In the past decade, smartphones and smart devices have changed the way we communicate, entertain, and work. The annual sales of smart devices exceed 1 billion units, and relying on a huge global supply chain, this market has now become a major pillar of the global economy.

The enormous market value of a single device category naturally brings fierce competition and innovation, accompanied by a very short product lifecycle. Therefore, smartphone users often have very high expectations for each new version of software and hardware. An always online high-speed connection is the cornerstone of many modern features, and when expectations become so high and pushed even higher by the latest generation of 5G cellular technology, any connectivity issues can be frustrating and in some cases potentially dangerous.

Add 5G to the combination

Due to the introduction of two main frequency ranges - Sub-6 GHz and millimeter waves above 24GHz -5G technology has significantly increased the complexity of smartphone design. The millimeter wave frequency band is a completely new frequency band for cellular communication, traditionally used for radar detection in aerospace or automotive applications.

As shown in the figure, the main advantage of millimeter wave for cellular communication is providing high bandwidth and potential data rates, typically exceeding 1Gbps. The disadvantage is the short distance of less than 500 meters, and the signal is easily blocked or reflected by solid objects, so it is used for radar applications. Short distance restrictions mean that millimeter wave frequency bands typically need to be deployed street by street and may only be used in heavily congested and densely populated areas of cities, such as city center streets and sports stadiums. The advantage of short distance is to achieve frequency reuse within a relatively short distance.

The design challenges at the level of smartphones or devices are numerous:

1. High frequency millimeter wave design challenge: The electrical scale of 5G millimeter wave antennas is very small (in the millimeter range), and they are particularly sensitive to small geometric changes. In addition to overall packaging constraints and the general sensitivity of the antenna to surrounding materials, there are still a series of challenges in achieving the required 5G antenna performance.

2. 5G beamforming and MIMO: In the millimeter wave range, 5G technology cannot provide spherical or isotropic coverage for devices using a single antenna unit because too much power is needed to address signal path loss - at these frequencies, signal strength rapidly decreases with distance. The solution is to use antenna arrays at both ends of the connection to form a beam that can concentrate power in a specific direction. By utilizing the changes in relative amplitude and signal phase to drive each part of the array separately, it is possible to electrically control the beam pointing in a specific direction, thereby providing overall isotropic coverage.

3. The codebook or beamforming manual for smartphones: Ensuring that the millimeter wave array inside the phone provides a wide spherical coverage range is not an easy task. This type of array adopts integrated "on-chip antenna" technology, such as the QTM525 provided by Qualcomm, which is designed to be installed on the side of smartphones. Suppliers of such modules will provide a 'codebook', which is a text file that lists all beams that can be generated by combining array units, where each unit is driven by a specific signal amplitude and phase. By searching this codebook, relevant modules can be utilized to achieve optimal coverage.

The key role of simulation and automation post-processing

Measuring the antenna performance on 5G millimeter wave plates separately and in user devices is very time-consuming, as evaluating the complete spherical coverage area requires running a large number of tests. A faster and lower cost solution is to use electromagnetic simulation. Although high demands are still placed on model complexity and the required number of simulations, modern high-performance computing technologies can provide controllable runtime at a reasonable cost.

In order to generate meaningful coverage or power density indicators, it is necessary to process a large amount of data generated from measurements or simulations. Simulation data can undergo automatic post-processing to generate the desired results with minimal user effort or intervention. This type of automation is very valuable for OEM manufacturers, as each manual step is multiplied by the need to run a large number of simulations and consider numerous phone models.

Efficient 5G antenna design for smartphones

Scan the QR code above to download the white paper "Efficient 5G Antenna Design for Smartphones" and learn about the important role of electromagnetic simulation in ensuring optimal connectivity and meeting compliance standards within a very short product design cycle, as well as the design process of 5G millimeter wave antennas.

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Source: Dassault Systemes