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New Measures Tackle LTE Radiated Emissions

paulWhytock168x144Wireless designers consistently face the daunting task of dealing with a product’s level of radiated emissions and how these emissions interfere with other electronics systems in the vicinity. No doubt then that accurately measuring such emissions becomes a critical design objective.

German instrument manufacturer Rohde & Schwarz (R&S) says the conventional approach to measuring radiated spurious emissions (RSE) involves filtering out high-level wireless communications signals. However, when it comes to the LTE standard and its 258 combinations of frequency bandwidths, this turns into a very expensive and time-consuming process.

R&S took a radical approach to address the problem, one that makes it easier for users to measure RSE in the presence of LTE carrier power. Its solution—the R&S OSP open switch and control platform equipped with the new R&S OSP-B155 option—costs the same as a conventional test setup with notch filter, according to the company.

Standardisation institutes such as the ITU or the European R&TTE define tests for measuring RSE on wireless devices. With conventional wireless communications techniques, the high-level radio signal can be filtered out to enable RSE measurements. LTE, though, defines 43 frequency bands and can transmit—at full power—in six bandwidths in each band.

As a result, to filter out all LTE signals present in each band and bandwidth, a separate cabinet must be available to accommodate the 258 filters needed to cover all frequency-bandwidth combinations.

The R&S solution requires only two height units in the control cabinet. The R&S OSP-B155 plug-in module shifts the entire received signal spectrum into the optimum power range, enabling full use of the dynamic range of the connected EMI test receiver. The receiver can analyse the entire LTE signal spectrum without requiring a notch filter.

When using this technique, high receiver sensitivity is essential to obtain accurate measurements. Only a high-performance EMI test receiver can detect all spurious emissions. The test receiver also must also have high dynamic range to prevent peak levels of the transmitted wireless signals from distorting measurement results.

To that end, the R&S ESU EMI test receiver features sensitivity of typically -155dBm/Hz. And dynamic range measures 80dB in the relevant frequency range.

The OSP-B155 option fits into two slots on the OSP. It’s designed for use with the ESU test receiver and the company’s EMC32 EMC measurement software. Combined with its CMW500 wideband radio communication tester, which provides LTE signaling, the new R&S measurement solution also seamlessly integrates into existing applications and systems.

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