| 摘要 |
PURPOSE:To accurately detect an electric field strength of a received digital modulation input signal whose instantaneous level is fluctuated. CONSTITUTION:The detection circuit is provided with a logarithmic amplifier 1 receiving a digital modulation wave 101 such as a pi/4 shift QPSK modulation wave whose instantaneous level is fluctuated and outputting a DC voltage 102 corresponding to its electric field strength, an A/D converter 2 receiving the DC voltage 102 and converting it into a digital value 103, and an averaging circuit 3 receiving plural digital values 103 and outputting the averaging result, and even when a band limit characteristic of a receiver is in dispersion resulting in causing fluctuation of a level corresponding to a symbol point, an electric field strength close to a substantial electric field strength at the symbol point is obtained through the averaging processing. |
