Timing Synchronization Algorithm of Large Range Roll-down Coefficient of Oscilloscope

Vector signal analysis requires digital down-conversion, low-pass filtering, matching filtering, timing synchronization, carrier synchronization, equalization and other modules. Timing synchronization is the key to vector signal analysis. Traditional timing synchronization, such as Gardner feedback algorithm, has self-noise. The method to reduce self-noise is to design a pre-filter for a specific roll down coefficient before timing synchronization. However, these methods need to redesign the pre-filter coefficient when the roll down coefficient changes, so the signal roll down coefficient can't meet the test requirements when the signal roll down coefficient changes in a wide range. Therefore, this paper proposes a timing synchronization algorithm based on Farrow structure FIR pre-filter. The sub-filter coefficients of Farrow structure of pre-filter are solved offline by minimax algorithm. Pre-filter redesign can be avoided according to different roll down coefficients. The proposed pre-filtering algorithm can be used in vector signal analysis modules with roll down coefficients ranging from 0.1 to 1 and symbol rates ranging from 1kBaud to 8GBaud. The experimental results show that the modulated signal can be demodulated successfully in the range of 0.1-1 roll down coefficient, and the timing jitter can be reduced by 2-3 orders of magnitude when the signal-to-noise ratio(SNR) is greater than 20dB.