Method and apparatus for zero-mixing spectrum analysis with Hilbert transform

摘要

An apparatus (1) for analyzing a spectrum of an input signal ( x ( t )) having at least one line with a center frequency (É x ) at the center of the line comprises: a mixer (2) for zero-mixing the input signal ( x ( t )) to produce a base band signal ( z ( t )) by sweeping a local oscillator frequency (É s ) generated by a local oscillator (3), a resolution filter (4) for filtering the base band signal ( z ( t )) to produce a filtered base band signal ( y ( t )) and envelope reconstruction means (27) for reconstructing the envelope ( E (É)) of the spectrum of the input signal ( x ( t )) by using an estimated amplitude ( y x ) at an estimated center frequency (É x ) of each line of the input signal ( x ( t )).
Only the reel component (I) of the base band signal ( z ( t )) is filtered with the resolution filter (4) and the imaginary component (Q) is generated from the filtered base band signal ( y ( t ) by performing a Hilbert transform in a Hilbert filter (21) arranged downstream of the resolution filter (4).