Radio ranging using sequential time-difference-of-arrival estimation
View Patent ↗A method determines a position of a target object. A window function is applied repeatedly to a first signal and a second signal of a pair of radio signals received at a pair of passive sensors from a target object while time shifting the window function during a correlation interval to produce a first windowed signal and a second windowed signal for each application. The first windowed signals are cross-correlating with the second windowed signals to determine a peak for each cross-correlation. The peaks are compared sequentially in time with a predetermined threshold to detect a first pulse in the first signal and a first pulse in the second signal. A delay between the first pulses indicative of a position of the target object.
1. A method for determining a position of a target object, comprising the steps of:
applying repeatedly a window function to a first signal and a second signal of a pair of radio signals received at a pair of passive sensors from a target object while time shifting the window function during a correlation time interval to produce a first windowed signal and a second windowed signal for each application of the window function;
cross-correlating each first windowed signal with each second windowed signal to determine a peak for each cross-correlation;
comparing, sequentially in time, the peaks to a predetermined threshold to detect a first pulse in the first signal and a first pulse in the second signal, a delay between the first pulses indicative of a position of the target object; and
outputting the position of the target.
2. The method of claim 1 , further comprising:
adjusting a width of the window function while applying.
3. The method of claim 1 , further comprising:
adjusting an amount of the time shifting while applying.
4. The method of a claim 2 , in which the width of the window function is approximately equal to a width of the first pulses.
5. The method of claim 1 , in which each signal in the pair has the first pulse received via a direct, line-of-sight-path, and in which later pulses in the correlation time interval are due to multipath propagation.
6. The method of claim 1 , further comprising:
adjusting a size of the correlation time interval while applying.
7. The method of claim 1 , in which the window function performs a multiplication on the first and second windowed signals in the time domain.
8. The method of claim 1 , in which the window function is rectangular.
9. An apparatus for determining a position of a target object, comprising the steps of:
a first sensor configured to receive to a first signal of a pair of radio signals received from a target object;
a second sensor configured to receive to a second signal of the pair of radio signals;
means for applying repeatedly a window function while time shifting the window function during a correlation time interval to produce a first windowed signal and a second windowed signal for each application of the window function;
means for cross-correlating each first windowed signal with each second windowed signal to determine a peak for each cross-correlation;
means for comparing, sequentially in time, the peaks to a predetermined threshold to detect a first pulse in the first signal and a first pulse in the second signal, a delay between the first pulses indicative of a position of the target object; and
means for outputting the position of the target.