Frequency shift compensation, such as for use in a wireless utility meter reading environment

• US 7,994,933 B2
• Filed: 03/30/2005
• Issued: 08/09/2011
• Est. Priority Date: 03/30/2004
• Status: Expired due to Fees

• Current Assignee: Itron, Inc.
• Original Assignee: Itron, Inc.
• Inventors: Cahill-O'Brien, Barry, Cornwall, Mark K.
• Primary Examiner(s): WONG, ALBERT KANG
• Application Number:
  US10/591,995
• Publication Number:
  US 20080001779A1
• Time in Patent Office: 2,323 Days
• Field of Search: 34087002-87003, 375/316, 375/376, 455/39, 455/500, 455/63.1, 370/503
• US Class Current: 340/870.02
• CPC Class Codes: G01D 4/002 Remote reading of utility meters
• CPC Class Codes: H04L 1/0036 arrangements specific to the receiver
• CPC Class Codes: H04L 2027/0065 Frequency error detectors H04L2027/0067 takes precedence
• CPC Class Codes: H04L 27/14 Demodulator circuits; Receiver circuits
• CPC Class Codes: Y02B 90/20 Smart grids as enabling technology in buildings sector smart grids supporting the management or operation of end-user stationary applications in general, or like technologies with no associated climate change mitigation effect Y04S20/00
• CPC Class Codes: Y04S 20/30 Smart metering, e.g. specially adapted for remote reading

Abstract

Methods and apparatus for computing the carrier frequency of a transmitter using frequency modulated digital data to compensate for frequency shifting of the transmitter and the receiver local oscillators and for bandwidth adjustment of the receiver'"'"'s filter. In particular, methods and apparatus are disclosed for binary systems transmitting “1” and “0” data using decoded or undecoded received signals.

Claims

1. In a communication system, an apparatus for compensating for drift between a receiver and a transmitter local oscillator frequencies, the apparatus comprising:

a receiver for receiving a first frequency modulated signal with frequency (F.sub.T+f.sub.1) representing a first data value, and a second frequency modulated signal with frequency (F.sub.T−

f.sub.2) representing a second data value, where F.sub.T is a local oscillator frequency of the transmitter, and f.sub.1 and f.sub.2 are frequency deviations for modulating the first and the second data values, respectively;

a mixer for down-converting or intermediate frequency (IF) converting the first and the second received signals by mixing the first and second received signals with the receiver'"'"'s local oscillator frequency, wherein the receiver'"'"'s local oscillator frequency is associated with conversion frequency; and

calculating a drift between the transmitter'"'"'s local oscillator frequency and the receiver'"'"'s local oscillator frequency, F.sub.D, by;

F.sub.D=F.sub.M2+f.sub.2(F.sub.M1−

F.sub.M2)/(f.sub.1+f.sub.2), where F.sub.M1 and F.sub.M2 are first and second down- or IF-converted frequencies, respectively.

2. The apparatus of claim 1, wherein during an initial communication period, the receiver widens a receiver bandwidth and receives data at a first data rate, and wherein during a subsequent period the receiver adjusts the bandwidth, based on the received data, and receives subsequent data at a second data rate that is higher than the first data rate.

3. The apparatus of claim 1, wherein the first and second data values are “

1” and

“

0,”

respectively, and wherein at least one controller provides a compensation signal and adjusts a bandwidth of the receiver based on an estimated frequency drift and compensated receiver frequency.

4. The apparatus of claim 1, wherein one of the down-converted signals is a baseband in-phase signal and the other down-converted signal is a baseband quadrature signal.

5. In a wireless data acquisition network, a system for narrowing a receiver bandwidth for receiving higher rate data signals, the system comprising:

a receiver for receiving a known frequency modulated (FM) data signal at a first data rate, with frequency (F.sub.T+f) or (F.sub.T−

f), wherein F.sub.T is a corresponding transmitter'"'"'s LO frequency and f is a frequency deviation for modulating the data value;

a mixer for down-converting the signal by mixing it with a signal generated by the receiver LO, wherein the receiver LO frequency is an estimate of the transmitter'"'"'s LO frequency;

a processor for computing a difference between the transmitter'"'"'s LO frequency and the receiver'"'"'s LO frequency by subtracting the deviation frequency f from the down-converted signal if the received signal represents the data value with frequency (F.sub.T+f), or by adding the deviation frequency f to the down-converted signal if the received signal represents the data value with frequency (F.sub.T−

f); and

a controller for centering and narrowing the receiver bandwidth, using the down-converted signal, to allow higher data rate signals with maximum estimated drift to pass, if the bandwidth needs to be adjusted.

6. A utility meter data communication method comprising:

transmitting binary data signals at a first data rate, by a first utility meter data transceiver;

receiving at least one binary data signal, by a second utility meter data transceiver;

zero-IF or IF converting the received signal;

computing a value that is a difference between the first transceiver carrier frequency and the second transceiver carrier frequency, using the converted signal; and

transmitting the computed information from the second transceiver to the first transceiver to be used for adjusting the first transceiver'"'"'s carrier frequency, if adjustment is needed.

7. The method of claim 6, wherein the second utility meter data transceiver alters a bandwidth of the second transceiver, based on the computed difference value, if the bandwidth needs to be altered.

8. The method of claim 7, wherein bandwidth alteration comprises:

centering the bandwidth around a frequency substantially similar to the first transceiver'"'"'s frequency;

narrowing the bandwidth; and

transmitting subsequent data at a second data rate that is higher than the first data rate.

9. In a communication system, an apparatus for compensating for drift between receiver and transmitter local oscillator frequencies, the apparatus comprising:

a receiver for receiving a first frequency modulated signal with frequency (F.sub.T+f.sub.1) representing a first data value, and a second frequency modulated signal with frequency (F.sub.T−

f.sub.2) representing a second data value, where F.sub.T is a local oscillator frequency of the transmitter, and f.sub.1 and f.sub.2 are frequency deviations for modulating the first and the second data values, respectively;

a mixer for mixing the first frequency modulated signal with frequency (F.sub.R+f.sub.1) to generate a first mixed signal and mixing the second frequency modulated signal with frequency (F.sub.R−

f.sub.1) to generate a second mixed signal, where F.sub.R is a local oscillator frequency of the receiver, and wherein the receiver local oscillator frequency is an estimation of the local oscillator frequency of the transmitter; and

calculating a drift between the transmitter local oscillator frequency and the receiver local oscillator frequency by averaging between the frequencies of the first and the second mixed signals.