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DDS devices are now available that can generate frequencies from less than 1 Hz up to 400 MHz (based on a 1-GHz clock).

The benefits of their low power, low cost, and single small package, combined with their inherent excellent performance and the ability to digitally program (and reprogram) the output waveform, make DDS devices an extremely attractive solution—preferable to less-flexible solutions comprising aggregations of discrete elements.

Since sampling theory dictates that at least two samples per cycle are required to reconstruct the output waveform, the maximum fundamental output frequency of a DDS is /2.

However, for practical applications, the output frequency is limited to somewhat less than that, improving the quality of the reconstructed waveform and permitting filtering on the output.

One revolution of the vector around the phase wheel, at a constant speed, results in one complete cycle of the output sine wave.

The phase accumulator provides the equally spaced angular values accompanying the vector’s linear rotation around the phase wheel.

Many possibilities for frequency generation are open to a designer, ranging from (DAC) outputs to generate arbitrary waveforms at lower frequencies.

But the DDS technique is rapidly gaining acceptance for solving frequency- (or waveform) generation requirements in both communications and industrial applications because single-chip IC devices can generate programmable analog output waveforms simply and with high resolution and accuracy.

Each designated point on the phase wheel corresponds to the equivalent point on a cycle of a sine wave.

As the vector rotates around the wheel, visualize that the sine of the angle generates a corresponding output sine wave.


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