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DDS Block Diagram
This diagram shows the internal components of a Direct Digital Synthesizer and how they work together to generate the output waveform.
Direct Digital Synthesis generates precise frequencies using digital techniques.
Core DDS Configuration
DAC Sampling Rate:250.000 MHz
Output Frequency:73.920 MHz
Output Amplitude:0 dBFS
Frequency Control
Frequency Tuning Word:0x4BB1AF3A
FTW (Decimal):1,269,935,930
Frequency Resolution:0.058 Hz
Output Nyquist Zone:1
DDS Architecture
Phase Accumulator:32 bits
LUT Address Bits:12 bits
Phase Truncation:20 bits
LUT Size:4,096 entries
Phase Truncation Spurs
Worst-case SFDR:-120.4 dBc
Minimum Spur Separation:61.035 kHz
DAC Performance
DAC Resolution:14 bits
INL:±0.5 LSB
DNL:±0.3 LSB
DAC SFDR Spec:75 dB
Sin(x)/x Effects
Sin(x)/x Roll-off:1.29 dB
Normalized Frequency:0.2957
System Performance
Actual SFDR:75.0 dB
SNR:74.0 dB
ENOB:12.00 bits
Theoretical Limits
Quantization SNR:86.0 dB
Noise Floor:-86.0 dBc
Spurious Sources
Phase TruncationEnabled
DAC Non-linearityEnabled
Quantization NoiseEnabled
Clock FeedthroughDisabled
Phase NoiseDisabled
Reconstruction Filter
Filter Type:Zero Order Hold
Output Characteristics
Total Attenuation @ Fout:1.29 dB
Output Power:-1.3 dBm
Design Considerations
Output/Nyquist Ratio:0.591
Oversampling Factor:1.7×
Phase Noise Impact:Minimal
LUT Size Adequacy:Adequate
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DDS Theory & Reference
Overview
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Direct Digital Synthesis (DDS) is a method of producing analog waveforms by generating a time-varying signal in digital form and then performing a digital-to-analog conversion. The DDS architecture is based on the principle of phase accumulation, where a phase increment (frequency tuning word) is added to a phase accumulator on each clock cycle.
The output frequency is given by:
fout=2NFTW⋅fclk
where:
- FTW is the frequency tuning word
- fclk is the clock frequency
- N is the number of bits in the phase accumulator
DDS Architecture
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Input Parameters
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Spurious Sources
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Key Calculations
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References
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DDS Configuration
DDS Configuration
Spur Modeling
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