Math software provides tracking-loop simulation

WHILE spread-spectrum technology originated as a method for reducing interference and improving security in military communications systems, it is playing a key role in commercial applications such as cellular telephony. A novel modem design based on direct-sequence, spread-spectrum (DSSS) technology developed by Robotiker (Zamudio, Spain) provides transmission through medium-voltage powerlines, The modem design uses a combination of a searching loop and a tracking loop to achieve chip synchronization, resulting in lower system cost, The design of the tracking loop (Fig, I) is described, including simulation results obtained with the SIMULINK toolbox that is used in conjunction with the MATLAB software package from The MathWorks, Inc, (Natick, MA).