Wireless communication system for adapting to frequency drift

• US 5,734,966 A
• Filed: 01/20/1995
• Issued: 03/31/1998
• Est. Priority Date: 01/20/1995
• Status: Expired due to Term

• Current Assignee: PTC Inc.
• Original Assignee: Diablo Research Corporation
• Inventors: Chan, Joseph S., Garry, Jr., Robert F., Glorioso, Charles A., Krasner, Norman F., Farrer, Leland M.
• Primary Examiner(s): Urban, Edward F.
• Application Number:
  US08/376,109
• Time in Patent Office: 1,166 Days
• Field of Search: 455/53.1, 455/54.1, 455/62, 455/63, 455/76, 455/75, 455/84, 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 communication system for adapting to carder frequency drift, comprising:

a base transceiver including a receiver circuit for receiving a radio frequency (RF) data signal at an expected frequency corresponding to a sum of a pre-determined frequency and a last frequency error, a frequency discriminator coupled to the receiver circuit for determining a frequency difference between said expected frequency and an actual frequency of said RF data signal that differs from said pre-determined frequency by a current frequency error, and a microcontroller system coupled to said receiver circuit and said frequency discriminator for using said frequency difference for tuning said receiver circuit to said actual frequency for receiving said RF data signal including application data, and a synthesizer coupled to the microcontroller system for responding to said RF data signal by generating an RF return signal at said actual frequency including control information; and

a remote transceiver for transmitting said RF data signal and receiving said RF return signal at said actual frequency.

2. The communication system of claim 1, wherein:

the remote transceiver is further for transmitting said RF data signal in a burst at a selected time; and

the base transceiver further includes means for receiving said RF data signal at said selected time.

3. The communication system of claim 2, wherein:

said burst has a time duration in a range of 1 microsecond to 400 milliseconds.

4. The communication system of claim 2, wherein:

said pre-determined frequency is an entry in a pseudo-random sequence of frequencies and a successive said burst is a successive said entry in said pseudo-random sequence, whereby successive bursts of said RF data signal are frequency hopping.

5. The communication system of claim 4, wherein:

said pseudo-random sequence is unique to each of the multiplicity of the remote transceivers.

6. The communication system of claim 2, further including:

a multiplicity of the remote transceivers, where each remote transceiver is for transmitting said RF data signal at said selected time that is unique to the remote transceiver.

7. The communication system of claim 2, wherein

said control information includes said selected time.

8. The communication system of claim 1, wherein:

the base transceiver includes means for adjusting to said actual frequency for said current frequency error in a range of up to 30×

10^-6 times said pre-determined frequency.

9. The communication system of claim 1, wherein:

said pre-determined frequency is in a range of approximately 902 MHz to 928 MHz.

10. The communication system of claim 1, wherein the remote transceiver includes:

a synthesizer having a transmit mode for generating said RF data signal having a carrier frequency of said actual frequency and having modulation in response to a digital data signal, and having a receive mode for generating a local oscillator (LO) signal having said actual frequency;

a receiver circuit for receiving said LO signal for down converting said RF return signal to a baseband return signal;

a frequency discriminator for receiving said baseband return signal and for issuing a demodulated return signal; and

a microcontroller system for providing said digital data signal including said application data, and for receiving said demodulated return signal.

11. The communication system of claim 1, wherein the base transceiver includes:

said synthesizer for generating a local oscillator (LO) signal at said expected frequency in response to a first frequency control signal, for generating a local oscillator (LO) signal at an actual LO frequency in response to a second frequency control signal, and for generating said RF return signal at an RF frequency in response to said second frequency control signal, and having modulation in response to a digital return signal;

said receiver circuit for receiving said LO signal for down converting said RF data signal to a baseband data signal;

said frequency discriminator for demodulating said baseband data signal, issuing a frequency difference signal representative of said current frequency error, and issuing a demodulated data signal; and

said microcontroller system having a receive adjust mode for providing said first frequency control signal based upon data of said expected frequency and for receiving said frequency difference signal, having a receive data mode for providing said second frequency control signal based upon said current frequency error and for receiving said demodulated data signal, and having a transmit mode for providing said digital return signal including said control information.

12. The communication system of claim 1, wherein:

the remote transceiver is further for receiving an application data signal from a data source, said application data signal including data indicative of said application data.

13. The communication system of claim 12, wherein:

said data source is at least one of an electricity meter, a water meter, a thermostat, and a gas meter.

14. The communication system of claim 1, wherein:

the base transceiver includes means for issuing information indicative of said application data to a user.

15. A method for compensating for drift in carrier frequency in a radio frequency (RF) communication system, including the steps of:

tuning a base transceiver to an expected frequency of the sum of a pre-determined frequency and a last frequency error for receiving an RF data signal;

receiving an RF data signal from a remote transceiver at an actual frequency equal to the sum of said pre-determined frequency and a current frequency error;

determining said actual frequency from said last frequency error, said pre-determined frequency, and a frequency difference between said actual frequency and said expected frequency; and

transmitting an RF return signal at said actual frequency from said base transceiver to said remote transceiver.

16. The method of claim 15, further including a step of:

receiving said RF data signal in a burst at a selected time.

17. The method of claim 16, wherein:

said pre-determined frequency is in a range of approximately 902 MHz to 928 MHz.

18. The method of claim 16, wherein:

said burst has a time duration in a range of 1 microsecond to 400 milliseconds.

19. The method of claim 16, wherein:

said pre-determined frequency is an entry in a pseudo-random sequence of frequencies and a successive said burst is a successive said entry in said pseudo-random sequence.

20. The method of claim 19, further including a step of:

transmitting said RF data signal from a multiplicity of said remote transceiver where said pseudo-random sequence is unique for each of said remote transceiver.

21. The method of claim 16, further including a step of:

transmitting said RF return signal including information for selecting said selected time.

22. The method of claim 15, wherein:

said current frequency error is in a range of up to 30×

10^-6 times said actual frequency.

23. The method of claim 15;

further including steps of;

receiving said RF data signal including data indicative of application information; and

issuing a user output signal including said application information from said base transceiver to a user.

24. The method of claim 23, further including steps of:

receiving an application data signal from a data source, said application data signal including data indicative of said application information; and

transmitting said RF data signal including said data indicative of said application information from said remote transceiver.

25. The method of claim 24, wherein:

said data source is at least one of an electricity meter, a water meter, a thermostat, and a gas meter.

26. A method for adjusting for carrier frequency error in a radio frequency (RF) communication system, comprising the steps of:

providing one or more remote transceivers;

transmitting an RF data signal which includes a preamble and application data from said remote transceiver at an actual frequency equal to the sum of a predetermined frequency and a current frequency error;

providing a base transceiver;

retrieving, in said base transceiver, a last frequency error;

tuning said base transceiver to an expected frequency of the sum of a predetermined frequency and said last frequency error having steps of;

a) providing a microcontroller system in said base transceiver;

b) issuing a first frequency control signal from said microcontroller system, said first frequency control signal corresponding to said expected frequency;

c) providing a synthesizer operationally connected to said microcontroller system; and

d) generating, with said synthesizer, a local oscillator (LO) signal at said expected frequency in response to said first frequency control signal;

receiving said RF data signal at an actual frequency equal to the sum of a pre-determined frequency and a current frequency error;

determining said actual frequency from said last frequency error, said predetermined frequency, and a frequency difference between said actual frequency and said expected frequency;

receiving at said base transceiver, said preamble in said RF data signal;

determining said frequency difference between said actual frequency and said expected frequency; and

adjusting said base transceiver to said actual frequency, said adjustment based upon said frequency difference;

receiving said application data in said RF data signal;

computing said current frequency error; and

storing said current frequency error as said last frequency error.

27. The method of claim 26, wherein the step of receiving said preamble includes the steps of:

providing a direct conversion receiver operationally connected to said synthesizer; and

down converting, with said direct conversion receiver, said RF data signal with said LO signal to a baseband data signal.

28. The method of claim 27, wherein the step of determining said frequency difference includes the steps of:

providing a frequency discriminator operationally connected to said direct conversion receiver and said microcontroller system;

receiving said baseband data signal in a frequency discriminator;

discriminating said frequency difference with said frequency discriminator;

issuing data proportional to said count representing said frequency difference in a frequency difference signal to said microcontroller system.

29. The method of claim 28, wherein the step of adjusting said base transceiver includes the steps of:

issuing a second frequency control signal which is based upon said current frequency error; and

generating, with said synthesizer, a local oscillator (LO) signal at said actual frequency in response to said second frequency control signal.

30. The method of claim 29, wherein the step of receiving said application data includes the steps of:

demodulating said baseband data signal with said frequency discriminator; and

issuing a demodulated data signal including said application data from said frequency discriminator to said microcontroller system.

31. A frequency tolerant wireless transceiver to receive and transmit on the wireless signal energy on the same frequency and to automatically adjust to that frequency, the transceiver comprising:

an antenna to receive a wireless data signal, including application data from one or more remote transceivers, at an actual frequency and issue this signal as a conducted radio frequency (RF) data signal and to transmit a wireless return signal at said actual frequency to said remote transceiver in response to a conducted RF return signal;

a synthesizer to generate a local oscillator (LO) signal sequentially in response to a first and a second frequency control signal, and to generate said RF return signal at said actual frequency in response to said second frequency control signal and having modulation in response to a digital return signal;

a direct conversion receiver to receive said LO signal to down convert said RF data signal to a baseband data signal;

a frequency discriminator to receive said baseband data signal, to provide a frequency difference signal for the current frequency difference between said expected frequency and said actual frequency, and to demodulate said baseband data signal, and to issue a demodulated data signal; and

a microcontroller system having a receive adjust mode to provide said first frequency control signal predictive of an expected frequency and to receive said frequency difference signal, having a receive data mode to process said frequency difference signal, to provide said second frequency control signal predictive of said actual frequency, and to receive said demodulated data signal, including said application data, and to provide said digital return signal.

32. A frequency tolerant transceiver to automatically adjust to receive a radio frequency (RF) data signal on an actual frequency and to transmit an RF return signal on that same frequency, the transceiver comprising:

a synthesizer for sequentially generating a local oscillator (LO) signal and said RF return signal, said LO signal sequentially having a first frequency corresponding to an expected frequency of said RF data signal and a second frequency corresponding to said actual frequency of said RF data signal in response to a first and a second frequency control signal, respectively, said RF return signal having said second frequency in response to said second frequency control signal; and

a microcontroller system having a receive adjust mode for providing said first frequency control signal predictive of said expected frequency and providing said second frequency control signal for said actual frequency based upon a frequency difference between said actual frequency and said expected frequency.

33. The transceiver of claim 32, wherein:

the microcontroller system further includes means for predicting said expected frequency based upon the sum of a pre-determined frequency and a last frequency error, computing a current frequency error based upon said frequency difference and storing a new said last frequency error based upon said current frequency error for predicting said expected frequency of a next said RF burst.

34. The transceiver of claim 33, wherein:

said pre-determined frequency is an entry in a pseudo-random sequence of frequencies, a successive said RF burst to be a successive said entry in said pseudo-random sequence.

35. The transceiver of claim 33, wherein:

said RF data signal is transmitted by one of a multiplicity of remote transceivers; and

said pseudo-random sequence for said one of said remote transceivers is unlike a pseudo-random sequence for any other of said remote transceivers.

36. The transceiver of claim 33, wherein:

said current frequency error is in a range of up to 30×

10^-6 times said actual frequency.

37. The transceiver of claim 33, wherein:

said pre-determined frequency is in a range of approximately 902 MHz to 928 MHz.

38. The transceiver of claim 32, wherein:

said RF data signal includes application data; and

said application data is indicative of flow in at least one of an electricity meter, a water meter, and a gas meter.

39. The transceiver of claim 38, wherein:

the microcontroller system includes means for issuing information indicative of said application data in a user output signal to a user.

40. The transceiver of claim 32, further including:

a receiver circuit coupled to the synthesizer for using said LO signal for down convening said RF data signal and providing a representative baseband data signal; and

a frequency discriminator for receiving said baseband data signal and coupled to the microcontroller system for providing information for said frequency difference.

41. The transceiver of claim 40, wherein:

the frequency discriminator is further for demodulating said baseband data signal and providing a demodulated data signal; and

the microcontroller system is for receiving said demodulated data signal and coupled to the synthesizer for providing a digital return signal for modulating said RF return signal.

42. The transceiver of claim 41, wherein:

said RF data signal is an RF burst; and

the microcontroller system includes means for receiving said demodulated data signal as a data burst at a selected time.

43. The transceiver of claim 42, wherein:

said RF burst has a time duration in a range of 1 microsecond to 400 milliseconds.