PLL tricks

The information is:

F = 1

A = 1

P = 0

How is that an infinite amount of information? It doesn't look very interesting to me. Sime waves are boring anyhow.

I might try another computer. The one I scanned it on has excellent OCR text accuracy, but strips *all* the formatting and puts the text in odd places.

I've got a few more choices on the office computer.

Cheers, James Arthur

It was probably the DMARC header in the replyto. I forgot to delete it. My email host screws it up and the emails get bounced. Here's some information in case you find it happens often:

"

Some more:

"

The cure is to simply delete the replyto line in the header. This forces the email client to use the From: address which probably doesn't have the DMARC info.

Thanks for the files James.

Similar descriptions to the several er..." legacy" oscillator books I have at work. What I will say is that, by and large, pretty much ALL these techniques have been superseded in commercial mass market precision oscillators from oscillator vendors. These, ahmmm... legacy methods try and achieve several competing performance criteria, e.g, noise, frequency verses power supply voltage, temp stability etc by a using a few parts. As a result, they never compete with todays methods.

Modern oscillator asics typically use one transistor for the oscillator, and

Kevin Aylward

You mean F = 1.0000000.... etc.

Yeah, they are boring if you look at them as discreet like digital.

Sure thing Kevin.

Luxury!

Yep.

This ovenized VCXO specs -188dBc/Hz @ 100KHz, and -108dBc/Hz @ 10Hz offset:

Using digital tempco correction would save a lot of power.

That makes sense. I was quite interested in doing the same nearly 20 years ago, adding a uC to a VCXO for all those benefits. That's why I collected a lot of oscillator / crystal literature.

I realized I'd be in the oscillator-making business then though, which wasn't what I really wanted to do the rest of my life.

Small world, isn't it?

Cheers, James Arthur

The test for the feedback system I gave before should be an easy bar to pass. I think that because approaching the Shannon limit typically requires significant cleverness on the part of the designer, and the limits placed on the feedback loop by your requirement for speed and precision probably limit the feedback system to fairly simple modulation methods. These simple methods will likely fall well short of the maximum theoretical limit on information transfer given by the channel capacity formula.

A test that calculates the information content of a specific feedback signal should come a lot closer to a necessary and sufficient condition.

Calculating and measuring information is just another tool. Eschewing it is a bit like never learning about Fourier transforms or relying on intuition instead of Boolean algebra when designing combinatorial logic. One can get along without these things, they just need to be significantly smarter than if they had used the available tools. I think that once a certain level of education and experience is reached that the major limits are in intuition and imagination. I know I can certainly use all of the helpful tools I can get.

Anyone who thinks information theory is only of academic interest and is of no use to 'real' designers should read about the work of Claude Berrou and the founding of Qualcomm.

This has been fun, but I have to get back to work now. Deadlines loom.

ChesterW

What channel do you refer to?

Funny, but I never use Boolean logic or Karnaugh maps or any of those classic things. I just look at things and draw logic. Given that FPGAs are LUT based, and compilers do logic reduction for you (whether you want them to or not), that old stuff hardly matters any more.

I can't see how information theory is especially helpful in my PLL problem. It's a control loop issue.

With Dagmar's approval, I've put those two files on my Dropbox. get them here:

Thanks Dagmar!

Clifford Heath.

Thanks Clifford, very considerate of you. I'm sure many people will appreciate it.

Cheers, James Arthur

I seem to remember that your attitude to office computers was nearly as Spartan as your attitude to central heating. Something modern and fast might do better.

it is if you know it's not F.0.9999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999

I?ll try again. Anything to support our nuclear deterrence. Seriously. By putting our leaders inextricably on the front lines and squarely in the cross-hairs of any major conflict, those weapons have saved countless regular folks from being sacrificed in furtherance of political ambitions. The human world still rings like a bell from the first effective harnessing of science and industrialization in support of political leaders stupid plans a century ago. One can still see the effects in the psychological stunting of anyone spending their formative years behind the iron curtain. Without those ultimate weapons to keep them in check, the mischief caused by the world?s leaders would likely know few bounds. And who knows, maybe the data from all of those lasers will be the key that enables some smart kid to finally crack fusion power and we can turn those ugly brown spots on our planet to lovely green.

Communication depends largely on pre-existing shared ideas. I?ll try to find some common ground. Here?s how I?ve observed myself solving tough problems, the process of which I think is fairly universal:

Step 1. Get a problem. Step 2. Use simple analysis and try to show a solution is impossible to avoid wasting time. Step 3. Mull it over. Roll the problem around. Really think about it, even for years sometimes. Step 4. Have an idea for a solution that I believe will work. The belief is not completely rational. It?s based on informed intuition. I don?t know for a fact the idea will work, but I believe it will work. Step 5. Prove or disprove the idea using analysis and/or simulation and/or building parts of the system and making measurements.

There is of course a step 0 where one spends considerable time becoming an expert in some area.

Step 6 is where one writes down all of the analysis for presentation with little or no reference to the idea?s origin in intuition. I think this leads to the myth that new ideas come mostly from analysis.

In my view, the main good use of the ?old tools? is in step 0. I think analysis is the easiest way to develop understanding which is what leads to informed intuition. It?s the difference between an engineer and a technician. In my experience, the smartest technician, who may be smart indeed, can usually only come up with solutions better than those of the worst engineer. I?m not disrespecting technicians, I started out as one, I?m recognizing the power of learning from those who came before.

So, in recognition of the intrinsic limits of my tiny mark-one human brain, I made the simplest model of your system I could imagine. The

Left to its self, the osc drifts away from the desired time synchronization, which I visualize as a loss of precision, or that the information bucket has a leak.

The feedback loop has a measurement element which senses the loss of synchronization, which information is routed back to control the osc, which fills up the bucket. This is the channel to which I referred, and about which you asked, in previous posts.

The idea is that if the feedback loop does not supply the necessary information - at least the amount that is lost through the leak, then the bucket can not stay full, and the system will not stay in sync.

You?ve had a lot of domain experts submit solutions. This is a suggested tool for use in step 5 for helping evaluate which may work best.

Using information theory to understand control loops is not new. If you Google ?information theory control systems? you?ll find lots of useful references.

Good luck with your project. Let us hear how it all turns out.

ChesterW

I have a few of those--they're neat. I'm not sure what the resonator Q's range is. I assumed for starters that making 10GHz to make 155.52 MHz was getting there the hard way!

Yep, those are DROs (dielectric resonator oscillators), I think. The structures at 10 and 8 o'clock look like tapped tuned feedback across the c/e (or more likely s/d) of the transistor.

The key is finding a stable piezo or dielectric material with low frictional or dielectric losses. Quartz wins for mechanical vibration.

I couldn't read the .PCX (pictures(?), but the station display was awfully cool.

Cheers, James Arthur (catching up with sed posts...)

Q's up to 15K @ 10GHz, 7K @ 1 GHz.

There's always YIG...

Mechanical cavities are another possibility.

I got Q > 300 from a piece of copper refrigeration tubing resonator inside a tin can (Clabber Girl baking powder--can is nicely tinned, solders beautifully) for a cavity @ 908MHz, once upon a time in a pinch. (We had to block out traffic @ ~880 MHz, IIRC)

It wasn't even hard--worked first try.

But somehow I don't think John wants to dig this hard for eight units. He could just buy one of the finer VCXOs, diode-sample at 80KHz, LPF, and he's done.

Cheers, James

On a sunny day (Mon, 22 Sep 2014 05:38:05 -0700 (PDT)) it happened snipped-for-privacy@yahoo.com wrote in :

Yes, but mixing a few hundred MHz VCO with a 10 GHz that is extremely stable could perhaps have advantages in some apps. The output would also be very stable (but needs a filter).

Not sure which one you mean but you could be on Pacific Time and I am on Central European Time :-) Anyways, the 2 transistors on the left are connected to a horizontal -, and vertical 1/4 wave dipole wire in the horn, one or the other is powered depending on the required polarization. The one directly above the big hole is the first preamp stage, then a 10 - 12 GHz bandpass, then more to the right the second preamp stage. All the way top right is the mixer chip. The resonaters have each a transistor to cause negative impedance so they oscillate, coupled by the big horseshoe like tracks, one or the other is activated depending on the selected band. The chip bottom left does the gate control voltage of these FETS, and decoding of the 22 kHz control tone on the power line, that selects the band, polarization is switched by supply voltage change from 12 to 18 V, that chip decodes that too. This is a Universal LNB ("Astra" LNB), see

All teh way top right (under the green solder mask) is teh IF filer (about 1.somethin gGHz, longer tracks obviously. The coupling of the secodn RF stage to the mixer chip is a bit mysterious, looks like and other transformer.

The real interesting part is the filter i u n u i Almost like tuning forks.

The other zig-zag tracks to the transistors are RF chokes basically. Mind you, this picture is BIG, the real thing is just a few cm, you need very strong magnification and a steady hand soldering on that.

Yes, pictures, I use the xv viewer in Linux, dunno about windows, but pcx is a normal image format.

I once worked in a place where there was a guy who would just design these things from a piece of paper, and they workled too, we made a 10 GHz link, I did the demodulator. No simulations in that time, used a gun diode... That showed me a lot about microwaves, it is not that hard.

We will see, ordered some real thin coax to make some modifications..

Sure, like spectrum analyzers do. I was trying to stay close to John's problem though--I'm pretty sure he'd prefer "simpler."

I found some 1GHz NHK DR pucks with Q's of 40K, but their df/dt was several ppm.

The lower-frequency center puck, right under the center mounting hole. Flip description 180 degrees for the high-band puck on the right hand side.

I would've thought the "Ea" parts are the mixers, diode quads. The filters are nicely realized on the PCB, and I'd have guessed the right-top chip you mentioned is an output amplifier.

Yep.

That looks to me like bandswitching by gating two DROs L.O.s to a single mixer. The DROs are gated on and off, only one running at a time.

That's a "hair pin" filter. (It's always neat when the board *is* the circuit.)

Thanks for the nice photo--that was fun.

Cheers, James Arthur

The other interesting part is the ceramic coaxial resonator.

These are essentially shorted coaxial lines made with a very hi-K ceramic dielectric. Qs get into the thousands and TCs are very low. They start at about 500 MHz and get really good in the low GHz.

But at my frequency, a quartz crystal would have higher Q and lower TC and phase noise. Not to mention that I can buy a small VCXO from stock.

Am 22.09.2014 um 17:20 schrieb John Larkin:

BTW, ordinary solder eats the thin silver coating away in no time.

Good crystals at 100 MHz have a Q of 100 - 110K. The product of Q and operating frequency is abt. constant for a given crystal technology / quality.

Gerhard