Patent ID: 7239855

Claim:
A communication semiconductor integrated circuit device comprising: a gain variable amplification circuit for amplifying I-signals of in-phase component and Q-signals of quadrature component with respect to fundamental wave; and a signal synthesis circuit for synthesizing the amplified I-signals and Q-signals and local oscillation signals to carry out modulation and frequency conversion, wherein said communication semiconductor integrated circuit device being capable of transmission by two or more different modulation methods, wherein a low-pass filter of second or higher order is provided between said gain variable amplification circuit and said signal synthesis circuit, wherein a second gain variable amplification circuit and an amplification circuit having a limiter function are provided in the stage subsequent to said signal synthesis circuit, wherein said amplification circuit having a limiter function modulated transmission signals having information in the phase component, and wherein said second gain variable amplification circuit amplifies modulated transmission signals having information in the phase component and in the amplitude component.