The article mentions miniaturization from a 6 foot (~184 cm) containing 200 antennas to an 18 inch cube containing 20,000 antennas--while this is possible (maybe) to build, it simply will not work.
Phased array beam-forming requires a minimum distance between transmitters in order to both form the wave and to reduce the mutual coupling between antennas. (Mutual coupling is a near-field phenomena that can significantly degrade antenna performance: for example, mutual coupling = -3dB means 50% of the transmitted power form one antenna is absorbed back into the circuit of the adjacent antenna).
Most antenna phased array systems assume a minimum separation distance of half-wavelength between antennas in order to achieve mutual coupling below -15 dB. At 2.4 GHz, the wavelength is roughly 12cm, so the minimum separation distance in free space is 6cm. Assuming they use FR4 as the PCB material to support the antennas, the physical separation can be reduced to roughly 3cm between antennas (Rogers is another material with dielectric constant of 10, but very expensive). The current size of their transmitter is 184cm tall, so it is conceivable that if the width is at least 6cm, it is possible to contain 200 transmitters. (However this is basically a vertical phased array--this means the beam-scanning is mostly in the vertical orientation--very little ability to perform horizontal beam-forming).
Now, examine the 18 inch cube with 20,000 antennas: They will conceivably place transmitters along the all 6 sides. Each side has a surface area of roughly 45 x 45 cm and will contain roughly 3,300 antennas. Assuming the antennas are miniaturized such that each antenna length is ~ 1 cm, then each side of the cube can support roughly 256 antennas with optimal mutual coupling. If each side were to contain over 3,000 antennas, the separation would decrease to almost zero, resulting in mutual coupling close to 100%; thereby rendering the system useless.
Note: All the antennas would need to be placed along the surface of the cube, if more antennas were placed inside, the transmitted power from the inner antennas would just get absorbed by the outer layers.
And while some of us may place faith in the FCC (and the goodness of Apple and Nokia), they (FCC) know very little as well. For example, the FCC regulation specifies that the EM absorption is measured and certified in the brain tissue next to the users' ears. Since the EM absorption is a near field effect (within 1-2 cm), the cell phone manufacturers (including the Apple iPhone and most of the ultra-slim phones) started placing their antennas at the bottom of the handset. The ultra-slim phones have to reduce the thickness of the antenna. Since the internal antenna's bandwidth (ie performance) is dependent on its height above a PCB, they removed the PCB completely (which increases the EM absorption in tissue by almost double). Since consumers demand thinner phones and the phone manufacturers needed a way to get around the FCC certification, place the antennas in the base of the handset instead and voila.....!
So while your brain is now absorbing much less energy, your lymph nodes are getting much more and the manufacturers can pass the FCC certification.....
This is all common knowledge among most RF engineers, so wonder how long it will take before the FCC tightens up their certification....if ever...
That article in New Scientist was supported by a manufacturer of those little EM blockers a few years ago. We have our own testing equipment and have thoroughly disproved their findings. While some of the EM field couples to the headset, it only does so for the first 0-3cm (depends on location of headset). In our measurements, the EM absorption from a wired headset is 0. The EM absorption from Bluetooth is 1/100th of that from a mobile phone. The only increase in radiation absorption from using a headset occurs when the phone is placed next to the body while using the headset since muscle mass near the phone (heart, leg, etc) absorbs microwave energy at 4 times the rate as your brain does.
RF engineers can only demonstrate how much radiation can be measured at a certain point within your head. We cannot show any medical causality without decades of statistics. All the medical studies that have been published over the past 10 years are largely inconclusive (there is a ratio of 50:50 for "no harm" vs "bad"). In addition, a 2-3 year study cannot effectively be used to predict a 20-30 year trend--especially with microwave energy since the effects are largely due to the intensity of the radiation.
And while some of us may place faith in the FCC, they know very little as well. For example, the FCC regulation specifies that the EM absorption is measured and certified in the brain tissue next to the users' ears. Since the EM absorption is a near field effect (within 1-2 cm), the cell phone manufacturers (including the Apple iPhone) started placing their antennas at the bottom of the handset. So while your brain is now absorbing much less energy, your lymph nodes are getting much more and the manufacturers can pass the FCC certification.....
In the end it is personal choice--do you "feel" safer using a headset. Are you ultra-paranoid--don't use a phone, stand next to a microwave oven, live in a shield box like some people in Northern Scandinavia do (they believe they are allergic to electricity).
We can still search youtube for Tibet videos, but when we try to view a youtube video, we get the following message:
"This video is not available in your country."
This means that it is youtube that is doing the blocking, not the Chinese government (we have access to all sorts of other "subversive" material including Tibet videos from other sources.
This is a highly disturbing development of youtube blocking videos in a place with normally free press--and then blaming the Chinese government for filtering.
On the other hand, once you open up the door of the microwave oven, the standing wave gets destroyed. This is why microwave ovens have certain sizes--to create a resonance of 2.4 GHz waves in order to amplify the power density up to 1000 Watts. So, would expect that once the microwave door is open, rather than causing adverse external radiation, it just makes the microwave oven rather in-efficient. But, that said, still not something recommended--the microwave is not nearly as soft as a pillow and not much maneuverability....:)
Comparing signal bars on various models of mobile phones is not a good test of field strength. In order to compare sensitivity in a scientific manner, need to rip apart the phones and measure their various RF parameters like antenna efficiency RF power levels, TIS, and TRP. Various phone-makers have been caught "cheating" with their signal bars as to show better reception than their rivals--so this is not a reliable comparison method. There is also a problem with multi-path, so phone reception will vary according to how you hold the phone, whether you use a BT headset, if there is a lorry passing down your street between the cell phone tower and your handset, the weather, rain, etc.....
Most of the phones you named (Nokia 6300, HTC, Razor) are well known for having poor antenna performance due to both the metal covers and the chrome plated material nearby the antenna (acts like a resistor and absorbs radiated power). A better comparison would be with a 5-7 year old phone with a much better antenna (like Nokia 3210).
While metal is shiny and slick, when it is too close to an antenna, the bandwidth decreases. So the antenna designer has a choice of which frequencies to focus their design effort. Since their initial target market was the USA, they probably targeted GSM850 (AT&T's GSM network). From the antenna photos, the GSM 1800/1900 part of the antenna is the part closest to the battery/metal covers, which further degrades performance in this band. One of the earlier replies said their iPhone worked fine in the country-side of the UK. This is most likely due to the GSM850/900 part of the antenna being furthest away from the battery/metal covers.
One can see a small little cable going from the RF Module to the antenna. In almost 99% of the GSM phones on the market today, the antenna is right next to the RF Module. This is to minimize the RF losses between the RFIC and the antenna. By using a cable, significant losses are introduced into the system by both the cable and the miss-match at both ends of the cable. The antenna is also at the bottom of the phone and is more likely to be covered by the user's hand (further decreasing sensitivity); though there are quite a few phone on the market with antennas at the bottom--it is how they get around the SAR limits which are specified as the peak radiation a user receives next to their ear (the mouth area is not measured in the FCC/EU tests.
So, while from an anecdotal perspective, it appears the iPhone has random sensitivity issues; from an antenna engineer's perspective however, it is no surprise why the iPhone has lower performance than most phones (but would still have similar performance to other phones with poor antenna designs--of which there are several for different reasons than cable losses).
If you are interested in reading more technical reports about antenna performance in mobile phones, go to the following website:
This is coming from an electrical engineer who uses 3D numerical solvers every day at work. The best package is something called CST Microwave office. You can adjust it to fit your problem by creating different dielectric materials in different regions (and thereby adjusting the velocity of the EM waves). You can adjust the material parameters (mu and epsilon) to create any material you want, including materials with negative refractive index...very interesting from a physics/mathematics point of view.
For broadband applications, CST is the fastest, most stable, and user-friendly in terms of parameterization, optimization, and learning curve. It has excellent post-processing of the results, including field distributions and animation. Other packages include XFDTD, SemCad, HFSS (FEM), Comsol (FEM). Writing the code to do this on your own is a big undertaking, especially for 3D, and you should expect to spend about 12-18 months being a code-monkey. There is free 3D fdtd source code written in fortran on the net and also part of the FDTD bible published about 12 years ago by Luebbers, et. al.
Out of curiosity, does this problem have a direct application, or just solving it out of academic interest?
Real Estate here is expensive in the expat districts. If you can stomach living in the new territories or lantau island, it is not bad and with the train/ferry links. Plus, it is nicer to live outside the city if you like sports--can live right on a paved bike only trail, or right next to the ocean for 500 USD a month. As for the pollution in HK, it is no worse than LA, and far better than any city in China. And I would take pollution over the politics in USA. In addition, despite the pollution, HK usually competes with Sweden for the number one position on the longest lifespan list and is number one in the highest IQ list (average here is 116 compared to 100 in USA).
Choose to move to Hong Kong (part of China, not Japan) about 12 years ago and work here as an enginerr on local terms (not expat extravaganza). I can safely say I will be here the rest of my life.
There are many advantages to living in HK: 1. Beautiful City with mountains ringing the downtown 2. Best public transport in the world: subways are safe and run every 1 to 3 minutes, buses and trains get you everywhere else 3. Safety: I can go anywhere and anytime of night without fear for my life or mugging (I cannot think of a single american city with population > 1 million that can match this) 4. Taxes: Some of the lowest in the world with a maximum of 16%, no capital gains taxes 5. Food: Awesome selection of food at cheap prices (HK is regulary listed as one of the world's most expensive cities to live in, but that only applies if you try to live like the Trumps, as a regular person, I find I save as much money in 1 year in HK as I did in 5 years in USA) 6. Language: English is widely used both as the language of law and daily usage 7. Freedom: It is more free than Singapore, and even more free than USA (especially now) 8. Sports: Some of the best hiking in the world. Excellent cycling on weekdays. Wake-boarding, surfing, paragliding, mountain climbing, scuba diving, etc all within 30-45 minutes of your apartment.
Slashdot Mirror
The article mentions miniaturization from a 6 foot (~184 cm) containing 200 antennas to an 18 inch cube containing 20,000 antennas--while this is possible (maybe) to build, it simply will not work.
Phased array beam-forming requires a minimum distance between transmitters in order to both form the wave and to reduce the mutual coupling between antennas. (Mutual coupling is a near-field phenomena that can significantly degrade antenna performance: for example, mutual coupling = -3dB means 50% of the transmitted power form one antenna is absorbed back into the circuit of the adjacent antenna).
Most antenna phased array systems assume a minimum separation distance of half-wavelength between antennas in order to achieve mutual coupling below -15 dB. At 2.4 GHz, the wavelength is roughly 12cm, so the minimum separation distance in free space is 6cm. Assuming they use FR4 as the PCB material to support the antennas, the physical separation can be reduced to roughly 3cm between antennas (Rogers is another material with dielectric constant of 10, but very expensive). The current size of their transmitter is 184cm tall, so it is conceivable that if the width is at least 6cm, it is possible to contain 200 transmitters. (However this is basically a vertical phased array--this means the beam-scanning is mostly in the vertical orientation--very little ability to perform horizontal beam-forming).
Now, examine the 18 inch cube with 20,000 antennas: They will conceivably place transmitters along the all 6 sides. Each side has a surface area of roughly 45 x 45 cm and will contain roughly 3,300 antennas. Assuming the antennas are miniaturized such that each antenna length is ~ 1 cm, then each side of the cube can support roughly 256 antennas with optimal mutual coupling. If each side were to contain over 3,000 antennas, the separation would decrease to almost zero, resulting in mutual coupling close to 100%; thereby rendering the system useless.
Note: All the antennas would need to be placed along the surface of the cube, if more antennas were placed inside, the transmitted power from the inner antennas would just get absorbed by the outer layers.
And while some of us may place faith in the FCC (and the goodness of Apple and Nokia), they (FCC) know very little as well. For example, the FCC regulation specifies that the EM absorption is measured and certified in the brain tissue next to the users' ears. Since the EM absorption is a near field effect (within 1-2 cm), the cell phone manufacturers (including the Apple iPhone and most of the ultra-slim phones) started placing their antennas at the bottom of the handset. The ultra-slim phones have to reduce the thickness of the antenna. Since the internal antenna's bandwidth (ie performance) is dependent on its height above a PCB, they removed the PCB completely (which increases the EM absorption in tissue by almost double). Since consumers demand thinner phones and the phone manufacturers needed a way to get around the FCC certification, place the antennas in the base of the handset instead and voila.....!
So while your brain is now absorbing much less energy, your lymph nodes are getting much more and the manufacturers can pass the FCC certification.....
This is all common knowledge among most RF engineers, so wonder how long it will take before the FCC tightens up their certification....if ever...
That article in New Scientist was supported by a manufacturer of those little EM blockers a few years ago. We have our own testing equipment and have thoroughly disproved their findings. While some of the EM field couples to the headset, it only does so for the first 0-3cm (depends on location of headset). In our measurements, the EM absorption from a wired headset is 0. The EM absorption from Bluetooth is 1/100th of that from a mobile phone. The only increase in radiation absorption from using a headset occurs when the phone is placed next to the body while using the headset since muscle mass near the phone (heart, leg, etc) absorbs microwave energy at 4 times the rate as your brain does.
RF engineers can only demonstrate how much radiation can be measured at a certain point within your head. We cannot show any medical causality without decades of statistics. All the medical studies that have been published over the past 10 years are largely inconclusive (there is a ratio of 50:50 for "no harm" vs "bad"). In addition, a 2-3 year study cannot effectively be used to predict a 20-30 year trend--especially with microwave energy since the effects are largely due to the intensity of the radiation.
And while some of us may place faith in the FCC, they know very little as well. For example, the FCC regulation specifies that the EM absorption is measured and certified in the brain tissue next to the users' ears. Since the EM absorption is a near field effect (within 1-2 cm), the cell phone manufacturers (including the Apple iPhone) started placing their antennas at the bottom of the handset. So while your brain is now absorbing much less energy, your lymph nodes are getting much more and the manufacturers can pass the FCC certification.....
In the end it is personal choice--do you "feel" safer using a headset. Are you ultra-paranoid--don't use a phone, stand next to a microwave oven, live in a shield box like some people in Northern Scandinavia do (they believe they are allergic to electricity).
We can still search youtube for Tibet videos, but when we try to view a youtube video, we get the following message: "This video is not available in your country." This means that it is youtube that is doing the blocking, not the Chinese government (we have access to all sorts of other "subversive" material including Tibet videos from other sources. This is a highly disturbing development of youtube blocking videos in a place with normally free press--and then blaming the Chinese government for filtering.
On the other hand, once you open up the door of the microwave oven, the standing wave gets destroyed. This is why microwave ovens have certain sizes--to create a resonance of 2.4 GHz waves in order to amplify the power density up to 1000 Watts. So, would expect that once the microwave door is open, rather than causing adverse external radiation, it just makes the microwave oven rather in-efficient. But, that said, still not something recommended--the microwave is not nearly as soft as a pillow and not much maneuverability....:)
In February 2008, we will do a report on the iPhone. Have to wait for funding from the government first.
Comparing signal bars on various models of mobile phones is not a good test of field strength. In order to compare sensitivity in a scientific manner, need to rip apart the phones and measure their various RF parameters like antenna efficiency RF power levels, TIS, and TRP. Various phone-makers have been caught "cheating" with their signal bars as to show better reception than their rivals--so this is not a reliable comparison method. There is also a problem with multi-path, so phone reception will vary according to how you hold the phone, whether you use a BT headset, if there is a lorry passing down your street between the cell phone tower and your handset, the weather, rain, etc..... Most of the phones you named (Nokia 6300, HTC, Razor) are well known for having poor antenna performance due to both the metal covers and the chrome plated material nearby the antenna (acts like a resistor and absorbs radiated power). A better comparison would be with a 5-7 year old phone with a much better antenna (like Nokia 3210).
While metal is shiny and slick, when it is too close to an antenna, the bandwidth decreases. So the antenna designer has a choice of which frequencies to focus their design effort. Since their initial target market was the USA, they probably targeted GSM850 (AT&T's GSM network). From the antenna photos, the GSM 1800/1900 part of the antenna is the part closest to the battery/metal covers, which further degrades performance in this band. One of the earlier replies said their iPhone worked fine in the country-side of the UK. This is most likely due to the GSM850/900 part of the antenna being furthest away from the battery/metal covers.
iPhone disassembled:
http://www.ifixit.com/Guide/iPhone/Communications-Board/105/8/Page-7/Communications-Board
One can see a small little cable going from the RF Module to the antenna. In almost 99% of the GSM phones on the market today, the antenna is right next to the RF Module. This is to minimize the RF losses between the RFIC and the antenna. By using a cable, significant losses are introduced into the system by both the cable and the miss-match at both ends of the cable. The antenna is also at the bottom of the phone and is more likely to be covered by the user's hand (further decreasing sensitivity); though there are quite a few phone on the market with antennas at the bottom--it is how they get around the SAR limits which are specified as the peak radiation a user receives next to their ear (the mouth area is not measured in the FCC/EU tests.
So, while from an anecdotal perspective, it appears the iPhone has random sensitivity issues; from an antenna engineer's perspective however, it is no surprise why the iPhone has lower performance than most phones (but would still have similar performance to other phones with poor antenna designs--of which there are several for different reasons than cable losses).
If you are interested in reading more technical reports about antenna performance in mobile phones, go to the following website:
http://antennas.astri.org/antennas_mirror
PDF Password = astriantennas
This is coming from an electrical engineer who uses 3D numerical solvers every day at work. The best package is something called CST Microwave office. You can adjust it to fit your problem by creating different dielectric materials in different regions (and thereby adjusting the velocity of the EM waves). You can adjust the material parameters (mu and epsilon) to create any material you want, including materials with negative refractive index...very interesting from a physics/mathematics point of view. For broadband applications, CST is the fastest, most stable, and user-friendly in terms of parameterization, optimization, and learning curve. It has excellent post-processing of the results, including field distributions and animation. Other packages include XFDTD, SemCad, HFSS (FEM), Comsol (FEM). Writing the code to do this on your own is a big undertaking, especially for 3D, and you should expect to spend about 12-18 months being a code-monkey. There is free 3D fdtd source code written in fortran on the net and also part of the FDTD bible published about 12 years ago by Luebbers, et. al. Out of curiosity, does this problem have a direct application, or just solving it out of academic interest?
Real Estate here is expensive in the expat districts. If you can stomach living in the new territories or lantau island, it is not bad and with the train/ferry links. Plus, it is nicer to live outside the city if you like sports--can live right on a paved bike only trail, or right next to the ocean for 500 USD a month. As for the pollution in HK, it is no worse than LA, and far better than any city in China. And I would take pollution over the politics in USA. In addition, despite the pollution, HK usually competes with Sweden for the number one position on the longest lifespan list and is number one in the highest IQ list (average here is 116 compared to 100 in USA).
Choose to move to Hong Kong (part of China, not Japan) about 12 years ago and work here as an enginerr on local terms (not expat extravaganza). I can safely say I will be here the rest of my life.
There are many advantages to living in HK:
1. Beautiful City with mountains ringing the downtown
2. Best public transport in the world: subways are safe and run every 1 to 3 minutes, buses and trains get you everywhere else
3. Safety: I can go anywhere and anytime of night without fear for my life or mugging (I cannot think of a single american city with population > 1 million that can match this)
4. Taxes: Some of the lowest in the world with a maximum of 16%, no capital gains taxes
5. Food: Awesome selection of food at cheap prices (HK is regulary listed as one of the world's most expensive cities to live in, but that only applies if you try to live like the Trumps, as a regular person, I find I save as much money in 1 year in HK as I did in 5 years in USA)
6. Language: English is widely used both as the language of law and daily usage
7. Freedom: It is more free than Singapore, and even more free than USA (especially now)
8. Sports: Some of the best hiking in the world. Excellent cycling on weekdays. Wake-boarding, surfing, paragliding, mountain climbing, scuba diving, etc all within 30-45 minutes of your apartment.
And I could go on and on....