Comparison of Two Different Upsampling Methods Used for Interpolation in Symbol Timing Recovery in Digital Receivers

The digital method for symbol timing recovery has been used for several years and many scholars have proposed a great deal of methods for it. This paper describes the fundamentals of interpolation for timing recovery, and compares the differences between the two upsampling: zero-insertion expander and zero-order-hold expander used before the symbol timing interpolation. It is shown that, through simulation, zero-order-hold expander performs better than zero-insertion expander in the frequency domain, and has better attenuation for signal images caused by upsampling using the same low band filter.