PLL tricks

On Tuesday, September 30, 2014 9:02:15 PM UTC-4, Bill Sloman wrote:

On 30/09/2014 11:31 PM, dagmargoo...@yahoo.com wrote:

John wants to produce *exact* zero-crossings. A frequency
multiplier has been suggested in the signal chain.

Simulate this better-than-life quasi-ideal frequency multiplier:

(10mA pulsed current source into 1nF + 22uH LC tank.
Pulse width=500nS, period=5.2uS.)

<snip LTSpice>>

Look at the voltage waveform--are the zero-crossings uniform?
If the LC drifted or were mistuned, would the zero-crossings
stay fixed in time, or would they move?

That's the point.

The tank circuit is resonant at 1.073MHz. The period of the excitation
is 5.2usec, or 192.3KHz, a multiple of 5.578. Moving the multiple to 5
or 6 produces a better looking waveform - with a much higher amplitude,
but still with an amplitude spike at the excitation points.

Two pole tuning clearly isn't good enough, and broad band excitation is
clearly putting a whole lot of energy into the tank circuit at at all
the other harmonics of the excitation frequency.

That James Arthur doesn't understand how to get a high quality waveform
out of a frequency multiplication system isn't all that interesting.
People with rather more expertise in the area do seem to be able to
manage it.

Bill, I'm not sure why you're still beating this horse.

The question was regarding the effect of of mistuning the tank. You
thought it didn't matter. So, I posted two simulations showing tank
tuning does matter.

The issue is objectively, unambiguously resolved.

I deliberately mistuned the simulation specifically to illustrate how
tuning and drift affect the zero-crossing placements. Posting a circuit
with ideal tuning would not have illustrated the deleterious effects
of non-ideal tuning.

Cheers,
James Arthur

 

On Tuesday, September 30, 2014 10:49:19 PM UTC-4, Bill Sloman wrote:

On Wednesday, 1 October 2014 11:22:19 UTC+10, dagmarg...@yahoo.com wrote:
On Tuesday, September 30, 2014 4:24:29 PM UTC-4, rickman wrote:
On 9/30/2014 9:31 AM, dagmargoo...@yahoo.com wrote:

Look at the voltage waveform--are the zero-crossings uniform?
If the LC drifted or were mistuned, would the zero-crossings
stay fixed in time, or would they move?

That's the point.

That may be your point, but it helps if you actually can explain what is
happening. You don't seem to be able to do that. This is my point.

No, your point was that the tank didn't add any harmonics that weren't
in the drive waveform, which was both irrelevant to the zero-crossings'
placement, and not strictly true (due to interaction with the driver's
collector).

The extra harmonic content from the collector imperfections isn't going to be big, and it's highly unlikely to be significant.

An irrelevancy to the overall question, but an excuse to look at something
fun...

It depends on the circuit design, (Vpp * dCc/dv)/C(tank). Modulating the
effective tank capacitance modulates the waveshape, which is otherwise
known as harmonic distortion.

If we're multiplying a 20MHz oscillator to 155MHz, a 50 ohm tank cap will
be 20.5pF. If the transistor is a BFR92, the collector will vary 0.14pF
for a 4v p-p swing.
(Fig. 5)
http://www.nxp.com/documents/data_sheet/BFR92A_N.pdf

That distorts the waveform, and modulates the tank frequency between
two values 0.34% apart, e.g. 155.52Mhz and 156.05MHz.

In practice the technician will compensate by tuning the center
frequency where it's wanted, and the output's peaks will be somewhat
taller and narrower, whilst its troughs will be shallower and
wider. IOW, distorted, and asymmetrical.

External idlers can recirculate and reinforce the effect deliberately,
or unintentionally.

> The fact is that it's the externally generated harmonics that mess up the zero-crossings, and you took a long time to articulate this insight in way that was comprehensible to onlookers who didn't have your - no doubt - deep but poorly articulated insight into how frequency multipliers work in practice.

There was no intention to explain frequency multipliers--this isn't seb.
Kevin suggested one. I was trying to ask Kevin how he'd avoid edge-
placement woes if the frequency multiplier's tuned circuits drifted
or were imperfectly tuned.

I took pains to describe and illustrate the difficulty in the time-domain,
where it's easier to appreciate (and which is John's application domain
as well).

You responded in the negative then retreated to the frequency domain
and its confusions for the unwary.

I explained the issue at the outset: the tank rings at its natural
resonant frequency, irrespective of the excitation, which causes the
intermediate zero crossings to be misplaced.

That's one way of articulating the problem. Since there's very little -
essentially none - of the tank's natural resonant frequency in the
frequency content of the of the signal coming out of the tank circuit,
it probably isn't a helpful formulation.

The time-domain formulation is edifying, yet after all this exchange you
continue to reject it as not addressing your misunderstandings in the
frequency domain. That's your doing, not mine.

Cheers,
James Arthur

 

[Bill Sloman]

On Wednesday, 1 October 2014 21:59:09 UTC+10, dagmarg...@yahoo.com wrote:

On Tuesday, September 30, 2014 9:02:15 PM UTC-4, Bill Sloman wrote:
On 30/09/2014 11:31 PM, dagmargoo...@yahoo.com wrote:

John wants to produce *exact* zero-crossings. A frequency
multiplier has been suggested in the signal chain.

Simulate this better-than-life quasi-ideal frequency multiplier:

(10mA pulsed current source into 1nF + 22uH LC tank.
Pulse width=500nS, period=5.2uS.)

snip LTSpice

Look at the voltage waveform--are the zero-crossings uniform?
If the LC drifted or were mistuned, would the zero-crossings
stay fixed in time, or would they move?

That's the point.

The tank circuit is resonant at 1.073MHz. The period of the excitation
is 5.2usec, or 192.3KHz, a multiple of 5.578. Moving the multiple to 5
or 6 produces a better looking waveform - with a much higher amplitude,
but still with an amplitude spike at the excitation points.

Two pole tuning clearly isn't good enough, and broad band excitation is
clearly putting a whole lot of energy into the tank circuit at at all
the other harmonics of the excitation frequency.

That James Arthur doesn't understand how to get a high quality waveform
out of a frequency multiplication system isn't all that interesting.
People with rather more expertise in the area do seem to be able to
manage it.

Bill, I'm not sure why you're still beating this horse.

The question was regarding the effect of of mistuning the tank. You
thought it didn't matter. So, I posted two simulations showing tank
tuning does matter.

Moving the goal-posts again? The problem seems to have been that you wanted to say that mistuning the tank wasn't a good idea (on which point I've always agreed with you).

Sadly, what you posted was "You bang the tank and it rings--so far so good. But if the tank isn't *perfectly* tuned, it rings off frequency, and the 'ring' cycle wander off phase, right?"

In fact the tank circuit doesn't "ring at it's resonant frequency", it responds to the mix of harmonics being driven into it. There's no resonant component in the output if there wasn't any in the input.

That mix wouldn't be useful to John if there was much higher or lower harmonic content - if you want the third harmonic, having second and fourth harmonic content in the output even 40dB down give visibly erratic zero-crossing spacing - and nobody was suggesting that it would be.

Kevin Alyward did suggest that the best way of getting a clean and stable 155.52MHz waveform was via frequency-multiplication from a 38.88MHz crystal, but he wasn't suggesting John try to cobble one together for himself. Serious frequency multiplication circuits do seem to use frequency multiplication scheme that produce a reasonably pure output at the desired harmonic, and tank circuits with rather higher than two-pole selectivity.

> The issue is objectively, unambiguously resolved.

It ought to be. It's taken a whole scad of posts to get it clarified, and you still seem to be claiming that what you posted on Monday, 29 September 2014
10:57:24 UTC+10 didn't need correction or clarification.

I deliberately mistuned the simulation specifically to illustrate how
tuning and drift affect the zero-crossing placements. Posting a circuit
with ideal tuning would not have illustrated the deleterious effects
of non-ideal tuning.

I posted one with closer to ideal tuning that still gave crummy zero-crossings - though it's easier to see the fluctuations in output amplitude, which tell you the same thing.

The first LTSpice .asc file that you posted didn't illustrate anything useful. With a bit of prodding, you've done better since. Using a pulsed current source is lot neater than my transistor.

--
Bill Sloman, Sydney

 

[Bill Sloman]

On Wednesday, 1 October 2014 23:40:00 UTC+10, dagmarg...@yahoo.com wrote:

On Tuesday, September 30, 2014 10:49:19 PM UTC-4, Bill Sloman wrote:
On Wednesday, 1 October 2014 11:22:19 UTC+10, dagmarg...@yahoo.com wrote:
On Tuesday, September 30, 2014 4:24:29 PM UTC-4, rickman wrote:
On 9/30/2014 9:31 AM, dagmargoo...@yahoo.com wrote:

Look at the voltage waveform--are the zero-crossings uniform?
If the LC drifted or were mistuned, would the zero-crossings
stay fixed in time, or would they move?

That's the point.

That may be your point, but it helps if you actually can explain what is happening. You don't seem to be able to do that. This is my point.

No, your point was that the tank didn't add any harmonics that weren't
in the drive waveform, which was both irrelevant to the zero-crossings'
placement, and not strictly true (due to interaction with the driver's
collector).

The extra harmonic content from the collector imperfections isn't going to be big, and it's highly unlikely to be significant.

An irrelevancy to the overall question, but an excuse to look at something
fun...

It depends on the circuit design, (Vpp * dCc/dv)/C(tank). Modulating the
effective tank capacitance modulates the waveshape, which is otherwise
known as harmonic distortion.

If we're multiplying a 20MHz oscillator to 155MHz, a 50 ohm tank cap will
be 20.5pF. If the transistor is a BFR92, the collector will vary 0.14pF
for a 4v p-p swing.
(Fig. 5)
http://www.nxp.com/documents/data_sheet/BFR92A_N.pd

That distorts the waveform, and modulates the tank frequency between
two values 0.34% apart, e.g. 155.52Mhz and 156.05MHz.

In practice the technician will compensate by tuning the center
frequency where it's wanted, and the output's peaks will be somewhat
taller and narrower, whilst its troughs will be shallower and
wider. IOW, distorted, and asymmetrical.

But not in a fashion that will mess up the zero-crossings. If there's ferrite in the inductor, it's inductance will vary through the cycle with the changing current through the coil (aka magnetic field) which introduces it's own distortions. LTSpice lets you model that too.

External idlers can recirculate and reinforce the effect deliberately,
or unintentionally.

The fact is that it's the externally generated harmonics that mess up the zero-crossings, and you took a long time to articulate this insight in way that was comprehensible to onlookers who didn't have your - no doubt - deep but poorly articulated insight into how frequency multipliers work in practice.

There was no intention to explain frequency multipliers--this isn't seb.

Kevin suggested one. I was trying to ask Kevin how he'd avoid edge-
placement woes if the frequency multiplier's tuned circuits drifted
or were imperfectly tuned.

I took pains to describe and illustrate the difficulty in the time-domain,
where it's easier to appreciate (and which is John's application domain
as well).

What you actually posted doesn't read as if you were taking pains to illustrate that particular difficulty

"You bang the tank and it rings--so far so good. But if the tank
isn't *perfectly* tuned, it rings off frequency, and the 'ring' cycles
wander off phase, right?"

It's pitched at the s.e.b. level, and it happens to be misleading.

You responded in the negative then retreated to the frequency domain
and its confusions for the unwary.

You were the one that posted a duff LTSpice sim.

I explained the issue at the outset: the tank rings at its natural
resonant frequency, irrespective of the excitation, which causes the
intermediate zero crossings to be misplaced.

It doesn't. The output of a resonant tank being repeatedly pinged with a waveform that hasn't any content at it's resonant frequency doesn't contain any frequency content at the resonant frequency. The zero-crossings are misplaced when the tank circuit is responding to several harmonics at once, which add and subtract as they slide past one another.

That's one way of articulating the problem. Since there's very little -
essentially none - of the tank's natural resonant frequency in the
frequency content of the of the signal coming out of the tank circuit,
it probably isn't a helpful formulation.

The time-domain formulation is edifying, yet after all this exchange you
continue to reject it as not addressing your misunderstandings in the
frequency domain. That's your doing, not mine.

The misunderstanding in the frequency domain is all yours.

Pinging a tank circuit can only excite its resonant frequency if the pings are far enough apart that the Fourier transform of the "pinging waveform" includes the resonant frequency. For sufficiently widely separated "pings" that's pretty much guaranteed. It's not a useful way of thinking about the tank circuit in a frequency multiplier.

--
Bill Sloman, Sydney

 

On Wednesday, October 1, 2014 1:51:53 AM UTC-4, rickman wrote:

On 9/30/2014 9:22 PM, dagmargoo...@yahoo.com wrote:

I explained the issue at the outset: the tank rings at its natural
resonant frequency, irrespective of the excitation, which causes the
intermediate zero crossings to be misplaced.

That is *exactly* the part that is not correct. When a tank is pinged
with an impulse there is energy at all frequencies. The tank will
resonate for some time. But the tank in this design is being stimulated
with specific frequencies which according to you and others, is *not* at
the resonance peak. So the tank can not "resonate" at that frequency.
It will resonate at the frequency it was stimulated with and those
frequencies will be attenuated much more than one at the peak of
resonance.

You have utterly missed that, in John's case, the tank can *never* be
dependably tuned to the ppm needed, plus it will drift.

The tank circuit is a linear circuit. You seem to be saying that the
transistor turns the stimulating frequencies into *all* frequencies. I
don't think it works that way. The inter-modulation products don't
cover the entire electromagnetic spectrum, just the few frequencies that
can be obtained by the various sums and differences of the initial
frequencies and with reducing amplitude as you compound these sums and
differences. Eventually a wide range of individual frequencies are
obtained, but at enormously reduced amplitudes.

In the stimulating waveform, the phases of all the various frequency
components are such that the zero crossings are equally spaced. In
passing through the filter the different frequencies have different
delays so that the phases no longer align resulting in changes to the
timing of the zero crossings.

I chose the time-domain as simpler to understand.

If your assumptions in the frequency domain prevent you from understanding
my description in the time-domain, that's not my fault.


Cheers,
James Arthur

 

On Wednesday, October 1, 2014 10:06:30 AM UTC-4, Bill Sloman wrote:

On Wednesday, 1 October 2014 23:40:00 UTC+10, dagmarg...@yahoo.com wrote:
On Tuesday, September 30, 2014 10:49:19 PM UTC-4, Bill Sloman wrote:
On Wednesday, 1 October 2014 11:22:19 UTC+10, dagmarg...@yahoo.com wrote:

No, your point was that the tank didn't add any harmonics that weren't
in the drive waveform, which was both irrelevant to the zero-crossings'
placement, and not strictly true (due to interaction with the driver's
collector).

The extra harmonic content from the collector imperfections isn't going to be big, and it's highly unlikely to be significant.

An irrelevancy to the overall question, but an excuse to look at something
fun...

It depends on the circuit design, (Vpp * dCc/dv)/C(tank). Modulating the
effective tank capacitance modulates the waveshape, which is otherwise
known as harmonic distortion.

If we're multiplying a 20MHz oscillator to 155MHz, a 50 ohm tank cap will
be 20.5pF. If the transistor is a BFR92, the collector will vary 0.14pF
for a 4v p-p swing.
(Fig. 5)

http://www.nxp.com/documents/data_sheet/BFR92A_N.pd

That distorts the waveform, and modulates the tank frequency between
two values 0.34% apart, e.g. 155.52Mhz and 156.05MHz.

In practice the technician will compensate by tuning the center
frequency where it's wanted, and the output's peaks will be somewhat
taller and narrower, whilst its troughs will be shallower and
wider. IOW, distorted, and asymmetrical.

But not in a fashion that will mess up the zero-crossings.

Please tell me you're kidding.

No, on second thought, never mind.

Cheers,
James Arthur

 

[Bill Sloman]

On Thursday, 2 October 2014 00:20:41 UTC+10, dagmarg...@yahoo.com wrote:

On Wednesday, October 1, 2014 1:51:53 AM UTC-4, rickman wrote:
On 9/30/2014 9:22 PM, dagmargoo...@yahoo.com wrote:

I explained the issue at the outset: the tank rings at its natural
resonant frequency, irrespective of the excitation, which causes the
intermediate zero crossings to be misplaced.

That is *exactly* the part that is not correct. When a tank is pinged
with an impulse there is energy at all frequencies. The tank will
resonate for some time. But the tank in this design is being stimulated
with specific frequencies which according to you and others, is *not* at
the resonance peak. So the tank can not "resonate" at that frequency.
It will resonate at the frequency it was stimulated with and those
frequencies will be attenuated much more than one at the peak of
resonance.

You have utterly missed that, in John's case, the tank can *never* be
dependably tuned to the ppm needed, plus it will drift.

Kevin Alyward seems to differ. In any event, since John isn't going to build his 155.52MHz VCXO, but rather buy if from people who can do it right, who cares?

The tank circuit is a linear circuit. You seem to be saying that the
transistor turns the stimulating frequencies into *all* frequencies. I
don't think it works that way. The inter-modulation products don't
cover the entire electromagnetic spectrum, just the few frequencies that
can be obtained by the various sums and differences of the initial
frequencies and with reducing amplitude as you compound these sums and
differences. Eventually a wide range of individual frequencies are
obtained, but at enormously reduced amplitudes.

In the stimulating waveform, the phases of all the various frequency
components are such that the zero crossings are equally spaced. In
passing through the filter the different frequencies have different
delays so that the phases no longer align resulting in changes to the
timing of the zero crossings.

I chose the time-domain as simpler to understand.

But backed it up with an LTSpice sim of circuit which didn't work the way it should have done, and consequently explained nothing - mess from which we had to rescue you.

If your assumptions in the frequency domain prevent you from understanding
my description in the time-domain, that's not my fault.

Your description "in the time domain" was - to put it kindly - less than clear. It's difficult to see anybody other than you being at fault there.

--
Bill Sloman, Sydney

 

[Bill Sloman]

On Thursday, 2 October 2014 00:39:40 UTC+10, dagmarg...@yahoo.com wrote:

On Wednesday, October 1, 2014 10:06:30 AM UTC-4, Bill Sloman wrote:
On Wednesday, 1 October 2014 23:40:00 UTC+10, dagmarg...@yahoo.com wrote:
On Tuesday, September 30, 2014 10:49:19 PM UTC-4, Bill Sloman wrote:
On Wednesday, 1 October 2014 11:22:19 UTC+10, dagmarg...@yahoo.com wrote:

No, your point was that the tank didn't add any harmonics that weren't in the drive waveform, which was both irrelevant to the zero-crossings' placement, and not strictly true (due to interaction with the driver's collector).

The extra harmonic content from the collector imperfections isn't going to be big, and it's highly unlikely to be significant.

An irrelevancy to the overall question, but an excuse to look at something fun...

It depends on the circuit design, (Vpp * dCc/dv)/C(tank). Modulating the
effective tank capacitance modulates the waveshape, which is otherwise
known as harmonic distortion.

If we're multiplying a 20MHz oscillator to 155MHz, a 50 ohm tank cap will
be 20.5pF. If the transistor is a BFR92, the collector will vary 0.14pF
for a 4v p-p swing.
(Fig. 5)

http://www.nxp.com/documents/data_sheet/BFR92A_N.pd

That distorts the waveform, and modulates the tank frequency between
two values 0.34% apart, e.g. 155.52Mhz and 156.05MHz.

In practice the technician will compensate by tuning the center
frequency where it's wanted, and the output's peaks will be somewhat
taller and narrower, whilst its troughs will be shallower and
wider. IOW, distorted, and asymmetrical.

But not in a fashion that will mess up the zero-crossings.

Please tell me you're kidding.

The waveform will repeat exactly from cycle to cycle. If you squared it up, you might be able to detect the deviation from the perfect 50% duty cycle, but you'd have a bunch of competing other error sources which might have created the same effect. It doesn't look like a source of cycle-to-cycle jitter to my inexpert eye. If you can come up with a mechanism where it can, do tell us about it.

> No, on second thought, never mind.

What? And deny you another chance to pose as someone a trifle more expert than you actually are? Clearly, you are working on the principle that there's no such thing as bad publicity, and it would be churlish to deny you a chance to advertise your expertise (erratic though that may be).

--
Bill Sloman, Sydney

 

[John Larkin]

On Wed, 1 Oct 2014 07:39:40 -0700 (PDT), dagmargoodboat@yahoo.com
wrote:

On Wednesday, October 1, 2014 10:06:30 AM UTC-4, Bill Sloman wrote:
On Wednesday, 1 October 2014 23:40:00 UTC+10, dagmarg...@yahoo.com wrote:
On Tuesday, September 30, 2014 10:49:19 PM UTC-4, Bill Sloman wrote:
On Wednesday, 1 October 2014 11:22:19 UTC+10, dagmarg...@yahoo.com wrote:

No, your point was that the tank didn't add any harmonics that weren't
in the drive waveform, which was both irrelevant to the zero-crossings'
placement, and not strictly true (due to interaction with the driver's
collector).

The extra harmonic content from the collector imperfections isn't going to be big, and it's highly unlikely to be significant.

An irrelevancy to the overall question, but an excuse to look at something
fun...

It depends on the circuit design, (Vpp * dCc/dv)/C(tank). Modulating the
effective tank capacitance modulates the waveshape, which is otherwise
known as harmonic distortion.

If we're multiplying a 20MHz oscillator to 155MHz, a 50 ohm tank cap will
be 20.5pF. If the transistor is a BFR92, the collector will vary 0.14pF
for a 4v p-p swing.
(Fig. 5)

http://www.nxp.com/documents/data_sheet/BFR92A_N.pd

That distorts the waveform, and modulates the tank frequency between
two values 0.34% apart, e.g. 155.52Mhz and 156.05MHz.

In practice the technician will compensate by tuning the center
frequency where it's wanted, and the output's peaks will be somewhat
taller and narrower, whilst its troughs will be shallower and
wider. IOW, distorted, and asymmetrical.

But not in a fashion that will mess up the zero-crossings.

Please tell me you're kidding.

No, on second thought, never mind.

Cheers,
James Arthur

In an LC tuned 5x multiplier, harmonic distortion of the 155 MHz, 5x
multiplied waveform won't affect zero crossings. It's the fundamental
and 3x and 7x etc components that do. A single finite-Q LC is a pretty
sloppy bandpass filter.


--

John Larkin Highland Technology, Inc

jlarkin att highlandtechnology dott com
http://www.highlandtechnology.com

 

[John Larkin]

On Wed, 1 Oct 2014 07:20:41 -0700 (PDT), dagmargoodboat@yahoo.com
wrote:

On Wednesday, October 1, 2014 1:51:53 AM UTC-4, rickman wrote:
On 9/30/2014 9:22 PM, dagmargoo...@yahoo.com wrote:

I explained the issue at the outset: the tank rings at its natural
resonant frequency, irrespective of the excitation, which causes the
intermediate zero crossings to be misplaced.

That is *exactly* the part that is not correct. When a tank is pinged
with an impulse there is energy at all frequencies. The tank will
resonate for some time. But the tank in this design is being stimulated
with specific frequencies which according to you and others, is *not* at
the resonance peak. So the tank can not "resonate" at that frequency.
It will resonate at the frequency it was stimulated with and those
frequencies will be attenuated much more than one at the peak of
resonance.

You have utterly missed that, in John's case, the tank can *never* be
dependably tuned to the ppm needed, plus it will drift.

The tank circuit is a linear circuit. You seem to be saying that the
transistor turns the stimulating frequencies into *all* frequencies. I
don't think it works that way. The inter-modulation products don't
cover the entire electromagnetic spectrum, just the few frequencies that
can be obtained by the various sums and differences of the initial
frequencies and with reducing amplitude as you compound these sums and
differences. Eventually a wide range of individual frequencies are
obtained, but at enormously reduced amplitudes.

In the stimulating waveform, the phases of all the various frequency
components are such that the zero crossings are equally spaced. In
passing through the filter the different frequencies have different
delays so that the phases no longer align resulting in changes to the
timing of the zero crossings.

I chose the time-domain as simpler to understand.

If your assumptions in the frequency domain prevent you from understanding
my description in the time-domain, that's not my fault.


Cheers,
James Arthur

An FFT of the output of the 5x multiplier is instructive. A lot more
comes out than a single spectral line at 5x. There is some output at
every multiple of the 1x drive.

The resulting waveform does NOT exactly repeat every cycle of the
desired 5x output, because other frequencies are present. It takes a
higher-order bandpass filter (like 6 LCs in the posted examples) to
get a picosecond-purity clock out of such a multiplier.




--

John Larkin Highland Technology, Inc

jlarkin att highlandtechnology dott com
http://www.highlandtechnology.com

 

[Kevin Aylward]

wrote in message
news:e90bed2e-2b51-4308-84b6-9c01a536db28@googlegroups.com...

On Tuesday, September 30, 2014 2:14:09 PM UTC-4, Kevin Aylward wrote:

wrote in message
dagmargoo...@aol.com wrote:
Bill Sloman wrote:
"Ringing the tank" doesn't produce anything that wasn't in the
drive waveform.

Absolutely FALSE.

I sense misunderstanding on terms here.

In the frequency domain, there can be no frequencies present in the
output
that are not present at the input, if the system is linear. Not
debatable.

Understood. It's not linear though--the transistor collector is a varactor,
for one, and a parametric multiplier.

Well, in principal yes, but not really relevant to the specific points being
made.

Interestingly, it is the failure to appreciate non-linear time constants
that is the root to the complete failure of the Hajimiri-Lee phase noise
method, i.e. errors of 50db! to wit, again...

http://www.kevinaylward.co.uk/ee/phasenoise/phasenoise.html

Specifically, non-linear analysis bit:

http://www.kevinaylward.co.uk/ee/phasenoise/LTV.xht

It wasn't entirely a waste--I did read in several places that 20-ish MHz
3rd overtone crystals have lower phase noise than 5th-overtone 100-ish MHz
crystals, even after multiplication. IOW, exactly as you said.

Its easier to design circuitry at lower frequencies. e.g. the ft limitation
of bipolar can result in excessive (nonlinear) input capacitance, upsetting
tuning.

Overtones have advantages, but one of them is also a disadvantage for VCXOs.
They are much harder to pull!


Kevin Aylward
www.kevinaylward.co.uk
www.anasoft.co.uk - SuperSpice

 

[Tom Miller]

"Kevin Aylward" <ExtractkevinRemove@kevinaylward.co.uk> wrote in message
news:McedneHEE9-SoLHJnZ2dnUVZ8rmdnZ2d@bt.com...

wrote in message
news:e90bed2e-2b51-4308-84b6-9c01a536db28@googlegroups.com...

On Tuesday, September 30, 2014 2:14:09 PM UTC-4, Kevin Aylward wrote:
wrote in message
dagmargoo...@aol.com wrote:
Bill Sloman wrote:
"Ringing the tank" doesn't produce anything that wasn't in the
drive waveform.

Absolutely FALSE.

I sense misunderstanding on terms here.

In the frequency domain, there can be no frequencies present in the
output
that are not present at the input, if the system is linear. Not
debatable.

Understood. It's not linear though--the transistor collector is a
varactor,
for one, and a parametric multiplier.

Well, in principal yes, but not really relevant to the specific points
being made.

Interestingly, it is the failure to appreciate non-linear time constants
that is the root to the complete failure of the Hajimiri-Lee phase noise
method, i.e. errors of 50db! to wit, again...

http://www.kevinaylward.co.uk/ee/phasenoise/phasenoise.html

Specifically, non-linear analysis bit:

http://www.kevinaylward.co.uk/ee/phasenoise/LTV.xht

It wasn't entirely a waste--I did read in several places that 20-ish MHz
3rd overtone crystals have lower phase noise than 5th-overtone 100-ish MHz
crystals, even after multiplication. IOW, exactly as you said.

Its easier to design circuitry at lower frequencies. e.g. the ft
limitation of bipolar can result in excessive (nonlinear) input
capacitance, upsetting tuning.

Overtones have advantages, but one of them is also a disadvantage for
VCXOs. They are much harder to pull!

But that should not be an issue here as you don't need to pull it very far.
Hopefully.

 

[Phil Hobbs]

On 10/01/2014 03:24 PM, Tom Miller wrote:

"Kevin Aylward" <ExtractkevinRemove@kevinaylward.co.uk> wrote in message
news:McedneHEE9-SoLHJnZ2dnUVZ8rmdnZ2d@bt.com...
wrote in message
news:e90bed2e-2b51-4308-84b6-9c01a536db28@googlegroups.com...

On Tuesday, September 30, 2014 2:14:09 PM UTC-4, Kevin Aylward wrote:
wrote in message
dagmargoo...@aol.com wrote:
Bill Sloman wrote:
"Ringing the tank" doesn't produce anything that wasn't in the
drive waveform.

Absolutely FALSE.

I sense misunderstanding on terms here.

In the frequency domain, there can be no frequencies present in the
output
that are not present at the input, if the system is linear. Not
debatable.

Understood. It's not linear though--the transistor collector is a
varactor,
for one, and a parametric multiplier.

Well, in principal yes, but not really relevant to the specific points
being made.

Interestingly, it is the failure to appreciate non-linear time
constants that is the root to the complete failure of the Hajimiri-Lee
phase noise method, i.e. errors of 50db! to wit, again...

http://www.kevinaylward.co.uk/ee/phasenoise/phasenoise.html

Specifically, non-linear analysis bit:

http://www.kevinaylward.co.uk/ee/phasenoise/LTV.xht

It wasn't entirely a waste--I did read in several places that 20-ish MHz
3rd overtone crystals have lower phase noise than 5th-overtone
100-ish MHz
crystals, even after multiplication. IOW, exactly as you said.

Its easier to design circuitry at lower frequencies. e.g. the ft
limitation of bipolar can result in excessive (nonlinear) input
capacitance, upsetting tuning.

Overtones have advantages, but one of them is also a disadvantage for
VCXOs. They are much harder to pull!



But that should not be an issue here as you don't need to pull it very
far. Hopefully.

The other issue is that the capacitance between the electrodes can
prevent the crystal impedance ever going inductive, so you can't make an
oscillator without an auxiliary parallel inductor. That makes the whole
thing lossier and therefore noisier.

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC
Optics, Electro-optics, Photonics, Analog Electronics

160 North State Road #203
Briarcliff Manor NY 10510

hobbs at electrooptical dot net
http://electrooptical.net

 

[Bill Sloman]

On Thursday, 2 October 2014 08:19:02 UTC+10, Maynard A. Philbrook Jr. wrote:

In article <28ff5d13-58c9-4cc4-b16b-d082ce6f1ea3@googlegroups.com>,
bill.sloman@gmail.com says...

<Jamie's usual unmarked snip>

T.S.Elliot does seem to write stuff that resonates with engineering.

All of this was quite clearly expressed at the outset.

If it had been, we might have got here rather quicker.

See, it's all your fault that Ricky doesn't understand

Rickman and I both understood what James Arthur was saying, and that he was saying something wrong. Now that James Arthur has explained what he really meant, or at least what he would now like us to think that he really meant, the world is full of sweetness and light.

Although I imagine you are still intending to use that inappropriate bang-bang phase detector.

I've been monitoring this thread and you have back stepped,
twisted many, and I say many of your own detailed break downs
of how this should play off.

Jamie does have delusions of competence.

Hell, I've even seen where you reject ideas exactly as you quoted them
from your own posts, earlier in the thread, wtf is that all about?

Do post an example. I'll have fun exposing your failure of comprehension.

Now I see you are correcting yourself and trying to run interference to
cover your tracks. Maybe someone else here actually
knows much more of what they're talking about on the subject and you're
just spinning the tables around so that you can somehow, label it as
your idea.. Yeah, you all come to me now, cause I am the only one that
knows anything on this planet, even if it is wrong.

Gerhard Hoffmann and Kevin Aylward clearly know more than I do on this subject, and I've said so once or twice. Again, if you can post an example of what you see as me correcting myself I'll be happy to explain what's really going on - you probably won't be able to understand the explanation, even if I do my best to keep it simple.

With all the attempted steering you're running here, I don't see much
of a chance of you coming out looking pretty in the end.

I'm certainly not going to look pretty to you. Since you don't seem to understand what's going on, it's all going to look like buzzwords to you.

Maybe you should slip under the radar and sit back and learn something
instead of putting your foot in your mouth and talking about how you
steal ideas from references (sources) that you forgotten about.

Searching the literature is all about stealing ideas. You are supposed to acknowledge where you got the ideas from, but everybody forgets stuff from time to time, and it's embarrassing when it happens.

Don't you have any thing of your own? or do you just leach off others
and hope no one notices and holds you to it?

I've got a couple of patents, so it does look as if I've had a few genuinely original ideas. Engineering is all about finding solutions that work, and you won't know if anything that you've invented will work until you've tried it.

If I intentionally recycle an idea from the literature, I do say where I got it, because that does make the approach look as if it might work.

You remind of a person that works with me, he talks just like you. He
has never been able to actually demonstrate any abilities to test
any of the garbage that comes out of his month. Tries like hell to
steal others work. Basically, the only thing that has kept him there
is that he's an excellent bull shit artist, so good that he even has his
bosses fooled beyond belief.

I've seen that happen. It's fairly rare. It takes brains to be a good bullshit artist, and some of them actually do something useful from time to time..

But there is one difference though, he is still employed, so maybe
he's smarter than you.

How old is he?

--
Bill Sloman, Sydney

 

[Bill Sloman]

On Thursday, 2 October 2014 08:26:03 UTC+10, Maynard A. Philbrook Jr. wrote:

In article <m0fkif$cfs$1@dont-email.me>, bill.sloman@ieee.org says...

Everyone here knows how much of a wart you are i
they disagree with you.

Some people don't get stuff wrong as often as you do, or persist in
their errors with quite such enthusiasm. I'm happy to see my errors
corrected - it doesn't happen often enough to damage my self-esteem.
Other people seem to feel that they have more to lose.

"Proof is in the pudding"

Intellectually speaking, you'd be more of a fruit-cake.

No, I hit the target dead on.

Or so you think.

> You are a leach and back stepper.

Make up your mind. A leech can't keep on sucking blood if it steps back.

You just want the world to kiss your feet and say how
almighty brilliant you are. Well, I hate to the break the
news to you, you don't have the credentials for it.

I can't say that I feel any need to have my feet kissed, and if somebody like you were to say that I was brilliant I'd have wonder what you were after, because you lack the intellectual resources to make that kind of judgment reliably.

I'm happy with what I've got, which is a few people whose judgement I respect who take me seriously - but not all that seriously.

--
Bill Sloman, Sydney

 

[rickman]

On 10/1/2014 11:43 AM, John Larkin wrote:

On Wed, 1 Oct 2014 07:39:40 -0700 (PDT), dagmargoodboat@yahoo.com
wrote:

On Wednesday, October 1, 2014 10:06:30 AM UTC-4, Bill Sloman wrote:
On Wednesday, 1 October 2014 23:40:00 UTC+10, dagmarg...@yahoo.com wrote:
On Tuesday, September 30, 2014 10:49:19 PM UTC-4, Bill Sloman wrote:
On Wednesday, 1 October 2014 11:22:19 UTC+10, dagmarg...@yahoo.com wrote:

No, your point was that the tank didn't add any harmonics that weren't
in the drive waveform, which was both irrelevant to the zero-crossings'
placement, and not strictly true (due to interaction with the driver's
collector).

The extra harmonic content from the collector imperfections isn't going to be big, and it's highly unlikely to be significant.

An irrelevancy to the overall question, but an excuse to look at something
fun...

It depends on the circuit design, (Vpp * dCc/dv)/C(tank). Modulating the
effective tank capacitance modulates the waveshape, which is otherwise
known as harmonic distortion.

If we're multiplying a 20MHz oscillator to 155MHz, a 50 ohm tank cap will
be 20.5pF. If the transistor is a BFR92, the collector will vary 0.14pF
for a 4v p-p swing.
(Fig. 5)

http://www.nxp.com/documents/data_sheet/BFR92A_N.pd

That distorts the waveform, and modulates the tank frequency between
two values 0.34% apart, e.g. 155.52Mhz and 156.05MHz.

In practice the technician will compensate by tuning the center
frequency where it's wanted, and the output's peaks will be somewhat
taller and narrower, whilst its troughs will be shallower and
wider. IOW, distorted, and asymmetrical.

But not in a fashion that will mess up the zero-crossings.

Please tell me you're kidding.

No, on second thought, never mind.

Cheers,
James Arthur

In an LC tuned 5x multiplier, harmonic distortion of the 155 MHz, 5x
multiplied waveform won't affect zero crossings. It's the fundamental
and 3x and 7x etc components that do. A single finite-Q LC is a pretty
sloppy bandpass filter.

Ahhh, so you have seen the light now... So have you given up on the
ping and ring explanation?

--

Rick

 

[Kevin Aylward]

"Gerhard Hoffmann" wrote in message
news:c93e1bFsnfdU1@mid.individual.net...

Am 01.10.2014 um 19:42 schrieb Kevin Aylward:

Interestingly, it is the failure to appreciate non-linear time constants
that is the root to the complete failure of the Hajimiri-Lee phase noise
method, i.e. errors of 50db! to wit, again...

http://www.kevinaylward.co.uk/ee/phasenoise/phasenoise.html

Specifically, non-linear analysis bit:

http://www.kevinaylward.co.uk/ee/phasenoise/LTV.xht

Interestingly, U. Rohde writes in [1] that the Hajimiri method gives
consistent results and that its only drawback is that it does not lead to
design formulas.

He is quite mistaken. I referenced in my link, a real expert that proves,
mathematically and conclusively that the Hajimiri Lee paper is, toilet
paper

http://www.kevinaylward.co.uk/ee/phasenoise/A-Demir.pdf

My additions on my site attempt to make it more understandable to us less
able engineers. For example, in the above LTV.xht paper I show quite
conclusively, and trivially, that it is simply impossible to generate up
conversion simply by remodelling a linear LC oscillator as a linear time
variant system.

If you have a disproof, I would be most interested to know.

Kevin Aylward
www.kevinaylward.co.uk
www.anasoft.co.uk - SuperSpice

 

[Kevin Aylward]

"Gerhard Hoffmann" wrote in message
news:c93avpFs05rU1@mid.individual.net...

I have once written an article on simulations of oscillators for DUBUS,
a microwave-oriented ham radio periodical and it covers that.

A version of this article (minus the final editing) is at

>http://www.hoffmann-hochfrequenz.de/downloads/Hoffmann_VHF_Quarzoszillatoren_Teil1.pdf

Ahmmm.... why.... ?

The fatal bit is: "That makes it possible to analyze this basically
nonlinear circuit with a linear only simulator."

In fact, analysing oscillators with a linear approach is, essentially,
useless.

Today, and for the last 15 years or so, millions have downloaded LTSpice,
that simulates oscillators in considerable exact detail, in non-linear
transient analysis.

The smarter ones, use SuperSpice.

Unfortunately, to reliable do phase noise, one has to spend serious money,
e.g. Cadence Spectre R.F.

Kevin Aylward
www.kevinaylward.co.uk
www.anasoft.co.uk - SuperSpice

 

[Kevin Aylward]

"Gerhard Hoffmann" wrote in message
news:c93e1bFsnfdU1@mid.individual.net...

Am 01.10.2014 um 19:42 schrieb Kevin Aylward:

Interestingly, it is the failure to appreciate non-linear time constants
that is the root to the complete failure of the Hajimiri-Lee phase noise
method, i.e. errors of 50db! to wit, again...

http://www.kevinaylward.co.uk/ee/phasenoise/phasenoise.html

Specifically, non-linear analysis bit:

http://www.kevinaylward.co.uk/ee/phasenoise/LTV.xht

Interestingly, U. Rohde writes in [1] that the Hajimiri method gives
consistent results and that its only drawback is that it does not
lead to design formulas. Given how hard it seems for him to
acknowledge progress that does not come from AEG, R&S, HP, Ansoft
or Synergy microwave there must be something to it.

http://en.wikipedia.org/wiki/Argument_from_authority

seems to be happy with it, and he is the pricipal
author of the Agilent Genesys system that includes a nonlinear
simulator targeted to exactly this.

Again, an appeal to authority. Please present some actual data that refutes
the mathematics and simulating results in the referenced papers by A.
Demir, or "Emad, Real, Abidi" or myself.

>These happen to be my 2 favourite authors on oscillator design,

I suggest you consider other authors :

http://www.amazon.com/Designers-Guide-High-Purity-Oscillators-Series/dp/1402076665
- "Emad, Real, Abidi"

Hint:

The actual abstract of the HL paper emphasis and states:

“…In particular, it explains the details of how 1/f noise in a device
up-converts into close-in-phase noise and identifies methods to suppress
this up-conversion…”

However, Hegazi, Real, Abidi – “The Designers Guide To High Purity
Oscillators” book state:

“…[HL] does not formally address flicker noise at all. The treatment of
flicker noise in the original paper is performed without clear analysis or
conclusive answers…”


>so, frankly, I don't give too much on your simulation gone wrong.

In fact, in http://www.kevinaylward.co.uk/ee/phasenoise/LTV.xht

There is a high school level trigonometry calculation, not simulation, on
the phase noise of a nonlinear circuit proving that a fundamental assumption
of the H-L theory is false. That is, the H-L theory requires that the noise
of individual generators can be combined linearly, yet it is trivial to
prove that this is, essentially, never true for a real circuit. i.e. one
with a nonlinear capacitor. Hint: cgs and cbe of nmos and npn respectively.

For reference, Spice is a non-linear, numerical equation solver. Solving
mathematical equations numerically is an accepted method to, essentially,
prove or disprove theories. Noting that theories, are mathematical models of
physical processes.

well, this is a long weekend here, and I'm headed for the Alps
of southern France with my motorbike, so I'll leave it with that.

In other words, you have no actual data support for your claims.

Kevin Aylward
www.kevinaylward.co.uk
www.anasoft.co.uk - SuperSpice

 

[dougfgd@gmail.com]

On Wednesday, September 10, 2014 12:54:53 AM UTC+1, John Larkin wrote:

If I hypothetically had a 10 MHz reference and wanted to lock a 155.52
MHz VCXO to it, the obvious way would be to divide both down to 80 KHz
(the GCD) and drive a phase detector back into the VCXO. But that's a
pretty low frequency to run the PD at; to get picosecond stability, an
ordinary analog phase detector would need better than 1 PPM analog
accuracy, which ain't gonna happen.

I can build an ECL edge-sensitive phase detector that might work, but
80K is still pretty low.

There must be tricks to run the phase detector at a higher frequency.

I could DDS the 155.52 down to 10 MHz, and phase detect at 10 MHz, but
that sounds jitterey to me, and it looks like I can't hit the exact
frequency ratio anyhow.



--

John Larkin Highland Technology, Inc

jlarkin att highlandtechnology dott com
http://www.highlandtechnology.com

This is the first time I have returned in 10 years after nasty infections put me off.
A pll controlled SAW vco referenced to a bulk crystal will give lowest noise floor outside the loop -170dbc possible as the saw can run at a high level. dougfgd at frequencyprecision.com