All options are deployed when dealing with 5G radio thermal issues in base stations and handsets. Depending on the circumstance, thermal challenges are addressed using a combination of passive and active thermal management, packaging and hardware design improvements, and advanced software. This article presents a brief overview of this complex landscape.
Due to the increased data rates and transmission technologies like beamforming and massive MIMO, 5G base stations generate more heat than technologies like 4G LTE. Still, basic air cooling is the most common thermal management tool in 5G base stations. The potential for the fans to generate electromagnetic interference (EMI) that can interfere with signal reception must be managed.
High heat-generating components use a combination of thermal gels and heat sinks to improve thermal dissipation. In some cases, phase change materials, air conditioning, and even liquid cooling using radiators are employed.
Software is also a common tool for 5G thermal management. It dynamically optimizes power levels based on network demand. Using machine learning and artificial intelligence, various levels of “sleep” modes can be implemented to optimize power consumption further and manage heat generation.
Millimeter wave bands in 5G require more powerful antennas, contributing to heat generation. Optimized antenna designs and better beamforming that produce more focused radiation patterns reduce unnecessary power dissipation.
Reimaging antenna packaging
RF signal chain efficiency can be a particularly thorny thermal problem. Massive MIMO antenna arrays consist of large numbers of antenna modules like the 32T32R configuration (32 transmit, and 32 receive antennas) and the 64T64R (64 transmit, and 64 receive antennas).
The antenna modules combine LDMOS and GaN semiconductor technologies to support high gain and efficiency but still require cooling. Reimagining the packaging can boost performance. The use of top-side cooling can bring several benefits, including (Figure 1):
- Lower thermal resistance from the simplified thermal path.
- Separation of thermal and RF paths.
- Fewer and shorter connections.
- Heatsink also serves as the RF shield.
- Simpler design results in a 30% thinner and lighter solution.
Figure 1. Comparison of a conventional 5G radio module structure (left) with the new top-side cooling approach (right). (Image: NXP)
Hot handsets
Multiple heat sources are present in 5G handsets, including the application processor (AP), power management integrated circuits (PMICs), antenna systems, and cameras. The AP, which includes multiple sub-components, such as a graphics processing unit (GPU), multimedia codec, and computer processing unit (CPU), is the primary heat source.
Handsets employ an array of passive cooling technologies. Materials like copper or graphite sheets spread heat across a larger surface area, improving heat dissipation. Conductive thermal pads can be placed between the processor and the chassis to enhance heat transfer.
More advanced thermal management tools for APs include vapor chambers, also called heat pipes, which efficiently transfer heat to the handset’s body. If the processor still gets too hot, some phones automatically slow the processing speed to reduce heat generation.
Handset batteries are often covered with a graphite sheet that evenly distributes heat to the screen, dissipating heat and maintaining a proper operating temperature.
Compared with batteries and APs, PMICs are small devices and require a different approach. Thermal grease is often used to improve heat transfer from the PMIC to a heat spreader like a copper or graphite sheet.
4G is a smartphone cooling option
Smartphones can be designed to handle the maximum thermal load and continue to operate normally, which can be an effective but expensive approach. Simpler handsets react to overheating by displaying error messages and allowing the user to take action to reduce the heating.
Another group of handsets automatically shut down applications working in the background. It can switch from 5G to slower 4G LTE operation, slowing the data transfer and allowing the device to cool, then returning to 5G data rates (Figure 2).
Figure 2. This handset briefly switched to 4G LTE data rates (dark yellow band 6 minutes into the test) when it sensed the temperature rising, and when the battery temperature hit 45.4 °C, it remained in 4G LTE mode. (Image: SmartViser)
Summary
Thermal management is important to optimize the operation and reliability of radios in 5G base stations and handsets. It’s also complex and can involve a wide range of active and passive hardware solutions for dissipating heat, as well as software algorithms and sleep modes for minimizing heat generation.
References
5G base stations and the challenge of thermal management, Essentra Components
5G Devices and Thermal Management, Advanced Thermal Solutions
Smartphones Overheating on 5G, SmartViser
Thermal-Aware Synthesis of 5G BaseStation Antenna Arrays, IEEE Access
Thermal Management Challenges in the 5G Era, Northwest Engineering Solutions
Thermal Management for 5G, IDTechEx
Thermal Management for 5G Smartphone, Prostech
Top-side cooling RF power modules for 5G infrastructure, NXP
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