Technical Insights > RF + Microwave

I’ve Got the Power! Does Your Field Communications System Have It Too?

2020-02-03  |  4 min read 

What happens when your communications system isn’t outputting enough power? What about too much power? Verifying the power levels of your systems in the field is crucial for performance and compliance. If power is too low, you risk noise obscuring your signal, subsequently affecting components or systems later in the signal chain. If power is too high, it causes distortion, component damage, and outages. In addition to performance and compliance verification, power level measurements give you insight into unknown signals that may be threatening your system. This blog discusses two important power measurements you should be able to make with the tools in your field kit: channel power and adjacent channel power.

Channel Power (CHP)

Modern communications depend on digital modulations at very high data rates and other spread-spectrum formats. To find the power of a spread-spectrum, modulated signal, you find the average (or the area under the curve). You can do this manually, but for obvious reasons, it’s easier to perform this measurement on a spectrum analyzer.

The CHP measurement on a spectrum analyzer measures the total average power present in the channel bandwidth of your DUT. All you have to do is input the center frequency and the integration bandwidth. See Figure 1 for an example CHP measurement made on Keysight’s FieldFox handheld analyzer.

Figure 1. A CHP measurement made using FieldFox’s Spectrum Analyzer mode

Performing a CHP measurement is the simplest way to quickly verify the output and performance of your system. Sometimes, however, it doesn’t give you the full story behind your signal.

Adjacent Channel Power (ACP)

In addition to measuring the total average power of your system, it is useful to verify how your signal affects neighboring frequency channels. An ACP measurement on a spectrum analyzer tells you the relative power of the main channel in addition to three or more adjacent channels above and below the main channel. These results can be displayed in either the frequency spectrum or in an easy-to-read bar chart. Figure 2 depicts this type of measurement using FieldFox.

Figure 2. An ACP measurement made using FieldFox’s Spectrum Analyzer mode and displayed in a bar chart

ACP measurements play an important role in verifying power leakage into adjacent channels. Strict regulatory requirements limit power leakage, especially in industries involving wireless and broadcast communications. ACP measurements help to ensure companies meet compliance.

Conclusion

If your field kit can perform both CHP and ACP measurements, then you’re halfway there. To learn about two other equally important power measurements to make in the field — occupied bandwidth and spectrum emission mask — read this white paper.

Once you verify that your system meets power performance and compliance specs, you’ll be singing, “I’ve Got the Power,” too.

Keysight’s FieldFox functions as a spectrum analyzer in addition to a network analyzer, cable and antenna tester, power meter, and more. It performs 5G over-the-air (OTA) measurements and captures elusive interference signals with real-time spectrum analysis (RTSA). Find out more about FieldFox here.