Research of the Method of High Accuracy Time Delay Estimation

The requirement of nanosecond level, 10^-9 second, time delay estimation has been proposed in concentration measurement of trace gas like SF6. Discrete Fourier transform can only distinguish the time delay as small as the sampling interval. A method is proposed that nanosecond time delay can be measured. Firstly, using discrete Fourier transform, spectrum of received data with sampling interval like 40ns have been divided by the spectrum of transmitted signal in frequency domain to acquire the transfer function, the singular values which are because of 0/0 will be removed by interpolating or smoothing method. Secondly, the m-th power of the transfer function will be calculated to let the discrete Fourier transform can distinguish the m times of the delay. Lastly, the original micro-time delay can be estimated by peak searching. Computer simulation shows that for received signal with more than 25dB carrier-to-noise, time delay estimation can have a resolution of nanosecond or less.