Patent ID: 6501410
Filing Date: 2002-12-31
Classification: G01R

Abstract:
A signal analyzing apparatus comprising:an analog/digital (A/D) converter for converting a to-be-measured analog signal to digital data while being sampled with a predetermined sampling frequency; a data sorting circuit for sorting the digital data which is outputted from the A/D converter alternately into two signal paths and outputting two digital data each having a Â½ rate of the sampling frequency in parallel form; a first frequency shift circuit for multiplying the two digital data which are outputted in parallel form from the data sorting circuit by a first local signal whose local frequency is set to Â¼ of the sampling frequency to shift a band center frequency of the digital data signal by Â¼ of the sampling frequency toward a lowband side and generating corresponding two quadrature signals; two Â½ decimating circuits for receiving the two quadrature signals outputted from the first frequency shift circuit, performing band limitation processing with Â¼ of the sampling frequency as an upper limit and generating two quadrature signals whose rates are reduced to Â½ relative to input signals; a second frequency shift circuit for multiplying the two quadrature signals which are outputted from the two Â½ decimating circuit by a second local signal of a pre-set local frequency to shift the band center frequency to a lowband side and outputting corresponding two quadrature signals with the band center frequency set to zero; a controller for setting the second local frequency so as to obtain baseband components of the to-be-measured analog signal as outputs from the second frequency shift circuit; and calculating means for calculating characteristic values of the to-be-measured analog signal by performing calculation processing on the baseband components on the basis from the outputs from the second frequency shift circuit.