Interference Hunting –– APPLICATION NOTE
APPLICATION NOTE Interference Hunting Introduction The Interference of Things Over the past decade there has been a dramatic increase in One of the drawbacks of having so many electronic devices in the population of wireless transmitters found in the world, our world is that they all emit electronic signals which causes with the inevitable result being a dramatic increase in radio- the disruption of radio and wireless signals. The “noise” frequency noise pollution.
APPLICATION NOTE Interference Hunting Understanding interference performance. It usually means that a signal is impacting your Type and Source of Intermodulation Interference system or device causing a coverage issue, a reception issue, For anyone in spectrum management, sooner or later you or an access issue. To put it simply, interference is associated will need to track down an intermodulation product that is with unwanted energy at the wrong place and at the wrong causing interference.
APPLICATION NOTE Interference Hunting In looking at interference, it helps to understand how receivers filter out unwanted signals. As shown in Figure 1, the received or assigned channel is in blue. Interference can occur when there is energy inside the preselector of the victim receiver. This means if there is any energy falling under the preselector passband it could impact the performance of the receiver, by blocking the receiver directly or through a form of desensitization.
APPLICATION NOTE Interference Hunting When analyzing interference problems, the RBW control is very important. The RBW filter helps us discriminate signals in the spectrum display so that we can determine individual sources of RF energy within the span we are monitoring. Figure 2 illustrates why the RBW setting is so important. If RBW is too wide, as it is on the left side, the spectrum analyzer is going to miss smaller signals that might be close to a larger signal.
APPLICATION NOTE Interference Hunting Deeper Signal Insight The Real Time Difference As discussed in the previous section, the sweeping nature of Figure 5 shows the Digital Phosphor Spectrum (DPX) display. traditional spectrum analyzers limits the POI when analyzing Like a classic spectrum analyzer, it shows frequency vs. short duration signals. This problem is particularly acute when amplitude information. In addition, the pixels in the display we need to make “Over The Air” (OTA) measurements.
APPLICATION NOTE Interference Hunting The spectrogram measurement is designed to address this type of problem. Like the spectrum display it will show low frequency on the left-hand side, and higher frequencies on the right-hand side. Unlike a basic spectrum display, color is used to represent amplitude, and all of this information is plotted versus time on the y-axis. The spectrogram is effectively a strip chart recorder showing the spectrum activity over time.
APPLICATION NOTE Interference Hunting The challenge for most systems that employ some form of mask testing is actually creating the mask itself. SignalVuPC takes care of this by providing a means of automatically creating the mask based on the trace the user defines. Essentially you can create a “golden signal” and use this as a template for SignalVu-PC to create the mask condition. In the figure below, a mask violation has occurred in red on the mask, and a picture of the screen was saved as a result.
APPLICATION NOTE Interference Hunting CASE STUDY: WIMAX NETWORK INTERFERENCE CASE STUDY: TRUNK LMR INTERFERENCE In this example of interstitial channel interference, two WiMAX A trunked land mobile radio (LMR) system is a complex type of operators were running into problems trying to the get the computer-controlled two-way radio system that allows sharing maximum performance out of their spectrum by utilizing of relatively few radio frequency channels among a large group channels on the edge of th
Summary Radio noise is everywhere, and the problem is only getting worse with the explosion of electronic and wireless-enabled devices. The coming IoT is certain to lead to the “interference of things.
