Patent ID: 7738844

Claim:
A radio communication device comprising: a local oscillator; an amplifier including first and second stages, the first stage amplifying an output signal of the local oscillator and having a linear gain region and a saturated gain region over which a frequency region of the output signal of the local oscillator is located so as to generate a harmonic wave component of the output signal of the local oscillator and to output the output signal of the local oscillator and the harmonic wave component thereof, the second stage being a linear gain amplifier; and a harmonic mixer receiving the output signal of the local oscillator from the amplifier and the harmonic wave component and an information signal, and generating a harmonic wave of the output signal of the local oscillator and mixing the harmonic wave with the information signal to output an up-converted signal, and allowing the harmonic wave component to pass through without change, the harmonic mixer having an anti-parallel diode including at least a short stub which has a length equal to ¼ of the wavelength corresponding to a center frequency of at least one of two side bands included in the up-converted signal, said up-converted signal being a modulated signal, the radio communication device outputting for transmission the up-converted signal and the harmonic wave component, wherein: the harmonic wave component is unmodulated; and each of the harmonic wave component and the harmonic wave is a second harmonic wave component of the output signal of the local oscillator.