Dual mode AM-FM receiver with I-Q decoding, such as for utility data collection

• US 7,400,904 B2
• Filed: 03/30/2005
• Issued: 07/15/2008
• Est. Priority Date: 12/03/2004
• Status: Active Grant

• Current Assignee: Itron, Inc.
• Original Assignee: Itron, Inc.
• Inventors: Delamater, Jeffrey L., Cornwall, Mark K., Weyrauch, Bruce N.
• Primary Examiner(s): Nguyen; Duc M
• Application Number:
  US11/096,269
• Publication Number:
  US 20060121862A1
• Time in Patent Office: 1,203 Days
• Field of Search: 455/522.1, 455/553.1, 455/132, 455/334, 375/334, 375/335
• US Class Current: 455/552.1
• CPC Class Codes: H04L 1/0025 Transmission of mode-switching indication
• CPC Class Codes: H04L 27/0012 arrangements for identifying the type of modulation

Abstract

Methods and apparatus demodulate and decode a plurality of AM and FM arriving signals, which permit, for example, a utility data-collecting unit to concurrently receive and decode transmitted signals of legacy transmitters as well as more recent FM based transmitters, or signals arriving from hybrid systems configured to transmit both AM and FM.

Claims

1. In a utility meter reading system having multiple utility meters wirelessly transmitting utility meter data to a data collection unit, a data collection system comprising:

a utility data encoder-transmitter connected to each of the utility meters, wherein the encoder-transmitter is configured to wirelessly transmit AM or FM utility metering data, wherein the transmitted AM or FM utility metering data includes differing AM or FM preambles, respectively; and

a data collection unit comprising a dual-mode receiver configured to demodulate and decode the wirelessly transmitted AM, FM, or AM and FM utility metering data signal, wherein the mobile data collection unit is configured to;

receive the transmitted AM or FM signal;

sample and quantize the received signal;

compute a frequency spectrum from the received signal;

demodulate the received signal by both an AM demodulator and an FM demodulator that both use the computed frequency spectrum;

check both demodulated signals for either the AM preamble or the FM preamble;

select and route the demodulated signal having either the AM preamble or the FM preamble to be decoded in a decoder; and

decode the routed demodulated signal.

2. The system of claim 1, wherein the encoder-transmitter transmits ASK, FSK, or ASK and FSK modulated signal types, and wherein the data collection unit is mobile.

3. The system of claim 1, wherein an FFT (Fast Fourier Transform) engine computes the frequency spectrum.

4. The system of claim 1, wherein the AM demodulator and the FM demodulator demodulate the received signal substantially simultaneously.

5. The system of claim 1, wherein a correlator checks the demodulated signal from the AM demodulator for a first preamble and another correlator checks the demodulated signal from the FM demodulator for a second preamble, and wherein the first and the second preambles are orthogonal.

6. The system of claim 1, wherein a DSP (Digital Signal Processing) facility decodes the routed demodulated signal.

7. The system of claim 1, wherein the AM and FM demodulators bit slice and output demodulated data bit-by-bit.

8. The system of claim 1, wherein demodulating the received signal comprises calculating a cross-product of a carrier signal phasor, computed from IQ channel samples, with a carrier signal phasor, computed from preceding IQ channel samples.

9. The system of claim 1, wherein data signals are ASK and/or FSK modulated, and wherein demodulating FSK modulated data comprises calculating a cross-product of a carrier signal phasor computed from most recent IQ channel samples with a carrier signal phasor computed from IQ channel samples immediately preceding the most recent samples, and wherein a change in the calculated cross-product indicates a change in modulating logic level from a ‘

1’

to a ‘

0’

or from ‘

1’

to a ‘

0’

.

28. The apparatus of claim 1, wherein a single correlator or two correlators in series validate the preambles to identify valid signals, and wherein the valid signals are routed to a decoder by a selector module.

10. In a wireless data communication system, an apparatus comprising:

a dual-mode receiver configured to;

receive data signals from at least one transmitter unit;

sample the received data signal;

transform the sampled signal into frequency components;

demodulate the sampled signal by an AM and FM demodulator utilizing the frequency components;

analyze preambles of the demodulator output to identify information-bearing AM and FM signals;

select and route demodulated signals according to the analyzed preambles; and

decode the selected and routed demodulated signal.

11. The apparatus of claim 10, wherein frequency components are computed by a Fast Fourier Transform (FFT) facility.

12. The apparatus of claim 10, wherein the AM demodulator and the FM demodulator demodulate the signal substantially simultaneously and the two demodulation outputs are analyzed by two correlators working in parallel or in series.

13. The apparatus of claim 10, wherein all functions are implemented by general purpose processors, dedicated processors, computers, programmable gate arrays, or a combination thereof.

14. The apparatus of claim 10, wherein demodulated signals are routed to the decoder by a selector module based on information received from preamble correlators.

15. The apparatus of claim 10, wherein demodulated signals are decoded by a Digital Signal Processing (DSP) facility.

16. The apparatus of claim 10, wherein the FM demodulation of the signal comprises computing a cross-product of two consecutive instances of carrier signal phasors.

17. A dual-mode AM-FM decoding method comprising:

receiving at least one data signal from at least one of multiple transmitter units, wherein the received data signal is either an AM signal or an FM signal;

sampling the received data signal;

transforming the sampled signal into its frequency components;

AM and FM demodulating the signal utilizing the signal frequency components;

identifying information-bearing demodulated signals;

selecting and routing the information-bearing signals to a decoder; and

decoding the selected signals.

18. The dual-mode AM-FM decoding method of claim 17, wherein demodulating the signal comprises ASK and FSK demodulation in parallel, and wherein the FSK demodulation comprises calculating a cross-product of a carrier signal phasor computed from a most recent IQ channel sample with a carrier signal phasor computed from an IQ channel sample immediately preceding the most recent sample, and wherein a change in the calculated cross-product indicates a change in the modulating logic level, from a binary ‘

1’

to a ‘

0’

or from a ‘

0’

to a ‘

1’

.

19. The dual-mode AM-FM decoding method of claim 17, wherein selecting and routing the information-bearing signals comprises correlating the demodulated AM signal with an AM preamble and the demodulated FM signal with an FM preamble and selecting a signal which has matching preamble based on outputs of the correlators, and wherein decoding the selected and routed signals comprises decoding by a DSP (Digital Signal Processing) facility.

20. A wireless data acquiring system, comprising:

a means for receiving at least one data signal from at least one of multiple transmitter units, wherein the received data signal is either an AM or an FM signal;

a means for sampling the received signal;

a means for transforming the sampled signal into frequency components;

a means for AM and FM demodulating the signal utilizing the frequency components;

a means for identifying information-bearing demodulated signals;

a means for selecting and routing information-bearing signals to a decoder; and

a means for decoding the selected signals.

21. An apparatus for use with a data acquiring system, the apparatus comprising:

a fast Fourier transformer to convert a received signal into frequency components, wherein the received signal is either an AM or an FM signal having distinguishing portions;

an AM demodulator, coupled with the fast Fourier transformer, to demodulate the received signal utilizing the signal frequency components;

an FM demodulator, coupled with the fast Fourier transformer, to demodulate the received signal utilizing the signal frequency components;

at least one correlator, coupled with the AM demodulator and with the FM demodulator, to identify whether the received signal is an information-bearing signal based on the distinguishing portion of the received signal; and

a selector to select and route an output from the AM demodulator or the FM demodulator based on the identified distinguishing portion of the received signal.

22. The apparatus of claim 21, wherein the distinguishing portions of the AM signal and the FM signal are different.

23. The apparatus of claim 21, wherein the distinguishing portions of the AM signal and the FM signal are unique and orthogonal preambles.

24. The apparatus of claim 21, wherein the distinguishing portions of the AM signal and the FM signal are identical.

25. A dual-mode wireless data acquisition apparatus comprising:

a signal processing system configured to receive frequency components of a first signal, a second signal, or a combination of the first and the second signal, and further configured to;

demodulate, in parallel, the first and the second signals, utilizing the frequency domain components of the first and the second signals;

validate one of two preambles of the first and the second demodulated signals; and

identify for further processing the first or second demodulated signal based on which of the two preambles is valid.

26. The apparatus of claim 25, wherein two parallel correlators validate the preambles to identify valid signals, and wherein the valid signals are routed to a decoder by a selector module operating based on information received from the two correlators, and wherein the preambles are either the same, orthogonal, arbitrary, or Manchester coded.

27. The apparatus of claim 25, wherein demodulating the signal comprises ASK and FSK demodulation in parallel, and wherein the FSK demodulation comprises calculating a cross-product of a carrier signal phasor computed from a most recent I-Q channel sample with a carrier signal phasor computed from an I-Q channel sample immediately preceding the most recent sample, and wherein a change in the calculated cross-product indicates a change in the modulating logic level, from a binary ‘

1’

to a ‘

0’

or from a ‘

0’

to a ‘

1’

.