"I have a relatively good hybrid coupler"

I, uh, have always used 'directional couplers'
to sample the RF in each direction in order
to test and characterizs devices.

Have you got some new technique that you plan to use
the hybrid in to do the same thing?

As to 'four ports' on a HP transmission/reflection
test unit -

- the old 8475A "S-Param Test Set" I employ has five RF
  'ports':

1) One RF input Type-N. This must actually deliver RF to both
   the 'Reference' input channel on the 8410B/8411A as well as
   RF to the 'test' channel through a suitable a RF 'splitter'.

2) Two ports (APC-7)to the 8410B/8411A harmonic converter
   (which is basically a two-channel amplitude and phase
    measuring 'receiver').
   These are outputs (I have to presume) are from directional
   couplers that a) sample the RF from an RF signal generator
   and also sample the RF on the 'test' channel as per the
   S parameter to be measured.

3) Two (APC-7) ports to the DUT for transmision (S21) and Refl (S11).
   Internal directional couplers in the 8475A do the 'magic' in
   sampling the RF to/through/reflected from the DUT and direct this
   RF to the 8410B/8411A's 'Test' channel.

I use I only deal with three ports - the RF input port and the
two APC-7 ports to the DUT. The 8410B/8411A harmonic converter
'bolts' into position in an area aboard the 8475A S-Parm Test
Set.

This is rather old gear today - but the basics are there!

Jim


----- Original Message -----
From: "Brendan Moran" <bmoran@MILLENNIUM.CA>
To: <PICLIST@MITVMA.MIT.EDU>
Sent: Friday, July 05, 2002 4:06 PM
Subject: [EE]: Directional couplers & T/R test sets


> Hi,
>
> I'm hoping that we've got a few RF engineers floating around that can help
> me out with this.  I'm a digital systems type person, myself, but I'm
> working in a place that needs me to do work on RF circuitry, so I'm a bit
> stuck.
>
> I have a relatively good hybrid coupler that was built as a power
splitter.
> It has -41dB isolation and -3.08dB ouput ports.
>
> I want to use it to measure scattering parameters of a preamplifier but I
> don't know how to connect it.  I know that the HP transmission/reflection
> test set, which I am trying to emulate with this device, is a 4-port unit,
> and that 2 of the ports go to a network analyser input, 1 port that get RF
> in, and 1 port that goes to the DUT.  I do not, however know what the 2
> ports that go to the inputs are.
>
> My directional coupler has the following ports: In, 50ohms, 0 degrees and
90
> degrees.  What ports do I connect to the network analyser?
>
> I assume that the IN port gets the RF out from the network analyser, and
> that the 50-ohm port goes to one of the inputs (but don't know which one),
> but I don't know whether the 90-deg or the 0-deg port goes to the DUT.
>
> Anyone done this before?
>
> --Brendan
>
> --
> http://www.piclist.com hint: To leave the PICList
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>
>

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