Patent ID: 6069925
Filing Date: 2000-05-30
Classification: H04B

Abstract:
An apparatus for adaptively switching the frequency band of a second intermediate frequency in a dual mode, dual band radio transceiver for use in a cellular communication system, the apparatus comprising:a phase locked loop integrated circuit (PLL IC) for comparing sync data with a reference frequency signal to output Alternating Current (AC) data;a first loop filter coupled to said phase locked loop integrated circuit for converting the AC data to Direct Current (DC) data with a given level according to a first band;a second loop filter coupled to said phase locked loop integrated circuit for converting the AC data to DC data with a given level according to a second band;a first tank circuit connected to the first loop filter, for generating a second intermediate frequency for the first band;a second tank circuit connected to the second loop filter, for generating a second intermediate frequency for the second band;a switch operatively coupled to said first and second tank circuits for selecting one of the second intermediate frequencies output from said first and second tank circuits according to an operation mode; anda buffer connected to said switch, for buffering the selected second intermediate frequency to be output as a local oscillation frequency to a reception IF mixer.