DUAL MODE CELLULAR TELEPHONE SYSTEM

摘要

PROBLEM TO BE SOLVED: To provide a dual mode cellular telephone system suppressing a narrow band disturbing wave generated in a mobile station of the dual mode cellular telephone system corresponding to both an analog system and a digital CDMA system. SOLUTION: A CDMA signal from a CDMA base station and a narrow band signal from an analog base station are received by a reception antenna 101 and amplified and frequency-converted by a reception section 102 and the resulting signals are inputted to a variable notch filter 105. A control signal to vary a notch frequency is given to the variable notch filter 105 from a disturbing wave detection circuit 106. The disturbing wave detection circuit 106 sweeps the control signal to change the notch frequency thereby detecting an output level of the variable notch filter 105 to the minimum. Then, the control signal at that time is given to the variable notch filter 105.