iPhone 'Death Grip' effect is real, plastic cases don't help
UK boffinry suggests external antenna not clever
The so-called 'death grip' effect, in which a user's hand touching a smartphone antenna degrades its radio connections - a major issue for the iPhone 4 with its external antennae - is real and is a serious problem, according to British boffins researching the matter.
Furthermore they found that plastic insulation between hand and metal has no useful effect - so that "bumper" case may be a completely pointless addition.
The new boffinry comes from the Centre for Communications Research at Bristol uni. The centre's Professor Mark Beach is an expert in the engineering of MIMO (multiple input multiple output, aka multi-element or "smart") antennae, nowadays de rigueur in modern smartphones enabled for various kinds of cell and Wi-Fi networking.
The prof and his colleagues examined the performance of MIMO antennae in various circumstances: with the signal obstructed by a user's hand as one might see in any smartphone, then with the antenna actually in contact with a "thumb phantom" with the same dielectric properties as human skin. Finally performance was examined under the circumstances of handsfree operation, with no inconvenient flesh-sacks nearby.
According to a Bristol uni statement accompanying the research:
The results from the study indicate a 100-fold reduction in sensitivity of the device when held, or when the user’s thumb is mimicked by phantom material. This de-tuning of the antenna was found not to significantly alter the shape of the radiation pattern, but dramatically worsened the electrical match between the antenna and the electronic circuitry.
“Antenna position and user grip on smartphones may lead to obstruction of radio signal paths and antenna detuning," confirms Beach. It appears that you can perfectly well muck up the performance of any modern smartphone by enclosing it in your hand, but actually touching the antenna offers a further opportunity for trouble.
The famous 'death grip' or 'antennagate' brouhaha which emerged following the debut of the iPhone 4 - which is pretty hard to use without touching its antennae - has now largely died down. At the time, the only solution offered by Apple (other than software fixes) was to wrap the handset in a plastic insulating "bumper".
What do Beach and his colleagues have to say to that?
Well, according to the Bristol uni statement:
Further tests concluded that providing a gap between the antenna surface and the phantom thumb using a layer of plastic electrical insulator did not restore the matching and operational sensitivity of the phone for the antennas under evaluation. Thus, some phone covers in the market place may not improve the situation.
That said, the "bumper" advice from Apple may not have been totally wrong: the iPhone 4 also had an additional problem with a gap between two external antennae being bridged by a user's hand, something that hasn't been investigated here.
Meanwhile Beach and his crew are looking at ways around the issue. The prof says that the CCR at Bristol is working on “automated re-tuning of the antenna elements" which might change the technical landscape in future.
Full details on the research are available here for subscribers to the IEEE journal Antennas and Wireless Propagation Letters. ®
COMMENTS
RDF induced fact blindness.
It's quite a common ailment amongst fanboys.
No doubt someone will also attempt to explain how holding the precious while using it with no measurement equipment other than the reception bars is far superior to controlled conditions in a lab performed by an expert in the field.
Never mind guys.. Tell us again about the market cap..
Not at all odd
Apple design products for their known fanbase. Accommodating people with an opposable thumb is therefore not required.
In the article
It mentioned that smartphones were bad, but when the antenna is actually touchable (i.e. iPhone) it's worse.
At least that's how I read it.
@opposite is true
There is no simple answer (as you might have guessed) as you have a number of conflicting aspects to antenna design.
In general, if you are talking about an electrically small antenna (i.e. physically much less than 1/4 wavelength, etc) then you might find that adding your fleshy touch improves reception by adding to the area able to intercept signals.
However, the converse aspect also applies (probably here), in order to make any antenna work efficiently they are normally in resonance (i.e. tuned to a specific narrow range of frequencies) and by touching them you de-tune them and so make the job of getting power in/out of them more difficult. In addition, the body is not a *good* conductor, so tends to make the thing lossy and not only to re-tune it to a different frequency.
Over all I expect flesh decreases reception.
The iPhone problem is certainly *not* unique, just that the close proximity of the antenna to the hand makes the effect significantly stronger, and on top you have Apple's attitude to the problem with their high-end device where style has prevailed over best-practice RF engineering.
This is the first step
This is the first step of such a project.
It may be that the results don't come as a surprise, but in order to gauge the problem, you need to perform controlled, scientific tests.
The next stage, which he has said he will be doing, is to find a way round the problem. This is much easier when you have accurate measurements to start with.
