Miscellaneous active electrical nonlinear devices – circuits – and – Signal converting – shaping – or generating – Frequency or repetition rate conversion or control
Patent
1996-02-28
1998-02-03
Callahan, Timothy P.
Miscellaneous active electrical nonlinear devices, circuits, and
Signal converting, shaping, or generating
Frequency or repetition rate conversion or control
327117, 377 47, 377 48, H03K 2100
Patent
active
057148961
ABSTRACT:
A fractional-N frequency divider system generates an output signal having frequency of an input signal divided by a desired frequency division ratio (N+A/M) in which N is an integer and A/M is a fraction, A.ltoreq.M, and includes a programmable frequency divider receiving input frequency and providing divided frequency in which division ratio (N, N+1) is an integer and is externally supplied, a selector supplying one of the externally supplied integers (N, N+1) to the divider according to a selection signal, and a fractional part set having a first counter initialized to count M, a second counter initialized to count A, and a logic circuit for supplying the selection signal according to the counters. The counters are decremented by an output of the divider and reach zero when they receive M and A number of pulses, respectively. The second counter stops counting operation when it reaches zero. The logic circuit makes the selector select an integer N in a condition when content of the first counter is not zero and content of the second counter is zero, and N+1 in other conditions, so that the division ratio in the divider is N+1 for A number of output pulses of the divider among M number of output pulses, and is N for M-A number of the output pulses.
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Kamoto Tsutomu
Nakagawa Tadao
Suzuki Masao
Tsukahara Tsuneo
Callahan Timothy P.
Nippon Telegraph and Telephone Corporation
Shin Eunja
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