High-resolution link-path delay estimator and method for estimating a signal-path delay

A method for estimating signal-path delay of a signal path between a master device and a remote device, the method comprising:

• phase-shifting a transmit signal by one of a plurality of phase-shift values, the transmit signal comprising a waveform of alternating symbols such that each successive symbol alternates between high and low, each symbol having a symbol period;
• receiving a loopback signal from the remote device;
• sampling the loopback signal on one of either rising or falling edges of the phase-shifted transmit signal to generate a sampled signal output, the loopback signal being a delayed version of the transmit signal returned from the remote device;
• generating a noise-reduced output from the sampled signal output;
• and
• generating a fine-delay estimate based on the noise-reduced output resulting from a selected one of the phase-shift values for use in determining the signal path delay.

A signal-source locating system comprising:

• a master device;
• a plurality of spatially-distributed remote devices, each coupled to the master device by a two-way signal path,
• wherein the master device includes a high-resolution link-path delay estimator arranged to:
• delay the transmit signal by one of a plurality of delay values, the transmit signal comprising a waveform of alternating symbols such that each successive symbol alternates between high and low, each symbol having a symbol period;
• receive a loopback signal from the remote device;
• sample the loopback signal on rising edges of the delayed transmit signal to generate a sampled signal output, the loopback signal being a delayed version of the transmit signal that is returned from the remote device;
• generate a noise-reduced output from the sampled signal output;
• correlate the noise-reduced output with a step function to generate a correlation value for each of the delay values;
• and
• cause the transmit signal to be delayed by a selected one of the delay values and generate a fine-time data output based on the correlation value, the fine-time data output being an indicator of the signal-path delay to within the fraction of a symbol period of the transmit signal,
• wherein the high-resolution link-path delay estimator that is arranged to estimate a relative signal-path delay between the master device and each of the spatially-distributed remote devices to within a fraction of the symbol period.