Patent ID: 6647072
Filing Date: 2003-11-11
Classification: H04B

Abstract:
A transmitting circuit comprising an intermediate frequency amplifier that amplifies an intermediate frequency signal, a frequency converter that applies frequency conversion to said intermediate frequency signal into a transmission signal of a higher frequency than said intermediate frequency, a high frequency amplifier that amplifies said transmission signal, and a driver amplifier that further amplifies the transmission signal amplified by said high frequency amplifier and inputs it to a power amplifier, wherein said intermediate frequency amplifier, said high frequency amplifier, and said driver amplifier are configured using variable gain amplifiers, and a gain of said intermediate frequency amplifier, a gain of said high frequency amplifier, and a gain of said driver amplifier are made to be varied by an automatic gain control voltage, wherein said automatic control voltage varies from a first voltage to a second voltage, the gain of said intermediate frequency amplifier and the gain of said high frequency amplifier vary between said first voltage and said second voltage, each of the gains becomes maximum at said first voltage and each becomes minimum at said second voltage, the gain of said driver amplifier is made to be attenuated gradually from the maximum gain to a specific gain, as said automatic gain control voltage varies from said first voltage to a third voltage intervening between said first voltage and said second voltage, and said specific gain is made to be maintained between said third voltage and said second voltage.