Patent ID: 6937954
Filing Date: 2005-08-30
Classification: G01C

Abstract:
1. A signal processor for use in an electronic compass for processing signals from a geomagnetic compass sensor detecting sine or cosine wave signals induced by a drive signal according to an azimuth angle, said signal processor comprising: an analog signal processor for amplifying the signals from the geomagnetic compass sensor, canceling an offset voltage generated during an amplification process in response to an offset control signal, and controlling an amplitude of a signal in which the offset voltage is cancelled out in response to a gain control signal; an analog/digital (AD) converter for converting analog signals from the analog signal processor into a digital signal; and a digital signal processor for measuring a maximum value and a minimum value associated with the digital signal from the AD converter, determining the offset voltage and the amplitude on the basis of the maximum and minimum values, and outputting, to the analog signal processor, the offset control signal to be used for canceling the determined offset voltage and the gain control signal to be used for controlling the determined amplitude so that the amplitude lies within an allowable input range for the AD converter; wherein the analog signal processor comprises: a chopper for detecting the signals from the geomagnetic compass sensor; an input amplifier for amplifying the detected signals output from the chopper on the basis of a preset gain; a low pass filter for carrying out a preset low pass filtering operation for a signal output from the input amplifier; an offset controller for generating a canceling voltage for canceling the offset voltage in response to the offset control signal and providing the generated canceling voltage to input terminals of the input amplifier; and an automatic gain control (AGC) amplifier for setting an amplification gain in response to the gain control signal and amplifying a signal from the low pass filter in response to the set amplification gain.