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3D Time-of-flight distance measurement with custom - Universität ...

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42 CHAPTER 2<br />

In Figure 2.13 we show an illustration <strong>of</strong> the sampling influences and aliasing<br />

situation when detecting a square wave <strong>with</strong> the 4-tap mechanism.<br />

input signal<br />

short-time<br />

integration<br />

ideal sampling<br />

Amplitude spectrum Phase spectrum<br />

S()<br />

f<br />

0.5<br />

ϕ()<br />

f<br />

()<br />

f<br />

S int<br />

DFT-amplitude spectrum<br />

<strong>of</strong> naturally sampled<br />

square wave<br />

⎛<br />

⎜<br />

f<br />

sinc 2π<br />

⋅<br />

⎝ 4f0<br />

0.5<br />

f 3<br />

0 f0<br />

0<br />

f 3<br />

0 f0<br />

0<br />

⎞<br />

⎟<br />

⎠<br />

F () samp f<br />

1<br />

0<br />

()<br />

f<br />

S samp<br />

int,<br />

0 f0<br />

f<br />

1<br />

f0 0 f 2 0 f 4 0 f 6<br />

0<br />

f<br />

4f0<br />

3ϕ0<br />

ϕ0<br />

f 3<br />

f0 0<br />

4f0 0 f 8 0 f 12 f<br />

aliasing<br />

f<br />

ϕ () int f<br />

3ϕ0<br />

ϕ0<br />

8f0 0 f 12<br />

f 3<br />

f0 0<br />

Figure 2.13 Aliasing for a square wave sampled <strong>with</strong> only four sampling points.<br />

Influence on amplitude and phase spectrum.<br />

f<br />

f<br />

f

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