Keeping ahead of the interference challenges: Page 2 of 5

September 06, 2016 //By Dean Miles, Tektronix
In our highly wireless world, interference is an unwelcome addition to the equation that results in noise, interrupts cell phone calls and just generally messes up communication. In the case of cellular networks, interference is actually part of the network. While more networks today have built-in features to detect interference, these tools often lack context as they are geared towards only a few types of signals and may only be able to measure the impact of the problem over a single channel.

Real-time spectrum analyzers address this shortcoming by being able to measure the spectrum with a narrower RBW filter, faster than basic sweeping spectrum analyzers. Figure 1 shows an example of what a LTE signal looks like OTA. In this case the span is set to 40 MHz, which results in a default RBW of 300 kHz. Note that determining the emission in the center of the display is quite difficult. If there was a narrow-band (< 300 kHz) interferer it would be almost impossible to see it with this setup.

Figure 1: This is an example of how an LTE signal looks OTA.

Figure 2 shows the same setup using a 1 kHz RBW filter. In this case, it’s clear that the LTE channel and the effective sweep time has only increased to 40 ms. This is one of the first benefits of using a real-time spectrum analyzer (RTSA) to measure interference on the radio channel. Once expensive and desk-bound, a new class of affordable, battery-powered, USB-based real-time spectrum analyzers are now becoming available on the market, making RTSA a practical choice for interference-hunting applications.

Figure 2: A real-time spectrum analyzer with a 1 kHz RBW filter improves visibility on a LTE signal.

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