Matched filtering is an important signal processing function. The
transducer sends out unique transmit sequences, each of which can be
recognized by a matched filter. The key advantage is that the transmit
sequence can be expanded in time at a lower amplitude and transmitted
at a lower peak pressure amplitude level. This can reduce bioeffects
and contrast agent effects. It can also preserve axial resolution with
depth, and increased sensitivity and tissue penetration depth.
A variety of Matched filtering have been implemented. There are two
classical types of transmit waveforms, a coded binary sequence and a
chirped pulse, which are borrowed from radar.