MIT6_003S10_lec23

MIT6_003S10_lec23 - .003: Signals and Systems uantization...

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Unformatted text preview: .003: Signals and Systems uantization and Modulation ay 4, 2010 Last Time uantization: discrete representation of amplitudes. 1 2 bits 4 bits 00 01 10 3 bits Output voltage-1-1 1-1 1-1 1 Input voltage Input voltage Input voltage 0.5 1-1 1 Time (second) 0.5 1 Time (second) 0.5 1 Time (second) Digital representations of signals require discrete representations of both the independent variable (time, space, ...) and dependent variable (amplitude). uantizing Images uantizing creates distortion. 8 bits 6 bits 4 bits 3 bits 2 bits 1 bit uantization Adding noise (dither) can reduce the perceptual effect of quantiza- tion. uantization: y = Q ( x ) uantization with dither: y = Q ( x + n ) uantizing Images Adding noise (dither) reduces banding in images. 3 bits 2 bits 1 bit 3 bits dither 2 bits dither 1 bit dither uantizing Sound Adding noise (dither) can reduces distortions in sound. 16 bits/sample 4 bits/sample 4 bits with dither/sample 3 bits/sample 3 bits with dither/sample 2 bit/sample 2 bit with dither/sample J.S. Bach, Sonata No. 1 in G minor Mvmt. IV. Presto Nathan Milstein, violin oberts Technique Roberts technique decorrelates quantization errors from the signal. uantization: y = Q ( x ) uantization with dither: y = Q ( x + n ) uantization with Roberts technique: y = Q ( x + n ) n uantizing Images Roberts technique decorrelates quantization errors from the signal. 3 bits dither 2 bits dither 1 bit dither 3 bits Roberts 2 bits Roberts 1 bit Roberts uantizing Sound Roberts technique decorrelates quantization errors from the signal. 16 bits/sample 2 bits/sample 2 bits with dither/sample 2 bits with Roberts technique/sample J.S. Bach, Sonata No. 1 in G minor Mvmt. IV. Presto Nathan Milstein, violin Fourier Analysis uantization x ( t ) | X ( j ) | t Dither x ( t ) | X ( j ) | t Roberts Technique x ( t ) | X ( j ) | t odulation Applications of signals and systems in communication systems. Example: Transmit voice via telephone wires (copper) mic amp telephone wire amp speaker orks well: basis of local land-based telephones. ireless Communication In cellular communication systems, signals are transmitted via elec- tromagnetic (E/M) waves....
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This note was uploaded on 12/14/2011 for the course EE 6.003 taught by Professor Freeman during the Fall '11 term at MIT.

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MIT6_003S10_lec23 - .003: Signals and Systems uantization...

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