| 摘要 |
PURPOSE:To prevent the deterioration of measuring accuracy caused by temperature change and time aging change, by commonly using a detector for level detection of carrier and noise. CONSTITUTION:A burst signal received at an input terminal 1 is split into two directions at a hybrid 2. One is inputted to a switch circuit 18 via a BPF3 passing only through carrier, and another is inputted to the circuit 18 via a BPF7 passing only through noise. The selection of the circuit 18 for signals depends on the control of an output signal 15 of a logical circuit 14. The output signal of this circuit 18 is detected at a detector 4'. The output of the detector 4' is inputted to a sampling hold circuit 5 for carrier detection voltage pickup and a sampling hold circuit 9 for noise detection voltage pickup. The output of the circuits 5, 9 is smoothed at LPFs 6 and 10 and a divider 11 takes the ratio. Thus, a signal corresponding to signal-to-noise ratio can be obtained at the output of the divider 11. |
