Patent ID: 6882698

Claim:
A fraction frequency divider which divides an input signal by a frequency dividing number N/M of a ratio N/M of an integer M to N involving a decimal to output a frequency-divided signal, the divider comprising: an integer setting section which sets an integer portion n of the frequency dividing number; a decimal setting section which sets a decimal portion f of the frequency dividing number; an accumulation/addition section including a decimal section which accumulates/adds a value of the decimal portion f in response to the outputted frequency-divided signal to provide a decimal value of an accumulation/addition result and an integer section to provide a carry signal; an adder which adds the value of the integer portion n of the integer setting section and the value of an integer portion of the accumulation/addition result; a dividing section which switches the frequency dividing number to a result obtained by the adder to divide the input signal and which outputs the frequency-divided signal; a dividing number setting section which sets a number Mn of n-dividing operations to be performed, and a number Mn+1 of n+1-dividing operations to be performed, these numbers being obtained from a relation of the integers M, N, and n; a counter section including a first counter which counts the number of performed n-dividing operations in response to the frequency-divided signal and a second counter which counts the number of performed n+1-dividing operations in response to the frequency-divided signal based on the carry signal of the integer section of the accumulation/addition section; and a calculation processing section which sets the integer portion of the accumulation/addition result to one of 0 and 1 in accordance with a content of one of the first and second counters and which resets the first and second counters and the accumulation/addition section in accordance with the content of the other of the first and second counters and which sets the contents of the counters and the accumulation/addition section to 0.