Altera NCO MegaCore Function User Manual
Page 33
To meet the specification, the design uses the following parameters:
• Multiplier-based algorithm. By using the dedicated multiplier circuitry in Stratix devices, the NCO
architectures that implement this algorithm can provide very high performance.
• Clock rate of 200 MHz and 32-bit phase accumulator precision to give a frequency resolution of 47
mHz.
• Angular and magnitude precision settings give an SFDR of approximately 100.05 dB to meet the SFDR
requirement, while minimizing the required device resources. s.
Figure 4-3: Spectrum After Setting Angular and Magnitude PrecisionAngular precision = 17 bits;
magnitude precision = 18 bits
• Dither level to increase the variance of the dithering sequence until the design reaches the trade-off
point between spur reduction and noise level augmentation. At a dithering level of 3, the SFDR is
approximately 110.22 dB, which exceeds the specification.
Figure 4-4: Spectrum After the Addition of Dithering
• The frequency modulation input allows an external frequency for modulating the input signal. The
modulator resolution is 32 bits and the modulator pipeline level is 1.
• A phase modulation input, which is necessary with 32 bits for modulator precision and the modulator
pipeline level is 1.
• Dual output for generating both the sine and cosine outputs.
• Four multichannels.
Simulation Specification
UG-NCO
2014.12.15
NCO Design Example Specification
4-3
NCO Multichannel Design Example
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