Digital/Analog conversion

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# Digital/Analog conversion - PowerPoint PPT Presentation

Digital/Analog conversion. How do we convert analog signals to digital data and vice versa?. Analog-to-digital conversion. Converting analog signals to digital data is relatively straightforward.

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## PowerPoint Slideshow about 'Digital/Analog conversion' - oria

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### Digital/Analog conversion

How do we convert analog signals to digital data and vice versa?

Analog-to-digital conversion
• Converting analog signals to digital data is relatively straightforward.
• Sampling is the process by which we measure the value of the analog signal at discrete points in time.
• The sampling rate is how frequently the signal is sampled. To accurately capture the analog signal, the sampling rate must be twice the highest component frequency of the signal.
• After sampling, the signal is quantized - which is to say the set of continuous possible values is converted to a set of discrete digital values.
• Pulse Code Modulation (PCM) samples the absolute amplitude of the signal
• Delta Modulation (DM) samples the change in the amplitude of the signal
Digital-to-analog conversion
• This is the trickier problem - how do we accurately represent digital data in an analog signal?
• In the simplest versions, we vary one of amplitude, frequency, or phase to capture our digital data.
• The carrier frequency is the base signal for the information carrying signal. Information is carried by modifying the carrier signal.
• Just like it sounds, we shift the amplitude of the carrier signal
• Binary ASK uses only two amplitude levels - 0 and the level of the carrier signal.
Frequency Shift Keying (FSK)
• Here we manipulate the frequency of the carrier signal.
• Binary FSK essentially uses two carrier frequencies - a high and a low - to represent different data elements.
• Multilevel FSK uses more than two carrier frequencies, where each level represents multiple data elements.
Phase Shift Keying (PSK)
• Shift the phase of the carrier signal.
• Binary PSK: One element has phase of 0°, the other 180°.
• Quadrature PSK: Uses two BPSK modulations to pack two bits into each signal element. Essentially has four levels: 45°, 135°, -45°, and -135°.