Quadrature clock divider
View Patent ↗A divide-by-n process is effected via a scale-by-four/n process followed by a divide-by-four process. A quadrature input clock facilitates a scale-by-four/n process, via a clock-phase selection process. By incorporating a terminal divide-by-four process, quadrature output signals are easily provided. A divide-by-three quadrature divider effects the scale-by-4/n process via a selection of every third quadrature clock phase, and the quadrature output of the divide-by-four process provides the control signals to effect this every-third clock phase selection.
1. A divide-by-n system comprising:
a scaler that is configured to effect a scaling of an input frequency of an input clock to produce an intermediate clock at an intermediate frequency of 4/n times the input frequency, and
a counter that is configured to effect a division of the intermediate frequency to produce an output clock at an output frequency that is ¼ times the intermediate frequency;
wherein the output clock includes a set of four output quadrature clock signals (Iout, Iout−, Qout, Qout−).
2. The system of claim 1 , wherein the scaler includes a 4:1 multiplexer.
3. The system of claim 2 , wherein the input clock includes a set of input quadrature clock signals (Iin, Iin−, Qin, Qin−).
4. The system of claim 1 , wherein the input clock includes a set of input quadrature clock signals (Iin, Iin−, Qin, Qin−).
5. The system of claim 1 , wherein the set of output quadrature clock signals (Iout, Iout−, Qout, Qout−) are operatively coupled to the scaler to facilitate the scaling of the input clock.
6. The system of claim 1 , wherein the input clock comprises a set of quadrature input clock signals Iin, Iin−, Qin, and Qin−; and the scaler provides the intermediate clock Ck as: Ck=(Iout−*Qout−)*Iin+(Iout*Qout−)*Qin−+(Iout*Qout)*Iin−+(Iout−*Qout)*Qin, thereby effecting a divide-by-three process.
7. The system of claim 1 , further including another output clock that is generated via an exclusive-OR of two of the output quadrature clock signals (Iout, Qout).
8. The system of claim 1 , wherein the intermediate clock is provided as another output clock of the system.
9. A method of dividing an input frequency of an input clock to produce an output clock at an output frequency that is equal to the input frequency divided by a factor of n, comprising:
scaling the input clock to produce an intermediate signal at 4/n times the input frequency, and
dividing the intermediate signal by a factor of 4 to produce the output clock at the output frequency;
wherein the output clock includes a set of four output quadrature clock signals (Iout, Iout−, Qout, Qout−).
10. The method of claim 9 , wherein the input clock includes a set of quadrature input clock signals (Iin, Iin−, Qin, Qin−).
11. The method of claim 10 , wherein scaling the input clock is effected by a selection from among the set of quadrature input clock signals (Iin, Iin−, Qin, Qin−).
12. The method of claim 9 , wherein the input clock comprises a set of quadrature input clock signals Iin, Iin−, Qin, and Qin−; and scaling ( 210 ) the input clock to produce the intermediate signal Ck is effected as: Ck=(Iout−*Qout−)*Iin+(Iout*Qout−)*Qin−+(Iout*Qout)*Iin−+(Iout−* Qout)*Qin, thereby effecting a divide-by-three process.
13. The method of claim 9 , further including generating another output clock via an exclusive-OR of two of the quadrature output clock signals (Iout, Qout).
14. The method of claim 9 , wherein the intermediate signal is provided as another output clock.
15. A divide-by-n system comprising:
a scaler that is configured to effect a scaling of an input frequency of an input clock to produce an intermediate clock at an intermediate frequency of 4/n times the input frequency, and
a counter that is configured to effect a division of the intermediate frequency to produce an output clock at an output frequency that is ¼ times the intermediate frequency;
wherein the intermediate clock is provided as another output clock of the system.
16. A method of dividing an input frequency of an input clock to produce an output clock at an output frequency that is equal to the input frequency divided by a factor of n, comprising:
scaling the input clock to produce an intermediate signal at 4/n times the input frequency, and
dividing the intermediate signal by a factor of 4 to produce the output clock at the output frequency;
wherein the intermediate signal is provided as another output clock.