System and method for fast detection of specific on-air data rate

• US 7,412,235 B2
• Filed: 09/01/2004
• Issued: 08/12/2008
• Est. Priority Date: 09/05/2003
• Status: Expired due to Fees

• Current Assignee: Itron, Inc.
• Original Assignee: Itron, Inc.
• Inventors: Fitzgerald, Aaron, Larson, Gary, Stroda, Kris
• Primary Examiner(s): Appiah; Charles N.
• Assistant Examiner(s): Stephen; Emem
• Application Number:
  US10/931,945
• Publication Number:
  US 20050057371A1
• Time in Patent Office: 1,441 Days
• Field of Search: 455/115.1, 455/115.4, 455/67.11, 455/574, 455/343.1, 455/343.2, 455/343.5, 340/870.02, 340/870.03, 340/870.29, 340/310.01, 705/63
• US Class Current: 455/422.1
• CPC Class Codes: G08C 17/02 using a radio link
• CPC Class Codes: H04Q 9/00 Arrangements in telecontrol or telemetry systems for selectively calling a substation from a main station, in which substation desired apparatus is selected for applying a control signal thereto or for obtaining measured values therefrom

Abstract

A system and method for fast detection of specific on-air data rates are disclosed which, in one example embodiment, enable endpoint devices in automatic meter reading (AMR) systems to quickly determine the existence of over-the-air information that is specifically targeted to a unique class of AMR devices. An endpoint device utilizing the digital squelch circuit arrangement and algorithm of the invention can quickly and precisely determine if the AMR system is communicating with its class of AMR device by looking for a specific non-standard data rate present on the air. This method therefore allows for a significant improvement in battery life in two-way RF communication units by avoiding unnecessary data processing and data transmissions. The digital squelch method also enables even faster determination of inappropriate data rates and of no signal present situations, further improving battery life.

Claims

1. An automatic meter reading (AMR) system comprising:

at least one meter reading device adapted to transmit radio frequency (RF) communications having at least one predetermined target data rate for use by at least one of a plurality of endpoint devices; and

at least one endpoint device of the plurality of endpoint devices, the at least one endpoint device having a meter interface module in communication with a meter device and adapted to receive the RF communications having the at least one predetermined target data rate and to reject non-target data rate RF signals that do not have any of the at least one target data rate and are not for use by the at least one endpoint device;

the meter interface module including a digital squelch circuit arrangement adapted to distinguish from among the at least one predetermined target data rate and a non-predetermined non-target data rate in on-air RF communication signals, wherein the digital squelch circuit arrangement is adapted to determine occurrences of good edges indicative of the at least one predetermined target data rate and occurrences of bad edges indicative of the non-predetermined non-target data rate in the on-air RF communication signals, the squelch circuit arrangement further adapted to determine whether the on-air communication signals include a data rate that corresponds to the at least one predetermined target data rate by at least monitoring an edge count of the good edges and an edge count of the bad edges;

wherein the meter interface module is adapted to respond to a detection of the data rate of an inbound-RF communication signal corresponding to the at least one predetermined target data rate by conducting reception activity to receive that RF communication signal having the at least one target data rate and to respond to a detection of the data rate of an on-air RF communication signal not matching the target data rate by immediately discontinuing reception of that on-air RF communication signal having the non-target data rate.

2. The AMR system of claim 1, wherein the RF communications are Manchester-encoded and the digital squelch circuit arrangement is adapted to detect a specific Manchester on-air data rate of the inbound RF communication that matches the target data rate.

3. The AMR system of claim 1, wherein the inbound RF communication is encoded according to at least one encoding scheme selected from the group consisting of:

Manchester encoding, non-return to zero encoding, and binary encoding.

4. The AMR system of claim 1, wherein upon detection of a signal the squelch circuit arrangement of the meter interface module is adapted to initialize a device timer of the at least one endpoint device and start a communication capture and compare sequence in the at least one endpoint device, the squelch circuit arrangement further adapted to filter incoming signals until a valid communication is detected, wherein a valid communication comprises an inbound signal having a data rate that matches the target data rate, and wherein the squelch circuit arrangement is further adapted to decode and process the valid communication for communication data.

5. The AMR system of claim 4, wherein a filtering arrangement of the squelch circuit arrangement is adapted to filter incoming communications upon detecting a base edge and a second edge so as to identify the second edge as a good edge or a bad edge as a function of a time of the edge, such that

if the second edge is a good edge, a good count register of the filter arrangement is incremented, and

if the second edge is a bad edge, a bad count register of the filter arrangement is incremented and the good count register is cleared;

and clearing the good count register; and

wherein the filter arrangement is adapted to detect and identify subsequent edges as good edges or bad edges until the target data rate is detected.

6. The AMR system of claim 5, wherein the squelch circuit arrangement is further adapted to perform a selectivity test after the second edge and subsequent edges are detected, wherein the selectivity test includes analysis of a time between the base edge and the second edge, a review of the bad count register and a review of the good count register to determine if the bad count register is below a predetermined limit.

7. The AMR system of claim 1, wherein the meter interface module of the endpoint device is adapted to include:

an extraction circuit adapted to receive and quantize an incoming data signal; and

an edge detector circuit adapted to receive a quantized data signal from the extraction circuit and detect edges in the quantized data signal, wherein the edge detector circuit includes a first counter to track a number of good edges and a second counter to track a number of bad edges;

wherein the extraction circuit is adapted to pass a recovered clock signal and a recovered data signal to the edge detector circuit when the first counter reaches a first predetermined value, and wherein the extraction circuit is adapted to reject the incoming data signal when the second counter reaches a second predetermined value.

8. The AMR system of claim 7, further comprising a divider circuit adapted to derive a plurality of clock frequencies and pass at least one frequency to the extraction circuit and to the edge detector circuit.

19. The AMR system of claim 1, wherein the meter interface module is further adapted to

detect edges corresponding to data transitions in the inbound communication, wherein good edges occurring in time intervals corresponding to the target data rate are tracked with a first counter, and bad edges occurring outside of the time intervals are tracked with a second counter;

and

in response to the second counter reaching a second predetermined value before the first counter reaches a first predetermined value, produce the detection of the data rate that does not correspond to the target rate.

20. The AMR system of claim 1, wherein upon detection of an RF inbound signal the squelch circuit arrangement is adapted to initialize a device timer of the at least one endpoint device and start a communication capture and compare sequence in the at least one endpoint device, the squelch circuit arrangement further adapted to filter inbound signals until a valid communication is detected, wherein a valid communication comprises an inbound signal having a data rate that matches the target data rate, and wherein the squelch circuit arrangement is further adapted to decode and process the valid communication for communication data;

wherein a filtering arrangement of the squelch circuit arrangement is adapted to filter inbound communications upon detecting a base edge and a second edge so as to identify the second edge as a good edge or a bad edge as a function of a time of the edge, such that;

if the second edge is a good edge, a good count register of the filter arrangement is incremented, and

if the second edge is a bad edge, a bad count register of the filter arrangement is incremented and the good count register is cleared; and

clearing the good count register;

wherein the filter arrangement is adapted to detect and identify subsequent edges as good edges or bad edges until the target data rate is detected;

wherein the squelch circuit arrangement is further adapted to perform a selectivity test after the second edge and subsequent edges are detected, wherein the selectivity test includes analysis of a time between the base edge and the second edge, a review of the bad count register and a review of the good count register to determine if the bad count register is below a predetermined limit;

wherein the inbound RF signal encoded according to at least one encoding scheme selected from the group consisting of;

Manchester-encoding, non-return to zero encoding, and binary encoding.

23. The automatic meter reading (AMR) system of claim 1, wherein the squelch circuit arrangement is adapted to detect whether the data rate corresponds to the target data rate by determining whether a counted value of good edges reaches a predetermined threshold before a counted value of bad edges reaches a predetermined threshold.

9. A method for communicating with at least one endpoint device in an automatic meter reading (AMR) system, wherein the at least one endpoint device includes a meter device and a meter interface module adapted for radio frequency (RF) communications, the method comprising:

initializing a device timer of a digital squelch circuit arrangement of the meter interface module of the at least one endpoint device, wherein the squelch circuit arrangement is configured to respond differently to a predetermined at least one target data rate of an on-air signal transmitted for use by the endpoint device than to a non-predetermined non-target data rate of any other on-air signal;

filtering inbound RF communication signals at the at least one endpoint device until a valid communication is detected, wherein a valid communication comprises the inbound RF communication signal having a data rate that matches the target data rate, wherein the filtering includes monitoring the inbound RF communication signal to determine a count of good edges indicative of a data rate that matches the target data rate and monitoring the inbound RF communication signal to determine a count of bad edges indicative of a data rate that does not match the target data rate;

performing a communication capture sequence in the at least one endpoint device in response to a detection of the target data rate represented by the count of good edges exceeding the count of bad edges; and

stopping communication activity in the at least one endpoint device in response to a detection of the non-target data rate represented by the count of bad edges exceeding the count of good edges.

10. The method of claim 9, wherein the filtering of the incoming communications further comprises:

detecting a base edge;

detecting a second edge and identifying the second edge as a good edge or a bad edge based upon a time of the edge,

if the second edge is a good edge, incrementing a good count register,

if the second edge is a bad edge, incrementing a bad count register; and

detecting and identifying subsequent edges as good edges or bad edges until the target data rate is detected, until determining the target data rate is not present, or until a predetermined acquisition timeout is reached.

11. The method of claim 10, further comprising:

performing a selectivity test after the second edge and subsequent edges are detected, wherein the selectivity test includes;

analyzing a time between the base edge and the second edge;

reviewing the bad count register; and

reviewing the good count register if the bad count register is below a predetermined limit.

12. The method of claim 9, wherein the starting of the communication capture and compare sequence includes detecting and receiving inbound RF communications.

13. The method of claim 12, wherein the receiving of the inbound RF communications includes receiving data that is encoded according to at least one of the encoding schemes selected from the group consisting of:

Manchester encoding, non-return to zero encoding, and binary encoding.

21. The method of claim 9, wherein the starting of the communication capture and compare sequence in the squelch circuit arrangement includes:

initiating counting of good edges derived from the inbound RF communication signals to produce a first count, the good edges corresponding to the target data rate;

initiating counting of bad edges derived from the inbound RF communication signals to produce a second count, the bad edges corresponding to a data rate that is not the target data rate; and

wherein the stopping of the communication capture and compare sequence includes determining whether the second count reaches a second predetermined count value before the first count reaches a first predetermined count value.

22. The method of claim 9, wherein the filtering of the incoming communications further comprises:

detecting a base edge;

detecting a second edge and identifying the second edge as a good edge or a bad edge based upon a time of the edge,

if the second edge is a good edge, incrementing a good count register,

if the second edge is a bad edge, incrementing a bad count register;

detecting and identifying subsequent edges as good edges or bad edges until the target data rate is detected, until determining the target data rate is not present, or until a predetermined acquisition timeout is reached; and

performing a selectivity test after the second edge and subsequent edges are detected, wherein the selectivity test includes;

analyzing a time between the base edge and the second edge;

reviewing the bad count register; and

reviewing the good count register if the bad count register is below predetermined limit.

14. An endpoint meter device for use in an automatic meter reading system, wherein the endpoint meter device includes a meter interface module adapted to filter inbound radio frequency (RF) communication signals received from a meter reading device, the endpoint meter device comprising:

an extraction circuit adapted to receive and quantize an incoming data signal; and

an edge detector circuit adapted to receive a quantized data signal from the extraction circuit and detect edges in the quantized data signal, wherein the edge detector circuit includes a first counter to track a number of good edges indicative of a predetermined at least one target data rate of an on-air signal transmitted for use by the endpoint meter device and a second counter to track a number of bad edges indicative of a non-predetermined non-target data rate of any other on-air signal;

wherein the extraction circuit is adapted to pass a recovered clock signal and a recovered data signal to the edge detector circuit when the first counter reaches a first predetermined value, and wherein the extraction circuit is adapted to reject the incoming data signal when the second counter reaches a second predetermined value.

15. The device of claim 14, wherein the RF communication is encoded according to at least one encoding scheme selected from the group consisting of Manchester- encoding, non-return to zero encoding, and binary encoding.

16. The device of claim 14, further comprising a divider circuit adapted to derive a plurality of clock frequencies and pass at least one frequency to the extraction circuit and to the edge detector circuit.

17. A digital squelch circuit arrangement adapted for use with a meter interface module of an automatic meter reading (AMR) system, the squelch circuit arrangement comprising:

means for detecting an inbound radio frequency (RF) data signal having a data rate, wherein the data rate is represented by a series of edges and wherein the squelch circuit arrangement is adapted to respond differently to a target data rate of an inbound RF data signal transmitted for use by the meter interface module than to a non-predetermined non-target data rate of any other signal;

means for detecting good edges corresponding to the at least one predetermined target data rate and bad edges corresponding to the non-predetermined non-target data rate within the inbound RF data signal;

means for determining whether the data rate of the inbound data signal as a function of the detected good edges and bad edges matches the target data rate of the squelch circuit arrangement;

means for processing the data within the data signal if the data rate matches the target data rate; and

means for terminating signal detection in response to a detected failure of the data rate to match the target data rate based on a count of bad edges exceeding a count of good edges.

18. The endpoint device meter interface module of claim 17, wherein said inbound data signal detection means includes an extraction circuit, and wherein said means for detecting good edges and bad edges within the inbound data signal comprises a digital squelch circuit arrangement that includes an edge detector circuit adapted to receive a quantized data signal from the extraction circuit and detect edges in the quantized data signal, wherein the edge detector circuit includes a first counter to track a number of good edges and a second counter to track a number of bad edges.