LEVEL CALIBRATION METHOD FOR PROPAGATION DELAY TIME MEASURING INSTRUMENT

摘要

PURPOSE:To obtain a correlation output with a level corresponding to a level of an input signal continuously and to attain stable level calibration with high accuracy by calibrating the level while a code phase of a pseudo noise signal (PN signal) is coincident and a calibration input signal is received in a detuning state with a frequency difference within a range of able to take correlation. CONSTITUTION:A spread modulation wave from a calibrated transmitter 20 or the like is received in advance as an input signal for calibration and the code phase of a PN signal of a propagation delay time measuring instrument 30 is made coincident with that of a PN signal resulting from modulating the calibration input signal. Then the calibration input signal is subject to correlation detection while being detuned by frequency difference within a range from which the correlation output is able to be obtained and the level of the signal in response to the frequency difference outputted at the correlation detection is detected and the level of the input signal to be received at the propagation delay time measurement is calibrated based on the level. Thus, a correlation output with a level corresponding to the level of the input signal is obtained continuously and stable level calibration with high accuracy is implemented.