator 3 modulates said pattern by a carrier from a carrier generator 4 and transmits the modulated pattern to an opposite station through a filter 6. At the reception part of the opposite station, when said pattern is detected through a filter 11, a variable gain amplifier 12, a demodulator 13, a filter 14, an equalizer 15, an AD converter 16, and a pattern detector 18, the gain of the amplifier 12 is fixed. The transmitting station varies the level of the succeeding carrier signal of the carrier generator 4, and the receiving station when detecting variation in carrier level by a detector 17A loops the digital signal output back to the transmission part of the station. |
