Half duplex does not mean one way communication. It means one way at a time switching back and forth for xmit and receive. Simplex means one way communication. Your definition of full Duplex is correct.
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Technical explanation on iPhone 4 Antenna issue
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Half duplex does not mean one way communication. It means one way at a time switching back and forth for xmit and receive. Simplex means one way communication. Your definition of full Duplex is correct.
If you have a wave guide (read antenna), and you change its structure, it messes up all sorts of things.
In this case, touching the gap creates a sort of loop I would imagine, making the signal not propagate out as much as they would hope.
You can place your finger on the left side band while the phone is laying on the table (i.e. not being touched anywhere else), and it will experience the signal loss.
That's pretty much what I assumed. I was just pointing out that the OP's explanation doesn't address this at all.
My limited knowledge is that 3G cell phone signals (antenna #1) operate at around 850MHz and around 1.9GHz. GPS/Wifi/Bluetooth (antenna #2) all operate around 2GHz (2.4 to be precise for Wifi and BT). Perhaps when the two antenna are bridged, the 1.9GHz cell signals just get eaten up by the 2-ish GHz tuned antenna #2. And maybe some of the people who say they have no problems are all operating at 850MHz.
I must be really close to a tower then, because I can't replicate this right now w/ my iPhone 3G iOS4.
this guy must manufacture bumpers.
kidding - but seems weird this was not tested. That said, I cannot replicate here. Maybe my hands are too clean.
I am still waiting to pick up an iPhone 4. I went to the mall at lunch today to see how bad the lines were. I hadn't seen an iPhone 4 in person, yet, so it was cool to play with it. While there, I tested this problem. I was able to get all seven phones (not at the same time, of course) at the demo table to go from about 3-4 bars to 1 or no bars by touching them. Meanwhile, I couldn't get my 3G to lose any signal strength.
The OP's analysis makes sense. I, too, am surprised this issue exists, assuming the phones have been extensively tested.
The OP's analysis makes sense. I, too, am surprised this issue exists, assuming the phones have been extensively tested.
Another RF experienced electrical engineer here. The OP has a valid theory. At cellular frequencies your finger acts as a capacitor in the tens of picofarads range. We routinely use our "calibrated fingers" here at work to quickly experiment with modified impedances in some of our high frequency electronic prototypes where ESD isn't a concern.
Touching an antenna like this creates a makeshift path to ground through your body which will mess up impedance match and VSWR for whatever drives the antenna. This can have detrimental and unpredictable effects on the antenna.
Another possibility is that your finger capacitance bridges two antennas. Maybe in some situations the wifi antenna is being internally pulled to ground when not in use instead of being held to high impedance and then your finger shorts the cellular antenna to that ground thereby reducing radiated power.
If I could actually get my iPhone 4 I could take it into the lab with a spectrum analyzer or high freq scope and a sniffer antenna and actually see what is going on.
Only the apple engineers know for sure at this point.
Touching an antenna like this creates a makeshift path to ground through your body which will mess up impedance match and VSWR for whatever drives the antenna. This can have detrimental and unpredictable effects on the antenna.
Another possibility is that your finger capacitance bridges two antennas. Maybe in some situations the wifi antenna is being internally pulled to ground when not in use instead of being held to high impedance and then your finger shorts the cellular antenna to that ground thereby reducing radiated power.
If I could actually get my iPhone 4 I could take it into the lab with a spectrum analyzer or high freq scope and a sniffer antenna and actually see what is going on.
Only the apple engineers know for sure at this point.
And yet another electronic engineer weighing in and I don't really give a goddamn if the rest of you like it or not, the OP is basically correct. An antenna is very much like a tuning fork with a resonant frequency and the capacitance of your hand, which is a known quantity used in many things, will screw up that resonance. That's assuming there's not a short being created between sections of the case that will also throw off resonance. Try this sometime...tune in a weak FM station using a small portable radio with the antenna extended. Got it tuned in so there's little static? Now grab the antenna. Same thing. I was kind of wondering how Apple was going to pull off an external antenna that wasn't wide open to problems like this. Now I know. They didn't. It does seem awfully odd that no one in QC caught this. A real disappointment to an otherwise nice phone.
I’m hungry now.
I don’t doubt the article or what you and others have been writing, but I still find it hard to believe Apple engineers wouldn’t know about all this. Also, many users don’t have the problem. It’s a definite facepalm for Apple if this ends up being a big issue.
Ok, come on, this is an actual problem, we need to quit bickering. There are posters here with actual ideas. So here's an idea: why don't those of you who are just arguing without knowing what you're talking about (that's quite a few of you) quit being jackasses, stop trying to start flame wars and maybe, just maybe, try to have a *gasp* reasonable, informed debate?
EDIT:
Just found this article linked via Daring Fireball. It's from Jim Dalrymple. Here's the most interesting tidbit. So far, this is the best explanation as to how this major hardware problem slipped through testing, and it's actually very plausible:
"I talked to a number of people this morning familiar with the iPhone 4 development and said much of the testing of the iPhone 4 was done with the device in a case to disguise it. Think back to Gray Powell’s iPhone 4 and the fact it was found in a case that made it look like it was a regular iPhone.
This may have hidden the cause of the antenna problems from engineers. The fact that Apple’s campus is fitted with repeaters for wireless service, also helped blocked what could be the cause for the problem."
Here's the rest of the article for reference: http://www.loopinsight.com/2010/06/...ers-could-be-causing-iphone-4-antenna-issues/
EDIT:
Just found this article linked via Daring Fireball. It's from Jim Dalrymple. Here's the most interesting tidbit. So far, this is the best explanation as to how this major hardware problem slipped through testing, and it's actually very plausible:
"I talked to a number of people this morning familiar with the iPhone 4 development and said much of the testing of the iPhone 4 was done with the device in a case to disguise it. Think back to Gray Powell’s iPhone 4 and the fact it was found in a case that made it look like it was a regular iPhone.
This may have hidden the cause of the antenna problems from engineers. The fact that Apple’s campus is fitted with repeaters for wireless service, also helped blocked what could be the cause for the problem."
Here's the rest of the article for reference: http://www.loopinsight.com/2010/06/...ers-could-be-causing-iphone-4-antenna-issues/
Ok, come on, this is an actual problem, we need to quit bickering. There are posters here with actual ideas. So here's an idea: why don't those of you who are just arguing without knowing what you're talking about (that's quite a few of you) quit being jackasses, stop trying to start flame wars and maybe, just maybe, try to have a *gasp* reasonable, informed debate?
EDIT:
Just found this article linked via Daring Fireball. It's from Jim Dalrymple. Here's the most interesting tidbit. So far, this is the best explanation as to how this major hardware problem slipped through testing, and it's actually very plausible:
"I talked to a number of people this morning familiar with the iPhone 4 development and said much of the testing of the iPhone 4 was done with the device in a case to disguise it. Think back to Gray Powells iPhone 4 and the fact it was found in a case that made it look like it was a regular iPhone.
This may have hidden the cause of the antenna problems from engineers. The fact that Apples campus is fitted with repeaters for wireless service, also helped blocked what could be the cause for the problem."
Here's the rest of the article for reference: http://www.loopinsight.com/2010/06/...ers-could-be-causing-iphone-4-antenna-issues/
Interesting that they didn't go for something instead of stainless steel, like hard anodised aluminium in black, which would not only have high impedance to limit the conductivity between the antennae + coins/hands, but also make the seams almost unnoticeable. It would also retain all the advantages of keeping the antennae external and away from other HF paths in the iPhone circuitry that cause EMI.
Although if the stainless steel is supposedly coated with some sort of lacquer, that may be the next best thing. (Unfortunately, rumours of some batches having this mysterious coating are largely unsubstantiated - more info is needed and it would be good to have Apple comment on this.)
Although if the stainless steel is supposedly coated with some sort of lacquer, that may be the next best thing. (Unfortunately, rumours of some batches having this mysterious coating are largely unsubstantiated - more info is needed and it would be good to have Apple comment on this.)
That's exactly what I saw with mine, although the locations were metres apart. The first time I was near a few computers with Wi-Fi enabled and the signal slowly dropped, the second time not near computers and kept full signal. Both times I was inside a building near the middle of it (rather than close to a window etc.).
I wholly imagine we will not be able to change anybody's knee-jerk reaction opinion on the matter, regardless of how little effort/reasoning went into that opinion. Never mind.
+1 from me, another engineer with experience in mobile radio. In fact, you don't need to touch the antenna to affect it, just put your hand/body into the near field, like so. It's just that touching the antenna affects it to a much greater degree.
I did wonder about this when I saw the WWDC presentation but I assumed some cleverness on the part of Apple's engineers -- assumed too much, I guess. Not all parts of the antenna are equally sensitive to touch; it depends on a number of factors, including whether the touch is near a voltage or current node of the standing wave. I thought perhaps Apple was leveraging this fact in some way that wasn't clear from the presentation, but apparently not.
I don't see a real fix for this other than isolating the sides via bumpers or a case. (For me, the vast majority of my use is either near a cell tower or in my car, where the phone is in a mounting bracket so the problem doesn't crop up.)
Ok the problem stems from not just the bottom antenna. When the left antenna toutches the bottom one then the signal goes down and is all messed up. This only happens when somthing connects the 2 like your hand. The only the solid bottom part of ur had does this because the bridge is very short, but if u use 2 seperate fingers and toutch bolth it won't happen. Now the reason y some De affected and som not is because of where u live, if u live in an area where the signal is strong then whatever u do the signal will go down a little or not at all.
I'm also a EE and agree with the comments he's made. Very reasonable, good explanation. It does seem like RF101. I don't understand how Apple didn't realize this.
If someone could get the new test # for field mode for IOS4 maybe that would be of some assistance. *3001#12345#* no longer functions.
OP, I find your posts informative, thanks
OP, I find your posts informative, thanks
I honestly can't believe that some people want to pretend that the antenna design issue doesn't exist and deny the whole thing! lol, it really is just a problem of design and applies across the board, there just will be situations where it isn't noticeable, like being in very strong coverage, and the possibly of the dryness of your hands having a variable affect on antenna performance.
I can make signal drop on any phone just by cupping your hand over the antenna, may not drop as much, but it is still there.
I can make signal drop on any phone just by cupping your hand over the antenna, may not drop as much, but it is still there.