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2.1 Principle frame
2.2 Working principle of DDS
To generate a voltage signal, the traditional analog signal source adopts electronic
components as oscillator in different ways. So both frequency accuracy and stability are not
high enough. Besides, it is of the disadvantages of complicated technique, low resolution and
inconvenient frequency setting and realization of computer control. Direct Digital
Synthesize（DDS） technique is a new developing method of generating signals without any
oscillator components, by which a series of data stream are generated using digital synthesizing
method and then a pre-established analog signal is generated from digital-analog converter.
To generate a sine signal, for example, the function of y＝sinxshould be digitally
quantized first, and then taking x as the address and y as the quantized data to store them into
DDS
Digital circuit
Lowpass Comparator
TTL output
FM
Voltage
amplification
Amplitude
control
and AM
Power
amplification
Offset setting
Modulation input
Output
attenuation
20-60dB
Output
protection
Output A
Lowpass
Amplitude
control
Power
amplification
Output B
Keyboard
MCU
DDS
Knob
Displayer
Clock
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