Frequency multiplier

• US 7,741,885 B1
• Filed: 03/04/2009
• Issued: 06/22/2010
• Est. Priority Date: 03/04/2009
• Status: Expired due to Fees

• Current Assignee: Yazaki North America Incorporated (Yazaki Corporation)
• Original Assignee: Yazaki North America Incorporated (Yazaki Corporation)
• Inventors: Wang, Xiaopeng, Guo, Sam Y.
• Primary Examiner(s): Donovan; Lincoln
• Assistant Examiner(s): O'Neill; Patrick
• Application Number:
  US12/397,613
• Time in Patent Office: 475 Days
• Field of Search: 327/113, 327/114, 327/116, 327119-123, 377/47, 377/48
• US Class Current: 327/116
• CPC Class Codes: H03K 7/08 Duration or width modulation ; Duty cycle modulation
• CPC Class Codes: H04L 25/4902 Pulse width modulation; Pulse position modulation

Abstract

A device for modifying an input signal having an input signal frequency and a duty cycle is disclosed. The device determines two separate counts for each of the high and low pulses of the input signal. One of the two counts for each of the high and low pulses is divided. The divided count is then compared with the undivided count. Based on this comparison, an output module outputs an output signal that has the same duty cycle as the input signal but at a frequency that is a multiple of the input signal frequency.

Claims

1. A device for modifying an input signal having an input signal frequency and a duty cycle, comprising:

a clock that outputs a clock signal at a clock frequency;

a pulse counter that receives the clock signal and the input signal, wherein the pulse counter determines a first low pulse count corresponding to the input signal being at a low state and a first high pulse count corresponding to the input signal being at a high state;

a count divider that modifies the first low pulse count to obtain a divided first low pulse count and that modifies the first high pulse count to obtain a divided first high pulse count;

a low pulse counter that receives the clock signal, wherein the low pulse counter determines a second low pulse count corresponding to the input signal being at the low state;

a high pulse counter that receives the clock signal, wherein the high pulse counter determines a second high pulse count corresponding to the input signal being at the high state;

a low pulse comparator that compares the divided first low pulse count with the second low pulse count, wherein the low pulse comparator outputs a low pulse comparison signal when the divided first low pulse count and the second low pulse count are equal;

a high pulse comparator that compares the divided first high pulse count with the second high pulse count, wherein the high pulse comparator outputs a high pulse comparison signal when the divided first high pulse count and the second high pulse count are equal; and

an output module that receives the low pulse comparison signal and high pulse comparison signal and outputs an output signal having the duty cycle of the input signal and an output signal frequency that is a multiple of the input signal frequency.

2. The device of claim 1, further comprising an overflow module operably connected to the pulse counter and the output module, wherein the overflow module detects an overflow condition and directs the output module to output either a logical HIGH signal or logical LOW signal as the output signal based on the input signal.

3. The device of claim 2, wherein the input signal received by the pulse counter is first processed by an edge detector that detects an edge of the input signal and outputs a reset signal to the pulse counter upon detection of the edge.

4. The device of claim 2, further comprising a low pulse count latch and a high pulse count latch, wherein the low pulse count latch latches the divided first low pulse count and the high pulse count latch latches the divided first high pulse count.

5. The device of claim 1, wherein the input signal received by the pulse counter is first processed by an edge detector that detects an edge of the input signal and outputs a reset signal to the pulse counter upon detection of the edge.

6. The device of claim 1, further comprising a low pulse count latch and a high pulse count latch, wherein the low pulse count latch latches the divided first low pulse count and the high pulse count latch latches the divided first high pulse count.

7. A device for modifying an input signal having an input signal frequency and a duty cycle, comprising:

a clock that outputs a clock signal at a clock frequency;

a frequency divider that modifies the clock signal to obtain a divided frequency clock signal;

a pulse counter that receives the divided frequency clock signal and the input signal, wherein the pulse counter determines a divided low pulse count corresponding to the input signal being at a low state and a divided high pulse count corresponding to the input signal being at a high state;

a low pulse counter that receives the clock signal, wherein the low pulse counter determines a low pulse count corresponding to the input signal being at the low state;

a high pulse counter that receives the clock signal, wherein the high pulse counter determines a high pulse count corresponding to the input signal being at the high state;

a low pulse comparator that compares the divided low pulse count with the low pulse count, wherein the low pulse comparator outputs a low pulse comparison signal when the divided low pulse count and the low pulse count are equal;

a high pulse comparator that compares the divided high pulse count with the high pulse count, wherein the high pulse comparator outputs a high pulse comparison signal when the divided high pulse count and the high pulse count are equal; and

an output module that receives the low pulse comparison signal and high pulse comparison signal and outputs an output signal having the duty cycle of the input signal and an output signal frequency that is a multiple of the input signal frequency.

8. The device of claim 7, further comprising an overflow module operably connected to the pulse counter and the output module, wherein the overflow module detects an overflow condition and directs the output module to output either a logical HIGH signal or logical LOW signal as the output signal based on the input signal.

9. The device of claim 8, wherein the input signal received by the pulse counter is first processed by an edge detector that detects an edge of the input signal and outputs a reset signal to the pulse counter upon detection of the edge.

10. The device of claim 8, further comprising a low pulse count latch and a high pulse count latch, wherein the low pulse count latch latches the divided low pulse count and the high pulse count latch latches the divided high pulse count.

11. The device of claim 7, wherein the input signal received by the pulse counter is first processed by an edge detector that detects an edge of the input signal and outputs a reset signal to the pulse counter upon detection of the edge.

12. The device of claim 7, further comprising a low pulse count latch and a high pulse count latch, wherein the low pulse count latch latches the divided low pulse count and the high pulse count latch latches the divided high pulse count.

13. A method for modifying an input signal having an input signal frequency and a duty cycle, comprising:

providing a clock signal at a clock frequency;

determining a divided low pulse count corresponding to the input signal being at a low state;

determining a divided high pulse count corresponding to the input signal being at a high state;

determining a low pulse count corresponding to the input signal being at the low state;

determining a high pulse count corresponding to the input signal being at the high state;

comparing the divided low pulse count with the low pulse count;

comparing the divided high pulse count with the high pulse count;

outputting a low pulse comparison signal when the divided low pulse count and the low pulse count are equal;

outputting a high pulse comparison signal when the divided high pulse count and the high pulse count are equal; and

outputting an output signal having the duty cycle of the input signal and an output signal frequency that is a multiple of the input signal frequency based on the high pulse comparison signal and the low pulse comparison signal.

14. The method of claim 13, further comprising detecting an overflow condition, wherein the step of outputting the output signal comprises outputting either a logical HIGH signal or logical LOW signal as the output signal based on the input signal when the overflow condition is detected.

15. The method of claim 14, further comprising detecting an edge of the input signal, wherein the divided low pulse count and the divided high pulse count is based on the detection of the edge.

16. The method of claim 14, further comprising latching the divided low pulse count and latching the divided high pulse count.

17. The method of claim 13, further comprising detecting an edge of the input signal, wherein the divided low pulse count and the divided high pulse count is based on the detection of the edge.

18. The method of claim 13, further comprising latching the divided low pulse count and latching the divided high pulse count.

19. The method of claim 13, wherein the step of determining the divided low pulse count comprises determining an undivided low pulse count and dividing the undivided low pulse count.

20. The method of claim 13, wherein the step of determining the divided low pulse count comprises frequency dividing the clock signal to obtain a divided frequency clock signal and determining the divided low pulse count based on the divided frequency clock signal.