1. A signal acquisition apparatus for reducing a false alarm rate, comprising: a matched filter which calculates a correlation value of a received signal; an absolute value calculator which calculates an absolute value from an output value of the matched filter and outputs a magnitude of the correlation value; a received power estimator which measures a power of the received signal; a scale factor selector which selects a first scale factor to be applied to a first threshold in a first peak detection of the received signal, and selects a second scale factor which is different from the first scale factor, to be applied to a second threshold in a second peak detection after the first peak detection; a multiplier which multiplies an output value of the received power estimator by a scale factor selected by the scale factor selector; a comparator which compares an output value of the absolute value calculator with an output value of the multiplier; and a peak counter which counts in a sample interval a number of second peaks of which output value from the absolute value calculator exceeds the second threshold according to a comparison result of the comparator.