Nonlinear frequency modulated excitation signal and modified compressing filter for improved range resolution and side lobe level of ultrasound echoes

摘要

Purpose: A Compensated Frequency Modulated (CFM) code is proposed as an excitation signal of an ultrasound pulse-echo system. It has a flat envelope and a non-uniform spectral energy density distributed throughout the time span and is tuned to equalize the frequency losses imposed by the system, including the transmitting/receiving electronic instrumentation, the transducer and the propagation medium. The CFM synthesis and the compression filter rely on arbitrary variables, one in determining the CFM spectrum magnitude and the other in determining the spectral magnitude of the compression filter that optimizes the side lobe level and duration (range resolution) of the compressed echo pulse.