Millimeter-Wave Arrays for 5G Applications

5G is here and brings with it the promise of much higher data rates, lower latency, and increased network capacity. 5G systems are occupying a large portion of the available sub-6 GHz spectrum previously and currently used for 4G connectivity. One of the new aspects of 5G is that millimeter-wave capability is now available for broad commercial use. Along with the use of millimeter-wave spectrum comes the requirement to develop capable and cost-effective radio architectures that can be implemented in commercial products. These radio systems will require beam-steering arrays, capable of scanning over wide angular regions.

The Benefits and Issues Associated with 5G Millimeter-Wave Applications

Due to increases in bandwidth of available spectrum, improvements in modulation schemes, and increases in MIMO antenna order, 5G systems can provide higher data rates, increased network capacity, lower latency, and a lower cost per bit of data compared to 4G systems. A 5G system can provide “fiber-like” data rates without the need for a cabled connection, which translates into much higher data rates for mobile applications. As with the previous transitions from 2G to 3G or 3G to 4G, 5G is now providing the substantial improvements expected as cellular systems make the transition from 4G. Sub-6 GHz spectrum is being re-purposed along with bringing up the millimeter-wave spectrum.

As expected when bringing to market a commercialized millimeter-wave communication system capability, there are many challenges. A range decrease occurs as the frequency of propagation is increased, which results in the need for higher gains at millimeter-waves compared to sub-6 GHz frequencies. Figure 1 shows plots of path loss and aperture gain as a function of frequency, highlighting the need for higher gain at millimeter-wave frequencies. The need for a high gain steered antenna beam suggests the need for phase shifters in the array design, and to overcome the losses in the phase shifters LNAs and PAs will typically be integrated into the array design, driving cost and power issues.

With a close grouping of beamformer chipsets containing required phase shifters, PAs, etc thermal management becomes a driving issue in design and layout of the millimeter-wave array sub-system. And as always with commercial communication systems, cost must be considered from day one in the design process to ensure product success in the marketplace. Figure 2 lists the benefits and challenges of 5G implementations.

Path loss increases as a function of frequency, requiring more gain for similar range