Patent ID: 7224940

Claim:
A frequency modulating device comprising: a frequency generator for generating a frequency-modulated first carrier; an input terminal for receiving a non-modulated second carrier; an amplifier for amplifying the second carrier; a frequency converter receiving the first carrier and the second carrier for producing a difference between the second carrier and the first carrier as an intermediate frequency signal, an output terminal for outputting the intermediate frequency signal; a frequency filter for limiting a frequency band of the intermediate frequency signal to output a band-limited signal; a calculator for calculating a spectrum distribution of the band-limited signal; a first selector included in said frequency generator for selectively feeding the first carrier to either one of said frequency converter and a transmitter system; a second selector for selectively feeding the second carrier to said frequency converter or feeding a signal output from the transmitter system to said input terminal; and a third selector included in the semiconductor device for selectively feeding the intermediate frequency signal output from said frequency converter to either one of said output terminal and a circuit configured to process said intermediate frequency signal, wherein said frequency generator, said input terminal, said amplifier, said frequency converter, said output terminal, said second selector, and said third seleetorare included in a semiconductor device constructed on a semiconductor wafer in the form of an integrated circuit.