Does plastic reduce an antenna's signal?

Discussion in 'iPhone' started by netnothing, Jul 9, 2010.

  1. netnothing macrumors 68040

    netnothing

    Joined:
    Mar 13, 2007
    Location:
    NH
    #1
    Do you think that Apple made a calculated risk with it's new antenna design?

    Let's take the 3G/3GS.....the antenna is on the inside of the phone behind essentially an outer plastic shell. So a naked iPhone 3GS the antenna signal goes through 1 layer (the plastic back).

    Do you think Apple had enough research and statistics to show that the majority of users put an iPhone in some sort of case, whether that case is plastic or silicone? So now on a 3GS, the antenna has to go through the plastic back, then a plastic/silicone case....now it's going through 2 layers. Do you think they determined that this combo caused a lower/weaker signal?

    Now the iPhone 4....antenna on the outside. Do you think Apple took a calculated risk in knowing that most people put it in a case anyway (heck even Steve in one of his emails suggested using a case) and the fact they came out with the bumper....that they knew since most people would put a case on it....that the antenna being on the outside would provide a stronger signal?

    Yes, the people who choose to go caseless with their phones are more easily affected by the issue, but since that may be the minority of users, Apple is ok with saying "Hold it differently"? We all know Apple does things based on what they "think" the majority of users will do....ie: no firewire on low end Macbooks.

    I don't know anything about antenna signals, so I'm just guessing here.....but if an antenna's signal is degraded behind each layer of plastic etc, then by moving the antenna outside, Apple is giving it a better chance at getting a stronger signal, even though there is a side effect of direct contact with skin that can cause the signal to degrade significantly.

    Tests I would like to see are the difference in signal strength in a 3GS with the back on and the back off.

    Just my thoughts.

    -Kevin
     
  2. aforty macrumors 65816

    aforty

    Joined:
    Nov 27, 2007
    Location:
    Brooklyn, NY
    #2
    A thin plastic case does very little against signal attenuation. It's not that holding it in the hand and bridging the two antennas that somehow "shorts" the antenna, that's bogus. The signal will get blocked the closer the fleshy part of your hand is to the antenna, any antenna in any phone, period. Simple as that.

    The antenna simply needs some breathing room. The bumper will give it some, although not much. A thin coating like an InvisibleShield will do nothing.


    If you want to talk about calculated risk, I'd say the risk Apple took was to put the antenna on the outside. It will get better reception because it is not inside the phone but it is also more prone to signal attenuation because it is closer to your hands. The new antenna design is much better at holding a signal that's why less dropped calls are reported even though the signal may drop down to one or two bars. So you win some and you lose some.
     
  3. netnothing thread starter macrumors 68040

    netnothing

    Joined:
    Mar 13, 2007
    Location:
    NH
    #3
    Thanks, that's kind of what I'm thinking as well. Risk those without a case of having attenuation but for those with a case, the antenna gets and maintains a better signal.

    I'm guessing that by incorporating the antenna into the steel band around the outside of the iPhone 4, that the antenna itself is larger than the antenna inside the 3GS?

    -Kevin
     
  4. aforty macrumors 65816

    aforty

    Joined:
    Nov 27, 2007
    Location:
    Brooklyn, NY
    #4
    Point I was trying to make was that even without a case and higher signal attenuation when held, the iPhone 4 still gets better overall signal (less dropped calls) than the iPhone 3G/S. Yes the antenna is bigger and covers more area than that of the 3G/S.
     
  5. kdarling macrumors demi-god

    kdarling

    Joined:
    Jun 9, 2007
    Location:
    First university coding class = 46 years ago
    #5
    The 3GS antenna covers the entire inside bottom of the phone. Perhaps 2.25" x 0.6" = 1.4 square inches.

    As for the iPhone 4 antenna... well, some of us engineers think that there's still an internal antenna inside the bottom of the phone. (A coax goes from the RF power amps to the bottom enclosed section.) This location is even specifically pointed out in Apple's FCC documentation.

    The difference is that the iPhone 4 also has an external bezel piece. This piece is about 13" x .25" = 3.25 square inches. Whether it's active or a ground plane is unknown, but since it wraps up to the top of the user's head, it had better not radiate much from there. (And indeed, the SAR plots show the radiation is concentrated in the lower half of the phone.)

    IMO, we don't know all the facts yet as to what kind of antenna is designed into the phone, and what all its components are.
     

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