Reduction of periodic signals in pseudo-random noise produced with direct digital synthesis
US6732128B2 · kind B2 · utility
Assignee
Inventor
Key dates
| Filing date | Jan 30, 2001 |
| Grant date | May 4, 2004 |
| Priority date | — |
| Expiry date | May 28, 2022 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG06F1/03
- WIPO fieldComputer technology
- WIPO sectorElectrical engineering
Abstract
A DDS (Direct Digital Synthesis) frequency synthesizer can be adapted to operate as a pseudo random noise generator by including a swept address ingredient that distributes (but does not eliminate) repetitive frequency components that would otherwise appear in the output of the basic DDS technique, (which fetches fixed but randomized values from a waveform memory). These residual distributed long period frequency components in the output of a swept DDS pseudo random noise generator are suppressed by making the sweep itself irregular. The noise generator includes an Address Increment Register (AIR) whose content: (1) alters the address used to fetch fixed randomized values from the waveform memory; and (2) is incremented to produce the swept address (different sequences of addresses). At some point the AIR value has been incremented as high as it will go (i.e., the end of the sweep has been reached), and the process must start over. Instead of reloading the AIR with same start value at the end of each sweep, some number of residual least significant bits are left as they were at the end of the sweep, while the remaining upper bits are indeed reloaded to the previously used start val…
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