| 摘要 |
PURPOSE:To decide even a rear cycle and to perform three-cycle detection of a fast loran C signal of fine electric field intensity by finding the polarity of synchronous sum data on the peak value of the received loran C signal, the number of data in use, and the degree of saturation of data. CONSTITUTION:The loran C signal received by an antenna 1 is supplied to a zero-cross comparator 3 through an amplifier 2 and a band-pass filter 9, digitized, and supplied to a sampling circuit 4. The three-cycle detection of the loran C signal is carried out by respective circuits such as the circuit 4, an arithmetic circuit 5, a memory 6, and a timing pulse generating circuit 7. Namely, the peak value of the loran C signal is summed up synchronously to find the polarity of sum data, the number of data in use, and the degree of saturation of data, and a cycle decision is made unequivocally according to data at the time of a combination having a relatively large S/N. When the S/N is relatively small, a specific reference envelope is compared with the envelope of the loran C signal by deciding the threshold value of a residual square-law sum value by a method of least squares.
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