Apple iPhone 7 and 7 Plus (Image CC BY 2.0: Maurizio Pesce / https://flic.kr/p/LWNU7P)
While smartphones generally get better every year, there’s one feature that doesn’t really improve: the antenna.
The most famous example of poor antenna performance is iPhone 4, which would lose signal when it was held by the lower-left corner. This prompted Steve Jobs to say, “Just avoid holding it in that way.”
After initially claiming there was no problem, Apple did a U-turn and gave away free bumper cases so a user’s hand wouldn’t touch the edge of the phone. This scandal became known as “Antennagate”.
But even though Apple has released several phones since 2010, the company still hasn’t improved their antennas.
“Ever since, the iPhone has been worse,” says Professor Gert Frølund Pederson, an expert in antenna performance at Aalborg University in Denmark, who recently tested iPhone 7. “I’m shocked — I was hoping that would be so much better, but it’s not.”
Antennas convert electrical power to radio waves, or vice versa. A transmitter delivers current oscillating at radio frequency (RF) to the ends of the antenna, which radiates that energy as radio waves (electromagnetic radiation). A receiver produces current when the antenna absorbs energy from the waves.
Antennas are made of an electrical conductor — metal — so phone manufacturers sometimes use the outer casing as an antenna. If a nearby material is a partial insulator (i.e. it conducts some electric current) then current will “leak” from the antenna, causing power to be lost during the conversion to/from a radio. Such materials are “lossy”.
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The problem with iPhone 4 is its design. Radio waves enter and leave an antenna at the ends — an iPhone 4′s antenna is the device’s metal frame and the ends are a slot in the bottom-left edge of the frame, which is where you weren’t supposed to touch. Unfortunately, the antenna slot is in a place where a person’s fingers naturally fall, causing signal loss.
Squeezing iPhone 4 in your palm will reduce or even kill a network signal, so this hold was nicknamed the “death grip”. Because Apple couldn’t fix the problem, the company offered two workarounds: a software update to hide the signal drop, and the bumper to block contact between the antenna and your finger, which created a small gap to stop the signal being spoiled.
Apple iPhone 4 and bumper case (Image CC BY 2.0: Yutaka Tsutano / https://flic.kr/p/8du5Lt)
Apple didn’t learn from its mistake, however. In the next model, iPhone 4s, the company simply hid the antenna slot. The iPhone 6 added antenna lines (made of a rubbery material for electric insulation) to help prevent signal loss. But the placement of the antenna ends relative to how people hold phones — hasn’t really changed.
“It’s the same design all of the way from iPhone 4 and up,” says Pederson. “They put a lot of very fancy and good electronics inside, but they don’t do anything on the main thing, the slots.”
Signal loss isn’t unique to iPhones. Many handheld devices work fine until you make contact with the antenna. “When the hands touch it then you can lose sometimes a hundred or a thousand times of the signal,” says Pederson. “Your finger is a very lossy material.”
Pederson regularly tests the performance of phone antennas for transmitting and receiving radio signals via calls and data connections. This involves measuring signals next to objects that mimic the effect of a hand and head — fake “phantom” limbs. The test took 15 years to standardize and detects a difference in antenna efficiency with and without the phantom limbs, known as “body loss”.
In Pederson’s most recent study, he tested 26 of the most popular phones, measuring their receiver (‘total isotropic sensitivity’) and transmitter (via ‘total radiated power’) efficiency. Performance is measured by the radio energy that’s converted to electric power (or the other way around), given in decibels (dB).
Antenna performance was measured over a range of radio frequencies. At the GSM 900 frequency band, for instance, Pederson found that body loss was up to 20dB — equivalent to a phone sending 100 times less power to a signal mast.
One striking result is that being left-handed has a significant impact on antenna performance, particularly when making voice calls. “The good phones do not vary very much if you use right hand or left hand,” says Pederson.
Apple’s design is bad because it’s biased toward right-handed users. In Pederson’s ranking of devices for left-handed use at the GSM 900 frequency, the bottom positions are all iPhones. The antenna on Samsung’s Galaxy S6 Edge+ is over 10 times more efficient than that on the iPhone 6S Plus, for example (18.1dB vs 6.5dB. Note: as a logarithmic measure, a 10-decibel drop equals 10 times less power.)
It’s not that phone manufacturers don’t know that their antennas perform poorly, they simply refuse to reveal test results. “They don’t want to share it with the consumer,” says Pederson. “We see so large a variation, up to 40 times difference between a good and a bad phone. I think this information should be available to the user.”
Ironically, even though telephones are communication devices, manufacturers don’t prioritize telecommunications performance.
Why don’t they make better antennas? One reason is that the phone industry believes consumers want thinner devices, and smaller size puts constraints on the placement of internal components. Another explanation is that manufacturers focus on people living in urban environments, where a high density of telecoms masts can compensate for badly-designed phones.
Antenna performance is a priority to groups like elderly people and those who need signal in rural areas with low network coverage, however. “I have so many people asking me, ‘Which kind of phone should we buy?’,” says Pederson. “When they are so reliant on the coverage, they need to have the phones which perform the best.”
The influence of antennas was illustrated when the Danish government asked mobile operators to create a coverage map. While their report suggested only 16 post code zones had a problem, it had combined data from various phones. When a bad phone was used, the map changed completely. “Suddenly it was 264 zip codes where there was trouble,” says Pederson. “That’s half of all zip codes in Denmark.”
A consequence of poor antenna performance is that when consumers are unhappy with their phone signal, they blame the mobile network operator. The operators then respond by adding extra infrastructure — including more masts — than are needed. This raises operating costs, which is passed on to customers, so you ultimately end-up paying to overcome a phone’s design flaws.
Manufacturers often suggest their phones are better than those of a competitor by highlighting “key performance indicators” — what they consider to be important technical specifications. Such tech specs include camera resolution (in megapixels), but not antenna performance.
According to Pederson, who has spoken to several phone makers, antenna performance isn’t advertized because they don’t want to bombard users with too much detail. But this information-overload argument is weakened by the fact that they also present a long — and mostly meaningless — list of wireless bands and channels, only a few of which (like GSM 900) are relevant to the majority of people.
Pederson believes antenna performance doesn’t have to be needlessly complicated. “You can do many things to make this very muddy, but you don’t need to.”
Instead of listing frequency bands, for instance, phone manufacturers could give antenna performance (in decibels) for the most widely-used radio frequencies. Just as camera quality has moved on from boasting about megapixels, this would reveal a phone’s quality as a communications device.
Ideally, antennas would have a minimum performance level, which isn’t asking for much. “It’s not like they should be 100% efficient. If they’re 10% efficient, it’s excellent,” says Pederson, adding that some phones convert less than 1% of their power. “It’s really a waste.”
So which phone does the antenna expert use? “I would probably have a Nokia 2110 if I was not forced to follow what’s happening in this area,” says Pederson, who is currently using a Samsung Galaxy S7. “I’m not happy with it, I must say. I have never, ever had an iPhone — but still my children are asking for it.”
NEXT: Antenna performance for popular phones
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Antenna performance for popular phones.
Results are sorted by total radiated power (dBm) for voice calls using the GSM 900 radio frequency band, the most important for network signal coverage in Nordic countries.
RANK PHONE POWER
DORO PhoneEasy 530X
21.8 2 Microsoft Lumia 640 21.6 3 Microsoft Lumia 650 21.1 4 Sony Xperia Z3 Compact 21.0 5 Xiaomi Mi5 20.0 6 HTC Desire 626 19.8 7 Samsung Galaxy S7 Edge 19.6 8 Samsung Galaxy J1 19.3 9 Sony Xperia Z5 Compact 19.3 10 Huawei Y360 19.2 11 Samsung Galaxy S5 Mini 18.7 12 Sony Xperia Z5 18.3 13 HTC 10 18.2 14 Samsung Galaxy S6 Edge+ 18.1 15 DORO Liberto 825 18.0 16 Huawei Google Nexus 6P 17.2 17 Huawei Honor 7 16.0 18 Samsung Galaxy S7 15.5 19 Microsoft Lumia 950 15.3 20 Huawei P9 15.0 21 LG Google Nexus 5X 14.5 22 LG G5 12.2 23 Apple iPhone SE 12.1 24 Apple iPhone 6 10.1 25 Apple iPhone 6S 8.7 26 Apple iPhone 6S Plus 6.5
RANK PHONE POWER 1 HTC Desire 626 22.5 2 Samsung Galaxy S5 Mini 20.7 3 Samsung Galaxy J1 20.4 4 Microsoft Lumia 640 20.3 5 DORO PhoneEasy 530X 20.1 6 LG Google Nexus 5X 19.8 7 Sony Xperia Z3 Compact 19.8 8 Sony Xperia Z5 19.4 9 Samsung Galaxy S7 Edge 19.4 10 Microsoft Lumia 650 19.3 11 DORO Liberto 825 19.1 12 Apple iPhone 6S Plus 18.7 13 Huawei Google Nexus 6P 18.7 14 Xiaomi Mi5 18.6 15 LG G5 18.4 16 Apple iPhone 6 18.1 17 Samsung Galaxy S7 18.0 18 Huawei Y360 17.4 19 Sony Xperia Z5 Compact 17.1 20 Samsung Galaxy S6 Edge+ 16.7 21 Huawei Honor 7 16.4 22 Apple iPhone 6S 15.1 23 Apple iPhone SE 14.7 24 HTC 10 14.0 25 Microsoft Lumia 12.7 26 Huawei P9 8.3
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