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Although the 5G era is well underway, the rollout is still relatively new, only a few devices can handle all the available spectrum, and there are still column space-consuming questions.
The currently available 28 GHz mmWave band is new to the consumer market, so the upper end of the spectrum offers an opportunity for exploration. Higher frequencies come later. Extremely High Frequency (EHF) is another name for 30 to 300 GHz, and may provide a clue as to why some people want to understand the potential health effects before adopting this new technology.
While the upper reaches of the 5G spectrum offer both higher potential bandwidth and the open frequency allocation currently granted to cellular services, this frequency range is subject to very high atmospheric attenuation. This increases the likelihood that higher power output will be required at the antenna to reliably connect the user to the base station cell.
But outside air attenuation is only part of the problem. While the use of millimeter wave frequencies is new, another problem is not. The user’s flesh and blood also absorbs his RF energy. We do not discuss potential biological responses to mmWave energy. Regardless of whether the user experiences any physical effects, hands or head (or any part of the body) will definitely reduce, if not completely eliminate, 5G’s RF signal propagation (at least the output I hope the power is in the range to accomplish this).
Dylan Liu, Geehy Semiconductor March 21, 2024
Written by Lancelot Hu March 18, 2024
From EE Times Taiwan March 18, 2024
When we first considered the placement of the 5G antenna module on the phone, we wondered if it was designed with the majority of right-handed people in mind and placement on the head for voice calls. But I’m from an older generation and think of a phone as something you can hold to your mouth and ear to have a conversation. Cell phone design (or at least good design) in terms of 5G antenna placement will very likely be optimized for the ubiquitous hand-held screen, head-down posture for surfing and social media. This is true in 99% of use cases, but in rare cases you need to be able to connect when the handset is above your head. Must be able to adapt to changing conditions.
We know that MIMO and beamforming techniques are used at both ends of the connection: the base station and the user equipment or UE. Cell phone base stations and handsets work together so that their respective antenna arrays focus the RF energy to maximize the signal received at each end. However, there is another mechanism that can be used for objects that block the signal near the handset. This was revealed in a recent System Plus teardown of the iPhone 12.
One relatively small detail about the iPhone 12 highlights the value of information gained through the simple task of opening and researching a product on the market. The SystemPlus teardown also highlights the need for competent and experienced technicians to get the most out of the exercise. The SystemPlus teardown report is only a teaser of the full report, but it provides valuable information.
“With the Apple iPhone 12 series, we discover a 5G mmWave system unlike anything we’ve seen before. It’s built for high-speed communications with human safety in mind, all powered by a single chipset. It is controlled by.”
Another 5G antenna for the iPhone 12, the USI Fully Integrated Module with Antenna-in-Package (AiP), was recently featured in this column. Although very similar to Qualcomm’s second-generation QTM525 5G mmWave antenna module, there were notable differences. But his second iPhone antenna array is even more interesting.
A teardown of SystemPlus revealed that a single RF front-end module was used to drive the USI AiP module and a second passive phased array antenna under the logic board. This second antenna distinguishes the iPhone 12 from other cell phone designs. It’s unlikely we’ll find any meaningful comparisons of cellular connectivity performance between the 5G iPhone and its competitors, but it would be interesting to learn more about this (for now) Apple-only design choice.
Beyond passive antennas, there are other “human safety considerations” SystemPlus describes. His third component, controlled by a Qualcomm SDX55M modem and his SMR526 intermediate frequency chipset, is a millimeter wave radar. The function of this radar is to “detect a human body in order to limit the radiation from the 5G mmWave communication system if a human body is present”.
Is Apple concerned enough about the health effects to add expensive additional components to limit human exposure to mmWave energy? That’s one possibility. The other is to detect nearby absorbers and funnel the RF energy into another array, if for no other reason than to not waste energy. Power consumption is an issue on everyone’s mind when it comes to mobile devices, and this is especially true in his 5G era. Apple definitely wants to maximize battery performance. Presumably, they also want to limit or eliminate the exposure of their loyal users to concentrated mmWave RF energy.
Qualcomm, which is deeply involved in all aspects of 5G deployment, especially RF design, continues to work on controlling RF power in antennas with unintended absorbers in their vicinity. A quick search for patents reveals a very recently published application titled “Radar for Detecting Parts of the Human Body.” In this very recently published application, the SystemPlus teardown proposes an approach, namely a radar that detects proximity to parts of the human body, allowing a device to determine whether it is safe to transmit its RF signals. An approach to do so is disclosed.
It’s safe to say that SystemPlus’ analysis of the iPhone 12 mmWave radar and its features was spot on. However, as with the AiP module, questions remain as to where his RF design for Qualcomm ends and Apple’s begins. lucky. There is always more column space to fill.
