Patent ID: 6835925
Filing Date: 2004-12-28
Classification: B82Y,G01Q,Y10S

Abstract:
A signal detector comprising:a first frequency changing circuit adapted to receive an electric signal having a frequency modulated from a first reference of frequency f1 with a modulation width &Dgr;f as input, to convert the received electric signal to an electric signal having a second reference frequency f2 lower than the first reference frequency f1, and to output the converted electric signal; a first frequency/voltage conversion circuit adapted to receive the output of said first frequency changing circuit as input and output an electric signal having frequency modulated from a reference frequency Nf2 with a modulation width of N&Dgr;f (N: integer), a second frequency changing circuit adapted to receive said output of the first frequency/voltage conversion circuit as input, to convert the received electric signal to an electric signal having the reference frequency f2 without changing the modulation width, and to output the converted electric signal; and a second frequency/voltage conversion circuit adapted to receive the output of said second frequency changing circuit as input and output a voltage signal corresponding to the ratio of the modulation width N&Dgr;f to the reference frequency f2, or N&Dgr;f/f2.