Indoor GPS clock
First Claim
1. A method for providing a frequency standard signal, comprising:
- acquiring a global positioning system (GPS) signal using an acquisition time period of at least two GPS data bit times for determining correlation sums for code phases, respectively;
carrier-less tracking said GPS signal, after said GPS signal has been acquired, for providing a clock bias error; and
disciplining said frequency standard signal with said clock bias error for tracking said GPS carrier frequency wherein;
said GPS signal is less than or equal to about −
146 dBm.
0 Assignments
0 Petitions
Accused Products
Abstract
An indoor GPS clock using GPS signals lower that −143 dBm for issuing disciplined frequency and time standard signals. The indoor GPS clock includes a correlation machine using long integration periods for enabling the indoor GPS clock to operate with low signal levels; a carrier-less tracking loop for tracking the low level signals without carrier offset feedback, a clock bias loop for providing clock bias feedback; and a reference oscillator using the clock bias feedback for providing disciplined frequency and time signals having greater accuracy than is available in conventional GPS positioning receivers. The indoor GPS clock also includes a holdover driver providing compensation for predicted drift in clock bias error for disciplining the reference oscillator for several hours when the GPS signal is no longer being received.
39 Citations
36 Claims
-
1. A method for providing a frequency standard signal, comprising:
-
acquiring a global positioning system (GPS) signal using an acquisition time period of at least two GPS data bit times for determining correlation sums for code phases, respectively;
carrier-less tracking said GPS signal, after said GPS signal has been acquired, for providing a clock bias error; and
disciplining said frequency standard signal with said clock bias error for tracking said GPS carrier frequency wherein;
said GPS signal is less than or equal to about −
146 dBm. - View Dependent Claims (2, 3, 4, 5)
-
-
6. A method for providing a frequency standard signal, comprising:
-
acquiring a global positioning system (GPS) signal using an acquisition time period of at least two GPS data bit times for determining correlation sums for code phases, respectively;
carrier-less tracking said GPS signal, after said GPS signal has been acquired, for providing a clock bias error; and
disciplining said frequency standard signal with said clock bias error for tracking said GPS carrier frequency;
wherein;
said acquisition time period includes a plurality of coherent integration periods each covering at least ten epochs of said code phases;
acquiring includes determining a plurality of correlation levels for said plurality of coherent integration periods, respectively, for said code phases; and
then incoherently combining said correlation levels at corresponding ones of said code phases for providing said correlation sums; and
incoherently combining includes summing squares of at least first and second said correlation levels corresponding to at least first and second said coherent integration periods. - View Dependent Claims (7, 8, 9)
-
-
10. A method for providing a frequency standard signal, comprising:
-
acquiring a global positioning system (GPS) signal using an acquisition time period of at least two GPS data bit times for determining correlation sums for code phases, respectively;
carrier-less tracking said GPS signal, after said GPS signal has been acquired, for providing a clock bias error; and
disciplining said frequency standard signal with said clock bias error for tracking said GPS carrier frequency;
wherein;
said acquisition time period includes an extended coherent integration period having a plurality of coherent integration periods each covering at least forty epochs of said code phases; and
acquiring includes determining a plurality of correlation levels for a plurality of coherent integration periods, respectively, for said code phases;
stripping GPS data bit senses from said correlation levels for providing data stripped correlation levels; and
then coherently combining said data stripped correlation levels at corresponding ones of said code phases for providing said correlation sums for said extended coherent integration period. - View Dependent Claims (11, 12, 13, 14)
-
-
15. A method for providing a frequency standard signal, comprising:
-
acquiring a global positioning system (GPS) signal using an acquisition time period of at least two GPS data bit times for determining correlation sums for code phases, respectively;
carrier-less tracking said GPS signal after said GPS signal has been acquired, for providing a clock bias error; and
disciplining said frequency standard signal with said clock bias error for tracking said GPS carrier frequency;
wherein;
acquiring said GPS signal includes using coherent integration times for said acquisition time periods for a processing gain of at least 16 dB with respect to a coherent integration time of one millisecond. - View Dependent Claims (16, 17, 18)
-
-
19. A GPS clock using a GPS signal for providing a frequency standard signal, comprising:
-
a long integration correlation machine for acquiring a global positioning system (GPS) signal using an acquisition time period of at least two GPS data bit times for determining correlation sums for code phases, respectively;
a signal tracking loop using the correlation machine for carrier-less tracking said GPS signal, after said GPS signal has been acquired, for providing a clock bias error; and
a clock bias loop including the signal tracking loop for disciplining said frequency standard signal with said clock bias error for tracking said GPS carrier frequency;
wherein;
said GPS signal is less than or equal to about −
146 dBm. - View Dependent Claims (20, 21, 22, 23)
-
-
24. A GPS clock using a GPS signal for providing a frequency standard signal, comprising:
-
a long integration correlation machine for acquiring a global positioning system (GPS) signal using an acquisition time period of at least two GPS data bit times for determining correlation sums for code phases, respectively;
a signal tracking loop using the correlation machine for carrier-less tracking said GPS signal, after said GPS signal has been acquired, for providing a clock bias error; and
a clock bias loop including the signal tracking loop for disciplining said frequency standard signal with said clock bias error for tracking said GPS carrier frequency;
wherein;
said acquisition time period includes a plurality of coherent integration periods each covering at least ten epochs of said code phases;
the long integration correlation machine determines a plurality of correlation levels for said plurality of coherent integration periods, respectively, for said code phases; and
then incoherently combines said correlation levels at corresponding ones of said code phases for providing said correlation sums; and
the long integration correlation machine combines said correlation levels by summing squares of at least first and second said correlation levels corresponding to at least first and second said coherent integration periods. - View Dependent Claims (25, 26, 27)
-
-
28. A GPS clock using a GPS signal for providing a frequency standard signal, comprising:
-
a long integration correlation machine for acquiring a global positioning system (GPS) signal using an acquisition time period of at least two GPS data bit times for determining correlation sums for code phases, respectively;
a signal tracking loop using the correlation machine for carrier-less tracking said GPS signal, after said GPS signal has been acquired, for providing a clock bias error; and
a clock bias loop including the signal tracking loop for disciplining said frequency standard signal with said clock bias error for tracking said GPS carrier frequency;
wherein;
said acquisition time period includes an extended coherent integration period having a plurality of coherent integration periods each covering at least forty epochs of said code phases; and
the long integration correlation machine coherently determines a plurality of correlation levels for a plurality of coherent integration periods, respectively, for said code phases;
strips GPS data bit senses from said correlation levels for providing data stripped correlation levels; and
then coherently combines said data stripped correlation levels at corresponding ones of said code phases for providing said correlation sums for said extended coherent integration period. - View Dependent Claims (29, 30, 31, 32, 33, 34, 35)
-
-
36. A GPS clock using a GPS signal for providing a frequency standard signal, comprising:
-
a long integration correlation machine for acquiring a global positioning system (GPS) signal using an acquisition time period of at least two GPS data bit times for determining correlation sums for code phases, respectively;
a signal tracking loop using the correlation machine for carrier-less tracking said GPS signal, after said GPS signal has been acquired, for providing a clock bias error; and
a clock bias loop including the signal tracking loop for disciplining said frequency standard signal with said clock bias error for tracking said GPS carrier frequency;
wherein;
the long integration correlation machine uses coherent acquisition integration periods for a processing gain of at least 16 dB with respect to a processing gain for a coherent integration period of one millisecond.
-
Specification