Adjusting the timing and synchronization of a radio's oscillator with a signal from an SATPS satellite

• US 5,970,400 A
• Filed: 04/30/1996
• Issued: 10/19/1999
• Est. Priority Date: 04/30/1996
• Status: Expired due to Term

• Current Assignee: MiTAC International Corporation (MiTAC Holdings Corp.)
• Original Assignee: Magellan Corporation (Thales SA)
• Inventors: Dwyer, Rex
• Primary Examiner(s): Vo, Nguyen
• Assistant Examiner(s): Kincaid, Lester G.
• Application Number:
  US08/644,639
• Time in Patent Office: 1,267 Days
• Field of Search: 364/449.7, 342/357, 375/362, 375/200, 455/254, 455/255, 455/257, 455/258, 455/259, 455/266, 455/339, 455/295, 455/310, 455/307, 455/119, 455/63, 455/265, 455/13.2, 368/47, 968/922
• US Class Current: 455/254
• CPC Class Codes: H03J 7/04 where the frequency control is accomplished by varying the electrical characteristics of a non-mechanically adjustable element or where the nature of the frequency controlling element is not significant
• CPC Class Codes: H04B 1/40 Circuits

Abstract

A communication system is provided for increasing communication range between at least two radio communication devices without increasing the output power of transmitted radio signals from the devices, and without increasing the antenna gain of the received signals. Each radio device includes an oscillator for generating a carrier reference signal, and an SATPS receiver which receives at least one standard timing reference signal from at least one SATPS satellite. The received standard timing reference signal is used to continuously adjust the timing and synchronization of the oscillator to improve the accuracy of the carrier frequency signal. The improved accuracy in the carrier frequency signal may then be used to reduce the bandwidth of the modulated carrier frequency signals generated by the radio device to thereby increase the effective communication range and sensitivity of the device.

Claims

1. A portable, wireless radio communication system comprising:

at least one wireless spread spectrum radio communication device, said device including an oscillator for generating a clock signal and a carrier frequency signal, said carrier frequency signal having a predetermined frequency stability and further having a predetermined carrier minimum bandwidth determined by the extreme frequency excursion of said oscillator;

a channel filter accommodating a predetermined channel bandwidth only slightly larger than said predetermined carrier minimum bandwidth;

a SATPS receiver in communication with the radio device, wherein the SATPS receiver receives at least one standard timing reference signal from at least one SATPS satellite; and

correction means for using said timing reference signal to continuously adjust and improve the accuracy of said carrier frequency reference signal, said correction means increasing the frequency stability of said carrier frequency signal to a level higher than said predetermined frequency stability while also simultaneously reducing the channel bandwidth of said channel filter to a value smaller than that of said predetermined channel bandwidth and that of said predetermined carrier minimum bandwidth.

2. The system of claim 1 wherein said correction means includes at least one timing correction signal communicating between the SATPS receiver and the oscillator for continuously adjusting and maintaining precise timing of the oscillator in order to improve and maintain precise accuracy of said carrier frequency signal.

3. The system of claim 2 wherein said at least one spread spectrum radio device has specifications in compliance with Title 47, Section 15.247 of the United States Code of Federal Regulations, wherein a user of said radio device is not required to obtain an FCC license to operate said radio device.

4. The system of claim 3 wherein a rate of data transmission of said at least one spread spectrum radio device falls below 2400 bits per second (bps).

5. The system of claim 3 wherein said rate of data transmission of said at least one spread spectrum radio device is in the range of about 2400-10 bps.

6. The system of claim 3 wherein said at least one spread spectrum radio device includes a transmitter operating at an output power of at most one Watt, and wherein said system includes means for reducing a bandwidth of a transmitted radio signal such that said at least one radio device achieves an effective broadcast range of greater than 25 kilometers.

7. The system of claim 3 wherein said system includes means for reducing or filtering a bandwidth of a received radio signal such that said at least one spread spectrum radio device achieves a sensitivity of at least -120 dBm.

8. The system of claim 7 wherein said radio signal is devoid of oscillator synchronization information for synchronizing said oscillator of said at least one spread spectrum radio device with an oscillator of another radio device.

9. The system of claim 1 wherein the accuracy of said carrier frequency signal is within 0.08 parts per million (ppm).

10. A method for improving communication range of a spread spectrum radio communication system, said system including a mobile spread spectrum radio communication device including an oscillator for generating a carrier frequency signal, said carrier frequency signal having a predetermined carrier minimum bandwidth determined by the extreme frequency excursions of said oscillator, and a channel filter accommodating a predetermined channel bandwidth only slightly larger than said predetermined carrier minimum bandwidth, said system further including an SATPS receiver, said method comprising the steps of:

(a) receiving at least one standard timing reference signal from at least one SATPS satellite,

(b) using said received timing reference signal to continually correct and maintain precise timing and synchronization of said oscillator to thereby provide improved accuracy of said carrier frequency signal; and

(c) utilizing the improved accuracy of the carrier frequency signal to increase the frequency stability of said carrier frequency signal to a level higher than said predetermined frequency stability while also simultaneously reducing the channel bandwidth of said channel filter to a value smaller than that of said predetermined channel bandwidth and that of said predetermined carrier minimum bandwidth.

11. The method of claim 10 wherein said using step (b) includes the step of improving the accuracy of said carrier frequency signal to within 0.08 parts per million (ppm).

12. The method of claim 10 wherein said utilizing step (c) includes the step of increasing effective communication range of the spread spectrum radio device without increasing output power of transmitted signals from the spread spectrum radio device.

13. The method of claim 12 wherein said method further includes the step of complying with operating requirements of said radio device under Title 47, Section 15.247 of the United States Code of Federal Regulations.

14. The method of claim 13 further including the step of transmitting data from said spread spectrum radio at a rate of at most 2400 bits per second (bps).

15. The method of claim 13 wherein said step (c) includes the step of reducing or filtering a bandwidth of a radio signal such that said spread spectrum radio device achieves a sensitivity of at least -120 dBm without encoding oscillator synchronization information into said radio signal.

16. In a portable, wireless radio communication system having a reference oscillator generating a clock signal and a carrier signal, said carrier signal frequency having a predetermined frequency stability and further having a predetermined carrier minimum bandwidth determined by the extreme frequency excursions of said oscillator, and a channel filter accommodating a predetermined channel bandwidth only slightly larger than said predetermined carrier minimum bandwidth, the improvement comprising:

at least one wireless spread spectrum radio communication device having said reference oscillator and said channel filter,

a SATPS receiver in communication with said at least one radio device, wherein the SATPS receiver receives at least one standard timing reference signal from at least one SATPS satellite; and

a correction circuit responsive to said timing reference signal and coupled to said reference oscillator and said channel filter, said correction circuit increasing the frequency stability of said carrier signal to a level higher than said predetermined frequency stability while also simultaneously reducing the channel bandwidth of said channel filter to a value smaller than that of said predetermined channel bandwidth and that of said predetermined carrier minimum bandwidth.

17. The system of claim 16 wherein said correction circuit includes at least one timing correction signal communicating between the SATPS receiver and the oscillator for continuously adjusting and maintaining precise timing of the oscillator in order to improve and maintain precise accuracy of said carrier frequency signal.

18. The system of claim 16 wherein the accuracy of said carrier frequency signal is within 0.08 parts per million (ppm).

19. The system of claim 17 wherein said radio device is a spread spectrum radio having specifications in compliance with Title 47, Section 15.247 of the United States Code of Federal Regulations, wherein a user of said radio device is not required to obtain an FCC license to operate said radio device.

20. The system of claim 19 wherein a rate of data transmission of said spread spectrum radio falls below 2400 bits per second (bps).

21. The system of claim 19 wherein said rate of data transmission of said spread spectrum radio is in the range of about 2400-10 bps.

22. The system of claim 19 wherein said spread spectrum radio includes a transmitter operating at an output power of at most one Watt, and wherein said system includes means for reducing a bandwidth of a transmitted radio signal such that said at least one radio device achieves an effective broadcast range of greater than 25 kilometers.

23. The system of claim 19 wherein said system includes means for reducing or filtering a bandwidth of a received radio signal such that said at least one radio device achieves a sensitivity of at least -120 dBm.

24. The system of claim 19 wherein said radio signal is devoid of oscillator synchronization information for synchronizing said oscillator of said at least one radio device with an oscillator of another radio device.