Method for calibrating and AOA location system for frequency hopping air interfaces
View Patent ↗A method for calibrating an antenna and signal processing system enabling angle of arrival (AOA) determination for a frequency hopping signal, in which a calibration coefficient is determined in response to one or more calibration signals injected into the system at one or more of the frequencies in the hopping sequence and proximate in time to reception of the communication signal. The calibration coefficients are reflective of a frequency and time dependent parameter of a path between the antenna and wireless location sensor. The AOA is determined as a function of the calibration coefficient and the radio frequency energy of the received communication signal. Several embodiment of the method are illustrated.
1. A method of calibrating an antenna array and signal processing system for receiving a frequency hopping communication signal comprising the steps of:
obtaining a frequency hopping sequence of the communication signal;
receiving the communication signal;
injecting a calibration signal at one frequency of the frequency hopping sequence of the communication signal in response to receipt of said communication signal;
determining a calibration coefficient C 1 for said one frequency; and,
applying C 1 to a received signal at each frequency of the received signal.
2. The method of claim 1 wherein the received signal is said communication signal.
3. The method of claim 1 wherein the received signal is a later received signal.
4. The method of claim 1 further comprising the step of determining the AOA of the communication signal based on said communication signal and C 1 .
5. The method of claim 1 wherein said frequency hopping sequence is comprised of N frequencies f i where i=1 to N and the calibration coefficient C 1 is associated with each f i .
6. The method of claim 1 wherein the step of injecting the calibration signal is proximate in time to receiving the received signal.
7. The method of claim 1 wherein the one frequency is determined as a function of an average frequency of the hopping sequence.
8. The method of claim 1 wherein the one frequency is the first frequency in the frequency hopping sequence.
9. The method of claim 1 wherein the one frequency is arbitrarily chosen from the frequency hopping sequence.
10. The method of claim 1 wherein the one frequency is determined as a function of a first moment of the frequencies in the frequency hopping sequence.
11. A method of calibrating an antenna array and signal processing system for receiving a frequency hopping communication signal comprising the steps of:
obtaining a frequency hopping sequence of the communication signal
injecting a calibration signal at one frequency of the frequency hopping sequence of the communication signal in response to receipt of said communication signal;
determining a calibration coefficient C 1 for said one frequency;
storing said calibration coefficient C 1 ,
receiving the communication signal; and,
applying the calibration coefficient C 1 to the communication signal for each frequency of the communication signal.
12. The method of claim 11 wherein the step of injecting a calibration signal is initiated periodically.
13. The method of claim 11 wherein the step of injecting is triggered in anticipation of receiving said communication signal.
14. The method of claim 11 further comprising the step of determining the AOA of the communication signal based on said communication signal and C 1 .
15. The method of claim 11 wherein said frequency hopping sequence is comprised of N frequencies f i where i=1 to N and the calibration coefficient C 1 is associated with each f i .
16. The method of claim 11 wherein the one frequency is determined as a function of an average frequency of the hopping sequence.
17. The method of claim 11 wherein the one frequency is the first frequency in the frequency hopping sequence.
18. The method of claim 11 wherein the one frequency is arbitrarily chosen from the frequency hopping sequence.
19. The method of claim 11 wherein the one frequency is determined as a function of a first moment of the frequencies in the frequency hopping sequence.
20. In a network overlay geolocation system, a method for locating a mobile appliance including determining the AOA of an uplink signal from the mobile appliance at a base station from measurements, by a wireless location sensor, of an attribute of the uplink signal and a frequency specific calibration of a path between a multi element antenna array and the wireless location sensor, the improvement comprising the steps of:
(a) collecting segments of a frequency hopping signal associated with a specific hop;
(b) calibrating the path, at approximately the specific hop's frequency, proximate in time to the collecting of the segment, over a plurality of hopping sequence cycles; and,
(c) estimating the AOA of a frequency hopping signal from the collected segments associated with the specific hop and the path calibrations at approximately the specific hop's frequency.
21. The method according to claim 20 wherein the step of calibrating includes generating a calibration signal.
22. The method according to claim 20 wherein the step of calibrating includes tuning the calibration source to the specific hop frequency.
23. The method according to claim 20 where the plurality of hopping sequence cycles is based on hop duration.
24. The method according to claim 20 wherein the network is a GSM system.