Parameter Estimation Technique for the SNCK Scheme Based on the Spectral-Correlation Density
The Sine Non-linear Chirp Keying (SNCK) is one kind of the SFM schemes, which play an important role as the commonly useful signals in sonar, radar and wireless communication systems. By adjusting its time-bandwidth product, the SNCK can satisfy different requirements of the quality of service and has better ability in Doppler shift inhibition than the ordinary MSK. However, no mathematical analysis for the time-bandwidth product (modulation factor) estimation of the SNCK scheme has been available. In this paper, a SCD-based estimation algorithm for the modulation factor of the SNCK scheme has been proposed. The mathematical model and diagrams of the three-dimensional SCD and the corresponding bi-frequency plane make it easy to understand how the SCD-based algorithm localizes the center frequency and the keying rate, as well as estimates the modulation factor. The simulation results show that the proposed estimation algorithm is useful under different SNR conditions. The corresponding CramerRao lower bound are derived and used as the reference of the estimation algorithm. Moreover, we improve the estimation algorithm when the modulation factor varies, by using a set of the local ratio data, which compensates the differences between the simulation ratio values and the theoretical ratio results. This algorithm can be effective for the communication system with the SNCK scheme to synchronize the carrier and the symbol, as well as to demodulate the transmitted signals with unknown parameters. It is concluded that the obvious features of the SCD can be extracted for other similar signals with high reliability.
sine non-linear chirp keying (snck) spectra-correlation density (scd) time-bandwidth product estimation root mean square error (rmse)