Maintaining repeater accuracy for satellite signal delivery systems
Systems and methods for maintaining synchronization of repeater networks with Global Positioning System (GPS) signals using phase locked loops (PLLs) and based on generation of predicted control words for controlling local oscillator frequencies is described. The predicted control words can be generated based on performing a linear fit of control words generated over a predetermined duration of time. Phase locked loops with additional false GPS pulse identification and GPS signal loss compensation circuitry can enforce a false pulse count threshold and/or an error threshold. The additional circuitry and prediction of control words can overcome errors in GPS receiver outputs and maintain accuracy of signal timings across single frequency networks using inexpensive local oscillators.
1. A method comprising:
receiving, by a computing system, a Global Positioning System (GPS) signal;
synchronizing, by the computing system, a local reference signal with the GPS signal based on a plurality of control words;
determining, by the computing system, an amount of time during which the local reference signal was synchronized with the GPS signal; and
after identifying an interruption in the GPS signal, generating a predicted control word based on the plurality of control words and based on the amount of time satisfying a first predetermined time duration;
wherein the generating the predicted control word comprises: generating, based on the plurality of control words, a linear curve fit.
2. The method of claim 1 , further comprising:
maintaining, by the computing system and via a feedback path, synchronization of the local reference signal with the GPS signal based on the predicted control word.
3. The method of claim 2 , further comprising:
controlling, based on the predicted control word, a slew voltage; and
adjusting, via the feedback path, a frequency of the local reference signal based on the slew voltage.
4. The method of claim 1 , further comprising:
determining, by the computing system, that the amount of time during which the local reference signal was synchronized with the GPS signal satisfies a second predetermined time duration less than the first predetermined time duration;
generating, by the computing system and based on the plurality of control words, a second order estimate of the predicted control word; and
maintaining, by the computing system, synchronization of the local reference signal with the GPS signal based on the second order estimate of the predicted control word.
5. The method of claim 1 , further comprising:
after the determining the interruption in the GPS signal, determining, an absence of synchronization of the local reference signal with the GPS signal; and
adjusting a frequency of the local reference signal based on a most recent control word of the plurality of control words.
6. The method of claim 5 , further comprising:
maintaining synchronization of the local reference signal with the GPS signal based on the adjusted frequency of the local reference signal.
7. A system comprising:
a Global Positioning System (GPS) receiver configured to generate a GPS signal; and
a computing device including:
at least one processor; and
memory storing computer-readable instructions that, when executed by the at least one processor, cause the computing device to:
receive, from the GPS receiver, the GPS signal;
synchronize a local reference signal with the GPS signal based on a plurality of control words;
determine an amount of time during which the local reference signal was synchronized with the GPS signal; and
after identifying an interruption in the GPS signal, generate a predicted control word based on the plurality of control words and based on the amount of time satisfying a first predetermined time duration;
wherein the generating the predicted control word comprises: generating, based on the plurality of control words, a linear curve fit.
8. The system of claim 7 , the memory further storing computer-readable instructions that, when executed by the at least one processor, cause the computing device to:
maintain, via a feedback path, synchronization of the local reference signal with the GPS signal based on the predicted control word.
9. The system of claim 7 , the memory further storing computer-readable instructions that, when executed by the at least one processor, cause the computing device to:
control, based on the predicted control word, a slew voltage; and
adjust, via the feedback path, a frequency of the local reference signal based on the slew voltage.
10. The system of claim 7 , the memory further storing computer-readable instructions that, when executed by the at least one processor, cause the computing device to:
determine that the amount of time during which the local reference signal was synchronized with the GPS signal satisfies a second predetermined time duration less than the first predetermined time duration;
generate, based on the plurality of control words, a second order estimate of the predicted control word; and
maintain synchronization of the local reference signal with the GPS signal based on the second order estimate of the predicted control word.
11. The system of claim 7 , the memory further storing computer-readable instructions that, when executed by the at least one processor, cause the computing device to:
after the determining the interruption in the GPS signal, determine an absence of synchronization of the local reference signal with the GPS signal; and
adjust a frequency of the local reference signal based on a recent control word of the plurality of control words.
12. The system of claim 11 , the memory further storing computer-readable instructions that, when executed by the at least one processor, cause the computing device to:
maintain synchronization of the local reference signal with the GPS signal based on the adjusted frequency of the local reference signal.
13. A method comprising:
synchronizing, by the computing system and based on a plurality of control words, a local signal with a Global Positioning System (GPS) signal;
detecting, by the computing system, a loss of the GPS signal;
determining that the local signal was synchronized with the GPS signal before the loss of the GPS signal;
continuing to maintain synchronization, by the computing system, between the local signal and the GPS signal based on the plurality of control words and based on adjusting a frequency of the local signal;
wherein the generating the predicted control word comprises: generating, based on the plurality of control words, a linear curve fit.
14. The method of claim 13 , further comprising:
determining that the local signal was not synchronized with the GPS signal before the loss of the GPS signal;
determining a most recent control word of the plurality of words; and
adjusting a frequency of the local signal based on the most recent control word.
15. The method of claim 13 , wherein the adjusting the frequency of the local signal is based on:
determining an amount of time corresponding to a generation of the plurality of control words;
determining that the amount of time satisfies a predetermined duration of time; and
generating a predicted control word based on the plurality of control words.
16. The method of claim 13 , wherein the adjusting the frequency of the local signal is based on:
determining an amount of time corresponding to a generation of the plurality of control words;
determining that the amount of time does not satisfy a predetermined duration of time; and
generating a second order word based on the plurality of control words, wherein the second order word corresponds to an average value associated with the plurality of control words.
17. The method of claim 13 , wherein the plurality of control words are generated based on:
detecting a plurality of timing offsets between the GPS signal and the local signal.