Perhaps you need to stop arguing and look at what you said in earlier posts. The article said that Apple designed an antenna with half the antenna efficiency as somebody else's. This is perfectly logical to an antenna designer, somebody managed to make an antenna 3 dB better.
It also proves that it's difficult to design antennas, unlike what you claim. RFICs are straightforward in comparison to very free-form design of antennas. Further, any modern antenna design is heavily dependent on computational tools, it takes a lot of sim time to iterate a design, so you have to have a good intuitive feel of the system.
The article said an Apple antenna took twice as much electrical power to create the same radio power. Antenna efficiency is not mentioned anywhere. As I keep repeating, something like a bad match would indicate technical incompetence but inefficiency in itself is not an indication of a bad design. If I may quote an authoritative source:
Small antennas are bad at efficiency, by the laws of physics.
Fast Company didn’t give any detail to support their claim, other than the word of “one source”. I suppose you could be that source, or you could be assuming they botched the design, but I’m assuming they were working within different design constraints. No way to know really, unless you know of any public test data showing the performance difference.
We could endlessly argue the definition of “hard”, but I’d feel pretty confident betting that the recently acquired Intel modem team employs more people and is a greater capital expense than Apple’s antenna team. Not the only metric, for sure, but in general companies apply more resource and budget toward harder problems. Baseband design also requires a lot of sim time, if that's the metric you're using.
I didn't mean to offend by calling the modem "the hard part". None of this is meant to devalue the work of the antenna team-- a great modem will be degraded by a poor antenna and front end. My only point is that there's no reason to freak out that Apple is doing this themselves. It's not beyond their capabilities and some bad press about a 10 year old design and one person's vague comment aren't enough to convince me this is beyond their capabilities. My point was about risk.
Wrong. You are mistaken in calling d/lambda the "electrical length". It is not. That is the physical length of the antenna. Electrical length refers to the length of an antenna as it appears to a circuit at the feedpoint. This is affected by antenna loading, e.g. inductors, that shorten the physical length versus the electrical length.
Physical lengths have units convertible to meters. d/lambda does not, it is unitless. d is a physical length. lambda is a physical length. d/lambda is an electrical length. This is more obvious when represented as it is in the Chu limit, as k*a where k is the wavenumber, 2π/λ, and a is the physical length— the product giving the electrical length in radians.
Antenna loading changes the electrical length without changing the physical length. This allows
you to change the physical length of the antenna and then load it to maintain a resonant electrical length as measured into the feed network. That may be what you meant, but since I'm confused about your definition of physical length at this point I'm not sure if you meant "versus" to mean "as opposed to" (incorrect) or to mean a ratio (essentially correct).
You're falling into a very common trap by people who don't design antennas and that is thinking S11/VSWR describes the performance of an antenna and that problems can be fixed by matching. That is completely wrong. If antenna feedpoint impedance is low, then radiation resistance must be low, and therefore antenna losses (ohmic) will be high, both in the antenna and matching network.
The reason why people fall into this trap is that antenna efficiency is very difficult to measure, unlike S11. You went to school and stuck a VNA and go S11. They could not afford a free-space scanning field measurement system, so you never learned efficiency measurements.
You're falling into a very common trap of meeting a stranger on the internet and thinking you know something about them. Antenna efficiency isn’t an esoteric concept…
Saying that saying “s11 describes antenna performance and can be fixed by matching” is completely wrong is completely wrong. Matching is a critical performance parameter for any power transfer system, and some problems can be fixed by better matching. That’s different than saying it’s the only parameter to optimize in a design or that all problems are fixed by matching and I don’t think anyone has made that claim. Exaggeration isn't an effective form of argument.
If antenna feed point impedance is low, then ohmic losses can’t be high. Feed point impedance is the sum of radiation resistance, Ohmic resistance and ground losses. Assuming the point you're choosing to measure into only looks into passive components, then all of the resistances are positive quantities. You can’t have a small sum and a large summand with all positive quantities. Again, maybe you're being loose with the language, but I think what you mean is that if the other losses remain constant and the radiation resistance falls then the ratio of radiation resistance to feed point resistance falls leading to lower efficiency and more losses to heat for the same radiated output.
The Chu limit is a nice piece of theory that matches the loss due to low radiation resistance versus tricks like matching and loading.
The Chu limit is a nice piece of theory that sets an upper bound on bandwidth for an antenna of a given electrical dimension. As I said, loss (beyond radiation loss) doesn’t enter into the Chu limit at all— he assumes idealized, lossless elements. I’d link a source to support that, but you already did. The Wikipedia article you linked states "Chu established the limit on
Q for a lossless antenna...".
but this was the take by many people at the time of this problem. This sentiment used to bother me to no end. At the time of the IPhone 4, I had owned every other IPhone. I experienced the antenna problem from day one with my phone. I would call someone, start talking and about 1 minute into the conversation, realized I was getting no response. The call was dropped. At the time Apple was thinking the problem was the screen not turning of when placed by your ear. If the screen didn't turn of, your ear would hit either the mute button or end call button. This actually was a problem, but not what was causing the main issue. Apple send out updates to try and fix the screen not turning of issue. You could put the phone up to your ear, look sideways at it and see the screen turn of and then back on. But, the real issue turned out to be the antenna problem.
