Actually, my first posting was right all along, if Zo is always real.

From Les Besser's Applied RF Techniques:

"For passive circuits, 0=[rho]=1,

And strictly speaking: Reflection Coefficient =
(Zload-Zo*)/(Zload-Zo)

Where * indicates
conjugate.

But most of the literature assumes that Zo is real, therefore
Zo*=Zo."


And then i looked at the trusty ARRL handbook, 1993, page 16-2,
and lo and behold, the reflection coefficient equation doesn't have a
term for line reactance, so both this book and Pozar have indeed
assumed that the Zo will be purely real.

That doesn't mean Zload cannot have reactance (be complex).

Try your calculation again, and you will see that you can never
have a [rho] (magnitude of R.C.)greater than 1 for a passive network.

How could you get more power reflected than what you put in (do
you believe in conservation of energy, or do you think you can make
energy out of nothing)? If you guys can tell us, we could fix our
power problems in CA!

But thanks for checking my work, and this is a subtle detail that
is good to know.


Slick

"Dr. Slick" wrote
Actually, my first posting was right all along, if Zo is always real.

===============================

What a pity - it never is.

(Dr. Slick) wrote in message . com...
Actually, my first posting was right all along, if Zo is always real.

From Les Besser's Applied RF Techniques:

"For passive circuits, 0=[rho]=1,

And strictly speaking: Reflection Coefficient =
(Zload-Zo*)/(Zload-Zo)

Where * indicates
conjugate.

But most of the literature assumes that Zo is real, therefore
Zo*=Zo."


Fascinating... Please have a look at the following reply I got from
Besser... I still wish people would go through the simple math
themselves, and make up their own minds what's correct and what isn't.
I gather that Slick has made up his own mind, though see no evidence
that it's on the basis of the simple calcs from what I believe he
already agrees with. Oh, well, not MY problem. (This is twice now,
recently, that I've followed up on other people's references and found
them to be at best questionable in some way.)

Cheers,
Tom

=-=-=-=-=-=-=-=-= Beginning of quoted material =-=-=-=-=-=-=-=-=-=-=-

Hello Tom-

Thank you for your message. I do not know which specific course was
referenced by the person you mentioned in your message, but I did
check
the notes for our more popular course which covers linear RF circuits.
In the manuals for that course, the formula is given as you described,
except that the Zo term in the numerator is _not_ the complex
conjugate.
Thus the formula in the manual reads:

Gamma = Vr/Vf = (Zl-Zo)/(Zl+Zo)

This is in agreement with Guillermo Gonzalez's text, "Microwave
Transistor Amplifiers," which is one of the references used in writing
the course.

Please let me know if this information addresses your concern.

Have a good day.

Regards,

Rex


From: ]
Sent: Thursday, August 21, 2003 11:11 AM
To:
Subject: Other concern/question


Below is the result of your feedback form. It was submitted by
) on Thursday, August 21, 2003 at 14:10:53
------------------------------------------------------------------------
---

name: Tom Bruhns

body: I have recently seen someone attribute to Besser Associates
training a formula for reflection coefficient at a load Zl as Vr/Vf =
(Zl-Zo*)/(Zl+Zo), where Zo* is the complex conjugate of the line
characteristic impedance Zo. I'm curious if this is actually what you
teach, as it is counter to what is commonly in texts, and is also
counter to the commonly accepted boundary conditions on a TEM line at
such a load.

Yours in the interest of accurate models,
Tom Bruhns
--------
....
Rex Frobenius
Engineering Director
Besser Associates
650-949-3300
650-949-4400 FAX

www.besserassociates.com

=-=-=-=-=-=-=-=-= End of quoted material =-=-=-=-=-=-=-=-=-=-=-

So another way for the lurkers to check all this: assume a line Zo =
50-j5, and a load Zload = 1+j100. Assume some convenient Vf at the
load. Calculate rho = Vr/Vf from the equation quoted below. Now find
Vr, and from the line impedance and Vf and Vr, find If and Ir. Add
the V terms and I terms to get the net line voltage and current at the
load. Does that correspond to the expected load current for the given
Zload? If so, fine; if not, where does the difference in current come
from? If you assume the line current is correct from your If and Ir
calcs, and the load current is correct as the net line voltage = net
load voltage, and use Zload to get Iload, does the line power
dissipation plus the load power dissipation equal the power fed in
from a generator? Try all those calcs after revising the Vr/Vf
formula to match what Besser is now teaching, and see if things line
up a bit better.

The truth is all there to be seen with just a bit of work.

Cheers,
Tom

(yeah, I've done it, as you might guess. And so have a lot of
others.)

(Dr. Slick) wrote in message . com...
Actually, my first posting was right all along, if Zo is always real.

From Les Besser's Applied RF Techniques:

"For passive circuits, 0=[rho]=1,

And strictly speaking: Reflection Coefficient =
(Zload-Zo*)/(Zload-Zo)

Where * indicates
conjugate.

But most of the literature assumes that Zo is real, therefore
Zo*=Zo."


And then i looked at the trusty ARRL handbook, 1993, page 16-2,
and lo and behold, the reflection coefficient equation doesn't have a
term for line reactance, so both this book and Pozar have indeed
assumed that the Zo will be purely real.

That doesn't mean Zload cannot have reactance (be complex).

Try your calculation again, and you will see that you can never
have a [rho] (magnitude of R.C.)greater than 1 for a passive network.

How could you get more power reflected than what you put in (do
you believe in conservation of energy, or do you think you can make
energy out of nothing)? If you guys can tell us, we could fix our
power problems in CA!

But thanks for checking my work, and this is a subtle detail that
is good to know.


Slick

(Dr. Slick) wrote in message . com...
Actually, my first posting was right all along, if Zo is always real.

From Les Besser's Applied RF Techniques:

"For passive circuits, 0=[rho]=1,

And strictly speaking: Reflection Coefficient =
(Zload-Zo*)/(Zload-Zo)

Where * indicates
conjugate.


Opps! that should be :

And strictly speaking: Reflection Coefficient =
(Zload-Zo*)/(Zload+Zo)

MY Typo earlier!


Slick

Design, development and test of circuit and board level RF designs
including impedance matching networks (simulating on MIMP) for E-PHEMT
power amplifiers for the GSM, DCS, and PCS cellular bands
(880MHz-1900MHz). Simulations on ADS to assess manufacturability and
robustness. Bias tuning for EDGE mode EVM and Adjacent channel power.
Optimize circuit design and board layout for PAE, gain flatness,
stability under mismatched loads, receive-band noise, AM to PM, input
VSWR and harmonic suppression.
Design and construction of FM stereo multiplexed Phase Locked
Loop transmitters, broadband design (88-108MHz). Design and selection
of VCOs, pre-scalers, and loop filters. Antenna design and
construction: 5/8ths vertical groundplane, 1/4 wavelength, and
dipoles. Compressor-limiter and Chebychev Low-pass filter design.
Microwave (MMIC) testing and tuning (2-18GHz). Design of
equalizers and filters. Linearity of Detector Logarithmic Video
Amplifiers. Temperature compensation networks.


You win a prize if you can guess where i last worked...

Your turn Tom...


Slick

Very impressive. You've designed 5/8s vertical ground planes,
1/4 wavelength [something or others, I guess] and dipoles.
Where are you working now? Did you go to Lowell?
73,
Tom Donaly, KA6RUH

(Tdonaly) wrote in message ...

Very impressive. You've designed 5/8s vertical ground planes,
1/4 wavelength [something or others, I guess] and dipoles.
Where are you working now? Did you go to Lowell?
73,
Tom Donaly, KA6RUH


Did you skip the part about U. C. Davis?

I'm working part-time in the RF field, after being laid off among
what seems like everyone else. Gives me time to paint my next masterpiece!

Tit for Tat, maybe you can tell us something about you, Tom.

last school attended? Job responsibilities?


Slick

(Tdonaly) wrote in message
...

Very impressive. You've designed 5/8s vertical ground planes,
1/4 wavelength [something or others, I guess] and dipoles.
Where are you working now? Did you go to Lowell?
73,
Tom Donaly, KA6RUH


Did you skip the part about U. C. Davis?

I'm working part-time in the RF field, after being laid off among
what seems like everyone else. Gives me time to paint my next masterpiece!

Tit for Tat, maybe you can tell us something about you, Tom.

last school attended? Job responsibilities?


Slick



My pitifully inadequate education could be of no interest to you, Garvin; I'm
just a humble ham. (This is an _amateur_ newsgroup after all.) It is
interesting to me, though, that a person of your age and attainments
would pose as a potty-mouth little black-faced god whenever someone
disagreed with you about something as abstruse as the reflection
coefficient on a transmission line. I can only suppose that your social
education was deficient, or that you really do want your name to be the
most popular in the group's collective killfile. Anyway, you're wasting your
time with the infantile behavior. Most of the fellows on this group are old
men
who gave up that form of discourse when they learned to talk.
By the way, some of your art isn't half bad and shows the influence of some
training. Did you have an art minor in college?
73,
Tom Donaly, KA6RUH

(Tdonaly) wrote in message ...


My pitifully inadequate education could be of no interest to you, Garvin; I'm
just a humble ham. (This is an _amateur_ newsgroup after all.) It is
interesting to me, though, that a person of your age and attainments
would pose as a potty-mouth little black-faced god whenever someone
disagreed with you about something as abstruse as the reflection
coefficient on a transmission line. I can only suppose that your social
education was deficient, or that you really do want your name to be the
most popular in the group's collective killfile. Anyway, you're wasting your
time with the infantile behavior. Most of the fellows on this group are old
men
who gave up that form of discourse when they learned to talk.


Errmm...Pot calling the Kettle Black? You just described me as a
"a potty-mouth little black-faced god"!!! You don't call this
infantile behaviour?

And why "Black-faced"?

And many of the other "adults" in this NG act infantile IN THEIR
OWN WAY.
Witness how Roy will compare someone to his adolescent son, when they
don't agreed with him. And then look at Cecil. Same sh**.

And you know, you could be a high-school drop out for all i care.
The great thing about the NGs is that people don't judge you by your
age or looks, only by what you write. If you wrote logically, like
Richard, then i would respect you...but you don't. I don't care where
Richard went to school, he knows his sh**.



By the way, some of your art isn't half bad and shows the influence of some
training. Did you have an art minor in college?
73,
Tom Donaly, KA6RUH


No, i took one painting class and that's it. I'm a modern day
renaissance-man i guess...


Slick

And why "Black-faced"?

It's a classical allusion - a test. You failed. Now I know
more about you.


And many of the other "adults" in this NG act infantile IN THEIR
OWN WAY.
Witness how Roy will compare someone to his adolescent son, when they
don't agreed with him. And then look at Cecil. Same sh**.


Classic case of projection.


And you know, you could be a high-school drop out for all i care.
The great thing about the NGs is that people don't judge you by your
age or looks, only by what you write.

In that case, you're in trouble.

If you wrote logically, like
Richard, then i would respect you...but you don't. I don't care where
Richard went to school, he knows his sh**.

Because you think he agreed with you.

Anyway, you've satisfied my curiosity. Thank you. If the other
members of the newsgroup want to read and respond to your posts,
fine. Most of us, though, went through middle school once and don't
want to repeat the experience. Good luck with your job search.
73,
Tom Donaly, KA6RUH