SPECTRUM ARITHMETIC DEVICE

PURPOSE:To determine a spectrum with a high SN ratio by providing a band pass filter for passing a signal containing noise, and a transmission function arithmetic means for determining a transmission function. CONSTITUTION:A signal x (t) into which a noise n (t) is mixed with a signal x0 (t) is inputted to first and second band pass filters 10, 12, and first and second band limit signals x1 (t), xb (t) are outputted. In first and second square arithmetic means 14, 16, first power signal za (t) showing the square ¦x1 (t)¦ of the band limit signal xa (t) and a second power signal zb (t) showing the square lxb (t)¦ of the band limit signal xb (t) are determined. In first and second spectrum arithmetic means 18, 20, the spectrum Za (k) of the inputted first power signal za (t) and the spectrum Zb (k) of the second power signal zb (t) are determined. In a transmission function arithmetic means 22, the transmission function Hab(k) from the frequency ka component to the frequency kb of the signal x(t) is determined according to the equation by use of the inputted spectra Za (k), Zb (k). In the equation, E[...] represents an aggregation average, and *represents a conjugated complex number.