Circuit and method for clock correction in telecommunication system
Disclosed are a low-cost circuit, a communication apparatus and a method for correcting a clock and for application to a specific radio system with low electric power consumption. The communication apparatus comprises: a frequency data storage circuit for storing frequency set values corresponding to respective channels to output a frequency set value corresponding to a channel specified by a channel selection signal; a frequency correction circuit for calculating a frequency control value by performing a calculation using both the frequency control value and a frequency correction value determined in accordance with an ambient temperature; a voltage controlled oscillator for generating a first frequency based on a clock signal; and a PLL circuit for generating a desired second frequency by performing a calculation using the first frequency and the frequency control value.
1 . A clock correction circuit comprising:
a frequency data storage circuit for storing frequency set values corresponding to respective channels and outputting a frequency set value corresponding to a channel specified by a channel selection signal;
a frequency correction circuit for calculating a frequency control value by performing a calculation using both the output frequency set value and a frequency correction value determined in accordance with an ambient temperature;
a voltage controlled oscillator for generating a first frequency based on a clock signal; and
a PLL circuit for generating a desired second frequency by performing a calculation using the first frequency and the frequency control value.
2 . A clock correction circuit according to claim 1 , further comprising:
a reference clock generator for generating a reference clock as the clock signal; and
a control circuit for storing frequency correction values corresponding to respective temperatures and outputting the frequency correction value corresponding to a detected ambient temperature.
3 . A clock correction circuit according to claim 1 , further comprising a thermistor for measuring the ambient temperature as the detected ambient temperature.
4 . A clock correction circuit according to claim 1 , wherein said frequency correction circuit calculates the frequency control value using a center frequency correction value together with the output frequency set value and the frequency correction value.
5 . A communication apparatus comprising:
a frequency data storage circuit for storing frequency set values corresponding to respective channels and outputting a frequency set value corresponding to a channel specified by a channel selection signal;
a frequency correction circuit for calculating a frequency control value by performing a calculation using both the output frequency set value and a frequency correction value determined in accordance with an ambient temperature;
a voltage controlled oscillator for generating a first frequency based on a clock signal;
a PLL circuit for generating a desired second frequency by performing a calculation using the first frequency and the frequency control value; and
a transmitter and receiver circuit for transmitting or receiving data using the second frequency.
6 . A communication apparatus according to claim 5 , further comprising:
a reference clock generator for generating a reference clock as the clock signal; and
a control circuit for storing frequency correction values corresponding to respective temperatures and outputting the frequency correction value corresponding to a detected ambient temperature.
7 . A communication apparatus according to claim 6 , further comprising a thermistor for measuring the ambient temperature as the detected ambient temperature.
8 . A communication apparatus according to claim 5 , wherein said frequency correction circuit calculates the frequency control value using a center frequency correction value together with the output frequency set value and the frequency correction value.
9 . A clock correcting method comprising the steps of:
inputting a frequency correction value determined in accordance with an ambient temperature;
generating a frequency set value corresponding to a channel to be used, on the basis of a plurality of frequency set values that are stored;
performing a calculation using both the generated frequency set value and the frequency correction value to generate a frequency control value;
generating a first frequency based on a clock signal that is inputted; and
performing a calculation using both the first frequency and the frequency control value to generate a desired second frequency.
10 . A clock correction method according to claim 9 , further comprising the steps of:
generating a reference clock as the clock signal; and
reading out the frequency correction value corresponding to a detected ambient temperature from a storage memory that stores frequency correction values corresponding to respective temperatures.
11 . A clock correction method according to claim 10 , further comprising the step of measuring the ambient temperature as the detected ambient temperature.