Patent ID: 7154341

Claim:
A communication semiconductor integrated circuit device, comprising: a first oscillator capable of performing oscillating operations at a plurality of frequency bands and generating a oscillation signal to be combined with a received signal; a first frequency converter which combines the received signal and a signal related to the oscillation signal and converts the received signal to a converted signal which has a frequency lower than that of the received signal; a second oscillator capable of performing oscillating operations at a plurality of frequency bands and generating a transmit signal having a desired frequency; a high frequency signal generator which includes the first oscillator and generates the oscillation signal having a desired frequency with an signal output from a crystal oscillator as a reference signal and outputs the signal related to the oscillation signal; a reception system circuit including the first frequency converter; and a transmission system circuit including the second oscillator, wherein said communication semiconductor integrated circuit device is formed over one semiconductor substrate and has a first operation mode which does not perform transmission and reception, a second operation mode which performs a preparation prior to the start of transmission or reception, and a third operation mode which performs transmission or reception, wherein the first oscillator and the second oscillator are deactivated in the first operation mode, wherein the operation of selecting a used frequency band for the second oscillator or the first and second oscillators is performed in the second operation mode, and wherein said high frequency signal generator, said reception system circuit and said transmission system circuit are formed in different semiconductor regions isolated by insulators respectively.