Altera NCO MegaCore Function - Manual (Page 24)

Frequency Modulation
You can add an optional frequency modulator to your custom NCO variation. You can use the frequency
modulator to vary the oscillator output frequency about a center frequency set by the input phase
increment. This option is useful for applications in which the output frequency is tuned relative to a free-
running frequency, for example in all-digital phase-lock-loops.
You can also use the frequency modulation input to switch the output frequency directly.
You can set the frequency modulation resolution input in the IP core. The specified value must be less
than or equal to the phase accumulator precision.
The NCO IP core also provides an option to increase the modulator pipeline level; however, the effect of
the increase on the performance of the NCO IP core varies across NCO architectures and variations.
Phase Modulation
You can use the NCO IP core to add an optional phase modulator to your variation, allowing dynamic
phase shifting of the NCO output waveforms. This option is particularly useful if you want an initial phase
offset in the output sinusoid.
You can also use the option to implement efficient phase shift keying (PSK) modulators in which the
input to the phase modulator varies according to a data stream. You set the resolution and pipeline level
of the phase modulator in the NCO wizard. The input resolution must be greater than or equal to the
specified angular precision.
NCO IP Core Parameters
The wizard only allows you to select legal combinations of parameters, and warns you of any invalid
configurations.
Architecture Parameters
Table 3-3: Architecture Parameters
Parameter Value Description
Generation
Algorithm
Small ROM, Large
ROM, CORDIC,
Multiplier-Based
Select the required algorithm.
Outputs Dual Output, Single
Output
Select whether to use a dual or single output.
Device Family
Target
— Displays the target device family. The target device
family is preselected by the value specified in the
Quartus II or DSP Builder software. The HDL that
is generated for your variation may be incorrect if
you change the device family target in this wizard.
Number of
Channels
1–8 Select the number of channels when you want to
implement a multichannel NCO.
UG-NCO
2014.12.15
Frequency Modulation 3-7
NCO IP Core Functional Description Altera Corporation
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