Quotient Sync Filter Better Than Lock In

[Bret Cahill]

A lock in amplifier multiplies an AC signal + noise by a synchronous
reference signal. If the signal is sinwt and the ref is sinwt, the
output is sin^2(wt) which is always positive. Regardless of the
particular shape it can always be smoothed to a DC output proportional
to the signal -- with enough time.

Instead of multiplying it would be better to _divide_ the noisy AC
signal by the ref.

One advantage over lock in is a simple capacitor in parallel with the
output shorts out the AC component which is the noise.

A much greater advantage is when the noise drops, you aren't forced to
waste a lot of time smoothing a squared signal to DC.

It's already there.

Quotient sync filtering is better than lock in in every respect.


Bret Cahill

 

[doug]

Bret Cahill wrote:

A lock in amplifier multiplies an AC signal + noise by a synchronous
reference signal. If the signal is sinwt and the ref is sinwt, the
output is sin^2(wt) which is always positive. Regardless of the
particular shape it can always be smoothed to a DC output proportional
to the signal -- with enough time.

You really need to go back to your trig tables. There are two components
in the multiplied signal, one a 0 frequency and one at 2w. It is the
2w signal that is being filtered away. The whole point of a lockin
amplifier is that the low pass filter after the multiplier sets the
noise bandwidth and you can make that filter arbitrarily narrow.
You cannot make a bandpass filter arbitrarily narrow.

Instead of multiplying it would be better to _divide_ the noisy AC
signal by the ref.

One advantage over lock in is a simple capacitor in parallel with the
output shorts out the AC component which is the noise.

Using the term "shorts out" shows that you have very little electronics
knowledge.

A much greater advantage is when the noise drops, you aren't forced to
waste a lot of time smoothing a squared signal to DC.

The settling time is set by the filter bandwidth which is set by your
requirements for noise bandwidth. The laws of physics tell you what
the requirements are and they are not up for discussion.

It's already there.

Quotient sync filtering is better than lock in in every respect.

Except, of course, it is not.

Bret Cahill

 

[John Larkin]

On Sat, 1 Aug 2009 06:31:04 -0700 (PDT), Bret Cahill
<BretCahill@peoplepc.com> wrote:

A lock in amplifier multiplies an AC signal + noise by a synchronous
reference signal. If the signal is sinwt and the ref is sinwt, the
output is sin^2(wt) which is always positive. Regardless of the
particular shape it can always be smoothed to a DC output proportional
to the signal -- with enough time.

Instead of multiplying it would be better to _divide_ the noisy AC
signal by the ref.

Crazy. Near the signal zero crossings, you'd be applying an enormous
amount of gain to what's left, namely the noise and offset.
Multiplying weights the output by the best part of the signal;
division selects the worst.

There's actual math behind those statements, but I'm suspecting that
you're not a mathy type.

Some lockins, maybe most, multiply the input by a square wave, not a
sine, because that's easier to do precisely.

One advantage over lock in is a simple capacitor in parallel with the
output shorts out the AC component which is the noise.

Not an electronics type, either.

A much greater advantage is when the noise drops, you aren't forced to
waste a lot of time smoothing a squared signal to DC.

It's already there.

Quotient sync filtering is better than lock in in every respect.

If it were, it would be in widespread use by now.

Amateurs often assume, from ignorance, that they can have eureka
insights that generations of pros have missed. That's very, very
unlikely.

John

 

[doug]

Bret Cahill wrote:

A lock in amplifier multiplies an AC signal + noise by a synchronous
reference signal. If the signal is sinwt and the ref is sinwt, the
output is sin^2(wt) which is always positive. Regardless of the
particular shape it can always be smoothed to a DC output proportional
to the signal -- with enough time.
Instead of multiplying it would be better to _divide_ the noisy AC
signal by the ref.


Crazy.


Going in the "wrong direction" is SIP (Standard Inventing Procedure).

Is any expression more hackneyed than "thinking inside the cylinder?"

Well it is ok to think of new ideas. It is quite another
to make baseless claims like you are doing. But then you
were trying to make up your own physics on an earlier thread.

Near the signal zero crossings, you'd be applying an enormous
amount of gain to what's left, namely the noise and offset.


You actually have twice as many zero *touchings* -- both types of sync
filters are always greater than or equal to zero so it's not really
zero "crossings" -- with a lock in than quotient sync.

You really need to look at fourier analysis and see what is
going on.

Any smoothing advantages provided by the 2X higher frequency look
ridiculous compared to the quotient filter where only the noise needs
to be smoothed.

Yep, you have never looked at this.

Multiplying weights the output by the best part of the signal;
division selects the worst.


For that to be true there would need to be some fundamental reason one
type of sync filter is better than another.

Remember, both are, without question, sync filters.

Do a simulation and look at the frequency output. You have not
done that.

In this case there is a fundamental difference: Smoothing is only
necessary for the noise with the quotient filter.

You really need to look at the math.

There's actual math behind those statements,


Show us what you got.

I'm not holding anything back. This is full disclosure.

So you have not done the math.

but I'm suspecting that
you're not a mathy type.


This math proof is high skool level.

So you have not done the math.

Some lockins, maybe most, multiply the input by a square wave, not a
sine, because that's easier to do precisely.


One advantage over lock in is a simple capacitor in parallel with the
output shorts out the AC component which is the noise.


Not an electronics type, either.


You openly admit you think it's a big deal to smooth AC noise out of a
DC signal?

You are not familiar with filters either.

A much greater advantage is when the noise drops, you aren't forced to
waste a lot of time smoothing a squared signal to DC.
It's already there.
Quotient sync filtering is better than lock in in every respect.


If it were, it would be in widespread use by now.


You'ld be surprised as the $tuff you can find one step off trail.

Yes, empty cans, cigarette butts etc.

If you were a hiker a snake would have been bitten you by now.

If you were a surfer a shark would have eaten you by now.

If you were a student you would have failed.

Amateurs often assume, from ignorance, that they can have eureka
insights that generations of pros have missed. That's very, very
unlikely.


Many or most breakthroughs come shortly after switching fields.

Dream on that you have found anything.

Just yesterday Obama was talking about the economy running on
innovation.

Obama needs to put his money where his mouth is.

No, Obama puts OUR money where his mouth is.

He needs to pay engineers to go on sabbatical, industry hop, spend 6
months in another field asking "dumb" questions, start looking for
problems to solve _outside_ their specialty . . .

_Any_thing to break up the sclerosis.

Tech incendiary needs to be a cabinet level position.

Bret Cahill

While you are waiting for that to happen, why not study some
math and some electronics.

"Make things as simple as possible . . ."
-- Einstein

"The world revolves, not around the inventors of new noises, but
around the inventors of new values. It revolves *inaudibly*.

-- Nietzsche

 

[Bret Cahill]

A lock in amplifier multiplies an AC signal + noise by a synchronous
reference signal. If the signal is sinwt and the ref is sinwt, the
output is sin^2(wt) which is always positive. Regardless of the
particular shape it can always be smoothed to a DC output proportional
to the signal -- with enough time.
Instead of multiplying it would be better to _divide_ the noisy AC
signal by the ref.

Crazy.

Going in the "wrong direction" is SIP (Standard Inventing Procedure).

Is any expression more hackneyed than "thinking inside the cylinder?"

Near the signal zero crossings, you'd be applying an enormous
amount of gain to what's left, namely the noise and offset.

You actually have twice as many zero *touchings* -- both types of sync
filters are always greater than or equal to zero so it's not really
zero "crossings" -- with a lock in than quotient sync.

Any smoothing advantages provided by the 2X higher frequency look
ridiculous compared to the quotient filter where only the noise needs
to be smoothed.

Multiplying weights the output by the best part of the signal;
division selects the worst.

For that to be true there would need to be some fundamental reason one
type of sync filter is better than another.

Remember, both are, without question, sync filters.

In this case there is a fundamental difference: Smoothing is only
necessary for the noise with the quotient filter.

There's actual math behind those statements,

Show us what you got.

I'm not holding anything back. This is full disclosure.

but I'm suspecting that
you're not a mathy type.

This math proof is high skool level.

Some lockins, maybe most, multiply the input by a square wave, not a
sine, because that's easier to do precisely.

One advantage over lock in is a simple capacitor in parallel with the
output shorts out the AC component which is the noise.

Not an electronics type, either.

You openly admit you think it's a big deal to smooth AC noise out of a
DC signal?

A much greater advantage is when the noise drops, you aren't forced to
waste a lot of time smoothing a squared signal to DC.
It's already there.
Quotient sync filtering is better than lock in in every respect.

If it were, it would be in widespread use by now.

You'ld be surprised as the $tuff you can find one step off trail.

If you were a hiker a snake would have been bitten you by now.

If you were a surfer a shark would have eaten you by now.

Amateurs often assume, from ignorance, that they can have eureka
insights that generations of pros have missed. That's very, very
unlikely.

Many or most breakthroughs come shortly after switching fields.

Just yesterday Obama was talking about the economy running on
innovation.

Obama needs to put his money where his mouth is.

He needs to pay engineers to go on sabbatical, industry hop, spend 6
months in another field asking "dumb" questions, start looking for
problems to solve _outside_ their specialty . . .

_Any_thing to break up the sclerosis.

Tech incendiary needs to be a cabinet level position.

Bret Cahill

"Make things as simple as possible . . ."
-- Einstein

"The world revolves, not around the inventors of new noises, but
around the inventors of new values. It revolves *inaudibly*.

-- Nietzsche

 

[John Larkin]

On Sat, 1 Aug 2009 09:59:24 -0700 (PDT), Bret Cahill
<BretCahill@aol.com> wrote:

A lock in amplifier multiplies an AC signal + noise by a synchronous
reference signal. If the signal is sinwt and the ref is sinwt, the
output is sin^2(wt) which is always positive. Regardless of the
particular shape it can always be smoothed to a DC output proportional
to the signal -- with enough time.
Instead of multiplying it would be better to _divide_ the noisy AC
signal by the ref.

Crazy.

Going in the "wrong direction" is SIP (Standard Inventing Procedure).

Is any expression more hackneyed than "thinking inside the cylinder?"

Near the signal zero crossings, you'd be applying an enormous
amount of gain to what's left, namely the noise and offset.

You actually have twice as many zero *touchings* -- both types of sync
filters are always greater than or equal to zero so it's not really
zero "crossings" -- with a lock in than quotient sync.

Any smoothing advantages provided by the 2X higher frequency look
ridiculous compared to the quotient filter where only the noise needs
to be smoothed.

Multiplying weights the output by the best part of the signal;
division selects the worst.

For that to be true there would need to be some fundamental reason one
type of sync filter is better than another.

The best place to look for a signal is where you know it is. The worst
place is where you know it isn't. Mathematically, we're looking for
the signal that best cross-correlates to the input. For a sine wave,
that turns out to be another sine wave. I sure ain't the reciprocal of
a sine wave, which doesn't exist mathematically, much less physically.

Remember, both are, without question, sync filters.

In this case there is a fundamental difference: Smoothing is only
necessary for the noise with the quotient filter.

There's actual math behind those statements,

Show us what you got.

Let's start with something simple:

{ Limit (N/X) as X==>0 } ==> infinity for nonzero N.

Division is messy, mathematically and in real electronics.

There are lots of books that cover "signals and systems." It's
standard 2nd year EE stuff.

John

 

[John Larkin]

On Sat, 1 Aug 2009 12:05:27 -0700 (PDT), Bret Cahill
<BretCahill@aol.com> wrote:

A lock in amplifier multiplies an AC signal + noise by a synchronous
reference signal.  If the signal is sinwt and the ref is sinwt, the
output is sin^2(wt) which is always positive.  Regardless of the
particular shape it can always be smoothed to a DC output proportional
to the signal -- with enough time.
Instead of multiplying it would be better to _divide_ the noisy AC
signal by the ref.
Crazy.

Going in the "wrong direction" is SIP (Standard Inventing Procedure).

Is any expression more hackneyed than "thinking inside the cylinder?"

Near the signal zero crossings, you'd be applying an enormous
amount of gain to what's left, namely the noise and offset.

You actually have twice as many zero *touchings* -- both types of sync
filters are always greater than or equal to zero so it's not really
zero "crossings" -- with a lock in than quotient sync.

A correction here:

Ideally the unflitered / prefilter quotient output should _always_ be
DC except for the noise.

Both the numerator and denominator go to zero at the same time so the
noise will be large compared to the denominator when both the signal
and ref both go to zero.

The solution would be to only sample outside a certain +/- angle when
both the signal and ref are zero, say, say +/- pi/4 at 0 radians and
+/- pi/4 at pi rad for sin wt.

Keep at it and you may eventually invent the lock-in amplifier.

John

 

[Bret Cahill]

A lock in amplifier multiplies an AC signal + noise by a synchronous
reference signal.  If the signal is sinwt and the ref is sinwt, the
output is sin^2(wt) which is always positive.  Regardless of the
particular shape it can always be smoothed to a DC output proportional
to the signal -- with enough time.
Instead of multiplying it would be better to _divide_ the noisy AC
signal by the ref.
Crazy.

Going in the "wrong direction" is SIP (Standard Inventing Procedure).

Is any expression more hackneyed than "thinking inside the cylinder?"

Near the signal zero crossings, you'd be applying an enormous
amount of gain to what's left, namely the noise and offset.

You actually have twice as many zero *touchings* -- both types of sync
filters are always greater than or equal to zero so it's not really
zero "crossings" -- with a lock in than quotient sync.

A correction here:

Ideally the unflitered / prefilter quotient output should _always_ be
DC except for the noise.

Both the numerator and denominator go to zero at the same time so the
noise will be large compared to the denominator when both the signal
and ref both go to zero.

The solution would be to only sample outside a certain +/- angle when
both the signal and ref are zero, say, say +/- pi/4 at 0 radians and
+/- pi/4 at pi rad for sin wt.


Bret Cahill

 

[John Larkin]

On Sat, 1 Aug 2009 12:42:28 -0700 (PDT), Bret Cahill
<BretCahill@aol.com> wrote:

A lock in amplifier multiplies an AC signal + noise by a synchronous
reference signal.  If the signal is sinwt and the ref is sinwt, the
output is sin^2(wt) which is always positive.  Regardless of the
particular shape it can always be smoothed to a DC output proportional
to the signal -- with enough time.

Instead of multiplying it would be better to _divide_ the noisy AC
signal by the ref.

Crazy. Near the signal zero crossings, you'd be applying an enormous
amount of gain to what's left, namely the noise and offset.

Thanks for bringing that up.

The solution is to not sample too close to the indeterminate points.

The angle could be adjustable depending on the situation. It could
even be automatic.

With that minor correction it's definitely better than lock in.

Download LT Spice and simulate both circuits.

John

 

[Bret Cahill]

A lock in amplifier multiplies an AC signal + noise by a synchronous
reference signal.  If the signal is sinwt and the ref is sinwt, the
output is sin^2(wt) which is always positive.  Regardless of the
particular shape it can always be smoothed to a DC output proportional
to the signal -- with enough time.

Instead of multiplying it would be better to _divide_ the noisy AC
signal by the ref.

Crazy. Near the signal zero crossings, you'd be applying an enormous
amount of gain to what's left, namely the noise and offset.

Thanks for bringing that up.

The solution is to not sample too close to the indeterminate points.

The angle could be adjustable depending on the situation. It could
even be automatic.

With that minor correction it's definitely better than lock in.

Thanks again.


Bret Cahill

 

[doug]

Bret Cahill wrote:

A lock in amplifier multiplies an AC signal + noise by a synchronous
reference signal. If the signal is sinwt and the ref is sinwt, the
output is sin^2(wt) which is always positive. Regardless of the
particular shape it can always be smoothed to a DC output proportional
to the signal -- with enough time.
Instead of multiplying it would be better to _divide_ the noisy AC
signal by the ref.

Crazy.

Going in the "wrong direction" is SIP (Standard Inventing Procedure).

Is any expression more hackneyed than "thinking inside the cylinder?"


Near the signal zero crossings, you'd be applying an enormous
amount of gain to what's left, namely the noise and offset.

You actually have twice as many zero *touchings* -- both types of sync
filters are always greater than or equal to zero so it's not really
zero "crossings" -- with a lock in than quotient sync.


A correction here:

Ideally the unflitered / prefilter quotient output should _always_ be
DC except for the noise.

Both the numerator and denominator go to zero at the same time so the
noise will be large compared to the denominator when both the signal
and ref both go to zero.

The solution would be to only sample outside a certain +/- angle when
both the signal and ref are zero, say, say +/- pi/4 at 0 radians and
+/- pi/4 at pi rad for sin wt.

That is good, waste you time on working out the details without

having taken a look at the issues with the concept.

Bret Cahill

 

[doug]

Bret Cahill wrote:

A lock in amplifier multiplies an AC signal + noise by a synchronous
reference signal. If the signal is sinwt and the ref is sinwt, the
output is sin^2(wt) which is always positive. Regardless of the
particular shape it can always be smoothed to a DC output proportional
to the signal -- with enough time.

Instead of multiplying it would be better to _divide_ the noisy AC
signal by the ref.

Crazy. Near the signal zero crossings, you'd be applying an enormous
amount of gain to what's left, namely the noise and offset.


Thanks for bringing that up.

The solution is to not sample too close to the indeterminate points.

The angle could be adjustable depending on the situation. It could
even be automatic.

With that minor correction it's definitely better than lock in.

Except, of course, that it is not since you are just guessing and
ignoring the physics.

Thanks again.


Bret Cahill

 

[Bret Cahill]

On Aug 1, 12:59 pm, John Larkin
<jjlar...@highNOTlandTHIStechnologyPART.com> wrote:

On Sat, 1 Aug 2009 12:05:27 -0700 (PDT), Bret Cahill





BretCah...@aol.com> wrote:
A lock in amplifier multiplies an AC signal + noise by a synchronous
reference signal.  If the signal is sinwt and the ref is sinwt, the
output is sin^2(wt) which is always positive.  Regardless of the
particular shape it can always be smoothed to a DC output proportional
to the signal -- with enough time.
Instead of multiplying it would be better to _divide_ the noisy AC
signal by the ref.
Crazy.

Going in the "wrong direction" is SIP (Standard Inventing Procedure).

Is any expression more hackneyed than "thinking inside the cylinder?"

Near the signal zero crossings, you'd be applying an enormous
amount of gain to what's left, namely the noise and offset.

You actually have twice as many zero *touchings* -- both types of sync
filters are always greater than or equal to zero so it's not really
zero "crossings" -- with a lock in than quotient sync.

A correction here:

Ideally the unflitered / prefilter quotient output should _always_ be
DC except for the noise.

Both the numerator and denominator go to zero at the same time so the
noise will be large compared to the denominator when both the signal
and ref both go to zero.

The solution would be to only sample outside a certain +/- angle when
both the signal and ref are zero, say, say +/- pi/4 at 0 radians and
+/- pi/4 at pi rad for sin wt.

Keep at it and you may eventually invent the lock-in amplifier.

It's definitely a sync filter but a lock in will never be able to
clean up a signal as much in as short a time.


Bret Cahill

 

[greg]

Bret Cahill wrote:

Instead of multiplying it would be better to _divide_ the noisy AC
signal by the ref.

One advantage over lock in is a simple capacitor in parallel with the
output shorts out the AC component which is the noise.

Only if the noise occupies a higher frequency band
than the signal. If that's the case, your capacitor
on its own will filter out the noise, and you don't
need the lock-in arrangement at all.

--
Greg

 

[doug]

Bret Cahill wrote:

On Aug 1, 12:59 pm, John Larkin
jjlar...@highNOTlandTHIStechnologyPART.com> wrote:

On Sat, 1 Aug 2009 12:05:27 -0700 (PDT), Bret Cahill





BretCah...@aol.com> wrote:

A lock in amplifier multiplies an AC signal + noise by a synchronous
reference signal. If the signal is sinwt and the ref is sinwt, the
output is sin^2(wt) which is always positive. Regardless of the
particular shape it can always be smoothed to a DC output proportional
to the signal -- with enough time.
Instead of multiplying it would be better to _divide_ the noisy AC
signal by the ref.

Crazy.

Going in the "wrong direction" is SIP (Standard Inventing Procedure).

Is any expression more hackneyed than "thinking inside the cylinder?"

Near the signal zero crossings, you'd be applying an enormous
amount of gain to what's left, namely the noise and offset.

You actually have twice as many zero *touchings* -- both types of sync
filters are always greater than or equal to zero so it's not really
zero "crossings" -- with a lock in than quotient sync.

A correction here:

Ideally the unflitered / prefilter quotient output should _always_ be
DC except for the noise.

Both the numerator and denominator go to zero at the same time so the
noise will be large compared to the denominator when both the signal
and ref both go to zero.

The solution would be to only sample outside a certain +/- angle when
both the signal and ref are zero, say, say +/- pi/4 at 0 radians and
+/- pi/4 at pi rad for sin wt.

Keep at it and you may eventually invent the lock-in amplifier.


It's definitely a sync filter but a lock in will never be able to
clean up a signal as much in as short a time.

You keep thinking the laws of physics do not apply to you.

That shows your total ignorance of science. Your delusions
have no effect on the universe.

Bret Cahill

 

[Bret Cahill]

Instead of multiplying it would be better to _divide_ the noisy AC
signal by the ref.

One advantage over lock in is a simple capacitor in parallel with the
output shorts out the AC component which is the noise.

Only if the noise occupies a higher frequency band
than the signal.

If the signal is being divided by an in phase ref, then it's _already_
DC, at least everywhere the ref isn't zero.

The only AC is due to the noise.

If that's the case, your capacitor
on its own will filter out the noise, and you don't
need the lock-in arrangement at all.

Exactly!

The question is, does _anyone_ need a lock in when a quotient sync
filter is simpler and faster?


Bret Cahill

 

[Bret Cahill]

A lock in amplifier multiplies an AC signal + noise by a synchronous
reference signal.  If the signal is sinwt and the ref is sinwt, the
output is sin^2(wt) which is always positive.  Regardless of the
particular shape it can always be smoothed to a DC output proportional
to the signal -- with enough time.

Instead of multiplying it would be better to _divide_ the noisy AC
signal by the ref.

Crazy. Near the signal zero crossings, you'd be applying an enormous
amount of gain to what's left, namely the noise and offset.

Thanks for bringing that up.

The solution is to not sample too close to the indeterminate points.

The angle could be adjustable depending on the situation.  It could
even be automatic.

With that minor correction it's definitely better than lock in.

Download LT Spice and simulate both circuits.

Thanks again.

The UK Nat. Physical Lab has a lock in simulator. Feeding my problem
into it always seemed to require 90 seconds to get a clean output.

Using a LRC filter on spice only took - 5 - 8 seconds.


Bret Cahill

 

[doug]

Bret Cahill wrote:

Instead of multiplying it would be better to _divide_ the noisy AC
signal by the ref.

One advantage over lock in is a simple capacitor in parallel with the
output shorts out the AC component which is the noise.

Only if the noise occupies a higher frequency band
than the signal.


If the signal is being divided by an in phase ref, then it's _already_
DC, at least everywhere the ref isn't zero.

Except where it is infinity from dividing by zero.

The only AC is due to the noise.

And the above mentioned infinity.

If that's the case, your capacitor
on its own will filter out the noise, and you don't
need the lock-in arrangement at all.


Exactly!

The question is, does _anyone_ need a lock in when a quotient sync
filter is simpler and faster?

Because they want something that works.

Bret Cahill

 

[doug]

Bret Cahill wrote:

A lock in amplifier multiplies an AC signal + noise by a synchronous
reference signal. If the signal is sinwt and the ref is sinwt, the
output is sin^2(wt) which is always positive. Regardless of the
particular shape it can always be smoothed to a DC output proportional
to the signal -- with enough time.

Instead of multiplying it would be better to _divide_ the noisy AC
signal by the ref.

Crazy. Near the signal zero crossings, you'd be applying an enormous
amount of gain to what's left, namely the noise and offset.

Thanks for bringing that up.

The solution is to not sample too close to the indeterminate points.

The angle could be adjustable depending on the situation. It could
even be automatic.

With that minor correction it's definitely better than lock in.

Download LT Spice and simulate both circuits.


Thanks again.

The UK Nat. Physical Lab has a lock in simulator. Feeding my problem
into it always seemed to require 90 seconds to get a clean output.

Using a LRC filter on spice only took - 5 - 8 seconds.

Ok, so you do not know how to design circuits as well. Physics sets
what you have to do.

Bret Cahill

 

[doug]

Bret Cahill wrote:

Instead of multiplying it would be better to _divide_ the noisy AC
signal by the ref.

One advantage over lock in is a simple capacitor in parallel with the
output shorts out the AC component which is the noise.

Only if the noise occupies a higher frequency band
than the signal.

If the signal is being divided by an in phase ref, then it's _already_
DC, at least everywhere the ref isn't zero.

The only AC is due to the noise.


If that's the case, your capacitor
on its own will filter out the noise, and you don't
need the lock-in arrangement at all.

Exactly!

The question is, does _anyone_ need a lock in when a quotient sync
filter is simpler and faster?


If the noise is orders of magnitude higher than the signal, tossing
20% to 50% of the signal just doesn't seem like a big advantage.

If the signal is several times larger than the noise and needs to be
increased to 500 times larger, then the time saved can be critical.

You really should read up on noise bandwidth. It would keep
you from making your silly mistakes.

Bret Cahill