Patent ID: 8055218

Claim:
A wireless transmitter circuit comprising: a frequency-generating circuit; a quadrature modulator; a first frequency-converting phase-locked loop circuit to which an output of said quadrature modulator is input; a first variable divider; and a second variable divider associated with said frequency-generating circuit, wherein an output of said frequency-generating circuit is supplied via said first variable divider to said quadrature modulator as a local oscillation signal for said quadrature modulator, wherein said output of said frequency-generating circuit is supplied directly or via a third variable divider to said first frequency-converting phase-locked loop circuit as a local oscillation signal for said first frequency-converting phase-locked loop circuit, and wherein a frequency division factor of said first variable divider is set to a variable number, wherein said first frequency-converting phase-locked loop circuit comprises a first phase discriminator with first and second input terminals; a first loop filter circuit to which an output of said first phase discriminator is input; a first voltage controlled oscillator with a voltage control terminal to which an output of said first loop filter circuit is input; and a first mixer to which an output of said first voltage controlled oscillator is input, wherein an output of said first mixer is connected to said second input terminal of said first phase discriminator, and wherein an input of said first frequency-converting phase-locked loop circuit is supplied to the first input terminal of said first phase discriminator, wherein said frequency-generating circuit is formed by a phase-locked loop circuit comprising a second voltage controlled oscillator, the second variable divider, a second phase discriminator, a charge pump circuit, and a second loop filter circuit, wherein said frequency-generating circuit is a fractional phase-locked loop oscillation circuit in which a frequency division factor of said second variable divider is time changing, wherein the second voltage controlled oscillator is constructed such that its output is commonly used by the quadrature modulator and the first mixer, and wherein the frequency division factor of the first variable divider and a frequency division factor of the third variable divider are commonly controlled to vary in mutual coordination with each other, such that a frequency of the local oscillation signal for said first frequency-converting phase-locked loop circuit is separated from a harmonic frequency of a reference frequency of said frequency-generating circuit in a predetermined range of a transmission frequency by selectively changing the frequency division factors of the first and third variable dividers to avoid generating a spurious signal component.