Jitter and Audio, I agreee with Paul when he relates Jitter with sound stage.
https://www.youtube.com/watch?v=ZT_1UATci3c
https://www.youtube.com/watch?v=ZT_1UATci3c
Thank you for the link, I felt alittle dizzy with the cameras rapid movement!
The problem with his system is his noise floor, about -140dBc at 1MHz and only -100dBc at 100Hz - I would expect a high performance audio clock to measure better then this, Measurement noisefloor is the problem I have always faced
Looking forward to seeing how low we can go with our DIY solution.
I have a HP3589 - but its a horrid machine to use, the earlier HP3585 is much nicer (but without the digital based RBW fillters) - so its limited to a 3Hz RBW.
Yes, 3585 is a solid one. I happen to have a nice collection of those HPs - 3585 spectrum, 3577 network and 3562 FFT.
Yep,
I just bought a 3585B as my 3585A throws up an Error message every now an then - unfortunately everything decent state side, so it cost me almost as much to ship such a heavy beast to Czech rep. as the unit itself costs
I'm thinking of upgrading my 3577 with the Colour LCD from NewScope as there's little avaible today that covers the audio band and then upto 200MHz:-
"NewScope-5 Color LCD kit for HP 3577A 3577B Network Analyzer 1345A Display"
NewScope-5 Color LCD kit for HP 3577A 3577B Network Analyzer 1345A Display | eBay
I just bought a 3585B as my 3585A throws up an Error message every now an then - unfortunately everything decent state side, so it cost me almost as much to ship such a heavy beast to Czech rep. as the unit itself costs
I'm thinking of upgrading my 3577 with the Colour LCD from NewScope as there's little avaible today that covers the audio band and then upto 200MHz:-
"NewScope-5 Color LCD kit for HP 3577A 3577B Network Analyzer 1345A Display"
NewScope-5 Color LCD kit for HP 3577A 3577B Network Analyzer 1345A Display | eBay
Yep,
I just bought a 3585B as my 3585A throws up an Error message every now an then - unfortunately everything decent state side, so it cost me almost as much to ship such a heavy beast to Czech rep. as the unit itself costs
I'm thinking of upgrading my 3577 with the Colour LCD from NewScope as there's little avaible today that covers the audio band and then upto 200MHz:-
"NewScope-5 Color LCD kit for HP 3577A 3577B Network Analyzer 1345A Display"
NewScope-5 Color LCD kit for HP 3577A 3577B Network Analyzer 1345A Display | eBay
Yes I am familiar with that great mod for HP. I was thinking the same, but after I got my AP unit, I have very little usage for 3577.
I got price on the Microsemi Phase Noise Test Probe Kit 3120A:-
3120a (Sans basic software?) US$14,030
AM Noise software License US$1,677
Signal Statistic software License US$2520
Frequency Counter software License US$1677
Mask Test software License US$4905
Total without Tax, US$ 20,503
These are Prices quoted by the Czech Distributor - I tend to find we get ripped off here in Europe, Prices might be cheaper in the US.
When buying an expensive unit I tend to fly to the US and purchase directly, or ship to Hong Kong via my China office which has no sales tax and "use" the unit for 6 months...
I'm not sure what software is shipped with the unit if any, but it looks like Signal statistics and possibly AM noise licenses are basic requirements - I'm not sure who would spend US$1677 for frequency counter software when you can pick up a used HP unit for US$100... I'm not sure if the 3120A has an Oven oscillator...
If the world of Phase noise measurement, the price is very good, sure the software is a pure money "maker" but it looks like a decent unit.
Lets see if anything comes from our DIY effort, otherwise I'll have to lie again to my dear Wife
3120a (Sans basic software?) US$14,030
AM Noise software License US$1,677
Signal Statistic software License US$2520
Frequency Counter software License US$1677
Mask Test software License US$4905
Total without Tax, US$ 20,503
These are Prices quoted by the Czech Distributor - I tend to find we get ripped off here in Europe, Prices might be cheaper in the US.
When buying an expensive unit I tend to fly to the US and purchase directly, or ship to Hong Kong via my China office which has no sales tax and "use" the unit for 6 months...
I'm not sure what software is shipped with the unit if any, but it looks like Signal statistics and possibly AM noise licenses are basic requirements - I'm not sure who would spend US$1677 for frequency counter software when you can pick up a used HP unit for US$100... I'm not sure if the 3120A has an Oven oscillator...
If the world of Phase noise measurement, the price is very good, sure the software is a pure money "maker" but it looks like a decent unit.
Lets see if anything comes from our DIY effort, otherwise I'll have to lie again to my dear Wife
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I use my 3577 for loop gain measurements on Amplifiers etc. its about the only unit I'm aware that has the LF to 200MHz BW required.
https://dl.dropboxusercontent.com/u/86116171/3577 Loop Gain measurements.pdf
OK, here's how I built a phase noise rig for about $2 (including the cost of the oscillators being tested, which were $1 each).
Get two XO cans of same frequency.
Grab some AA batteries from battery bin for low noise supply (2AAs for each clock, 2 for mixer)
Grab 74AC00 from junk bin, this will be our mixer
Add some power supply caps from junk bin
The mixer output gives us a beat tone which is the difference in frequency between our clocks. Lowpass that and acquire with soundcard for 10 minutes.
This beat tone will be between a few Hz and a few hundred Hz. More Hz works better, so put some new or used AA batteries on one of the clocks to adjust its frequency slightly, to get a beat tone above 50 Hz.
Next comes a little bit of easy DSP in software on the PC. The nice thing is that the soundcard clock phase noise is rejected from the measurement. So we get a measurement of the difference of the "internal time" of our two clocks. It's the same as talking about phase.
Attached plots are how much those two clocks drift relative to each other during 1s. One of the graphs has a wad of kleenex put over the clocks, which makes them drift a lot less as expected.
Once you get the time delta between clocks is is easy to rebuild (in software) the mixer output that a real phase noise rig would generate, using a perfect VCO. I'm not showing plots cause my $1 clocks aren't very interesting... ok, the measured phase noise corresponds to what the datasheet says, but I'd like to check the system with better clocks to see if it really works first.
You only need a fancy VCO (which is the major cause of headache) if you want to measure an arbitrary clock, and if your measurement setup is only able to measure DC.... by acquiring the beat tone, as long as it is within the soundcard bandwidth, no problem. So this system needs two clocks of identical frequency, but the more difference between them, the better, as long as it is in the soundcard bandwidth...
Now, I need to figure out a way to generate a I/Q beat tone instead of a plain tone, to get much more precision. And maybe use autocorrelation, that would need 3 clocks...
Get two XO cans of same frequency.
Grab some AA batteries from battery bin for low noise supply (2AAs for each clock, 2 for mixer)
Grab 74AC00 from junk bin, this will be our mixer
Add some power supply caps from junk bin
The mixer output gives us a beat tone which is the difference in frequency between our clocks. Lowpass that and acquire with soundcard for 10 minutes.
This beat tone will be between a few Hz and a few hundred Hz. More Hz works better, so put some new or used AA batteries on one of the clocks to adjust its frequency slightly, to get a beat tone above 50 Hz.
Next comes a little bit of easy DSP in software on the PC. The nice thing is that the soundcard clock phase noise is rejected from the measurement. So we get a measurement of the difference of the "internal time" of our two clocks. It's the same as talking about phase.
Attached plots are how much those two clocks drift relative to each other during 1s. One of the graphs has a wad of kleenex put over the clocks, which makes them drift a lot less as expected.
Once you get the time delta between clocks is is easy to rebuild (in software) the mixer output that a real phase noise rig would generate, using a perfect VCO. I'm not showing plots cause my $1 clocks aren't very interesting... ok, the measured phase noise corresponds to what the datasheet says, but I'd like to check the system with better clocks to see if it really works first.
You only need a fancy VCO (which is the major cause of headache) if you want to measure an arbitrary clock, and if your measurement setup is only able to measure DC.... by acquiring the beat tone, as long as it is within the soundcard bandwidth, no problem. So this system needs two clocks of identical frequency, but the more difference between them, the better, as long as it is in the soundcard bandwidth...
Now, I need to figure out a way to generate a I/Q beat tone instead of a plain tone, to get much more precision. And maybe use autocorrelation, that would need 3 clocks...
Attachments
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VCO's dont scare me, I've just designed one for a project I'm working on - its a true differential design, with PECL outputs.
The design I'm working on has a 24Bit DAC so that not only can I design a digital controlled VCXO / Memory buffer, but I can modulate the clock with any required signal.
Heres the clock "Jittering" a 1ps 1KHz component:-
https://dl.dropboxusercontent.com/u/86116171/MDAC2 1.2pS 1KHz 10uV VGen.jpg
The noise floor at 6.3fS is limited by the Wavecrest measurement system.
Here's the test PCB with VCXO, PECL clock distribution, including switching PSU (the Power Resistors are to simulate the complete design load on the PSU).
The quality of the PSU is critical for any clock application and why I've tested the design complete with the switching supply.
https://dl.dropboxusercontent.com/u/86116171/MDAC2 section2.JPG
https://dl.dropboxusercontent.com/u/86116171/MDAC2 section3.JPG
I've built a new lab but not had time to move in and setup so I'm currently working in the corner of our living room, its a total pain as I have little space to set-up any test systems, balancing everything on a tiny desk as needed (not helped that our little dogs want to sit on the lab bench and help - you can see the pink basket)... I just need more time, I'm so late on all my projects...
Here is the HP PLL test system I use to characterise VCXO designs :-
https://dl.dropboxusercontent.com/u/86116171/PLL System.JPG
The design I'm working on has a 24Bit DAC so that not only can I design a digital controlled VCXO / Memory buffer, but I can modulate the clock with any required signal.
Heres the clock "Jittering" a 1ps 1KHz component:-
https://dl.dropboxusercontent.com/u/86116171/MDAC2 1.2pS 1KHz 10uV VGen.jpg
The noise floor at 6.3fS is limited by the Wavecrest measurement system.
Here's the test PCB with VCXO, PECL clock distribution, including switching PSU (the Power Resistors are to simulate the complete design load on the PSU).
The quality of the PSU is critical for any clock application and why I've tested the design complete with the switching supply.
https://dl.dropboxusercontent.com/u/86116171/MDAC2 section2.JPG
https://dl.dropboxusercontent.com/u/86116171/MDAC2 section3.JPG
I've built a new lab but not had time to move in and setup so I'm currently working in the corner of our living room, its a total pain as I have little space to set-up any test systems, balancing everything on a tiny desk as needed (not helped that our little dogs want to sit on the lab bench and help - you can see the pink basket)... I just need more time, I'm so late on all my projects...
Here is the HP PLL test system I use to characterise VCXO designs :-
https://dl.dropboxusercontent.com/u/86116171/PLL System.JPG
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Target is +/-200ppm
https://dl.dropboxusercontent.com/u/86116171/MDAC2 VCXO VCon curve with values.jpg
I'm pretty close - I need to get the correct spec'ed Crystals and the first Rev oscillator design had a slight non-symmetry, I issued PCB files earlier this month with the updated design, and will try the latest version when the boards return from the vendor.
I need a higher performance phase noise system as my current Agilent & Wavecrest systems are useless towards LF (from say 1kHz and below).
https://dl.dropboxusercontent.com/u/86116171/MDAC2 VCXO VCon curve with values.jpg
I'm pretty close - I need to get the correct spec'ed Crystals and the first Rev oscillator design had a slight non-symmetry, I issued PCB files earlier this month with the updated design, and will try the latest version when the boards return from the vendor.
I need a higher performance phase noise system as my current Agilent & Wavecrest systems are useless towards LF (from say 1kHz and below).
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