Personal communications device with ratio counter

• US 6,788,655 B1
• Filed: 04/18/2000
• Issued: 09/07/2004
• Est. Priority Date: 04/18/2000
• Status: Expired due to Term

• Current Assignee: CSR Technology Incorporated (Qualcomm, Inc.)
• Original Assignee: SIRF Technology Incorporated (Qualcomm, Inc.)
• Inventors: Underbrink, Paul A.
• Primary Examiner(s): Pham, Chi
• Assistant Examiner(s): Ferris, Derrick W
• Application Number:
  US09/552,469
• Time in Patent Office: 1,603 Days
• Field of Search: 370/252, 370/516-8, 370/335, 370/342, 370/350, 370/324, 342/352, 342/357, 375/355, 375/140, 455/575
• US Class Current: 370/324
• CPC Class Codes: H04B 1/707 using direct sequence modulation
• CPC Class Codes: H04B 2201/70715 with application-specific features

Abstract

The invention is directed to a personal communications device with a ratio counter providing tracking transitioning edges of two clocks so as to generate a signal to initiate capture of a clock cycle count. Provisions for tracking the transitioning edges include a storage memory for storing a first and a second value selected in accordance with the principles of convergents of continued fractions. A first and second counter each responding to first and second clock signal, respectively. The first and second counter each count clock cycles of the respective clock signal. A first register for capturing the count of the first counter and a second register for capturing the count of the second counter.

Claims

1. A personal communications device comprising:

first receiver comprising a first clock for generating a first clock signal;

second receiver comprising a second clock for generating a second clock signal

at least one register for storing first and second values; and

frequency ratio counter that receives one of the first and second values in response to the first clock signal and generates a control signal under control of the received value, counts pulses of the first clock signal and the second clock signal and captures the count of each clock signal in response to the control signal, and determines a ratio between a frequency of the first clock signal and a frequency of the second clock signal using the count.

2. A personal communications device according to claim 1, wherein the frequency ratio counter comprises:

first register for storing the first value;

second register for storing the second value;

control signal generator comprising a first input for receiving input of the value stored in the first register, a second input for receiving the value stored in the second register, third input for receiving the first clock signal, a forth input for receiving the second clock signal and an output for outputting the control signal in accordance with the value stored in the first and second register and the first and the second clock signals; and

count capture unit, responsive to the control signal output from the control signal generator, for capturing values representative of the number of clock cycles of the first and the second clock signal that occur within a given time duration.

3. A personal communications device according to claim 1 wherein the first value represents an approximation of the frequency of the first clock signal.

4. A personal communications device according to claim 1 wherein the second value represents an approximation of the frequency of the second clock signal.

5. A personal communications device according to claim 1 wherein the first and second values are selected in accordance with calculations based upon the principles of convergents of continued fractions.

6. A personal communications device according to claim 2 wherein the control signal generator further comprises:

switch responsive to an edge transition signal, for selecting between the input from the first register and the input from the second register;

decrementing counter for alternately receiving the value from the first or second register and decrementing the received value in synchronization with the first clock signal and generating an enable signal when the value reaches zero;

flip-flop responsive to the enable signal for generating the edge transition signal in accordance with the first clock signal and the second clock signal; and

pulse generator responsive to the edge transition signal, for outputting the control signal to the count capture unit.

7. A personal communications device according to claim 2 wherein the count capture unit further comprises:

first incrementing counter for counting the pulses of the first clock signal;

second incrementing counter for counting the pulses of the second clock signal;

first latch for storing the count value for the first incrementing counter in response to the control signal; and

second latch for storing the count value of the second incrementing counter in response to the control signal.

8. A method of determining a ratio between two clock frequencies comprising:

reading one of a first value and a second value in response to a first clock signal and generating a control signal under control of the read value;

counting successive clock pulses of the first clock signal for a duration of time determined in accordance with the control signal;

counting successive clock pulses of a second clock signal for the duration of time;

reading the count of the clock pulses of each of the first clock signal and the second clock signal upon the elapse of the duration; and

determining the ratio between a frequency of the first clock signal and a frequency of the second clock signal using the count.

9. A method of determining a ratio between two clock frequencies according to claim 8 wherein the first clock comprises a clock for providing clock signals to a telecommunications unit and the second clock comprises a clock for providing clock signals to a GPS receiver.

10. A method of determining a ratio between two clock frequencies according to claim 9 wherein the telecommunications unit comprises a CDMA based telecommunications unit.

11. A personal communications device having provisions for ratio counting comprising:

a first memory area for storing a first value;

a second memory area for storing a second value;

control signal generator for receiving one of the first and second values in response to a first clock signal and for outputting a control signal; and

count capture unit for receiving the first clock signal and a second clock signal and counting the pulses of the first clock signal and the second clock signal and capturing the count of each clock signal in response to the control signal.

12. A personal communications device according to claim 11 further comprising:

first radio receiver; and

second radio receiver.

13. A personal communications device according to claim 12 where in the first radio receiver comprises a code division multiple access (CDMA) based receiver.

14. A personal communications device according to claim 12 wherein the second radio receiver comprises a global positioning system (GPS) receiver.

15. A personal communications device according to claim 11 wherein at least one of the first value and the second value are generated using a principle of convergents of continued fractions.

16. A personal communications device according to claim 11 wherein the first memory area and the second memory area comprise at least one storage register.

17. A personal communications device according to claim 11 wherein the control signal generator further comprises:

multiplexer for selectively receiving the first and second storage values;

decrementing counter for receiving the value received by the multiplexer and decrementing the received value by a value of one in response to each pulse of the first clock signal to produce a decremented value, and outputting an enable signal once the decremented value reaches zero;

logic gating for receiving the first clock signal and the second clock signal and outputting an edge transition signal in accordance therewith upon receiving the input of the enable signal; and

pulse generator for generating the control signal in accordance with the edge transition.

18. A communication device comprising:

first means for receiving a radio frequency signal that includes a first means for generating a first clock signal;

second means for receiving a radio frequency signal that includes a second means for generating a second clock signal;

means for storing first and second values representative of the first and second clock signals; and

means for receiving one of the first and second values in response to the first clock signal and generating a control signal under control of the received value, counting pulses of the first and second clock signals and capturing the count of each clock signal in response to the control signal, and determining a ratio between the frequency of the first clock signal and the frequency of the second clock signal using the count.

19. A communications device according to claim 18, wherein the means for determining a ratio comprises:

first storage means for storing the first value;

second storage means for storing the second value;

means for generating the control signal comprising a first input for receiving the first value, a second input for receiving the second value, third input for receiving the first clock signal, a fourth input for receiving the second clock signal and an output for outputting the control signal in accordance with the values stored in the first and second storage means and the first and the second clock signals; and

wherein the means for capturing count, captures values representative of the number of clock cycles of the first and the second clock signal that occur during a given time duration.

20. A personal communications device according to claim 18, wherein the first means for receiving a radio frequency signal comprises a code division multiple access (CDMA) based telecommunications receiver.

21. A communications device according to claim 18, wherein the second means for receiving a radio frequency signal comprises a global positioning system (GPS) receiver.

22. A communications device according to claim 19, wherein the control signal is generated where a transitional edge of the first clock signal coincides with and is in synchronization with a transitional edge of the second clock signal.

23. A communications device according to claim 22, wherein the means for means for generating a control signal comprises a controller.

24. A communications device according to claim 22, wherein the means for means for generating a control signal comprises an application specific integrated circuit.

25. A communications device according to claim 22, wherein the means for determining a ratio comprises an application specific integrated circuit.

26. A communications device comprising:

a first receiver that includes a first clock generating a first clock signal;

a second receiver that includes a second clock generating a second clock signal;

memory that stores values representative of the first and second clock signals; and

a ratio counter that generates a control signal in accordance with one of the values, counts pulses of the first clock signal and the second clock signal and captures the count of each clock signal in response to the control signal, and determines a ratio between frequencies of the first and second clock signals using the count.