Hi Folks!
I have been wrestling with a project for a while at frequencies from 1
to 10 GHz. One of our clients is doing tests in this range at field
levels of 10V/m, and using the field uniformity restrictions of
1000-4-3. That is, using a planar grid, and showing uniformity of
-0,+6dB.
We are not using enough power to do the uniformity over the 1.5x1.5m
grid, but that is acceptable to the client. (We just do multiple antenna
positions.) The real problem is repeatability. Here are some of the
stated requirements from the client:
- uniformity -0,+6dB over the specified area
- second and third harmonic of the test frequency at least 20db below
the fundamental
- repeatability of +/-0.5 V/m (not dB) - this has to be demonstrated
before each test (4-6 weeks apart)
(repeatability meaning that using a pre-defined, pre-calibrated
generator output, the field
level at each position on the measurement grid is +/-0.5 V/m)
The test chamber is 16'x24'x13'h and is lined with a hybrid absorber.
(i.e.- ferrite tile, as well as 18" carbon loaded cones) We have paid
close attention to positioning of the measurement grid, the transmit
antenna, the cables, etc. We level on the output power. But..... we
can't get to this ideal of 0.5V/m.
Has anyone out there been able to demonstrate this kind of repeatability
above 1GHz? Has anyone even been ASKED to attempt to follow these
guidelines??!! I welcome any input that will either help me resolve the
difficulty, or demonstrate that it is out of the range of possibility!
Thanks in advance for any advice.
Bob Martin, P.E, N.C.E.
Sr. Technical Manager
ITS- NEBU
(978)263-2662
[email protected]
The views expressed are my own, and not necessarily those of my
employer.
