For wide bandwidth modulation formats this is a bit of a pain since you need a very wideband, high current, power supply. so they are doing an A/theta modulator but trying to simplify the bias control on the PA to avoid that.

No, they're doing something more complicated than A/theta modulation (aka envelope tracking aka envelope elimination and restorataion aka ...). They are doing an outphasing amplifier which splits the original signal into two constant amplitude variable phase signals which will reproduce the original signal when they are recombined, but they are adding some envelope tracking elements to further improve efficiency since wideband combiners will absorb the differential section of the input signals as loss.

What I'm not clear on is why they are doing this when they have a predistortion loop anyway. a pure predistortion loop should be able to achieve very similar results without any need for the PA bias adjust. you can also do it with 1 PA instead of two.

A predistorter doesn't have much of anything to do with PA efficiency (the point of this MIT research), PD's are for linearity. High efficiency PA topologies typically take a hit to linearity. Fancy techniques like outphasing and envelope tracking are better than some but they still reduce linearity. Poor linearity means increased distortion. Distortion increases error rates in digital transmissions, and it also leads to signal leaking into adjacent signal bands, which isn't allowed in the tight cellular spectral environment. So they put a PD in there to linearize things a bit further. That's probably why they are using discrete bias levels instead of continuously variable - they can optimize their PD loop to work best in these four well-characterized states which gets most of the efficiency gain while making the linearization easier.

I don't know, looks like somebody's thesis to me. Doesn't look like it's particular practical. Also, first rule of looking at schemes like this. How much of that power they saved is being used in the more complicated digital circuitry. That's the reason you don't see PD loops in cell phones. It's a wash, you spend so much power analyzing the signal to do PD that you burn up the savings . Now if you have a 10W transmitter, PD makes lots of sense.

These are not fundamental limitations. It's making more and more sense as digital processing and DSP chips get faster, cheaper, and lower power. The point of research is to try to push the state of the art and it may not be "practical" when the research paper is hot off the press. If it's good enough then it will be practical some time down the road, and if it isn't good enough then it will be left aside as a lesson learned. Apparently the researchers think its good enough to found a startup company, so they're either foolish or they understand it better than you. Time will tell.

Do you have an estimate of how much it does cost you as a percentage of the cash revenue?

This is a duplicate story posted on Slashdot on Oct 31: http://hardware.slashdot.org/story/12/11/01/0021213/breakthrough-promises-smartphones-that-use-half-the-power

Luckily this time the summary includes a link to an actual technical paper. The summary and the news article make it sound like this is an Envelope Tracking amplifier, but if you read the paper this is actually something different, it is more complicated and more interesting.

They are starting from an outphasing amplifier which divides a variable envelope signal into two constant amplitude but variable phase signals which can be amplified more efficiently since the amplifier doesn't need to output both large and small signals. But combining the signals is inefficient because the combiner must absorb some of the power when the two halves of the signal are very out of phase with each other. What the MIT researchers are doing is extending the outphasing technique to allow multiple discrete amplitudes on each amplifier to minimize the combiner inefficiency. It's more efficient than plain outphasing, I'm not sure how it compares to envelope tracking since the authors did not compare it to this in their paper.

Of course people really pay for porn. It costs money to create it, so somebody somewhere is paying for it to be made. Advertising doesn't add much to the industry revenue since most ads on free porn sites are for the paid porn sites and other adult sites. The free sites tend to have (in my opinion) pretty low quality in terms of the selection of content, and the display quality can be pretty bad. Some of the content there is placed by the entity who owns it, but much of it is surely pirated.

It's simply an entertainment expense and many people have no problem paying a fair price for something that they want. With a paid site you generally have a better selection of content in a genre that interests you, higher quality picture/video, and regularly added new content. In addition to people being cheap I think that there is some kind of guilt or shame that some people associate with paying for porn that they can sidestep if they only look at free porn.

Of course one problem is that many paid porn sites tend to be fairly expensive, probably because of the massive amount of marketing that they paid for on the free sites and the fact that a lot of people expect porn to be free these days, so there's a smaller number of paying customers.

Based on the article it sounds a lot like envelope tracking:

The new advance is essentially a blazingly fast electronic gearbox. It chooses among different voltages that can be sent across the transistor, and selects the one that minimizes power consumption, and it does this as many as 20 million times per second. The company calls the technology asymmetric multilevel outphasing.

But looking back at one of their papers: http://www-mtl.mit.edu/~jldawson/Dawson_digest2009.pdf it is not exactly envelope tracking. They are starting out with an outphasing amplifier (dividing the signal into two constant amplitude variable phase signals which can then be amplified with an efficient nonlinear amp and recombined into the original signal) and then adding a discretely variable drain bias (much like an envelope tracker) but the purpose of the variable drain voltage is actually to minimize power dissipation in the combiner's isolation resistor. Thus they compare their efficiency and linearity only to outphasing types of amplifiers. I would be curious to see how this stacks up to pure envelope tracking amplifiers.

I used a Graph Gear 1000 for a while. It has incredible style points, feels solidly built, and the retracting tip is a nice feature for when you keep the pencil in a bag or pocket. However after around 6 months of regular use with storage in a backpack the springiness in the clip was lost, and due to the unusual tip-retracting mechanism this mean that the tip would not stay retracted. Also I found that I was not a big fan of the narrow and hard metal grip, the heavy weight during long use, and the narrow eraser.

Nowadays my preferred pencil is the Pentel "Quicker Clicker" series, specifically the .7mm model, PD347. The wide body with a thin layer of rubber on the grip (enough to soften without being squishy) is very comfortable for me, and the large and easily accessible eraser is very handy. The non-retracting tip means I don't like to carry it around in my pocket, but since I only use it at my desk(s) and it's much cheaper than the Graph Gear I simply bought enough to cover all of the places where I'll need one.

Rather than simply modding you up I decided to try this out, and it works! Which is kind of creepy.

Since you dismiss the Newcastle University study only on the basis of Mark Bittman being a biased columnist (fair enough, he probably is), you may be interested to read the recent NY Times article which also explains some of the methodology differences between the studies which lead to different conclusions. In any case, I'm reserving judgement on both studies for now.

http://www.nytimes.com/2012/10/16/science/stanford-organic-food-study-and-vagaries-of-meta-analyses.html

True, a pick and place requires a large scale of operation before it becomes worth the capital and the reels. But it shouldn't take much effort to create a solderpaste mask - whenever you're defining a new pad just add the solderpaste to the pad definition and you're done, all you need to do is export the layer at the end. This is helpful even for relatively small board runs - you stencil on paste, place parts manually, and reflow in a lab toaster oven / hot plate, etc. There's very little capital and once you get above a few boards or so (depending on the board and the assembly guy) it can be faster than hand soldering.

I imagine you could even use the inverse of the soldermask layer as a paste layer, at least for non-RF boards where everything except pads is usually covered in solderpaste. It's not ideal because then a bit of misalignment puts some paste on top of the soldermask which risks bridging for fine pitches, but I know there's CAM software out there which could shrink the solderpaste layer to correct for that.

There's a huge difference! What you propose involves the actual loss of billions of dollars in property investment and a major impact on the sport in the US for some years due to loss of venues. What happened on WoW will require some overtime from the admin team to fix, resecure, and restore to pristine state from backups over a fairly short period of time.

So to better respond to the WoW hack: "Who cares, it's just an online game that they can restore from backups before you know it."

You missed some important points when you draw your conclusion:

This very important section of the article (emphasis mine) is conspicuously absent from your post:
Yet even within its narrow framework it appears the Stanford study was incorrect. Last year Kirsten Brandt, a researcher from Newcastle University, published a similar analysis of existing studies and wound up with the opposite result, concluding that organic foods are actually more nutritious. In combing through the Stanford study she’s not only noticed a critical error in properly identifying a class of nutrients, a spelling error indicative of biochemical incompetence (or at least an egregious oversight) that skewed one important result, but also that the researchers curiously excluded evaluating many nutrients that she found to be considerably higher in organic foods.

At this point that given that two research institutions have published metastudies with opposite conclusions, and that errors and oversights have been identified in the Stanford study, I'd have to say that the jury is out on this topic.

No, we haven't for a long time.

Taco Cowboy's link a few posts above addresses this and acknowledges the decreased energy density but made claims that large-scale supercaps would provide better economy in terms of $/(kWh*(number of cycles)). But of course $/kWh is also important because if they are highly capital intensive then they won't necessarily be attractive.

What is the $/kWh of industrial supercaps right now? The article you linked above had some projected numbers from startup companies, one of which seems to have gone under and the other of which is still in startup mode. I just helped put together an experimental off-grid PV system with 3kWh lead acid capacity at somewhere from $200-$250/kWh storage cost.

Is there anywhere a hobbyist or researcher could buy a few kWh of indsutrial supercaps?

Umm, this is how government funded R&D is supposed to work. The government spends money on projects that are too risky or too long-term for private companies to easily justify funding on internal dollars. Then when a higher level of technical maturity is reached private companies can take the body of knowledge, develop their own products for the government and private users, and start selling products to the government (and other customers) for less money than the government would have spent to build to develop and build it themselves (or pay a contractor to do for them). It's a win win win: the company wins, the government wins, and non-government customers win because they can now buy tech that up until then was controlled by the government.

It has happened in all sorts of fields including space. Government science and R&D funding has helped advance a huge number of fields.

But the government and many of the external researchers it funds are not in the business of making and selling products, so the plan for "technology transfer" and "transition" (to industry, whether real industry or the "prime" contractor industry) can be an important consideration in receiving govt dollars for a project depending on the work and technical readiness.