Time-delay discriminator

• US 20050033537A1
• Filed: 07/02/2004
• Published: 02/10/2005
• Est. Priority Date: 07/07/2003
• Status: Active Grant

• Current Assignee: Mitsubishi Denki Kabushiki Kaisha (Mitsubishi Electric Corporation)
• Original Assignee: Mitsubishi Denki Kabushiki Kaisha (Mitsubishi Electric Corporation)
• Inventors: Szajnowski, Wieslaw Jerzy
• Granted Patent: US 7,216,047 B2
• Time in Patent Office: Days
• US Class Current: 702/79
• CPC Class Codes: G04F 10/00 Apparatus for measuring unknown time intervals by electric means
• CPC Class Codes: G04F 10/04 by counting pulses or half-cycles of an ac G04F10/005 takes precedence
• CPC Class Codes: G05B 19/408 characterised by data handling or data format, e.g. reading, buffering or conversion of data
• CPC Class Codes: G05B 2219/37508 Cross correlation
• CPC Class Codes: G05B 2219/37512 Correction for detection delay

Abstract

A method of determining the delay between two corresponding noise-like signals comprises determining events at which the level of a first of the signal crosses a predetermined threshold, using each event to sample a second signal, combining the samples to produce an output value and determining the delay from the output value. Preferably, each sample is weighted according to one or more characteristics of the event used to define the sample. The magnitude of the output value could be an indication of the delay, or there could be several output values each for a respective differently-delayed version of the second signal, in which case these could be evaluated to select which corresponds to the actual delay.

Claims

1. A method for determining the delay between two corresponding signals, the method comprising determining events at which the level of a first of the signals crosses a predetermined threshold, using each event to sample a second signal, determining a weighting factor associated with each event, weighting each sample according to the weighting factor associated with the event defining the sample, and combining the weighted samples to produce an output value.

2. A method as claimed in claim 1, for determining delays which are smaller than the average interval between events, and wherein the delay is determined from the magnitude of the output value.

3. A method as claimed in claim 1, including the step of deriving multiple output values by sampling mutually-delayed respective versions of the second signal, and determining the delay by determining which output value represents the greatest number of combined events.

4. A method as claimed in any preceding claim, wherein each weighting factor is dependent upon the slope of the first signal at the time of the event.

5. A method as claimed in any preceding claim, in which the weighting factor is dependent upon the average level of the first signal in the vicinity of the event.

6. A method as claimed in claim 5, wherein the weighting factor is dependent upon the product of the slope of the first signal at the time of the event and the average level of the first signal in the vicinity of the event.

7. A method as claimed in any preceding claim, wherein the weighting factor is related non-linearly to at least one value representing at least one characteristic of the event.

9. A method as claimed in any preceding claim, wherein the events are defined by the crossing of one or more predetermined thresholds substantially different from the extreme values of the signal, whereby the output value changes monotonically as the delay changes over a range of interest.

10. A method as claimed in any preceding claim, wherein the signals are bipolar.

11. A method as claimed in any preceding claim, wherein the events are at least substantially aperiodic.

12. A method as claimed in any preceding claim, wherein one of the signals has been transmitted and received via a delay path, and the other signal comprises a reference signal, the method being used to determine the delay associated with the delay path.

13. A method as claimed in claim 12, wherein the reference signal is the first signal.

14. Apparatus for determining the delay between two corresponding signals, the apparatus being arranged to operate according to a method as claimed in any preceding claim.

15. A closed-loop feedback system having a device for generating an error signal by determining a delay offset, using a method as claimed in any one of claims 1 to 13, and an actuator responsive to the error signal for performing an operation to adjust the offset.

8. A method of determining the delay between two corresponding noise-like signals, the method comprising determining events at which the level of a first of the signal crosses a predetermined threshold, using each event to sample a second signal, combining the samples to produce an output value and determining the delay from the magnitude of the output value.