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Guest

Mon Feb 11, 2019 5:45 pm

On 2/10/19 1:58 PM, Joseph Gwinn wrote:

On Feb 6, 2019, Don Kuenz wrote

(in article <20190206a_at_crcomp.net>):

bloggs.fredbloggs.fred_at_gmail.com wrote:

On Wednesday, February 6, 2019 at 11:09:01 AM UTC-5, Jeroen Belleman wrote:

Do we have a handy term to say that two sinusoidal waves

of equal frequency differ only by amplitude and phase?

I would say 'correlated', but would that be the most

common term?

Jeroen Belleman

Those types of signals are called coherent. It is a very broad area of

study, but, when you say coherent sine waves, the people who know the

field will understand it to mean exactly what you describe.

Yes indeed. My _IEEE Dictionary_ says it this way:

coherent (1) (fiber optics). Characterized by a fixed phase relationship

between points on an electromagnetic wave. Note: A truly monochromatic

wave would be perfectly coherent at all points in space. In practice,

however, the region of high coherence may extend only a finite distance.

Thank you, 73,

_Coherent_ is correct, and it applies to reference signals generated from one

another by frequency multiplication or division. The key is that the ratio of

the rates of phase advance is constant. In the case of a signal and a

frequency-doubled (or -halved) version of the same signal, that ratio is

exactly two.

All correlated signals are coherent, but not all coherent signals are

correlated. A signal and a frequency doubled version of that signal are

coherent, but are uncorrelated.

The original definition of coherent was simply that coherent beams of light

could be made to interfere and cancel. This was subsequently expanded to

handle such things as frequency-doubled light.

Useful ref: "A unifying view of coherence in signal processing", William A.

Gardner, Signal Processing, Volume 29 Issue 2, Nov. 1992, Pages 113 - 140.

Joe Gwinn

(in article <20190206a_at_crcomp.net>):

bloggs.fredbloggs.fred_at_gmail.com wrote:

On Wednesday, February 6, 2019 at 11:09:01 AM UTC-5, Jeroen Belleman wrote:

Do we have a handy term to say that two sinusoidal waves

of equal frequency differ only by amplitude and phase?

I would say 'correlated', but would that be the most

common term?

Jeroen Belleman

Those types of signals are called coherent. It is a very broad area of

study, but, when you say coherent sine waves, the people who know the

field will understand it to mean exactly what you describe.

Yes indeed. My _IEEE Dictionary_ says it this way:

coherent (1) (fiber optics). Characterized by a fixed phase relationship

between points on an electromagnetic wave. Note: A truly monochromatic

wave would be perfectly coherent at all points in space. In practice,

however, the region of high coherence may extend only a finite distance.

Thank you, 73,

_Coherent_ is correct, and it applies to reference signals generated from one

another by frequency multiplication or division. The key is that the ratio of

the rates of phase advance is constant. In the case of a signal and a

frequency-doubled (or -halved) version of the same signal, that ratio is

exactly two.

All correlated signals are coherent, but not all coherent signals are

correlated. A signal and a frequency doubled version of that signal are

coherent, but are uncorrelated.

The original definition of coherent was simply that coherent beams of light

could be made to interfere and cancel. This was subsequently expanded to

handle such things as frequency-doubled light.

Useful ref: "A unifying view of coherence in signal processing", William A.

Gardner, Signal Processing, Volume 29 Issue 2, Nov. 1992, Pages 113 - 140.

Joe Gwinn

That's too restrictive a definition. For instance, I've built coherent

detection systems with offset frequencies as high as 8 GHz. (That one

was a homodyne interferometer for detecting submicron tin droplets

moving at up to 3 km/s [Mach 9].)

The basic definition of optical coherence is the ability to form

fringes. The fringes don't have to stay still. I took Joe Goodman's

statistical optics class long ago, and his book is an excellent read:

<https://www.amazon.com/exec/obidos/asin/1119009456>.

Cheers

Phil Hobbs

--

Dr Philip C D Hobbs

Principal Consultant

ElectroOptical Innovations LLC / Hobbs ElectroOptics

Optics, Electro-optics, Photonics, Analog Electronics

Briarcliff Manor NY 10510

http://electrooptical.net

http://hobbs-eo.com

Guest

Mon Feb 11, 2019 8:45 pm

Have you ever used a delay line discriminatory to measure oscillator phase noise ? It can only be used to see phase noise a fair distance from the carrier

Guest

Mon Feb 11, 2019 10:45 pm

On 2/11/19 2:10 PM, bulegoge_at_columbus.rr.com wrote:

Have you ever used a delay line discriminatory to measure oscillator

phase noise ? It can only be used to see phase noise a fair distance

from the carrier

phase noise ? It can only be used to see phase noise a fair distance

from the carrier

Yup. The first engineering thing I ever built for hire was a 12-GHz

cavity discriminator, which I still have. It was built for measuring

close-in phase noise. Eventually we got an HP 8566A, so we didn't need

the discriminator any more.

Cheers

Phil Hobbs

--

Dr Philip C D Hobbs

Principal Consultant

ElectroOptical Innovations LLC / Hobbs ElectroOptics

Optics, Electro-optics, Photonics, Analog Electronics

Briarcliff Manor NY 10510

http://electrooptical.net

https://hobbs-eo.com

Guest

Tue Feb 12, 2019 4:45 am

On Feb 11, 2019, Phil Hobbs wrote

(in article <q3s5us$v50$1_at_dont-email.me>):

On 2/10/19 1:58 PM, Joseph Gwinn wrote:

On Feb 6, 2019, Don Kuenz wrote

(in article <20190206a_at_crcomp.net>):

bloggs.fredbloggs.fred_at_gmail.com wrote:

On Wednesday, February 6, 2019 at 11:09:01 AM UTC-5, Jeroen Belleman

wrote:

Do we have a handy term to say that two sinusoidal waves

of equal frequency differ only by amplitude and phase?

I would say 'correlated', but would that be the most

common term?

Jeroen Belleman

Those types of signals are called coherent. It is a very broad area of

study, but, when you say coherent sine waves, the people who know the

field will understand it to mean exactly what you describe.

Yes indeed. My _IEEE Dictionary_ says it this way:

coherent (1) (fiber optics). Characterized by a fixed phase relationship

between points on an electromagnetic wave. Note: A truly monochromatic

wave would be perfectly coherent at all points in space. In practice,

however, the region of high coherence may extend only a finite distance.

Thank you, 73,

_Coherent_ is correct, and it applies to reference signals generated from

one

another by frequency multiplication or division. The key is that the ratio

of

the rates of phase advance is constant. In the case of a signal and a

frequency-doubled (or -halved) version of the same signal, that ratio is

exactly two.

All correlated signals are coherent, but not all coherent signals are

correlated. A signal and a frequency doubled version of that signal are

coherent, but are uncorrelated.

The original definition of coherent was simply that coherent beams of light

could be made to interfere and cancel. This was subsequently expanded to

handle such things as frequency-doubled light.

Useful ref: "A unifying view of coherence in signal processing", William A.

Gardner, Signal Processing, Volume 29 Issue 2, Nov. 1992, Pages 113 - 140.

Joe Gwinn

That's too restrictive a definition. For instance, I've built coherent

detection systems with offset frequencies as high as 8 GHz. (That one

was a homodyne interferometer for detecting submicron tin droplets

moving at up to 3 km/s [Mach 9].)

On Feb 6, 2019, Don Kuenz wrote

(in article <20190206a_at_crcomp.net>):

bloggs.fredbloggs.fred_at_gmail.com wrote:

On Wednesday, February 6, 2019 at 11:09:01 AM UTC-5, Jeroen Belleman

wrote:

Do we have a handy term to say that two sinusoidal waves

of equal frequency differ only by amplitude and phase?

I would say 'correlated', but would that be the most

common term?

Jeroen Belleman

Those types of signals are called coherent. It is a very broad area of

study, but, when you say coherent sine waves, the people who know the

field will understand it to mean exactly what you describe.

Yes indeed. My _IEEE Dictionary_ says it this way:

coherent (1) (fiber optics). Characterized by a fixed phase relationship

between points on an electromagnetic wave. Note: A truly monochromatic

wave would be perfectly coherent at all points in space. In practice,

however, the region of high coherence may extend only a finite distance.

Thank you, 73,

_Coherent_ is correct, and it applies to reference signals generated from

one

another by frequency multiplication or division. The key is that the ratio

of

the rates of phase advance is constant. In the case of a signal and a

frequency-doubled (or -halved) version of the same signal, that ratio is

exactly two.

All correlated signals are coherent, but not all coherent signals are

correlated. A signal and a frequency doubled version of that signal are

coherent, but are uncorrelated.

The original definition of coherent was simply that coherent beams of light

could be made to interfere and cancel. This was subsequently expanded to

handle such things as frequency-doubled light.

Useful ref: "A unifying view of coherence in signal processing", William A.

Gardner, Signal Processing, Volume 29 Issue 2, Nov. 1992, Pages 113 - 140.

Joe Gwinn

That's too restrictive a definition. For instance, I've built coherent

detection systems with offset frequencies as high as 8 GHz. (That one

was a homodyne interferometer for detecting submicron tin droplets

moving at up to 3 km/s [Mach 9].)

We do this kind of thing all the time in radar, and we would consider this a

coherent radar system.

But we would not claim that the doppler was coherent in the same sense as we

use for reference signal generation. Even though the whole radar is

considered coherent. IŽll think about this. We think of Doppler in

frequency terms, although phase is nonetheless lurking below. There is a

implied distinction in there somewhere.

The basic definition of optical coherence is the ability to form

fringes. The fringes don't have to stay still. I took Joe Goodman's

statistical optics class long ago, and his book is an excellent read:

https://www.amazon.com/exec/obidos/asin/1119009456>.

Forming fringes is exactly what happens when interference leads to

cancellation, so that part is the same. That definition sounds awfully like a

moire beat note, but another angle is always good. IŽll read the book.

Joe Gwinn

Guest

Tue Feb 12, 2019 1:45 pm

On Monday, February 11, 2019 at 4:02:43 PM UTC-5, Phil Hobbs wrote:

On 2/11/19 2:10 PM, bulegoge_at_columbus.rr.com wrote:

Have you ever used a delay line discriminatory to measure oscillator

phase noise ? It can only be used to see phase noise a fair distance

from the carrier

Yup. The first engineering thing I ever built for hire was a 12-GHz

cavity discriminator, which I still have. It was built for measuring

close-in phase noise. Eventually we got an HP 8566A, so we didn't need

the discriminator any more.

Cheers

Phil Hobbs

--

Dr Philip C D Hobbs

Principal Consultant

ElectroOptical Innovations LLC / Hobbs ElectroOptics

Optics, Electro-optics, Photonics, Analog Electronics

Briarcliff Manor NY 10510

http://electrooptical.net

https://hobbs-eo.com

Have you ever used a delay line discriminatory to measure oscillator

phase noise ? It can only be used to see phase noise a fair distance

from the carrier

Yup. The first engineering thing I ever built for hire was a 12-GHz

cavity discriminator, which I still have. It was built for measuring

close-in phase noise. Eventually we got an HP 8566A, so we didn't need

the discriminator any more.

Cheers

Phil Hobbs

--

Dr Philip C D Hobbs

Principal Consultant

ElectroOptical Innovations LLC / Hobbs ElectroOptics

Optics, Electro-optics, Photonics, Analog Electronics

Briarcliff Manor NY 10510

http://electrooptical.net

https://hobbs-eo.com

Was the cavity used to provide the delay?

Guest

Tue Feb 12, 2019 4:45 pm

Yup. Â The first engineering thing I ever built for hire was a 12-GHz

cavity discriminator, which I still have. Â It was built for measuring

close-in phase noise. Â Eventually we got an HP 8566A, so we didn't need

the discriminator any more.

Was the cavity used to provide the delay?

cavity discriminator, which I still have. Â It was built for measuring

close-in phase noise. Â Eventually we got an HP 8566A, so we didn't need

the discriminator any more.

Was the cavity used to provide the delay?

Sort of. It used the cavity to make a 90-degree phase shift. IIRC it used a circulator and a coax mixer, so we tuned it to null the DC, which also gets rid of most of the AM noise as well.

A high-Q resonator has a higher phase slope (d phi/df) than any feasible length of coax.

An unbalanced Mach-Zehnder interferometer is also a delay discriminator.

Cheers

Phil Hobbs

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