An FPGA-Based Measurement Generator for Cyclically Shifted Binary Signals

Abstract

Pseudo-random binary coded excitation signals are increasingly used for electromagnetic network analysis. Various types of sequences are available for this task. Flexible signal generators with high bandwidth are required for practical measurements. In this contribution, a concept for the generation of arbitrary binary coded signals with a chip frequency up to 5 Gchip/s based on a field programmable gate array (FPGA) is presented. Furthermore, an algorithm to fast and precisely shift the time lag between two coded signals to allow for correlating excitation and measurement signals in a hardware correlator has been developed. First, two different types of pseudo-random binary sequences, the maximum length sequence (MLS) and the almost perfect autocorrelation sequence (APAS), are compared with each other. Afterwards, the FPGA design with focus on the algorithm to realize a varying time lag between two generated signals is presented. Finally, the realization of a demonstrator system and measurement results for the validation of the system are presented.