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Wavenet Technology BM3-800D User Manual
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APPENDIX F – Guide to Desense _____________________________ Boomer-III User Manual & Integrator’s GuideCopyright Wavenet Technology © October 2003 134 BM310012WT04 Indirectly by recording the emission level from thehost/terminal and then calculating the effect on the modem. 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 mustnot be connected to the unit under test, as they can have a significanteffect on the receiver sensitivity results.Indirect testing is essentially FCC Part 15 EMI testing that occurstoday. Bear in mind that some assumptions have to be made toextrapolate the results and convert them to desense figures. Of course,these assumptions can create some error in the prediction.Alternate Measurement MethodWavenet can performed desense testing on an integrated host/terminalusing a special facility. The best alternate methods for determining thedesense is to measure the signal the receiver port sees by using aspectrum analyser (see below).Spectrum Analyser SetupUsing a spectrum analyser with an input impedance of 50 W, connectthe antenna of the product under test to the analyser. If an antenna iscurrently not developed, use a portable dipole antenna as ameasurement antenna.The measurement apparatus is capable of measuring signals as low as -120dBm. A preamplifier is required to allow the spectrum analyser toachieve these levels. Use the analyser’s smallest possible resolutionbandwidth, typically 1kHz, to improve the dynamic range of themeasurement.If the input impedance of the analyser is the same as that of the radioreceiver, and the antenna, you can measure the noise to which thereceiver will be subjected. The gain on the LNA will make low-levelnoise more visible. Ensure that the spectrum analyser’s input is notMeasurement AntennaUnit under TestLNA(Minicircuits ZFL-1000GH)Coaxial connection tomeasurement antennaSpectrumAnalyser |
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