Systems and Methods for Sharing an Oscillator Between Receivers

• US 20090109087A1
• Filed: 10/29/2007
• Published: 04/30/2009
• Est. Priority Date: 10/29/2007
• Status: Active Grant

• Current Assignee: CSR Technology Incorporated (Qualcomm, Inc.)
• Original Assignee: SIRF Technology Incorporated (Qualcomm, Inc.)
• Inventors: Gronemeyer, Steven A.
• Granted Patent: US 8,571,506 B2
• Time in Patent Office: Days
• US Class Current: 342/357.510
• CPC Class Codes: G01S 19/13 Receivers
• CPC Class Codes: G01S 19/35 Constructional details or hardware or software details of the signal processing chain
• CPC Class Codes: H03J 3/04 Arrangements for compensating for variations of physical values, e.g. temperature
• CPC Class Codes: H03L 1/02 against variations of temperature only

Abstract

Systems and methods for sharing an oscillator between receivers are disclosed. A representative method (among others) of responding to a change in frequency of a voltage-controlled temperature-compensated oscillator (VCTCXO), includes: determining a new value for VCTCXO frequency; determining a time at which the new value will be applied to the VCTCXO; transmitting the time and the new value to a subsystem that uses a second receiver which shares the VCTCXO with a first receiver; and in the subsystem, updating channel context data to use the time of the change in frequency and the new value.

Claims

1. A method of responding to a change in frequency of a voltage-controlled temperature-compensated oscillator (VCTCXO) shared by a first and a second receiver in a device, the method comprising the steps of:

determining a new value for the VCTCXO frequency;

determining a time at which the new value will be applied to the VCTCXO;

transmitting the time and the new value to a subsystem that uses the second receiver; and

in the subsystem, updating channel context data to use the time of the change in frequency and the new value.

2. The method of claim 1, further comprising the step of:

latching a first time related to a second time at which the new value is stored in a digital-to-analog-converter located in the first receiver.

3. The method of claim 1, further comprising the step of:

latching a time at which the new value is written to a digital-to-analog-converter located in the first receiver.

4. The method of claim 1, further comprising the step of:

at a time at which the new value is stored to a digital-to-analog-converter located in the first receiver, latching an index into a received sample stream.

5. The method of claim 1, further comprising the step of:

determining a time range during which the channel context data is in use; and

updating the channel context data at a time which is outside of the determined time range.

6. A method of responding to a change in frequency of a voltage-controlled temperature-compensated oscillator (VCTCXO) shared by a first and a second receiver in a device, the method comprising:

receiving a notification of VCTCXO frequency change, the notification including a new value and the time at which the new value will be applied to the VCTCXO; and

updating context data associated with one of a plurality of channels, during a period in which the one channels is idle, to use the time and the new value.

7. The method of claim 6, further comprising the steps of:

determining a time range during which the channel context data is in use for acquisition; and

updating the channel context data at a time which is outside of the determined time range.

8. The method of claim 6, further comprising the steps of:

determining a time range during which the channel context data is in use; and

updating the channel context data at a time which is outside of the determined time range.

9. The method of claim 6, further comprising the step of:

searching a plurality of frequency bins for detected signal energy greater than a threshold value, the plurality of frequency bins being at least partially defined by the channel context data.

10. A system comprising:

a voltage-controlled temperature-compensated oscillator (VCTCXO) used by a first receiver;

logic configured to change a frequency used by the VCTCXO to a new value;

logic configured to determine a time for the frequency change;

a subsystem comprising;

a second receiver configured to obtain a reference frequency from the VCTCXO;

a processor configured to;

receive a plurality of samples from the second receiver,

receive the time of the frequency change and the new value;

update channel context data with the time of the frequency update and the new value; and

process the plurality samples in accordance with the channel context data to determine whether a signal is present in one a plurality of search bins, the plurality of search bins at least partially defined by the channel context data.

11. The system of claim 10, wherein the processor is further configured to:

convert the time of the frequency change from a first timescale used by the first receiver to a second timescale used by the second receiver

12. The system of claim 10, wherein the processor is further configured to:

converting the time of the frequency change to a corresponding time relative to a local clock used by the second receiver.

13. The system of claim 10, further comprising:

a counter configured to index into the received samples; and

a latch configured to store the value of the counter at a first time related to a second time at which the new value is written to a digital-to-analog-converter located in the first receiver.

14. The system of claim 10, further comprising:

a counter configured to index into the received samples; and

a latch configured to store the value of the counter at a time at which the new value is written to a digital-to-analog-converter located in the first receiver.

15. The system of claim 10, wherein the processor is further configured to:

determine a time range during which the channel context data is in use; and

update the channel context data at a time which is outside of the determined time range.

16. A device comprising:

means for receiving a notification of a change in a reference frequency shared by a first and a second receiver, the notification including a new value and the time at which the new value will be applied to a VCTCXO;

means for receiving a set of samples derived from a received satellite signal;

means for processing the set of samples, using context data associated with a plurality of channels, to determine whether the received satellite signal has been acquired; and

means for updating context data associated with one of the plurality of channels, during a period in which the one channel is idle, to use the time and the new value.

17. The device of claim 16, further comprising:

means for determining a time range during which the channel context data is being used for acquisition by the means for processing; and

means for updating the channel context data at a time which is outside of the determined time range.

18. The device of claim 16, further comprising:

means for determining a time range during which the channel context data is in use; and

means for updating the channel context data at a time which is outside of the determined time range.

19. The device of claim 16, further comprising:

means for latching a first time related to a second time at which the new value is stored in a digital-to-analog-converter located in the first receiver.

20. The device of claim 16, further comprising:

means for latching a time at which the new value is written to a digital-to-analog-converter located in the first receiver.