Research on carrier tracking in Hybrid DS/FH spread spectrum TT&C system

A High Dynamic Velocity Locked Loop for the Carrier Tracking of a Wide-Band Hybrid Direct Sequence/Frequency Hopping Spread-Spectrum Signal

“…Hopping Rates (hops/s) Dynamics SNR (dB) Loop Structures [8] ≤1.2 k Acceleration 30 g ≥13 Second-order PLL [9] 10 k Unspecified Unspecified FLL and PLL Switching [10] 100 k Unspecified ≥0 PLL [11] 10 k Jerk 10 g/s ≥−30 Second-order VLL assisted third-order PLL [12] 9 k Jerk 10 g/s −25 Second-order VLL assisted third-order PLL As indicated in Table 1, the research on tracking algorithms for high dynamic hybrid DS/FH spread spectrum signals has remained relatively scarce in recent years. Nevertheless, it is reassuring to note that numerous research achievements have been made in the tracking of high dynamic DSSS signals in recent times.…”

“…The purpose of the carrier tracking loop is to generate a replica signal of the received carrier signal, that is, the error between the local instantaneous phase of the replica signal and the instantaneous phase of the received signal should be as small as possible at each moment. By comparing ( 6) with (8), it can be seen that ( 6) only takes into account the effect of velocity on the local instantaneous phase but leaves out the effects of acceleration and jerk. Consequently, there is an accumulated phase tracking error of π f cj aT 2 /c+ π f cj .…”

“…The authors of [7] analyze the effects of multiple interferences on the range and velocity measurement performance of a hybrid DS/FH spread spectrum system, providing a reference for the research on hybrid DS/FH spread spectrum signal tracking. A carrier tracking method aided by a frequency hopping pattern is presented in [8]. The Doppler shift variable introduced by the next frequency hopping point is estimated based on the predicted frequency hopping pattern and the current speed measurement.…”

“…Although the hopping rate reaches 10 khops/s, the coherent integration period only occupies one frequency hopping time slot, which is only applicable to high signalto-noise ratio (SNR) scenarios. The key technologies for the reception of hybrid direct sequence/fast frequency hopping (DS/FFH) spread spectrum signals are investigated in [10], including signal acquisition, tracking, and group delay equalization methods, in which the signal tracking part adopts the same method as that used in [8]. Although the frequency hopping rate involved is up to 100 khops/s, the information rate is set to be the same as the frequency hopping rate, making it only applicable to scenarios with a higher SNR.…”

“…The employed scheme simultaneously achieves the requirements of a high hopping rate and low SNR, yet the involved dynamic is merely 10 g/s, where g = 9.8 m/s 2 . Table 1 lists the hopping rates, dynamics, SNR, and loop structures involved in [8][9][10][11][12].…”