Forgot your password?
typodupeerror

Comment: The same as MIMO (Score 3, Informative) 147

by Jott42 (#39221103) Attached to: 'Twisted' Waves Could Boost Capacity of Wireless Spectrum
This is actually a subset of MIMO, which is already widely used in WiFi and other wireless networks. Thus it will, regrettably, not give access to any additional bandwidth. The details on the equivalence is in a paper from IEEE Transactions on Antennas and Propagation, titled "Is orbital angular momentum (OAM) based radio communication an unexploited area?" http://lup.lub.lu.se/luur/download?func=downloadFile&recordOId=2062936&fileOId=2339120

Comment: Re:Use the wireless spectrum for intertubes (-wave (Score 1) 246

by Jott42 (#27028885) Attached to: Spectrum Fees May Preclude US Low-Cost Cellular
Because the overhead would be prohibitive for a lot of battery-operated applications. The same goes for the size necessary to implement a complete IPv6 stack.

And there are services that can not use IPv6, due to technical reasons: GPS is one example. Emergency beacons is another. Some scientific applications do also need their own frequency allocations. The same goes for the military.

In summary: frequency application strategies are not as simple as the proponents for "open spectrum" assumes. Cognitive radios comes with huge overheads in size and power, and would make a lot of wireless applications we use everyday impossible. (Typical example: remote control car locks.)

Comment: Re:How about that inverse-square law? (Score 1) 160

by Jott42 (#26183677) Attached to: Student Invention May Significantly Extend Mobile Device Battery Life
The real strange thing is why they didn't compare their new capacitive coupling with a classic wired connection between the PA and the antenna. Instead they introduce an additional PA with corresponding power consumption when they test the wired connection.

The difference between the standalone chip antenna, with a maximum size of 1 mm, with the proposed antenna, with an size of 17 mm, is not revolutionary, it is expected due to the very bad efficiency of electrically small antennas.

Comment: Re:Counter-intuitive! (Score 3, Interesting) 160

by Jott42 (#26183003) Attached to: Student Invention May Significantly Extend Mobile Device Battery Life
Yes, it is counterintuitive. And also not what is actually claimed in the paper.
In the paper three designs are compared:

(1) One with only an antenna on chip. That is, an antenna on the actual chip, with a size of 1x0.5 mm. Draws 3.3 mW, "range" 1m.
("Range" is a very strange measure in RF design...) (2) The same chip but without the on-chip antenna. Instead the power is coupled to an additional PA-amplifier, and an external small folded dipole antenna: Size about 16x10 mm. Draws 38 mW, "Range" 75 m. (3) The same chip withou the PA, with the on-chip antenna coupling to an external patch antenna of size 17x17 mm. Draws 3.3 mW, "Range" 24 m.

In summary: Nice engineering work, but no conclusions can be drawn, as it is very much a case of apples and oranges. (No constant TX power, No constant size, Not very much constant between the designs at all.)

And a classic mobile phone does not use an on-chip antenna at all. So this design will not give any benefit to your iPhone or Blackberry etc.

Comment: Re:How about that inverse-square law? (Score 3, Insightful) 160

by Jott42 (#26182937) Attached to: Student Invention May Significantly Extend Mobile Device Battery Life
You can not get any gain in an on-chip antenna at this frequencies: it is to small. He is comparing the use of only an on-chip antenna, which is never used in mobile phones, with the use of a coupled external, somewhat bigger, antenna on a ceramic substrate. Not at all suprising that he gets a better performance with the latter, as it is bigger. He would get even better performance with a classic mobile phone antenna, though.

I.e. This will not revolutionize the battery life of your iPhone or Blackberry. The losses in the coupling between the integrated PA and the antenna are very small (if we disregard detuning due to human proximity effects. Which is another story, and which is not influenced at all by the design in question.)

The comparison between two different antennas at different powers is not very good science - it is somewhat suprising it got published. (But it is only at a small conference, so it is not that surprising.)

Comment: Re:AM Radio = Range (Score 4, Informative) 202

by Jott42 (#22838634) Attached to: Australian WiMax Pioneer Calls It a Disaster
Minor nitpick: 2.4 GHz is not the frequency of maximum aborbance of water. The frequency of the maximum is temperature dependent, and the absorbance peak is very broad. Thus there is no need to use any special frequency. 2.4 GHz is used in microwave ovens due to that it was free to use, being an ISM band, and that the penetration depth is useful for cooking.

"Irrationality is the square root of all evil" -- Douglas Hofstadter

Working...