The performance of GNSS(Global Navigation Satellite System) position estimation is critically degraded in multipath environments. Therefore, decomposing the multipath signals is desired to advance the positioning technique. To decompose the multipath signals, one concept has been proposed based on the Teager-Kaiser operator for estimating time delays of the BPSK, or BOC modulated multipath signals. However, the concept cannot be applied directly to the CBOC multipath signals. An estimated result of the Teager-Kaiser operator shows many large peaks when the input signal is an autocorrelation output of a CBOC signal. In the result, most of the large peaks are not related to time delays of the multipath signals. The false peaks, unrelated to the time delays, are shown because an autocorrelation function of a CBOC signal has lots of inflection points and peaks. Therefore, the Teager-Kaiser operator should be modified to reduce the amplitudes of the false peaks that degrade the performance of time delays estimation. In this paper, modified Teager-Kaiser operator and its estimated results about CBOC multipath signals are introduced. The estimated results show that the modified Teager-Kaiser operator successfully estimates the time delays of the CBOC multipath signals. This paper also contains an algorithm which detects a LOS(Line of Sight) signal with the modified Teager-Kaiser operator.

Keywords: Teager-Kaiser operator, CBOC signal, multipath