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| + | == Data Modulation == | ||
| + | In real life, speakers cannot play signals that are in the digital form. In order to play a sound, a physical voltage must be sent to the speakers. However, most soundtracks are now save in digital form in industry, a DAC, digital-to-analog converter, is needed in virtually every device that can produce a sound. In this page, i will introduce a type of DAC technique, whose name is Delta modulation, that is used in real life. | ||
| + | |||
• Delta modulation | • Delta modulation | ||
| − | + | A practical analog-to-digital conversion technique is delta modulation, whose output is a binary bit sequence, each consisting of either 0 or 1. | |
[[File:LOl12341.png]] | [[File:LOl12341.png]] | ||
| − | • Delta modulator at transmitter | + | • Delta modulator at transmitter |
[[File:22223.png]] | [[File:22223.png]] | ||
| + | |||
| + | • At receiver, the signal can be approximately reconstructed as | ||
| + | |||
| + | [[File:72223.png]] | ||
| + | |||
| + | • Two types of distortions: slope-overload distortion and granular noise | ||
| + | |||
| + | [[File:82223.png]] | ||
| + | |||
| + | • To avoid slope-overload distortion, we need to have | ||
| + | |||
| + | [[File:92223.png]] | ||
| + | |||
| + | |||
| + | • On the other hand, to reduce granular noise, it is desirable to have smaller ∆ | ||
| + | |||
| + | • Thus, there is a trade-off in selecting large or small step size ∆ to balance | ||
| + | between minimizing slope-overload distortion and granular noise | ||
| + | |||
| + | • One solution is to reduce 𝑇𝑠, but this increases transmission rate | ||
Latest revision as of 22:51, 2 December 2017
Data Modulation
In real life, speakers cannot play signals that are in the digital form. In order to play a sound, a physical voltage must be sent to the speakers. However, most soundtracks are now save in digital form in industry, a DAC, digital-to-analog converter, is needed in virtually every device that can produce a sound. In this page, i will introduce a type of DAC technique, whose name is Delta modulation, that is used in real life.
• Delta modulation
A practical analog-to-digital conversion technique is delta modulation, whose output is a binary bit sequence, each consisting of either 0 or 1.
• Delta modulator at transmitter
• At receiver, the signal can be approximately reconstructed as
• Two types of distortions: slope-overload distortion and granular noise
• To avoid slope-overload distortion, we need to have
• On the other hand, to reduce granular noise, it is desirable to have smaller ∆
• Thus, there is a trade-off in selecting large or small step size ∆ to balance between minimizing slope-overload distortion and granular noise
• One solution is to reduce 𝑇𝑠, but this increases transmission rate
