430 Tx waveguide measurements


General info:

16jan12: Waveguide measurements

Setup: (top)

    The network analyzer was attached to a waveguide transition where the waveguide exits the transmitter building. The network analyzer measures the reflection coef at each frequency channel (VoltTransmitted/Voltage Received). A reflection at a particular distance will cause a ripple in the spectra. Transforming the spectrum to the time domain will then give the distance for this ripple.
 Measurements were done with the following setups:

Assumptions made when correcting the data:

Dedispering the data. (top)

    When measuring reflections (S11) in the waveguide (w2100) we want a large bandwidth to give us high time (distance) resolution.  Since the group velocity in the waveguide is a function of the frequency, each frequency channel will arrive back from a reflection point at a slightly different time. This will smear out the distance measurements. To correct for the smearing we can try to dedisperse the data returned by the network analyzer.

    The plots show an attempt to dedisperse the data with the short at the end of the waveguide (.ps) (.pdf):

Summary dedispersion:

Processing: x101/tx430/wgmeas/120116/cmpdedisp.pro

Checking Vgrp, correcting for waveguide loss.  (top)

    The plots check the group velocity and compute how much loss we have in the transmission system (.ps) (.pdf):


processing: x101/tx430/wgmeas/120116/wgcal.pro

CH data results with short on waveguide  (top)

    The data was calibrated using the above procedure.
The plots show the data results with the short on the Ch waveguide (.ps) (.pdf):
processing: x101/tx430/wgmeas/120116/plotshort.pro

CH data results with waveguide connected to the antenna. (top)

    The data was calibrated using the same values as the short data.
The plots show the data results with the  Ch waveguide connected to the antenna (.ps) (.pdf):

Summary: (top)

Theoretical dbloss/100feet
w2100 waveguide
oneWay:  .054 to .034 db per 100 feet for (350 to 530 MHz).
twoWay:  .108 to .068 db/100 feet
measured dbloss/100feet
(assumes all loss in waveguide)
oneWay:   .081 db/100 feet
twoWay:  .162  db/100 feet
Group Velocity
Radius wg
420.08 feet
reflected power loss
40% (two way).
(resolution 9.3Ft)
distance (feet)
110 feet
end of bend where waveguide starts up the cliff
at the bend going up the hill from the tunnel.
using hagens waveguide distances this bend is at 110 feet.
196 feet
first bend at top of cliff.
start of last flex section before bend and run up the catwalk.
Start of straight run up the catwalk.

the 6th flex section after start of straight catwalk run.
1124 feet
end of catwalk straight run.
1250 feet
start of rotary joint
1294 feet
hagens start of slotted waveguide. No longer true since doesn't include power splitter.
.5 to 1.3%
 ampl changed with za
maybe start of lotted waveguide (or the power splitter?)
short za=0

short za=5

short za=10

short za=15

short za=19.6

Cumulative reflected power at short
about 75%
reflection short back to 111 feet and back up
about 5%  of power

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