Frequency synthesizer for providing a pseudo-constant frequency signal

Claim 1

A frequency synthesizer for providing an output signal having the same pseudo-constant frequency with a known period in response to a selected one of a plurality of input signals each having a different fixed frequency, the frequencies of said plurality of input signals being of the same order of magnitude as, or higher than, said pseudo-constant frequency, said frequency synthesizer comprising: decode means responsive to a coded signal representing a selected one of said plurality of input signals for providing a control signal corresponding to said selected input signal; first means responsive to said control signal for supplying a number representing a selected number of successive sub-groups of one or more cycles of said selected input signal, the number of cycles of said input signal in each said sub-group being one of two consecutive integers identifiable as a high integer and a low integer; counter means responsive to said selected number and to said output signal for providing a position count signal at each successive sub-group; parsing means responsive to said position count signal and to said control signal for providing a high/low signal specifying the sub-group position at which a high integer number of input cycles are used or a low integer number of input cycles are used; and second means responsive to said selected one of said input signals, to said control signal, and to said high/low signal for specifying said high integer and said low integer and for supplying an output cycle at each successive high or low sub-group of input cycles, said output cycles forming said output signal having said pseudo-constant frequency, the order in which said high and low sub-groups occur being selected to maintain any error in said output signal at a value less than or equal to the cycle time of said selected input signal.

Claim 8

A method for generating an output signal having a substantially constant output frequency in response to a selected one of a plurality of input signals each having a different, fixed input frequency, the frequencies of said plurality of input signals being of the same order of magnitude as, or higher than, said substantially constant output frequency, wherein the ratio of said input frequency to said output frequency is comprised of a whole number X and a fraction Y/z to take the form XY/z, said method comprising the steps of: (a) selecting an input signal from said plurality thereof having a fixed input frequency; (b) generating successive sub-groups of output cycles at a rate substantially corresponding to said output frequency wherein said successive sub-groups of cycles selectively include cycles corresponding to low count sub-groups containing X cycles at the input frequency of said selected input signal and cycles corresponding to high count sub-groups containing X+1 cycles at the frequency of said selected input signal; (c) counting the positions of said successive sub-groups of cycles to determine successive recycle periods, each said recycle period containing a recycle number z of said successive groups of cycles, and (d) responsive to step (c), selecting said successive sub-groups of output cycles to produce said output signal which includes cycles corresponding to Y high count sub-groups and to z-Y low count sub-groups in a selected order in each z successive sub-groups so that a maximum error in said output signal is equal to or less than the time period of the frequency of said input signal.

Claim 9

A method for generating an output signal having a substantially constant output frequency in response to a selected one of a plurality of input signals each having a different, fixed input frequency, the frequencies of said plurality of input signals being of the same order of magnitude as, or higher than, said substantially constant output frequency, wherein the ratio of said input frequency to said output frequency is comprised of a whole number X and a fraction Y/z to take the form XY/z, said method comprising the steps of: (a) selecting an input signal from said plurality thereof having a fixed input frequency; (b) generating successive sub-groups of output cycles at a rate substantially corresponding to said output frequency wherein said successive sub-groups of cycles selectively include cycles corresponding to low count sub-groups containing X cycles at the input frequency of said selected input signal and cycles corresponding to high count sub-groups containing X+1 cycles at the frequency of said selected input signal; (c) counting the positions of said successive sub-groups of cycles to determine successive recycle periods, each said recycle period containing a recycle number z of said successive groups of cycles, and (d) responsive to step (c), selecting said successive sub-groups of output cycles to produce said output signal which includes cycles corresponding to Y high count sub-groups and to z-Y low count sub-groups in a selected order in each z successive sub-groups so that a maximum error in said output signal is equal to or less than the time period of the frequency of said input signal.