| 摘要 |
PURPOSE:To remove noise components in the measurement by allowing the output of a correlation detecting means to be zero theoretically when the reflection is zero at a measuring point in the computation of a correlation based on reflection signals of a simulated noise system received after it is transmitted to an object to be measured. CONSTITUTION:A simulated noise generator 13 generates a simulated noise system containing 0 and 1 at random. When this system is delayed by a timer to obtain a self-correlation, the correlation is 1 at an interval of Mt with the cycle set at M and otherwise 1/2. So, a simulated noise system exclusive ORed with a clock with a cycle of 2t is given a delayed time D with a variable delay circuit 17 and inverted with an exclusive OR circuit 18 at an interval of 1/f0. The output of the circuit 18 is inputted into a switch 16 with an output b and taken out alternately therewith. When those thus obtained are transmitted to an object to be measured, a variation in the correlation of (M 1)/2M develops at a point + or -(D+t/2) at an interval equal to odd multiplication of Mt and, at the points other than the above, the output becomes zero thereby improving the signal noise ratio. |
