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Design Flaw in iPhone 4, Testers Say
On Mon, 12 Jul 2010 21:54:17 -0500, tom wrote:
On 7/12/2010 9:46 PM, Richard Clark wrote: The only thing that remains a mystery, for me if for no one else here, is the literal specification of the antenna. Google (gasp) fails me. 73's Richard Clark, KB7QHC And that does seem to be the crux of the matter. What is the antenna? And what does it interact with that's not, be it part of the phone or part of the user? Hi Tom, The antenna is reported as being the metal trim that surrounds the perimeter of the phone. As that is much too large for the frequencies involved to be taken literally, there is more to the story that remains clouded. Maybe I'm wrong.... If the loop (or dipole) is suitably matched, it doesn't give much polarization diversity. Perhaps no phone does anyway. Insofar as being "part of the user," we well know the EM of HTs and the hand/body contribution. If such were the case, then this would be an agnostic problem that users of all mobile phones would complain of (which mildly refutes what the gadget blogs dismissed). On the other hand, the über-hip, whose complaints are more vocal for their "pain," would be outraged at the notion of their simply enjoying the identical experience of techno-trash. Amazing what a 10 fold cost differential brings to your perception of quality of service. 73's Richard Clark, KB7QHC |
#2
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Design Flaw in iPhone 4, Testers Say
Richard Clark Inscribed thus:
On Mon, 12 Jul 2010 21:54:17 -0500, tom wrote: On 7/12/2010 9:46 PM, Richard Clark wrote: The only thing that remains a mystery, for me if for no one else here, is the literal specification of the antenna. Google (gasp) fails me. 73's Richard Clark, KB7QHC And that does seem to be the crux of the matter. What is the antenna? And what does it interact with that's not, be it part of the phone or part of the user? Hi Tom, The antenna is reported as being the metal trim that surrounds the perimeter of the phone. As that is much too large for the frequencies involved to be taken literally, there is more to the story that remains clouded. Maybe I'm wrong.... I think you're right. "Design Flaw" Someone messed up testing big time. If the loop (or dipole) is suitably matched, it doesn't give much polarization diversity. Perhaps no phone does anyway. Aren't cell stations vertically polarised. The one near me is, and one of the IF's is smack on 144.005 Mhz. Insofar as being "part of the user," we well know the EM of HTs and the hand/body contribution. If such were the case, then this would be an agnostic problem that users of all mobile phones would complain of (which mildly refutes what the gadget blogs dismissed). On the other hand, the über-hip, whose complaints are more vocal for their "pain," would be outraged at the notion of their simply enjoying the identical experience of techno-trash. Amazing what a 10 fold cost differential brings to your perception of quality of service. 73's Richard Clark, KB7QHC From a casual look at the phone the metal band seems to be a continuous loop. Its unlikely that there is a physical coupling between it and the RX/TX, so any tuner or coupling is going to be affected by the hand grasping it. Since suggestions have been made to hold the phone in a different place, I would guess that the coupling method is suseptible to adsorbtion effects and that the hot parts are near the base of the phone. FWIW Every mobile phone I've played with has the antenna and coupling circuitry near the top behind the display. 73's -- Best Regards: Baron. |
#3
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Design Flaw in iPhone 4, Testers Say
Baron wrote:
Richard Clark Inscribed thus: On Mon, 12 Jul 2010 21:54:17 -0500, tom wrote: On 7/12/2010 9:46 PM, Richard Clark wrote: The only thing that remains a mystery, for me if for no one else here, is the literal specification of the antenna. Google (gasp) fails me. 73's Richard Clark, KB7QHC And that does seem to be the crux of the matter. What is the antenna? And what does it interact with that's not, be it part of the phone or part of the user? Hi Tom, The antenna is reported as being the metal trim that surrounds the perimeter of the phone. As that is much too large for the frequencies involved to be taken literally, there is more to the story that remains clouded. Maybe I'm wrong.... I think you're right. "Design Flaw" Someone messed up testing big time. If the loop (or dipole) is suitably matched, it doesn't give much polarization diversity. Perhaps no phone does anyway. Aren't cell stations vertically polarised. The one near me is, and one of the IF's is smack on 144.005 Mhz. Insofar as being "part of the user," we well know the EM of HTs and the hand/body contribution. If such were the case, then this would be an agnostic problem that users of all mobile phones would complain of (which mildly refutes what the gadget blogs dismissed). On the other hand, the über-hip, whose complaints are more vocal for their "pain," would be outraged at the notion of their simply enjoying the identical experience of techno-trash. Amazing what a 10 fold cost differential brings to your perception of quality of service. 73's Richard Clark, KB7QHC From a casual look at the phone the metal band seems to be a continuous loop. Its unlikely that there is a physical coupling between it and the RX/TX, so any tuner or coupling is going to be affected by the hand grasping it. Since suggestions have been made to hold the phone in a different place, I would guess that the coupling method is suseptible to adsorbtion effects and that the hot parts are near the base of the phone. FWIW Every mobile phone I've played with has the antenna and coupling circuitry near the top behind the display. Not any more.. recent phones (last several years) put the antenna at the bottom to reduce the SAR number, since the top of the phone is next to your head, and the bottom isn't. There's a really good explanation from a guy who does, oddly, wireless device antenna design consulting.. http://www.antennasys.com/ specifically http://www.antennasys.com/antennasys...-antennas.html http://www.anandtech.com/show/3794/t...one-4-review/2 has some information |
#4
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Design Flaw in iPhone 4, Testers Say
On Tue, 13 Jul 2010 13:51:46 -0700, Jim Lux
wrote: http://www.anandtech.com/show/3794/t...one-4-review/2 has some information Thanx Jim, Everything Apple didn't want you to know (Antennas, and oddly enough, a report giving it an A+++ for signal quality). 73's Richard Clark, KB7QHC |
#5
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Design Flaw in iPhone 4, Testers Say
On Jul 13, 3:51*pm, Jim Lux wrote:
Baron wrote: Richard Clark Inscribed thus: On Mon, 12 Jul 2010 21:54:17 -0500, tom wrote: On 7/12/2010 9:46 PM, Richard Clark wrote: The only thing that remains a mystery, for me if for no one else here, is the literal specification of the antenna. *Google (gasp) fails me. 73's Richard Clark, KB7QHC And that does seem to be the crux of the matter. *What is the antenna? And what does it interact with that's not, be it part of the phone or part of the user? Hi Tom, The antenna is reported as being the metal trim that surrounds the perimeter of the phone. *As that is much too large for the frequencies involved to be taken literally, there is more to the story that remains clouded. *Maybe I'm wrong.... I think you're right. *"Design Flaw" Someone messed up testing big time. If the loop (or dipole) is suitably matched, it doesn't give much polarization diversity. *Perhaps no phone does anyway. Aren't cell stations vertically polarised. *The one near me is, and one of the IF's is smack on 144.005 Mhz. Insofar as being "part of the user," we well know the EM of HTs and the hand/body contribution. *If such were the case, then this would be an agnostic problem that users of all mobile phones would complain of (which mildly refutes what the gadget blogs dismissed). *On the other hand, the über-hip, whose complaints are more vocal for their "pain," would be outraged at the notion of their simply enjoying the identical experience of techno-trash. *Amazing what a 10 fold cost differential brings to your perception of quality of service. 73's Richard Clark, KB7QHC From a casual look at the phone the metal band seems to be a continuous loop. Its unlikely that there is a physical coupling between it and the RX/TX, so any tuner or coupling is going to be affected by the hand grasping it. *Since suggestions have been made to hold the phone in a different place, I would guess that the coupling method is suseptible to adsorbtion effects and that the hot parts are near the base of the phone. FWIW Every mobile phone I've played with has the antenna and coupling circuitry near the top behind the display. Not any more.. recent phones (last several years) put the antenna at the bottom to reduce the SAR number, since the top of the phone is next to your head, and the bottom isn't. *There's a really good explanation from a guy who does, oddly, wireless device antenna design consulting..http://www.antennasys.com/ specificallyhttp://www.antennasys.com/antennasys-blog/2010/6/24/apple-iphone-4-an... http://www.anandtech.com/show/3794/t...-4-review/2has some information My new antenna can easily handle this job. You make it for the lowest frequency and it will handle all the frequencies above at a constant impedance..... and with more gain and the radiater smaller in size! |
#6
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Design Flaw in iPhone 4, Testers Say
On Jul 13, 8:27*pm, Art Unwin wrote:
My new antenna can easily handle this job. You make it for the lowest frequency and it will handle all the frequencies above at a constant impedance..... and with more gain and the radiater smaller in size! Is it fractal? |
#7
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Design Flaw in iPhone 4, Testers Say
On Jul 13, 9:10*pm, Bill wrote:
On Jul 13, 8:27*pm, Art Unwin wrote: My new antenna can easily handle this job. You make it for the lowest frequency and it will handle all the frequencies above at a constant impedance..... and with more gain and the radiater smaller in size! Is it fractal? No! Total resistance = R1+ R2 The trick is to reduce R2 in value so more current is being applied to radiation. Very simple my dear Watson. |
#8
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Design Flaw in iPhone 4, Testers Say
On 7/13/2010 9:42 PM, Art Unwin wrote:
On Jul 13, 9:10 pm, wrote: On Jul 13, 8:27 pm, Art wrote: My new antenna can easily handle this job. You make it for the lowest frequency and it will handle all the frequencies above at a constant impedance..... and with more gain and the radiater smaller in size! Is it fractal? No! Total resistance = R1+ R2 The trick is to reduce R2 in value so more current is being applied to radiation. Very simple my dear Watson. And he tells you nothing. And he provides no proof. The master of vaportennas. tom K0TAR |
#9
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Design Flaw in iPhone 4, Testers Say
Jim Lux Inscribed thus:
Baron wrote: Richard Clark Inscribed thus: On Mon, 12 Jul 2010 21:54:17 -0500, tom wrote: On 7/12/2010 9:46 PM, Richard Clark wrote: The only thing that remains a mystery, for me if for no one else here, is the literal specification of the antenna. Google (gasp) fails me. 73's Richard Clark, KB7QHC And that does seem to be the crux of the matter. What is the antenna? And what does it interact with that's not, be it part of the phone or part of the user? Hi Tom, The antenna is reported as being the metal trim that surrounds the perimeter of the phone. As that is much too large for the frequencies involved to be taken literally, there is more to the story that remains clouded. Maybe I'm wrong.... I think you're right. "Design Flaw" Someone messed up testing big time. If the loop (or dipole) is suitably matched, it doesn't give much polarization diversity. Perhaps no phone does anyway. Aren't cell stations vertically polarised. The one near me is, and one of the IF's is smack on 144.005 Mhz. Insofar as being "part of the user," we well know the EM of HTs and the hand/body contribution. If such were the case, then this would be an agnostic problem that users of all mobile phones would complain of (which mildly refutes what the gadget blogs dismissed). On the other hand, the über-hip, whose complaints are more vocal for their "pain," would be outraged at the notion of their simply enjoying the identical experience of techno-trash. Amazing what a 10 fold cost differential brings to your perception of quality of service. 73's Richard Clark, KB7QHC From a casual look at the phone the metal band seems to be a continuous loop. Its unlikely that there is a physical coupling between it and the RX/TX, so any tuner or coupling is going to be affected by the hand grasping it. Since suggestions have been made to hold the phone in a different place, I would guess that the coupling method is suseptible to adsorbtion effects and that the hot parts are near the base of the phone. FWIW Every mobile phone I've played with has the antenna and coupling circuitry near the top behind the display. Not any more.. recent phones (last several years) put the antenna at the bottom to reduce the SAR number, since the top of the phone is next to your head, and the bottom isn't. There's a really good explanation from a guy who does, oddly, wireless device antenna design consulting.. http://www.antennasys.com/ specifically http://www.antennasys.com/antennasys...-antennas.html http://www.anandtech.com/show/3794/t...one-4-review/2 has some information Jim. Thanks for the above links. The Youtube vid was most interesting. I certainly wasn't aware of the gaps in the metal banding nor of the SAR requirements. 73s -- Best Regards: Baron. |
#10
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Design Flaw in iPhone 4, Testers Say
On Tue, 13 Jul 2010 13:51:46 -0700, Jim Lux
wrote: Not any more.. recent phones (last several years) put the antenna at the bottom to reduce the SAR number, since the top of the phone is next to your head, and the bottom isn't. There's a really good explanation from a guy who does, oddly, wireless device antenna design consulting.. http://www.antennasys.com/ specifically http://www.antennasys.com/antennasys...-antennas.html http://www.anandtech.com/show/3794/t...one-4-review/2 has some information Here's my wild guess as to what's happening, borrowed from my posting in ba.internet and alt.cellular.attws. Apple announced that there's going to be a press conference on Friday, where they'll announce something. Note that I goofed on the location of the wi-fi/BT antenna, but I'll leave the mistake here for now. On Wed, 14 Jul 2010 13:05:27 -0700, AES wrote: Is your assessment here that placing RF-lossy human flesh (with a high water content) close enough to the phone antenna loads down (or maybe just detunes?) the RF circuitry of the transmitter final stage to a point that the active transmitter circuitry in the phone no longer oscillates effectively? -- but just putting a dry and non-lossy dielectric there doesn't, and also moving the flesh even a short distance away reduces its loading on the circuitry enough that the active circuitry still works OK? Nope. My wild guess(tm), based upon what little I can extract from the FCC ID page and from the iFixit autopsy, is that something drastic is happening in receive. The -30dB (that's 1000 times drop) in signal appears in receive, when you're NOT making a call and the xmitter is inactive. Well, the xmitter is sending keep alive bursts every few minutes, but nothing more. Methinks it's a receive problem, not xmit. I'll go out on a limb and suggest that the receiver front end (probably a GASFET or HEMT) might be a bit regenerative (border line oscillatory). This gives it lots of gain, but only if nothing else changes. In effect, the antenna becomes part of an oscillator circuit, where the oscillatory conditions are partly provided by the antenna Q (i.e. antenna efficiency). http://en.wikipedia.org/wiki/Regenerative_circuit Touch the antenna, and you reduce the antenna Q. The front end stops acting regenerative (barely oscillating), and the sensitivity drops like a rock. It's the only explanation I can conjure the will cause a -30dB drop in received signal. It's been demonstrated (by me and others) that strangling the antenna of other cell phones drops the rx signal up to -10dBm (10 times drop). That's what I would normally expect to see from touching a cell phone antenna. However, the -30dB drop of the iPhone 4 requires some extra circuit design screwups. Unfortunately, detecting the regeneration is going to require internal probes, test fixturing, and plenty of expensive test equipment. There's another related possibility. Most of the finger tests have been with the finger bridging the gap. That means they're touching BOTH the cellular and wi-fi/BT antennas. It's obviously the hot end of the cellular antenna, but I can't tell if it's the hot end or ground end of the wi-fi/BT antenna. If the hot end, another possibility it that coupling to the 2nd antenna causes this antenna to radiate into the case, thus causing the cellular front end to oscillate. If the oscillations are bad enough, the signal level will be high enough to induce blocking (overload) in the cellular front end. This can be easily detected with a spectrum analyzer probe in the vicinity. If touching/bridging the antennas causes a new signal to appear on the SA, that's the problem. It would be very interesting to know if touching ONLY the cellular part of the antenna (the part that goes up the side of the phone), and not the wi-fi/BT antenna (bottom of phone), causes the same drop in signal. It would also be interesting to test the wi-fi signal strength to see if it's effected by touching its antenna. I have a few other guesses, but these are the best I can currently conjure at this time. [I'm an EE, but with no RF circuitry experience, much less any cellphone experience. So, I can understand this happening with an active transmitting circuit -- though I have somewhat more trouble seeing how it would interfere in such a sensitive way with a passive receiving antenna.] Think regeneration and borderline oscillation. The bad news is that if Apple stabilizes the rx front end, and eliminates the oscillation or regeneration, my guess(tm) is that the resultant phone is going to have a serious rx sensitivity problem. If you look at the cellular antenna in the iPhone 3G and other internal antenna cell phones, they're not very simple looking devices. Lots of strange lumps, traces, pads, and oddities, all designed to optimize performance in the 800/900 and 1800/1900 MHz bands. Getting them to look like 50 ohms for minimum VSWR is also important. Lots of articles in the IEEE Antenna and Prop proceedings on the topic of cramming a dual band antenna in the smallest possible package. On the other foot, the iPhone 4 antenna is crude. As far as I can tell from here, it's a crude monopole (single wire) antenna. There's no matching circuit for VSWR reduction, and no attempt to optimize performance in the desired bands. I might have missed something in the dissection, but all I can see is an end fed monopole, without a counterpoise or underlying ground. Such an antenna is going to have resonances at odd frequencies, and miserable antenna efficiency. Disclaimer: I haven't found anyone willing to let me tear into their iPhone 4 yet, so all the above is guesswork. -- Jeff Liebermann 150 Felker St #D http://www.LearnByDestroying.com Santa Cruz CA 95060 http://802.11junk.com Skype: JeffLiebermann AE6KS 831-336-2558 |
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