Patent ID: 7146148

Claim:
A receiver which converts a band to a base band by a local oscillator of a quadrature carrier wave signal to perform demodulation processing, comprising: a broad band limiting section which limits the band with respect to a received signal in a broad band; a first frequency conversion section which converts a frequency of the band-limited received signal into that of a low frequency band at a local oscillation frequency having an offset with respect to a reception frequency; a digital conversion section which converts the frequency-converted received signal to a digital signal at a specific sampling frequency; an image rejection section which subjects the digital signal to image rejection processing; a narrow band limiting section which extracts a narrow band signal of a desired wave from an image-rejected broad band signal; a second frequency conversion section which performs frequency conversion processing to remove the offset from the narrow band signal; a third frequency conversion section which reduces the frequency with respect to the image-rejected signal; and a rate conversion section which subjects an output from the third frequency conversion section to rate conversion to lower the sampling frequency, wherein the narrow band limiting section extracts the narrow band signal of the desired wave from a rate-converted broad band signal, wherein a plurality of sets of the image rejection section, third frequency conversion section, and rate conversion section are continuously connected and disposed; and wherein the image rejection section comprises: a HILBERT filter which subjects a quadrature component of the inputted digital signal to 90-degrees phase shift processing by HILBERT conversion; a delay unit which delays and outputs an in-phase component of the inputted digital signal by the same time as a delay time in the HILBERT filter; and an adder which performs addition or subtraction with respect to outputs from the HILBERT filter and delay unit.