Patent ID: 7342442

Claim:
A wireless communication apparatus comprising: a variable gain amplifying apparatus; a level detection circuit detecting the level of a receive signal in the rear of said variable gain amplifying apparatus; and a control circuit switching the gain of said variable gain amplifying apparatus, wherein said variable gain amplifying apparatus comprises: an amplifier directly connected between input and output terminals; one or more first switching elements connected in parallel to said amplifier; and a phase shifter connected in series to said first switching element, said series connected phase shifter and first switching element directly connected between the input and output terminals, said phase shifter comprised of multi-stage circuits using passive elements, an impedance of a passive element of each stage circuit monotonically increasing or monotonically decreasing from an input port to an output port of said phase shifter, wherein said first switching element is enabled if the level of an input signal or an output signal is higher than a predetermined level, and said first switching element is disabled if the level of said input signal or said output signal is equal to or lower than said predetermined level, said amplifier does not operate when said first switching element is enabled connecting said first switching element and said phase shifter in a closed circuit, the closed circuit in parallel with said amplifier, and said amplifier operates when said first switching element is disabled, and the amount of phase shift when said input signal is passed through said amplifier is substantially equal to the amount of phase shift when said input signal is passed through said first switching element and phase shifter, wherein said variable gain amplifying apparatus is switched to a low gain state if the level detected by said level detection circuit is higher than a predetermined level, and said variable gain amplifying apparatus is switched to a high gain state if the level detected by said level detection circuit is equal to or lower than said predetermined level.