Patent ID: 6035213
Filing Date: 2000-03-07
Classification: H04B

Abstract:
A dual-mode cellular telephone system adapted for an analog system and a digital CDMA system and having a mobile station with a narrow-band disturbing signal suppression circuit for suppressing intermodulation distortion produced from signals received from an analog base station, comprising:a receiver for receiving analog signals from an analog base station and CDMA signals from a CDMA base station;a notch filter for suppressing a disturbing signal resulting from intermodulation distortion within the received analog and CDMA signals, said notch filter supplied with a variable notch frequency;a level detecting circuit for monitoring an output level of said receiver; said level detecting circuit controlling said notch filter to possess a specified notch characteristic only in the case where said output level exceeds a predetermined reference level; anda disturbing signal detecting circuit for controlling said variable notch frequency, said disturbing signal detecting circuit selecting a specified value at which said notch filter has a minimum output to control the variable notch frequency supplied to said notch filter.