With incredibly fast speed and on-the-spot connections, 5G has dominated the technology news. It is soon going to change the pattern of how we live, work, communicate, and even play. 5G’s high-bandwidth and real-time capabilities offer massive opportunities by enabling many new and unexpected use cases, such as virtual and augmented reality, autonomous driving, and the Industrial Internet of Things (IIoT). We are all getting more and more excited about the possibility of extremely fast 5G data rates, letting us stream higher quality videos and download much larger files, faster. With a speed of 20 gigabits per second, we could easily download an Ultra HD movie in about 10 seconds, that’s 20 times faster than what we are capable to do now!
Making this happen in practice though, requires high frequency bands, exceeding the current low- and mid-band spectrum of 6 GHz and below, and taking it to a whole new level in Millimeter Waves (mmWave), where we can exploit hundreds of MHz of spectrum available, beyond 24 GHz. The main attraction of mmWave spectrum is its large bandwidth, which enables delivering multi-gigabit wireless services, to meet the growing demand for high speed data in the 5G world.
5G New Radio (NR) is the standard developed by the 3GPP for the fifth generation mobile networks, and is designed to be the global standard for the air interface of 5G networks. The 5G NR initial Release 15, focuses on Enhanced Mobile Broadband (eMBB) and Ultra-Reliable, Low-Latency Communications (URLLC), which result in high speed data rates and very low latency wireless communications. These specifications introduce new challenges for device and component designers, and impose the need to validate test protocols, and verify RF performance to deliver the expected quality of service.
The use of mmWave frequencies pose new challenges in signal quality, such as signal impairments. These impairments specifically at higher frequencies or with wider bandwidths, can impact the performance of your designs. One of the key indicators to characterize your transmitter performance is a numeric Error Vector Magnitude (EVM) measurement that provides an overall indication of your signal quality. To accurately characterize your signal quality without introducing new issues, you need a residual EVM floor of a test solution that is better than your Device Under Test (DUT). A low signal-to-noise ratio leads to poor EVM measurements, which in turn prevents you from truly understanding the performance of your DUT. And remember, this challenge is not going away anytime soon. Cellular technology continues to evolve. After mmWave, the industry will likely move to sub-THz frequencies with 6G.
Figure 1. Visualizes the EVM calculation
mmWave signals are also subject to signal propagation issues, which include increased path loss, delay spread, or even blockage. Over-the-Air (OTA) testing is a method used to predict the performance and reliability of a wireless device in the real world. It measures the entire signal path and antenna performance to ensure that the designed devices will perform the way they are intended to. OTA tests are typically carried out in either the near-field or far-field regions of the antenna array, and depending on the distance from the transmitter, the characteristics of the transmitted electromagnetic wave change. 5G cellular communication links typically require using far-field regions, in which the signals become more developed as they propagate from the antenna array, and the associated path loss grows bigger with the frequency. For example, an over-the-air path loss of 28 dB for a 4G LTE device operating at 2 GHz, would be 73 dB for a 5G NR device operating at 28 GHz. Therefore, the mmWave higher frequency means greater path loss and a lower signal-to-noise ratio, which is in direct conflict with the need for greater precision driven by more complex wireless systems.
Figure 2. Beam properties at different distances from the antenna array
Keysight’s latest X-Series signal analyzer, N9042B UXA, is the most powerful industry’s signal analyzer, designed to tackle your mmWave 5G NR test challenges. It covers frequencies up to 110 GHz, which can further be extended to 1.5 THz with an external converter, so you are covered even for 6G research. This analyzer delivers outstanding noise performance by leveraging a highly customized signal path front end. It provides the best Displayed Average Nosie Level (DANL) in the industry, down to -174 dBm at 1 GHz, and superior dynamic range for the most precise measurements. Therefore, you will be able to see small signals near noise and in the presence of large signals. For a 5G NR application at a frequency of 48 GHz with 100 MHz of bandwidth, N9042B is able to measure 50% better residual EVM than comparable instruments in the market.
The real kicker though is not the hardware, it’s the software. We have software for all your 5G measurement needs including 5G modulation analysis and 5G NR transmitter measurements for both release 15 and the latest release, release 16. The PathWave software is the heart of your signal analyzer. PathWave X-Series measurement applications address ever-changing measurement requirements for the latest standards with ready-to-use cellular communication measurements. The 89600 PathWave VSA software is a comprehensive set of tools for demodulation and vector signal analysis. With support for more than 75 signal standards and modulation types, these tools enable you to explore virtually every facet of a signal and optimize your most advanced designs. As these softwares span your workflow, you will spend less time on your measurement setup and will deliver more repeatable results.
Figure 3. N9042B X-Series signal analyzer, hardware and software
