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Subelement L13
Digital Signal Processing.
Section L13
Which of the following functions is not included in a typical digital signal processor?
• Mathematical transform
Aliasing amplifier
• Analog to digital converter
• Digital to analog converter

Digital Signal Processing first transforms an analog signal to digital via an analog-to-digital converter (ADC), performs mathematical operations to filter or demodulate, for example, and recreates an analog signal through a digital-to-analog converter (DAC). Aliasing is a situation where input frequencies above the sampling rate get erroneously reproduced as lower frequencies; the situation is prevented through the use of an anti-aliasing filter (a low-pass filter).

Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.

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How many bits are required to provide 256 discrete levels, or a ratio of 256:1?
• 6 bits
• 16 bits
• 4 bits
8 bits

256 levels in binary data spans the range 0 to 255. Add the value of each bit in an 8-bit binary number, starting with the lowest: 1 + 2 + 4 + 8 + 16 + 32 + 64 + 128 = 255.

Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.

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Adding one bit to the word length, is equivalent to adding ____ dB to the dynamic range of the digitizer:
• 1 dB
• 4 dB
• 3 dB
6 dB

The number of bits determines the maximum number of distinct values available to represent a signal. For each sample, the analog-to-digital converter selects the closest value to describe the instantaneous value of the input signal. The difference between the real value and its numerical representation is a quantization error: plus or minus half a bit, i.e., 1 bit total. In digital terms, Signal-to-Noise Ratio and Dynamic Range are synonyms specifying the ratio between the largest possible sample value to the quantization error. Dynamic Range for fixed-point processors can be approximated by the data word size: 6 dB times number of bits. Each bit doubles the value, doubling voltage is 6 dB.

Original copyright; explanations transcribed with permission from Francois VE2AAY, author of the ExHAMiner exam simulator. Do not copy without his permission.

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What do you call the circuit which employs an analog to digital converter, a mathematical transform, a digital to analog converter and a low pass filter?
• Digital formatter
• Mathematical transformer
• Digital transformer