Lecture 4.1 Flashcards
So although harmonics give better over resolution they also cause
A narrow bandwidth for each one causing
Longer SPL
Worse AR
worse resolution
What does pulse inversion
Gets rid of the fundamental frequency which had a super high amplitude. By getting rid of the of tall skinny signal the bandwidth is now focused on the short broad bandwidth of the second harmonic
How is pulse inversion accomplished
2 pulses sent out with slight delay ( one regular, one inverted)
Only harmonic wave preserved, the fundamental doesnt make it back
Transducer uses bandwidth for only second harmonic
While the wider bandwidth creates shorter SPL, better AR and resolution what is a disadvantage
Sending multiple pulses lowers decreases the frame rate
What occurs during detection
The conversion of radio frequency form of waves to video form/amplitude form
Detection is aka
Demodulation
Two steps of detection
Rectification
Smoothing `
What is rectification in detection
Turns negative voltages into positive voltages
What is smoothing in detection
Wraps an envelop around the signal to make it less bumpy
Levels out the differences in amplitude
in the true video form we only require
The maximum values of the signal
What function does compression perform
Dynamic range
Amplifiers can handle dynamic range of
100-170 dB
The display can handle a DR of
30 dB
Our human vision can only handle DR of
20 dB or 100x
What is the process of compression doing
Decreasing the differences between the smallest and largest echo amplitudes to a usable range
