Wireless communication semiconductor integrated circuit device and mobile communication system

Abstract

An RF IC in which a PLL circuit including a loop filter is incorporated into a semiconductor chip is achieved without increasing power consumption or chip size. The RF IC includes a VCO capable of switching oscillation frequency bands, a variable frequency divider, a phase comparator, and a loop filter, which are contained in the PLL loop. A discrimination circuit discriminates a lead or lag in a phase of an output signal from the variable frequency divider against a reference signal and an automatic band selecting circuit generates a signal for switching the frequency bands of the VCO based on output from the discrimination circuit. While switching the frequency bands of the VCO by means of bisection algorithm, the RF IC detects an optimum frequency band, and adds offset to it to determine a final usable frequency band.

1 . A semiconductor integrated circuit device for wireless communication, comprising:
 an oscillator which outputs oscillations in a plurality of frequency bands;   a variable frequency divider which divides a frequency of an output signal from the oscillator by a designated frequency dividing ratio;   a set frequency divider which divides a predetermined frequency of a reference signal by a predetermined frequency dividing ratio;   a phase comparator which compares a phase of an output signal from the variable frequency divider with a phase of an output signal from the set frequency divider to detect a difference between the phases; and   a filter which generates a voltage according to an output from the phase comparator; and   wherein the voltage generated by the filter control oscillation frequencies of the oscillator,   wherein the semiconductor integrated circuit device further comprising:   a switch which supplies one of a predetermined potential and the voltage generated by the filter to the oscillator as the control voltage of the oscillator,   a band selector which compares the phase of the output signal from the variable frequency divider and the phase of the output signal from the set frequency divider in a state that the switch supplies the predetermined potential to the oscillator, and selects an oscillation frequency band of the oscillation means, and   a register which accepts, in order to prevent wrong selection of the oscillation frequency band due to a time lag in releasing the variable frequency divides and the set frequency divider from being reset, setting of a value by which another oscillation frequency band different from the selected oscillation frequency band is selected.   
   
   
       2 . The semiconductor integrated circuit device for wireless communication according to  claim 1 , wherein the band selector includes a band switching circuit which compares the phase of the output signal from the variable frequency divider with the phase of the output signal from the set frequency divider and generates a frequency band instruction signal for the oscillator, and offset imparting circuit which adds band offset value set to the register to the frequency band instruction signal, and
 wherein the band selector generates a signal for designating a final selective frequency band.   
   
   
       3 . The semiconductor integrated circuit device for wireless communication according to  claim 1 , wherein the filter includes capacitive elements and resistive elements, and the capacitive elements and resistive elements are formed on the same semiconductor chip as one on which are formed elements constituting the oscillator, the variable frequency divider, and the phase comparator. 
   
   
       4 . The semiconductor integrated circuit device for wireless communication according to  claim 1 , wherein the variable frequency divider and the set frequency divider share part of each other. 
   
   
       5 . The semiconductor integrated circuit device for wireless communication according to  claim 1 , wherein the variable frequency divider and the set frequency divider are laid out with different distances from a circuit that outputs a reset signal for resetting these frequency divider.