Cellular technology shifts create new test demands and considerations, such as number and variety of frequencies, bandwidths and test performance requirements.

Global Spectrum Requirements

To accommodate global spectrum requirements, the 5G NR standard specifies two frequency ranges: sub-7GHz (FR1) and mmWave (also referred to as FR2). This means 5G devices and test instrumentation need to support one or both frequency ranges. The use of mmWave frequencies poses challenges related to path loss and signal propagation. At these higher frequencies, the excess path loss between instruments and devices under test (DUTs) is very high. Therefore, test engineers need to move the test plane closer to the DUT, shortening the path that signals at mmWave frequencies need to travel.

Wider Channel Bandwidths

The 5G NR maximum channel bandwidth for FR2 has been defined as 400 MHz. By using carrier aggregation (CA), it is possible to achieve up to 1200 MHz of aggregated channel bandwidth. To characterize the non-linear performance of power amplifiers (PAs) using advanced measurements, such as digital pre-distortion (DPD) techniques for RF, test engineers require signal generation and analysis test systems that support up to three times the channel bandwidth.

Test Performance Requirements

At mmWave frequencies, the components are compact and highly integrated with no place to probe test signals, resulting in the need for radiated tests, also known as over-the-air (OTA) tests. The excessive path loss between instruments and DUTs results in a lower signal-to-noise ratio (SNR) making accurate measurements challenging. Also, wider signal bandwidths introduce more broadband noise, which lowers the SNR. The low SNR causes the transmitter measurements to deliver insufficient error vector magnitude (EVM) and adjacent channel power ratio (ACPR) performance, mis-representing the true performance of the DUT. Wideband noise and phase noise at mmWave frequencies degrade modulation quality for signal generation.

To overcome these challenges at higher frequency bands and wider bandwidths, high-performance signal generators and signal analyzers are essential to ensure errors are not generated by the test instruments. The test system integration and test costs create higher barriers from R&D to volume production.

In summary, technology shifts and test requirements introduce challenges that can only be addressed using test instruments that deliver enhanced performance and capability.