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EETE JANUARY 2013

spotLiGHt When an approximation isn’t good enough: Reduced generating a true waveform Jitter The technologies used to digitally generate FiGUrE 1, for example, shows the twelve- analog waveforms have long been a case fold reduction in jitter that Trueform offers 500 ps study in compromise. over a traditional DDS generator. Lower jitter precise but expensive a key advantage with edge-based timing ap-increases the precision of timing-related tests, The point per clock (PPC) method, in which plications such as clocks, triggers, and many each point of the waveform file is cycled communication signals. FiGUrE 1 through a DAC, is conceptually simple but re- Trueform (left) exhibits up to 12 times less quires complicated and expensive clocking and FiGUrE 2 highlights another major advan- edge jitter than conventional DDS genera- filtering in order to be successful in real-world tage: high-fidelity signals that eliminate the tors (right). applications. point-skipping problems of DDS. With a DDS, the higher the frequency, the more likely Low cost but approximate gaps will appear in the output waveform— The approach widely used for mainstream increasing the odds that the generated signal function/arbitrary waveform generators, direct will be missing critical details. digital synthesis (DDS), is simpler and far less Trueform at 200 kHz expensive but renders approximations of the Better includeformOther major advantages of True desired waveform. These approximations are than DDS and full anti-aliasing with no external IntegritySignaltotal harmonic distortion up to five times lower acceptably close to the ideal for many ap- filtering required. plications, which is why lower-cost waveform generators typically use this technology. With these improvements in signal integrity, the Agilent 33500B Series waveform genera- However, because these signals are approxi- tors with Trueform are especially useful for the mations, there can be problems with harmonic following applications: distortion, jitter, aliasing, and even skipped FiGUrE 2 points in the waveform. • Simulating clock signals This 200 kHz signal was programmed with seven spikes riding on the square wave. Low cost—without compromise dard PRBS patterns seven spikes, but the waveform from aTrueform (upper) successfully created all-stanstreamingbybusesdataserial• Testing Engineers now have a third option that • Providing precise timing control, such as a DDS generator (lower) is missing four of combines the best of both worlds: exclusive trigger source or gate controller the seven. Trueform signal generation technology avail- • Economically playing baseband IQ signals able in the Agilent 33500B Series waveform (option IQP) generators. Trueform works by employing a virtual variable clock with advanced filtering To learn more about this revolutionary ap- that tracks the sample rate of the waveform. proach to waveform generation, visitwww. The result is the performance of PPC technol- agilent.com/find/33500B ogy at the same price point as DDS generators. Find an Agilent distributor today atGet a quick quote today at www.agilent.com/find/distributor


EETE JANUARY 2013
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