Testing mmWave devices require significant innovations, both in test equipment’s and test techniques: David Hall

An interview with David Hall, Head of Semiconductor Marketing, National Instruments. He shares his insights on Testing challenges associated with mmWave, Beamforming at mmWave its characterization and Verification and research area for 5G Testing.

What are the major challenges that must be contended with while deploying 5G using mmWave and other available solutions?

5G deployments in Frequency Range 2 (FR2) – or 24 to 40 GHz – pose considerable technical challenges compared to sub-6 GHz or FR1 deployments.  From the chip-level all the way to the network level, both the circuit-level and over-the-air behavior of signals at mmWave frequencies is quite different than lower frequencies.  For example, must consider that mmWave components like power amplifiers and transceivers historically did not face the efficiency, footprint, bandwidth or even linearity requirements necessary for mobile devices.

Of course, one of the most pronounced system-level challenges of deploying mmWave systems is signal propagation.  Although technologies like beamforming can improve receive signal strength for mobile devices – it primarily addresses concerns scenarios where there is a direct line of sight between the base station and the mobile devices.

Another major challenge to 5G mmWave deployments is manufacturing and testing these devices while keeping costs down.  The market demands for mmWave systems in mobile handsets could be an order of magnitude greater than current demands for 4G devices. The industry is desperately looking for cost-effective solutions that can help them test a large number of highly integrated, very complex mmWave devices, such as antenna-in-package (AiP), in less time.

What challenges does Millimeter wave Testing face in the consumer space?

Testing mmWave devices requires significant innovations both in the test equipment itself and in the test techniques engineers typically use.  Take production test as an example.  Traditional mmWave test equipment designed primarily for aerospace/defense applications like radar and satellite communications testing are not aligned with the price point, performance, and footprint required for massive commercial technologies like 5G.  In the consumer space, test equipment necessary for 5G mmWave components requires wider instantaneous bandwidth, higher dynamic range, and faster measurement speed than these traditional solutions delivered.  This is one of the driving factors for NI to address mmWave testing with a more speed-optimized and modular approach.

What makes 5G Beamforming more critical compared to 4G? What is its importance?

Beamforming is critical at mmWave because of the signal propagation characteristics at these frequencies.  Using a combination of both analog and digital beamforming techniques, base stations are able to deliver downlink signals to an end user at a higher receive strength, and user equipment can focus their beams right toward the base station, operating more efficiently.  The use of beamforming ultimately extends the range of operation and improve data rates through the use of higher-order modulation schemes and lower bit-error rates.

What is beamforming characterization and beamforming verification testing? How does it work?

Characterizing the beamforming capability of a mmWave radio requires over-the-air (OTA) testing.  In a typical test setup, the radio is placed on 3D gimbal within an anechoic chamber.  With an RF signal analyzer connected to a static receive antenna within the chamber, the radio is then configured to transmit an uplink signal at a specific beam pattern.  In order to characterize this beam pattern, the RF signal analyzer makes a series of RF power measurements while rotating the device under test.

As a result of scanning the device across azimuth and elevation angles, the engineer can then obtain a 3D antenna pattern for the device under test.  Note that one of the historical limitations of characterizing beamforming devices in this matter was the time required synchronize the RF signal analyzer with the movement of the DUT positioner.  One of NI’s recent innovations in beamforming test is to use the power of the PXI platform to more tightly synchronize these components for faster measurement results.

Please elaborate upon NI’s new offering for 5G New Radio test solution in sub-6GHz band.

For sub-6 GHz 5G devices, NI offers a comprehensive set of test solutions from the R&D lab to the production floor.  For validation test, NI’s vector signal transceiver (VST) offers up to 1 GHz of instantaneous bandwidth in order to test components such as RF front end modules (FEMs) and transceivers.  With wide bandwidth, engineers can even test RF FEMs under linearized conditions using NI’s software for digital predistortion (DPD).  In typical device characterization scenarios, the speed of NI’s solutions allows engineers to significantly reduce test time of engineering samples to improve time-to-market.

For production test, NI’s semiconductor test system (STS) offers industry leading measurement throughput and accuracy.  Using this system, engineers are able to conduct parallel testing of FEMs designed for both user equipment (UE) and base station applications.  With the measurement speed advantages of PXI, typical STS users are able to improve test throughput by 20% to 50% when using STS in place of traditional ATE systems.

What is the latest research being conducted by NI on 5G advanced communications systems? What are the services being offered?

One of the most significant areas of research on 5G testing is in the area of OTA testing.  Although lab-based OTA test systems have become fairly widespread – the current methodologies used in the lab environment do not scale to the cost and speed expectations of the manufacturing floor.  As a result, NI continues to investigate both near-field and far-field approaches to OTA testing in preparation for delivering OTA-based manufacturing test solutions in the future.

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