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nao113

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- Homework Statement
- 1. The transducer array of a linear-array real-time imaging instrument has 32 unfocused elements. Each element is 0.5 cm wide, and there is a nonradiating gap of 0.5 cm between neighboring elements. Only one element at a time is excited.

a) At a frequency of 3 MHz, find the lateral resolution of this instrument at a depth of 1 cm and a depth of 8 cm. The lateral resolution of a linear- array imager is given by the beam size or the line spacing, whichever is larger.

Use relationship:

c = 1540 m/s, c =frequency x l

b) If echo information out to a depth of 12 cm is desired, calculate the minimum time required to scan the entire array.

- Relevant Equations
- Z < ZR => LR = D

Z > ZR => LR = 2 tan(sin-1 lambda/D) x Z

a. lambda = 513 X 10^-6 m

ZR = 1, 2 cm

Z = 1 cm => Z < ZR => LR = D = 0.5 cm

Z = 8 cm => Z > ZR => LR = 2 tan(sin^-1 (lambda/D)) x Z

= 2 tan(sin^-1 (513 x 10^-6 m/0.005 m)) x 0.08

= 1.65 cm

b. t = Z/c => 0.12/1540 = 77.9 x 10^-6 s