Wireless communication system for adapting to frequency drift

• US 5,909,640 A
• Filed: 10/06/1997
• Issued: 06/01/1999
• Est. Priority Date: 01/20/1995
• Status: Expired due to Term

• Current Assignee: PTC Inc.
• Original Assignee: Whisper Communications LLC
• Inventors: Farrer, Leland M., Chan, Joseph S., Garry, Jr., Robert F., Glorioso, Charles A., Krasner, Norman F.
• Primary Examiner(s): Urban, Edward F.
• Application Number:
  US08/944,832
• Time in Patent Office: 603 Days
• Field of Search: 455/507, 455/517, 455/62, 455/63, 455/75, 455/76, 455/87, 455/85, 455/86, 455/69, 455/119, 375/200, 375/202, 375/326, 370/280, 340/825.54
• US Class Current: 455/63.1
• CPC Class Codes: H04B 1/713 using frequency hopping
• CPC Class Codes: H04B 1/7136 Arrangements for generation of hop frequencies, e.g. using a bank of frequency sources, using continuous tuning or using a transform
• CPC Class Codes: H04B 7/12 Frequency diversity

Abstract

A wireless communication system with one or more remote transceivers for transmitting a wireless data signal at an actual frequency that is different than the expected frequency and a base transceiver that can automatically adjust to receive the actual frequency. Each remote transceiver is adapted to initiate a wireless data signal at a selected time that is unique to that remote transceiver. The expected frequency is sequentially pre-determined in a pseudo-random sequence with each remote transceiver having a unique sequence. The base transceiver can respond to the remote transceiver at the actual frequency. Both the remote transceiver and the base transceiver can convert the wireless signals in a single step to baseband.

Claims

1. A frequency tolerant transceiver for communicating individually with each of a plurality of remote receivers, comprising:

a receiver for tuning to an expected frequency associated with a particular one of said remote transceivers and receiving energy in a data signal having an actual frequency from said particular remote transceiver, said actual frequency allowed to drift from said expected frequency;

a microcontroller coupled to the receiver for providing information for said expected frequency and determining said actual frequency from said expected frequency and frequency information derived from said energy in said data signal; and

a transmitter coupled to the microcontroller for transmitting a return signal at said actual frequency to said particular remote transceiver.

2. The transceiver of claim 1, wherein:

the microcontroller is further for determining said expected frequency from a predetermined frequency and an expected frequency error.

3. The transceiver of claim 2, wherein:

the microcontroller is further for determining said expected frequency error from said predetermined frequency and a last actual frequency.

4. The transceiver of claim 1, wherein:

the microcontroller is further for providing information for said actual frequency to the receiver; and

the receiver is further for tuning to said actual frequency for demodulating data from said data signal and passing said data to the microcontroller.

5. The transceiver of claim 4, wherein:

said data includes information from at least one of (i) a gas meter, (ii) a water meter, (iii) an electric meter, (iv) a thermostat, (v) a gas appliance, and (vi) an electric appliance.

6. The transceiver of claim 1, wherein:

the receiver includes a frequency discriminator for determining a current frequency error between said expected frequency and said actual frequency; and

the microcontroller is further for determining said actual frequency from said current frequency error and said expected frequency.

7. The transceiver of claim 1, wherein:

said expected frequency is one of a pseudo-random sequence of frequencies.

8. The transceiver of claim 1, wherein:

the receiver and the transmitter share a signal generator for sequentially (i) using information for said expected frequency for generating a first local oscillator (LO) signal for tuning to said expected frequency and (ii) using information for said actual frequency for generating a second LO signal having said actual frequency for receiving said data signal and transmitting said return signal at said actual frequency.

9. A method in a frequency tolerant transceiver for allowing for respective carrier frequency drifts of a plurality of remote transceivers, comprising steps of:

tuning to an expected frequency associated with a particular one of said remote transceivers,

receiving energy in a data signal having an actual frequency from said particular remote transceiver, said actual frequency allowed to drift from said expected frequency;

using said expected frequency and energy in said data signal for determining said actual frequency, and

transmitting a return signal at said actual frequency to said particular remote transceiver.

10. The method of claim 9, wherein:

said expected frequency is determined from a predetermined frequency and an expected frequency error.

11. The method of claim 10, wherein:

said expected frequency error is determined from said predetermined frequency and a last actual frequency.

12. The method of claim 9, further including steps of:

tuning to said actual frequency; and

demodulating data from said data signal at said actual frequency.

13. The method of claim 12, wherein:

said data includes information from at least one of (i) a gas meter, (ii) a water meter, (iii) an electric meter, (iv) a thermostat, (v) a gas appliance, and (vi) an electric appliance.

14. The method of claim 9, wherein:

the step of determining said actual frequency includes steps of determining a current frequency error between said expected frequency and said actual frequency; and

using said current frequency error and said expected frequency for calculating said actual frequency.

15. The method of claim 9, wherein:

said expected frequency is one of a pseudo-random sequence of frequencies.

16. The method of claim 9, wherein:

the step of tuning to said expected frequency includes generating a first local oscillator (LO) signal having said expected frequency;

the step of receiving said data signal includes generating a second LO signal having said actual frequency; and

the step of transmitting said return signal includes generating said second LO signal having said second frequency.

17. A communication system, comprising:

a plurality of remote transceivers for transmitting respective data signals, each of said data signals having an actual frequency that is allowed to drift from an expected frequency; and

a base transceiver having a receiver for tuning to said expected frequency associated with a particular one of said remote transceivers and then receiving energy in said data signal from said particular remote transceiver, a microcontroller coupled to the receiver for determining said actual frequency for said data signal from said expected frequency and frequency information derived from said energy, and a transmitter coupled to the microcontroller for transmitting a return signal at said actual frequency to said particular remote transceiver.

18. The system of claim 17, wherein:

the microcontroller is further for determining said expected frequency from a predetermined frequency and an expected frequency error.

19. The system of claim 18, wherein:

the microcontroller is further for determining said expected frequency error from said predetermined frequency and a last actual frequency.

20. The system of claim 17, wherein:

the microcontroller is further for providing information for said actual frequency to the receiver; and

the receiver is further for tuning to said actual frequency for demodulating data from said data signal and passing said data to the microcontroller.

21. The system of claim 20, wherein:

said data includes information from at least one of (i) a gas meter, (ii) a water meter, (iii) an electric meter, (iv) a thermostat, (v) a gas appliance, and (vi) an electric appliance.

22. The system of claim 20, wherein:

the receiver includes a frequency discriminator for determining a current frequency error between said expected frequency and said actual frequency; and

the microcontroller is further for determining said actual frequency from said current frequency error and said expected frequency.

23. The system of claim 17, wherein:

said expected frequency is one of a pseudo-random sequence of frequencies.

24. The system of claim 20, wherein:

the receiver and the transmitter share a signal source for sequentially (i) using information for said expected frequency for generating a first local oscillator (LO) signal for tuning to said expected frequency and (ii) using information for said actual frequency for generating a second LO signal having said actual frequency for receiving said data signal and transmitting said return signal at said actual frequency.