Operating the R&S
QAR
R&S
®
QAR
36
User Manual 1178.7200.02 ─ 04
Normalizing the transmission measurement
Normalizing the transmission measurement is done by a free-space measurement and
requires no additional devices. However, make sure that the line of sight between
R&S
QAR and transmitter module is free of obstacles.
1. Select the "Normalize Transmission" button to initiate the measurement.
When the normalization measurement is done, the R&S
QAR saves the correction
data. All subsequent measurements are corrected accordingly.
2. Optional: scan the free space with the "Measure" button to verify the normalization.
A valid normalization results in a straight trace at approximately 0
dB attenuation.
The trace should not exceed a certain deviation from that value - refer to the data-
sheet for exact values.
If the results do not meet the expectations, repeat the normalization.
If the second normalization still yields unexpected results, verify the test setup. For
details about the verification procedure, see
5.1.3.2
Reflection Measurement
The reflection measurement determines the amount of energy that is being reflected by
the DUT. This energy does not pass through the radome and contributes to perform-
ance degradation as a result. Reflected signals reduce the performance of the radar
and can even interfere with the received signals, leading to effects as described in
application note
. Areas with a high reflectivity can have various causes, for
example material defects, undesired interaction between several layers of materials,
excessive amount of certain materials, or foreign objects.
The R&S
QAR achieves spatially resolved reflection measurements of a DUT by link-
ing the information collected by the distributed transmit and receive antennas in a
coherent operation. The resulting millimeter wave image allows for an intuitive evalua-
tion of the DUTs reflection behavior.
Measurement results
The application shows the results of the spatially resolved reflection measurement as a
millimeter wave image with a linear scale from 10
% to 100
%. The x- and y-axis show
the dimensions of the image in mm (300
mm x 300
mm by default). The image is a
grayscale image. Small values, represented by dark areas, correspond to a low reflec-
tion, high values, represented by bright areas, correspond to a high reflection.
In addition to the image, the mean reflection and the standard deviation of the reflec-
tion are calculated as numeric results. Both values are shown under the millimeter
wave image in logarithmic units (dB) and as a percentage, with 100
% representing a
maximum reflection of 0
dB.
The application calculates the numeric results over a certain area of the complete milli-
meter wave image. The evaluation area is indicated by a mask that is superimposed
on the image. You can customize the size and form of this mask to analyze certain
Radome Measurements
