Wavenet Technology Pty Ltd. BM2900D Benutzerhandbuch
APPENDIX F – Guide to Desense ______________________________ Boomer II User Manual & Integrator’s Guide
Copyright Wavenet Technology © November 2003
134
BM210012WT37
Directly by using packet error rate testing off air.
Testing directly is preferred method because it is more of a system test.
The test must be non-intrusive. Peripheral test cables or apparatus must
not be connected to the unit under test, as they can have a significant
effect on the receiver sensitivity results.
Indirect testing is essentially FCC Part 15 EMI testing that occurs
today. Bear in mind that some assumptions have to be made to
extrapolate the results and convert them to desense figures. Of course,
these assumptions can create some error in the prediction.
The test must be non-intrusive. Peripheral test cables or apparatus must
not be connected to the unit under test, as they can have a significant
effect on the receiver sensitivity results.
Indirect testing is essentially FCC Part 15 EMI testing that occurs
today. Bear in mind that some assumptions have to be made to
extrapolate the results and convert them to desense figures. Of course,
these assumptions can create some error in the prediction.
Alternate Measurement Method
Wavenet can performed desense testing on an integrated host/terminal
using a special facility. The best alternate methods for determining the
desense is to measure the signal the receiver port sees by using a
spectrum analyser (see below).
using a special facility. The best alternate methods for determining the
desense is to measure the signal the receiver port sees by using a
spectrum analyser (see below).
Spectrum Analyser Setup
Using a spectrum analyser with an input impedance of 50 W, connect
the antenna of the product under test to the analyser. If an antenna is
currently not developed, use a portable dipole antenna as a
measurement antenna.
The measurement apparatus is capable of measuring signals as low as -
120dBm. A preamplifier is required to allow the spectrum analyser to
achieve these levels. Use the analyser’s smallest possible resolution
bandwidth, typically 1kHz, to improve the dynamic range of the
measurement.
If the input impedance of the analyser is the same as that of the radio
receiver, and the antenna, you can measure the noise to which the
receiver will be subjected. The gain on the LNA will make low-level
noise more visible. Ensure that the spectrum analyser’s input is not
over driven by other RF signals, such as FM radio stations. Any spikes
that appear might cause desense problems.
the antenna of the product under test to the analyser. If an antenna is
currently not developed, use a portable dipole antenna as a
measurement antenna.
The measurement apparatus is capable of measuring signals as low as -
120dBm. A preamplifier is required to allow the spectrum analyser to
achieve these levels. Use the analyser’s smallest possible resolution
bandwidth, typically 1kHz, to improve the dynamic range of the
measurement.
If the input impedance of the analyser is the same as that of the radio
receiver, and the antenna, you can measure the noise to which the
receiver will be subjected. The gain on the LNA will make low-level
noise more visible. Ensure that the spectrum analyser’s input is not
over driven by other RF signals, such as FM radio stations. Any spikes
that appear might cause desense problems.
Measurement Antenna
Unit under Test
LNA
(Minicircuits ZFL-1000GH)
Coaxial connection to
measurement antenna
measurement antenna
Spectrum
Analyser
Analyser