# US 7,610,175 B2 · Timestamping signal monitor device

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- Number: US 7,610,175 B2
- Document ID: US7610175B2
- Status: Granted
- Kind: B2
- Application number: 11/348,575
- Filed: 2006-02-06
- Published: 2007-08-09
- Granted: 2009-10-27
- Earliest claimed: 2006-02-06
- Assignees: Agilent Technologies, Inc.
- Inventors: John C. Eidson
- Web page: https://patentgrep.com/patent/US7610175B2

## CPC

- G01R 19/2509: {Details concerning sampling, digitizing or waveform capturing}
- H04J 3/0685: {Clock or time synchronisation in a node; Intranode synchronisation}
- G01R: MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES (indicating correct tuning of resonant circuits H03J3/12)
- H04J: MULTIPLEX COMMUNICATION (transmission in general H04B; peculiar to transmission of digital information H04L5/00; systems for the simultaneous or sequential transmission of more than one television signal H04N7/08; in exchanges H04Q11/00; stereophonic systems H04S)

## Abstract

A signal monitor device that detects a signal propagating on a signal line and that generates a timestamp when the signal is detected. The timestamp may be used in a variety of applications including measuring the propagation delays on signal lines and determining the timing in a system.

## Claims

### Claim 1

A signal monitor device, comprising:
a signal detector that detects a signal propagating on a signal line and that generates a timestamp when the signal is detected; and
a device controller that corrects the timestamp by subtracting delays introduced by the signal monitor device.

### Claim 2 (depends on 1)

The signal monitor device of claim 1, wherein the timestamp is derived from a clock in the signal monitor device that is synchronized to a system time.

### Claim 3 (depends on 1)

The signal monitor device of claim 1, comprising a pair of connectors that enable the signal monitor device to be inserted into the signal line.

### Claim 4 (depends on 1)

The signal monitor device of claim 1, wherein the signal detector presents a high impedance to the signal line.

### Claim 5 (depends on 1)

The signal monitor device of claim 1, comprising circuitry that injects a timed signal onto the signal line.

### Claim 6 (depends on 1)

The signal monitor device of claim 1, wherein the device controller transfers a message carrying the timestamp over a network.

### Claim 7 (depends on 1)

The signal monitor device of claim 1, further comprising:
an input circuit that decodes a signal received via the signal line for detection by the signal detector; and
an output circuit that encodes the decoded signal and outputs the signal back onto the signal line.

### Claim 8

A method for signal monitoring, comprising:
detecting a signal propagating on a signal line;
generating a timestamp when the signal is detected; and
correcting the timestamp by subtracting delays introduced by the signal monitoring.

### Claim 9 (depends on 8)

The method of claim 8, further comprising determining a propagation delay of the signal on the signal line in response to the timestamp.

### Claim 10 (depends on 8)

The method of claim 8, further comprising determining a time of an event in a system in response to the timestamp.

### Claim 11 (depends on 8)

The method of claim 8, wherein generating a timestamp includes obtaining the timestamp from a clock that is synchronized to a system time.

### Claim 12 (depends on 8)

The method of claim 8, wherein detecting a signal comprises physically connecting to the signal line.

### Claim 13 (depends on 8)

The method of claim 8, wherein detecting a signal comprises sensing electromagnetic energy emitted from the signal line.

### Claim 14 (depends on 8)

The method of claim 8, wherein detecting a signal comprises sensing light emitted from the signal line.

### Claim 15 (depends on 8)

The method of claim 8, further comprising injecting a timed signal onto the signal line.

### Claim 16

A system, comprising:
a set of two or more signal monitor devices that generate a set of timestamps in response to a set of signals propagating on a set of signal lines; and
a device that obtains the timestamps from the signal monitor devices via a network, the device having a clock that provides a time base for evaluating the timestamps.

### Claim 17 (depends on 16)

The system of claim 16, wherein the device determines a propagation delay of the signal lines in response to the timestamps.

### Claim 18 (depends on 16)

The system of claim 16, wherein the device determines a timing of the signal in response to the timestamps.

### Claim 19 (depends on 16)

The system of claim 16, wherein each device includes a local clock such that the local clocks are synchronized to the clock in the device.

### Claim 20 (depends on 16)

The system of claim 16, wherein the signal monitor devices inject a set of timed signals onto the corresponding signal lines in response to a message from the device.