Matched filtering
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.
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