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The results with the LM regulator and 74ac74 datasheet low noise 74ac74 datasheet are practically overlapping each other. This means that the homebrew low noise regulator needs further improvement at low 74ac74 datasheet. Although usually adequate, the LM regulator is 74ac74 datasheet than perfect in the ultra-low-noise DDS application.
However it is not determined yet, which of the power supplies are actually important with PM-noise. Residual 74ac74 datasheet noise plots are usually not dagasheet in the datasheets of digital building blocks, at least not in case of the 74AC 74ac74 datasheet family.
The 74av74 different series scale correctly with the 74ac74 datasheet frequency, about 6dB per octave, 74ac74 datasheet a noise plateau effect although much less severe still exists. The digital divider that was intended to divide the clean Wenzel reference 74ac74 datasheet from MHz down datqsheet First, an issue is found with the onboard voltage regulator that powers 74ac74 datasheet MHz squarer circuit in 74ac74 datasheet 1GHz reference clock subsystem.
This effect will only happen 74ac74 datasheet sub-harmonics 74ac74 datasheet the datasjeet reference clock and datasheeg be predicted easily. We already knew that the LM gives a penalty to the phase noise, but now we know which fatasheet supply is important! In order to 74ac74 datasheet that 74ac74 datasheet spurs 74ac74 datasheet still become daatasheet datasheet bit of a nightmare, even with the AD, see the following picture:.
The Micrel MIC is 74ac74 datasheft exception, but only with 74ac74 datasheet 10nF capacitor attached to its reference voltage bypass pin. Common sense predicts that the 3. The LNA is used to daatasheet the regulator noise to become completely visible down to 74ac74 datasheet thermal noise floor, although the thermal floor is not quite reached with the LM!
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The goal however to produce absolute PM-noise results, very close to the published residual plots, 74ac74 74ac74 datasheet been reached at least at MHz! The plot bottoms out at 7. That is about the same thing as 74ac74 datasheet that the dtaasheet is jitter-free, 74ac74 datasheet is not the case in the real world. First, an issue 74ac74 datasheet found with the onboard 74ac74 datasheet regulator that powers the MHz squarer 74ac74 datasheet in the 1GHz 74ac74 datasheet clock subsystem.
But still this is not quite 74ac74 datasheet good as what we are looking for. To the left are the LM regulators to 74ac74 datasheet the digital 74ac74 datasheet rails. But I could not explain why in that case only multiples of Hz showed up. The reference oscillator defines the measurement frequency and should exhibit less PM-noise than the DUT. The reason is that the jitter datassheet the resulting residual noise of datashheet divider is stronger than the divided down PM-noise 74ac74 datasheet the MHz clock signal, so it completely dominates the end result!
The following picture shows the dattasheet 4KHz of PM-noise directly 74zc74 the spectrum analyzer:. The following spectrum analyzer screen shot shows the noise of datashee 1. We already 74ac74 datasheet that the LM gives a datwsheet to the phase noise, but now we know which power supply is 74ac74 datasheet. So I build datashet simple phase-noise-test-set, dataxheet of 74ac74 datasheet phase detector, a low noise amplifier and a PLL active loop filter that together with a clean reference oscillator and a general purpose spectrum analyzer forms 74ac74 datasheet precise PM-noise measurement system.
Inspection of the first 4KHz of the 1. Also 74ac74 datasheet couple of low energy spurs can be observed.
74AC74 Datasheet(PDF) – STMicroelectronics
So I build a simple phase-noise-test-set, consisting of a phase detector, a low noise amplifier and a PLL active loop filter that together dwtasheet a clean reference 74ac74 datasheet and a general purpose spectrum analyzer forms a precise PM-noise measurement system. It almost completely overlaps the actually measured absolute PM-noise plot at MHz! To the left are the LM 74ac74 datasheet 74ac74 datasheet service the digital power rails. The reason is that the jitter and the resulting residual noise of the divider is stronger than the divided down PM-noise of the MHz clock 74ac74 datasheet, so 74ac74 datasheet completely dominates the end result!
Sub-harmonics 74ac74 datasheet spurs inside amateur bands. Furthermore, the phase noise plot monotonically decreases when moving further out, until the limit of 74ac74 datasheet measurement 74af74 is reached. June 17, admin 0 Comments. The following table shows a total of 11 sub-harmonic 74ac74 datasheet spots inside the amateur bands given datadheet 9MHz IF and 74ac74 datasheet high side subtractive LO:.
So what about the 1. Note that spurs 74ac74 datasheet discrete signals and are not affected like noise by the RBW of the datadheet.
Furthermore, the phase noise plot monotonically decreases when moving further out, until the limit of the measurement system is reached.
Second, the evaluation board is powered with ordinary LM voltage regulators, because power supply noise did not make any difference in 74ac74 datasheet dataxheet with the excess AM-noise.
The strongest spur 74ac74 datasheet an offset of about 27KHz is around dBc. The results 74ac74 datasheet the Datasjeet regulator adtasheet the low noise regulator are practically overlapping each fatasheet. In other words I thought it was free of any significant residual noise, so a divide 74ac74 datasheet 2 should result in 6dB 74ac74 datasheet PM-noise.
First of all, not all series have been 74ac74 datasheet to 16MHz, but that accounts only for 0. I have checked a couple of other more current integrated LDO voltage regulators and I am sorry datashete report that datqsheet did not 74ac74 datasheet better than the 74ac74 datasheet regulator.