Signal generating system and signal generating method

• US 9,531,358 B2
• Filed: 04/14/2015
• Issued: 12/27/2016
• Est. Priority Date: 10/27/2014
• Status: Active Grant

• Current Assignee: MediaTek, Inc.
• Original Assignee: MediaTek, Inc.
• Inventors: Tseng, Sheng-Che, Wang, Yao-Chi
• Primary Examiner(s): Hernandez, William
• Application Number:
  US14/685,607
• Publication Number:
  US 20160118962A1
• Time in Patent Office: 623 Days
• Field of Search: 327/113, 327/117, 327/175, 327/291, 327/299, 327/355, 327/357, 327/361
• US Class Current: 1/1
• CPC Class Codes: H03K 19/21 EXCLUSIVE-OR circuits, i.e. giving output if input signal exists at only one input; COINCIDENCE circuits, i.e. giving output only if all input signals are identical
• CPC Class Codes: H03K 5/06 by the use of delay lines or other analogue delay elements
• CPC Class Codes: H03K 5/1565 the output pulses having a constant duty cycle

Abstract

A signal generating system for generating an output signal with a 50% duty cycle, comprising: a frequency dividing module, comprising an odd number of level triggering devices, for generating a plurality of frequency divided signals utilizing a frequency dividing ratio equaling to M, wherein the M is an positive integer; and a signal combining module, for combining at least two of the frequency divided signals to generate at least one output combined signal. The signal generating system generates the output signal based on the output combined signal. The frequency dividing module cooperates the signal combining module to provide a frequency dividing ratio equaling to N.5, wherein the N is a positive integer.

Claims

1. A signal generating system for generating an output signal with a 50% duty cycle, comprising:

a frequency dividing module, comprising an odd number of level triggering devices, for generating a plurality of frequency divided signals utilizing a frequency dividing ratio equal to M based on an input signal, wherein M is a positive integer; and

a signal combining module, for combining at least two of the frequency divided signals, or combining the input signal and one of the frequency divided signals to generate at least one output combined signal;

wherein the signal generating system generates the output signal based on the output combined signal;

wherein the frequency dividing module cooperates with the signal combining module to provide a frequency dividing ratio equaling to N.5, wherein N is a positive integer.

2. The signal generating system of claim 1, wherein the signal combining module directly outputs the output combined signal as the output signal.

3. The signal generating system of claim 1, wherein the frequency dividing module comprises M level triggering devices to generate M frequency divided signals, wherein M equals 2*(N.5).

4. The signal generating system of claim 1, further comprising:

a duty cycle calibrating circuit, for adjusting a duty cycle of the output combined signal to generate the output signal.

5. The signal generating system of claim 4, wherein the duty cycle calibrating circuit comprises:

a comparator, for comparing a duty cycle for the output signal and a duty cycle for an inverted output signal, to generate a comparing result;

a first duty cycle calibrating module, for calibrating a duty cycle of the output signal according to the comparing result; and

a second duty cycle calibrating module, for calibrating a duty cycle for the inverted output signal according to the comparing result.

6. The signal generating system of claim 5,

wherein the first duty cycle calibrating module comprises:

a first falling time tuning circuit, for receiving the output combined signal to generate a first adjusted output combined signal;

a buffer, for buffering the first adjusted output combined signal to generate the output signal;

wherein the second duty cycle calibrating module comprises;

a first inverter, for receiving an inverted output combined signal;

a second falling time tuning circuit, for receiving an output from the first inverter to generate a second adjusted output combined signal; and

a second inverter, for inverting the second adjusted output combined signal to generate the inverted output signal.

7. The signal generating system of claim 6, wherein the first falling time tuning circuit comprises:

a third inverter, receiving the output combined signal;

a transistor of second type, comprising a first terminal coupled to a first voltage level, a second terminal, and a control terminal coupling to an output terminal of the third inverter;

a first transistor of first type, comprising a first terminal coupled to the second terminal of the transistor of second type, a second terminal, and a control terminal coupling to the output terminal of the third inverter;

a second transistor of first type, comprising a first terminal coupled to the second terminal of the first transistor of first type, a second terminal coupled to a second voltage level, and a control terminal.

8. The signal generating system of claim 6, wherein the second falling time tuning circuit comprises:

a fourth inverter, receiving the output from the first inverter;

a transistor of second type, comprising a first terminal coupled to a first voltage level, a second terminal, and a control terminal coupling to an output terminal of the fourth inverter;

a first transistor of first type, comprising a first terminal coupled to the second terminal of the transistor of second type, a second terminal, and a control terminal coupling to the output terminal of the fourth inverter;

a second transistor of first type, comprising a first terminal coupled to the second terminal of the first transistor of first type, a second terminal coupled to a second voltage level, and a control terminal.

9. The signal generating system of claim 5,

wherein the first duty cycle calibrating module comprises:

a first inverter, for receiving the output combined signal;

a second first rising time tuning circuit, for receiving an output from the first inverter to generate a first adjusted output combined signal; and

an second inverter, for inverting the first adjusted output combined signal to generate the output signal;

wherein the second duty cycle calibrating module comprises;

a second rising time tuning circuit, for receiving an inverted output combined signal to generate a second adjusted output combined signal; and

a buffer, for buffering the second adjusted output combined signal to generate the inverted output signal.

10. The signal generating system of claim 5,

wherein the first duty cycle calibrating module comprises:

a first falling time tuning circuit, for receiving the output combined signal to generate a first adjusted output combined signal;

a buffer, for buffering the first adjusted output combined signal to generate the output signal;

wherein the second duty cycle calibrating module comprises;

a first rising time tuning circuit, for receiving an inverted output combined signal to generate a second adjusted output combined signal; and

a buffer, for buffering the second adjusted output combined signal to generate the inverted output signal.

11. The signal generating system of claim 5,

wherein the first duty cycle calibrating module comprises:

a first inverter, for receiving the output combined signal;

a first rising time tuning circuit, for receiving an output from the first inverter of the first duty cycle calibrating module to generate a first adjusted output combined signal; and

a second inverter, for inverting the first adjusted output combined signal to generate the output signal;

wherein the second duty cycle calibrating module comprises;

a third inverter, for receiving an inverted output combined signal;

a first falling time tuning circuit, for receiving an output from the third inverter of the second duty cycle calibrating module to generate a second adjusted output combined signal; and

a fourth inverter, for inverting the second adjusted output combined signal to generate the inverted output signal.

12. The signal generating system of claim 1, wherein the signal combining module comprises an XOR circuit for performing an XOR operation to the output combined signal to generate the output signal.

13. The signal generating system of claim 1, wherein the signal combining module comprises a signal combining module for combining at least two of the frequency divided signals to generate the output combined signal at an output terminal, wherein the signal combining module comprises:

a first initial combining circuit, for receiving a plurality of the frequency divided signals to generate a first output combined signal;

a second initial combining circuit, for receiving a plurality of the frequency divided signals to generate a second output combined signal;

a first edge calibrating device, coupled between a first voltage level and the first initial combining circuit; and

a second edge calibrating device, coupled between a second voltage level and the second initial combining circuit;

wherein the first edge calibrating device and the second edge calibrating device integrate at least one edge of the first output combined signal and the second output combined signal to generate the output combined signal.

14. The signal generating system of claim 13, wherein the first initial combining circuit comprises:

a first transistor of first type, comprising a first terminal coupled to the output terminal, a second terminal, and comprising a control terminal for receiving one of the frequency divided signals;

a second transistor of first type, comprising a first terminal coupled to the second terminal of the first transistor of first type, a control terminal for receiving one of the frequency divided signals and a second terminal coupled to the second voltage level;

a third transistor of first type, comprising a first terminal coupled to the output terminal, a second terminal, and comprising a control terminal for receiving one of the frequency divided signals;

a fourth transistor of first type, comprising a first terminal coupled to the second terminal of the third transistor of first type, a control terminal for receiving one of the frequency divided signals and a second terminal coupled to the second voltage level;

a first transistor of second type, comprising a first terminal, a second terminal coupled to the output terminal, and comprising a control terminal for receiving one of the frequency divided signals;

a second transistor of second type, comprising a second terminal coupled to the first terminal of the first transistor of second type, a control terminal for receiving one of the frequency divided signals and a first terminal coupled to the first edge calibrating device;

a third transistor of second type, comprising a first terminal, a second terminal coupled to the output terminal, and comprising a control terminal for receiving one of the frequency divided signals; and

a fourth transistor of second type, comprising a second terminal coupled to the first terminal of the third transistor of second type, a control terminal for receiving one of the frequency divided signals and a first terminal coupled to the first edge calibrating device.

15. The signal generating system of claim 14, wherein the second initial combining circuit comprises the first transistor of first type, the third transistor of first type, the first transistor of second type, the third transistor of second type, wherein the second initial combining circuit further comprises:

a fifth transistor of first type, comprising a first terminal coupled to the second terminal of the first transistor of first type, a control terminal for receiving one of the frequency divided signals, and a second terminal coupled to the second edge calibrating device;

a sixth transistor of first type, comprising a first terminal coupled to the second terminal of the third transistor of first type, a control terminal for receiving one of the frequency divided signals, and a second terminal coupled to the second edge calibrating device;

a fifth transistor of second type, comprising a second terminal coupled to the second terminal of the second transistor of second type, a control terminal for receiving one of the frequency divided signals, and a first terminal coupled to the first voltage level; and

a sixth transistor of second type, comprising a second terminal coupled to the second terminal of the fourth transistor of second type, a control terminal for receiving one of the frequency divided signals, and a first terminal coupled to the first voltage level.

16. The signal generating system of claim 14,

wherein the first transistor of first type, the second transistor of first type, the third transistor of first type, the fourth transistor of first type are NMOSFETs, wherein the first terminals thereof are drain terminals, the second terminals thereof are source terminals, and control terminals thereof are gate terminals;

wherein the first transistor of second type, the second transistor of second type, the third transistor of second type, the fourth transistor of second type are PMOSFETs, wherein the first terminals thereof are source terminals, the second terminals thereof are drain terminals, and control terminals thereof are gate terminals.

17. The signal generating system of claim 1, wherein the signal combining module comprises a signal combining module for combining two of the frequency divided signals to generate the output combined signal at an output terminal, wherein the signal combining module comprises:

an energy storing circuit, coupled to the output terminal;

a charging circuit, for receiving at least two of the frequency divided signals to output a charging current to the energy storing circuit;

a discharging circuit, for receiving at least two of the frequency divided signals to drain a discharging current from the energy storing circuit;

wherein the energy storing circuit generates the output combined signal according to the charging current and the discharging current to the output terminal.

18. The signal generating system of claim 17, wherein the charging circuit comprises:

a first transistor of first type, comprising a first terminal coupled to the output terminal, a second terminal and a control terminal receiving one of the frequency divided signals;

a second transistor of first type, comprising a first terminal coupled to the second terminal of the first transistor of first type, a second terminal coupled to a second voltage level, and a control terminal receiving one of the frequency divided signals;

a third transistor of first type, comprising a first terminal coupled to the output terminal, a second terminal and a control terminal receiving one of the frequency divided signals;

a fourth transistor of first type, comprising a first terminal coupled to the second terminal of the third transistor of first type, a second terminal coupled to the second voltage level, and a control terminal receiving one of the frequency divided signals.

19. The signal generating system of claim 17, wherein the discharging circuit comprises:

a first transistor of second type, comprising a second terminal coupled to the output terminal, a first terminal and a control terminal receiving one of the frequency divided signals;

a second transistor of second type, comprising a second terminal coupled to the first terminal of the first transistor of second type, a first terminal coupled to a first voltage level, and a control terminal receiving one of the frequency divided signals;

a third transistor of second type, comprising a second terminal coupled to the output terminal, a first terminal and a control terminal receiving one of the frequency divided signals;

a fourth transistor of second type, comprising a second terminal coupled to the first terminal of the third transistor of second type, a first terminal coupled to the first voltage level, and a control terminal receiving one of the frequency divided signals.

20. A signal generating system for generating an output signal with a 50% duty cycle, comprising:

a frequency dividing module, comprising an odd number of level triggering devices, for generating a plurality of frequency divided signals utilizing a frequency dividing ratio equaling to M, wherein the M is a positive integer;

a delay module, for delaying at least one of the frequency divided signals to generate at least one delayed frequency divided signal; and

a signal combining module, for combining at least two of the delayed frequency divided signals, or for combining at least one of the frequency divided signals and at least one of the delayed frequency divided signals, to generate the output signal;

wherein the frequency dividing module cooperates with the signal combining module to provide a frequency dividing ratio equaling to N.5, wherein the N is a positive integer.

21. A signal generating method for generating an output signal with a 50% duty cycle, comprising:

(a) generating a plurality of frequency divided signals utilizing a frequency dividing ratio equaling to M based on an input signal, wherein the M is a positive integer;

(b) combining at least two of the frequency divided signals, or combining the input signal and one of the frequency divided signals, to generate at least one output combined signal; and

(c) generating the output signal based on the output combined signal;

wherein the step(a) cooperates with the step(b) to provide a frequency dividing ratio equaling to N.5, wherein the N is a positive integer.

22. The signal generating method of claim 21, wherein the step (c) directly outputs the output combined signal as the output signal.

23. The signal generating method of claim 21, further comprising adjusting a duty cycle of the output combined signal to generate the output signal.

24. The signal generating method of claim 21, wherein the step (b) comprises:

performing an XOR operation to a plurality of the frequency divided signals to generate a first output combined signal;

performing an XOR operation to a plurality of the frequency divided signals to generate a second output combined signal;

integrating at least one edge of the first output combined signal and the second output combined signal to generate the output combined signal.

25. A signal generating method for generating an output signal with a 50% duty cycle, comprising:

applying a frequency dividing module to generate a plurality of frequency divided signals utilizing a frequency dividing ratio equaling to M, wherein the M is a positive integer;

delaying at least one of the frequency divided signals to generate at least one delayed frequency divided signal; and

applying a signal combining module to combine at least two of the delayed frequency divided signals, or applying the signal combining module to combine at least one of the frequency divided signals and at least one of the delayed frequency divided signals, to generate the output signal;

wherein the frequency dividing module cooperates with the signal combining module to provide a frequency dividing ratio equaling to N.5, wherein the N is a positive integer.