DESIGN AND IMPLEMENTATION OF DIRECT DIGITAL SYNTHESIZER

• Main Author: Dewa Putu Surya Eko Bumi, I
• Format: Final Project
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/42984
• Institution: Institut Teknologi Bandung

SDR (Software Defined Radio) is one example of the development of radio technology that refers to economic principles and principles of operational convenience. In this SDR, there is an oscillator block which generates a sinusoidal signal. In its operation, DDS uses 4 modes including single tone, RAM modulation, digital ramp modulation, and parallel data port modulation. DDS can be used directly as a frequency generator oscillator whose out frequency can be adjusted by the DDS Controller via a Rotary Dial and the frequency display can be read directly on the TFT LCD The DDS Board that I use is equipped with AD9850 IC which is a clock generator that can output 2 frequency outputs, the output is square wave and sine with a frequency of up to 40 Mhz. In this final project research is discussed about signal generation with Direct Digital Synthesizer (DDS). The frequency used is in the range of 0 to 40 MHz. There are 2 output signals which are square signal and sine signal. The square signal is the output signal that is passed to the comparator, while the sine signal is the output signal that is passed to a lowpass filter to eliminate the ripplenya. Lowpass filter used is an elliptical lowpass filter of order 7 with the specifications of Maximum Passband Loss (????????) = 1 dB, Minimum Stopband Roll Off (????????) = 50 dB, Cutoff Passband Frequency (????????) = 40 MHz, Cutoff Stopband Frequency (????????) = 45 dB MHz, and has VSWR = 1,081 in the simulation and 1,076 in the test results at a frequency of 26 MHz. The AD9850 Direct Digital Synthesizer output signal has a signal gain of -41.15 dBm for sine signals and -23.53 dBm for square signals.