Patent ID: 7477680

Claim:
A de-spreading device comprising: a comparator for comparing a detection output of a received signal, which is subjected to spectrum spread by a direct sequence system, with a predetermined comparative value to produce virtual chip data; a frequency divider for dividing a frequency of a master clock signal to generate an operational clock signal; a correlation circuit for using a predetermined spread code to perform correlation operation on the virtual chip data to produce a correlation value; a timing estimator for determining a correlation peak value out of the correlation value to produce a timing signal based on the correlation peak value; and a decision circuit for deciding the correlation value in response to the timing signal and then outputting the correlation value determined as symbol data; and a channel quality estimator for estimating radio channel quality on a basis of the correlation peak value and selecting one of the plurality of modes in accordance with the radio channel quality estimated; said de-spreading device being selectively operable in any one of a plurality of modes including a first mode for regular operation and a second mode lower in power consumption than the first mode, said correlation circuit performing the correlation operation with, in the first mode, a first operational clock signal assigned to the regular operation, and, in the second mode, a second operational clock signal lower in rate than the first operational clock signal, wherein said channel quality estimator selects the first mode among the plurality of modes in an initial condition, selects the second mode when the radio channel quality estimated is high, or selects the first mode when the radio circuit quality estimated becomes low.