Systems and methods for sharing an oscillator between receivers

• US 8,571,506 B2
• Filed: 10/29/2007
• Issued: 10/29/2013
• Est. Priority Date: 10/29/2007
• Status: Active Grant

• Current Assignee: CSR Technology Incorporated (Qualcomm, Inc.)
• Original Assignee: CSR Technology Incorporated (Qualcomm, Inc.)
• Inventors: Gronemeyer, Steven G.
• Primary Examiner(s): HANNON, CHRISTIAN A
• Application Number:
  US11/926,474
• Publication Number:
  US 20090109087A1
• Time in Patent Office: 2,192 Days
• Field of Search: 455255-265
• US Class Current: 455/264
• 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 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 usage time range during which the second receiver is using the VCTCXO;

updating the VCTCXO with the new value before the usage time range if it is determined that updating before the usage time range will not overlap the usage time range; and

updating the VCTCXO with the new value after the usage time range if it is determined that updating before the usage time range will overlap the usage time range.

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, the updating comprising:

during the execution of a slice, storing a value of a counter of a last sample processed during the slice in one of a plurality of channel records.

6. The method of claim 5, the updating further comprising:

determining when a buffer is full of a slice by examining the channel records.

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

computing a difference between a current value of the counter and the stored value of the counter.

8. The method of claim 7, the updating further comprising:

determining the time range during which the channel is in use based on the computed difference.

9. 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, by the second receiver, a notification of VCTCXO frequency change, the notification including a new value and an update time at which context data will be updated and the new value will be applied to the VCTCXO,

setting the update time to occur before a usage time range when the VCTCXO is in use, if it is determined that updating the VCTCXO before the usage time range will not overlap the usage time range, and

setting the update time to occur after the usage time range if it is determined that updating the VCTCXO before the usage time range will overlap the usage time range.

10. The method of claim 9, 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.

11. The method of claim 9, 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.

12. The method of claim 9, 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.

13. 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 an update 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 update time of the frequency change and the new value;

setting the update time to occur before a usage time range when the VCTCXO is in use, if it is determined that updating the VCTCXO before the usage time range will not overlap the usage time range,

setting the update time to occur after the usage time range if it is determined that updating the VCTCXO before the usage time range will overlap the usage time range; 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.

14. The system of claim 13, 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.

15. The system of claim 13, 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.

16. The system of claim 13, 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.

17. The system of claim 13, 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.

18. A device comprising:

a receiver 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;

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

updating the VCTCXO with the new value before a usage time range when the VCTCXO is in use by one of the plurality of channels, if it is determined that updating before the usage time range will not overlap the usage time range; and

updating the VCTCXO with the new value after the usage time range if it is determined that updating before the usage time range will overlap the usage time range.