Interference Testing with Handheld Spectrum Analyzers Manual

Interference Testing with Handheld Spectrum Analyzers Manual
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Interference Testing with Handheld Spectrum Analyzers Manual

  • 20Once it has been reported that the system is not operating as expected and it is assumed that the root cause of the problem is interference entering the receiver of the system, a spectrum analyzer should be used to confirm the existence of wireless signals in the frequency channel of operation.The discovery process may involve uncovering the type of signal including dura-tion of transmission, number of occurrences, carrier frequency and bandwidth, and lastly the physical location of the interfering transmitter.If the system operates in full-duplex mode, then it may be necessary to examine both the forward and reverse link frequency channels for signs of interference. For the spectrum analyzer to measure the same signals and interference that the system receiver is capturing, the spectrum analyzer should be connected into the receive path or directly to the system antenna.Figure 13A shows a block diagram of a wireless system with the spectrum analyzer connected to a directional coupler placed between the antenna and the transceiver. Many wireless systems, including cellular base stations and radar stations, will have directional couplers installed along the cables connecting the transceiver to the system antenna. As shown in Figure 13A, some directional couplers will have two sample points for monitoring the signals coming from the transmitter or arriving to the receiver. After the spectrum analyzer is connected to the coupler, the signals and interference can be observed during normal system operation.Figure 13. Spectrum analyzer configurations for measuring wireless interference with (A) using a directional coupler and (B) direct connection to the antennaInterference Measurement ProcedureInterference measurement procedureBelow is a list of steps that can be used to determine the existence and location of an interfering signal. 1. Report that a reduction in the system performance is observed2. Confirm the existence of wireless interference using a spectrum analyzer3. Determine the type of inter-ference by knowing about other wireless signals in the environment4. Determine the location of the interference using a spectrum analyzer with a directional antenna5. Correct or remove the source of interferenceSystem antennaDirectional couplerReceive monitorN9342C HSAN9342C HSATransmit monitorSystem or external antenna(A)(B)Radio transceiver