Patent ID: 6680658
Filing Date: 2004-01-20
Classification: H03G

Abstract:
A modulation circuit comprising:a band restriction filter for receiving modulation data; an attenuator connected to the band restriction filter, the attenuator adjusting its attenuation in response to an attenuator control signal; a reference voltage generator connected to the attenuator for providing a reference voltage independent of a temperature and a power supply voltage to the attenuator; a comparing reference voltage generator connected to the reference voltage generator for providing a comparing reference voltage independent of the temperature and the power supply voltage; a modulator connected to the attenuator; a voltage comparator connected to the attenuator and the comparing reference voltage generator for comparing the comparing reference voltage with a voltage of an output of the attenuator and generating a comparison signal based on the comparison; and an attenuator controller connected to the attenuator and the voltage comparator, the attenuator controller generating the attenuator control signal in response to the comparison signal.