Transmission line vswr with unmathced generator
 

Hi everybody, I am troubled with transmission line vswr, I hope this is
the right place to ask this question. Is the sr formula same with
unmatched generator? I mean I know that

SWR = ( 1 + |Gamma_Load| ) / ( 1 - |Gamma_Load| )

Gamma_Load is reflection coefficient at load side.

But I think there is a problem with this formula when generator is
unmatched to the transmission line so that there is also a reflection
at generator side. Is that correct or am i making a mistake somewhere?
Thanx in advance.
Arif.

On 3 Jan 2005 20:31:57 -0800, "ozgun.harmanci"
wrote in
.com:

Hi everybody, I am troubled with transmission line vswr, I hope this is
the right place to ask this question. Is the sr formula same with
unmatched generator? I mean I know that

SWR = ( 1 + |Gamma_Load| ) / ( 1 - |Gamma_Load| )

Gamma_Load is reflection coefficient at load side.

But I think there is a problem with this formula when generator is
unmatched to the transmission line so that there is also a reflection
at generator side. Is that correct or am i making a mistake somewhere?
Thanx in advance.
Arif.


You are correct. There can be more than one mismatch in a system.
Group your system components so you have only two parts:

Effective Source (generator + transmission line)
Effective Load (load)

Then regroup the system again:

Effective Source (generator)
Effective Load (transmission line + load)

The number of possible mismatches depends on the number of components
in the system. For example, if your system has five components you can
have four possible mismatches.

Does that help?

"ozgun.harmanci" wrote in message
oups.com...
Hi everybody, I am troubled with transmission line vswr, I hope this is
the right place to ask this question. Is the sr formula same with
unmatched generator? I mean I know that

SWR = ( 1 + |Gamma_Load| ) / ( 1 - |Gamma_Load| )

Gamma_Load is reflection coefficient at load side.

But I think there is a problem with this formula when generator is
unmatched to the transmission line so that there is also a reflection
at generator side. Is that correct or am i making a mistake somewhere?

Why would the generator be "unmatched" in your case is the first question to
ask. However to answer your question I would say no. The logic proceeds as
follows.

Another common formula for calculating SWR is based on measuring the forward
and reflected power from the load.

SWR=(1+sqrt(Pref/Rfwd))/(1-sqrt(Pref/Pfwd))

In the case of a matched generator there is no power reflected from it. In
the mismatched case power is reflected and simply adds to the forward power
from the generator towards the miss matched load. Since the generator is now
miss matched it does not put out full power, it can't by definition of a
conjugally matched generator which can only put out max power in to a
matched load. This extra power is partly absorbed by the load and some is
reflected back toward the generator where it is again reflected back towards
the load. At some point this process of reflections and re-reflections
settles out to a steady state.

http://home.iag.net/~w2du1/Appendix%207.pdf

Look at examples A, B and C diagrams.
http://home.iag.net/~w2du1/Appendix%206.pdf

http://home.iag.net/~w2du1/Chapter%2023.pdf

The power absorbed by the load and what is reflected back is only a function
of the load miss match. The generator miss match only alters the forward
power. The load miss match controls the reflected power towards the
generator, which is always a fixed fraction of the forward power whatever it
maybe. Thus I would say the SWR is not dependent on the generator miss match
to the line, but can the generator miss match can affect the measured
forward power seen on the line. Also when you're measuring the miss match on
the line you are generaly interested in the "load miss match" which as I
stated above is stricly a function of the forward power sent to the load,
and the power reflected from it back towards the generator.


--
Leland C. Scott
KC8LDO

Wireless Network
Mobile computing
on the go brought
to you by Micro$oft



Thanx in advance.
Arif.

"ozgun.harmanci" wrote in message
oups.com...
Hi everybody, I am troubled with transmission line vswr, I hope this is
the right place to ask this question. Is the sr formula same with
unmatched generator? I mean I know that

SWR = ( 1 + |Gamma_Load| ) / ( 1 - |Gamma_Load| )

Gamma_Load is reflection coefficient at load side.

But I think there is a problem with this formula when generator is
unmatched to the transmission line so that there is also a reflection
at generator side. Is that correct or am i making a mistake somewhere?
Thanx in advance.
Arif.

You may have something there for the first few microseconds of the
transmission but after a quiescent state is reached all that matters is the
impedance of the line and the load. It has been argued if not settled that
power sent back to the generator is not reflected again but either adds or
subtracts from the generator power.

Testicles.. I only want testicles. LickingMyFreakinAssOrally

"Leland C. Scott" wrote in message
...

"ozgun.harmanci" wrote in message
oups.com...
Hi everybody, I am troubled with transmission line vswr, I hope this is
the right place to ask this question. Is the sr formula same with
unmatched generator? I mean I know that

SWR = ( 1 + |Gamma_Load| ) / ( 1 - |Gamma_Load| )

Gamma_Load is reflection coefficient at load side.

But I think there is a problem with this formula when generator is
unmatched to the transmission line so that there is also a reflection
at generator side. Is that correct or am i making a mistake somewhere?

Why would the generator be "unmatched" in your case is the first question
to
ask. However to answer your question I would say no. The logic proceeds as
follows.

Another common formula for calculating SWR is based on measuring the
forward
and reflected power from the load.

SWR=(1+sqrt(Pref/Rfwd))/(1-sqrt(Pref/Pfwd))

In the case of a matched generator there is no power reflected from it. In
the mismatched case power is reflected and simply adds to the forward
power
from the generator towards the miss matched load. Since the generator is
now
miss matched it does not put out full power, it can't by definition of a
conjugally matched generator which can only put out max power in to a
matched load. This extra power is partly absorbed by the load and some is
reflected back toward the generator where it is again reflected back
towards
the load. At some point this process of reflections and re-reflections
settles out to a steady state.

http://home.iag.net/~w2du1/Appendix%207.pdf

Look at examples A, B and C diagrams.
http://home.iag.net/~w2du1/Appendix%206.pdf

http://home.iag.net/~w2du1/Chapter%2023.pdf

The power absorbed by the load and what is reflected back is only a
function
of the load miss match. The generator miss match only alters the forward
power. The load miss match controls the reflected power towards the
generator, which is always a fixed fraction of the forward power whatever
it
maybe. Thus I would say the SWR is not dependent on the generator miss
match
to the line, but can the generator miss match can affect the measured
forward power seen on the line. Also when you're measuring the miss match
on
the line you are generaly interested in the "load miss match" which as I
stated above is stricly a function of the forward power sent to the load,
and the power reflected from it back towards the generator.


--
Leland C. Scott
KC8LDO

Wireless Network
Mobile computing
on the go brought
to you by Micro$oft



Thanx in advance.
Arif.