And while "baud rate" is now tacitly accepted as a term, baud already includes the unit of time. Saying "baud rate" is like saying "symbols/time/time" as if the data rate is accelerating. 2400 baud is already equivalent to 2400 symbols/second./pedant
(re-reading your post, I think you understand this but I think the distinction is important)
Any system will stop working when the battery dies. The point of saying POTS lasting through outages is because Telcos have to adhere (or should) to strict standards regarding availability of service and they maintain their centralized battery backup much better than a consumer does (or can).
I don't have any experience with VOIP, so I don't know how long their batteries last. However, given that people tend to use their smart phones for everything (GPS, video, audio, etc.) how much of a battery buffer is left at the end of the day to last a 24 hour outage (since power outages are generally unplanned). I know the smart phones I've used can handle a couple hours of GPS, video, audio, etc. and there usually isn't much battery left for voice or standby.
All I'm saying is that while centralization provides a single point of failure, it also provides a single point of maintenance and allows much larger battery backup than would otherwise be possible. Not to mention that it is much easier to restore power to every CO in the city to restore phone service than it is to restore power to the entire city (much like how blocks on the same grid as a fire station are usually the first to have power restored).
I don't find ultra "realistic" or difficult games fun to play. As a casual gamer, I want to play a game to pass the time and enjoy a sense of accomplishment. If I can't make any progress in what I feel to be a reasonable time, I drop the game and move to something else.
If you're doing anything non-trivial, why would you be working in Word to begin with? Word is just a little WYSIWYG word processor for student papers and unimportant documents. It's not capable of real typesetting or controlled document structure. For anything serious, more specialized software is absolutely necessary.
This is just plane ignorance on your part. Word has a powerful set of features for document and styles management. Sure, it is no LaTeX for scientific or mathematical papers, but I personally have reviewed thousand page proposals for various defense organizations that had made extensive use of Words advanced features. Your statement clearly shows that you have no such experience.
Not necessarily. Given that this is an apartment, the user will be in close proximity to his AP and many others. It is possible that boosting his power (in the presence of other interference) could simply overdrive the Wifi receiver in the laptop (driving it into compression). This creates an even higher noise floor (resulting from third order intermods) which desensitizes the receiver (and will of course reduce throughput). This will happen to even the most linear, low noise amplifier if you drive it hard enough. A properly designed receiver should have enough analog attenuator range to prevent this, but it could be a crappy/low cost design.
Well done:) Parenthesis have their place in technical writing for the non-technical. They allow you to set off portions of text as "tid-bits" which may help in the understanding but is not required for the technical reader.
Oh please, another software engineer? Amplifiers are by their very nature non linear devices as a whole (they just happen to have a linear region which we can make use of). The amplifiers in question are operated within their linear region as much as possible where possible, but certain requirements like efficiency force the designers to drive the transistor partly into its non-linear region (closer to P1dB). Some non-linearity is tolerated and is dictated by the FCC, ETSI or CRTC in the form of emissions masks or by the wireless standard in the form of modulation quality. The only way to ensure the amplifier is always inside the linear region under all conditions would be to back off from P1dB by so much that your efficiency tanks. But that is entirely not feasible for cellular design...consumers like long battery life and carriers like low operating costs.
Now, getting back to your comments. "As long as the mismatch is within spec, the only problem will be reduced efficiency". Amplifiers (or to be more specific, the transistors used in amplifiers) do not have real imput and output impedances. The real (resistive) component will generally not have the desired characteristic impedance (usually 50 ohms) and can be quite small (sometimes a few ohms or even tenths of an ohm). The imaginary (reactive) component will also be non-zero (which is undesirable, but a fact of life) which will tell whether the output (or input) is capacitive or inductive (depending on the sign of the reactive element). Real "high power" amplifiers (I say "high power" to describe the condition where the amplifier is operated towards the upper bounds of the linear region) are not simply matched for maximum power transfer and your done (the input is often matched this way since you would like to ensure any power available to the transistor will actually be taken into the device to be amplified...this is different for low noise amplifiers). This is called conjugate matching (where you set the real parts equal, and negate the reactive part).
On the output a different set of techniques is used. Loadpull is one technique which allows you to design your output matching network not only for linearity, but also efficiency or any other characteristic you can measure. The output matching network that produces the best efficiency (which is what we are talking about here) is most likely not the same as the one that produces the best P1dB or linearity. Also note that conjugate matching or other types of matching do not mean zero reflection (or VSWR=1). By the nature of the networks, the resulting VSWR (albeit low VSWR) is actually part of the desired characteristics of certain matching networks. Put another way, having the best VSWR response (i.e. zero reflection) will not get you the best efficiency (this is the aspect of your post that I take issue with). Reactive components do not dissipate energy (well, if you cosider the small resistive component they do, but this is orders of magnitude smaller than the other resistive components).
All this being said, another way to look at it is that if the reflections occur as part of the matching network, these can be tolerated since they are an inherent part of the design. Reflections after you have reached 50 ohms (i.e. between the matching network and the antenna) can be devastating to an amplifier. This is why they place a circulator or isolator directly after the matching network in most cases...this allows the output of the matching network to see a 20 dB match at least (depending on the circulator) regardless of what happens after (the antenna breaks, cable breaks, etc.). This prevents potentially devastating power from returning to the amplifier.
I am fully aware of how antennas are designed. Tuning the resonant frequency of an antenna should go without saying (though given the other posts on this story, I appreciate the fact that you spoke of what you knew, and limited yourself to just that).
My comment played off the OPs comment about a cantenna (which achieves its performance by increasing directivity). However, while tuning to your carrier frequency is generally accepted as the most basic guideline, you should take it one step further to include the radiation pattern in your overall design (and will ensure other performance characteristics are considered).
The problem is that if you make the antenna too directive, you may miss out on certain cell sites entirely (as you mention in the example with your pringles can). You may also notice that your pringles cantenna is highly symetrical about a few axes. You also provide a substantial ground plane which results in a design that better approaches theoretical design guidelines.
Cell phone designers have a lot to deal with, your big head, your hand, buildings, etc...in reality, a highly directive antenna on a mobile (that is truly mobile, unlike your cantenna) would be catastrophic in terms of being able to make a call.
Oh my god. Please not another "informative" post. I really wish you people would stop commenting on these articles when you clearly have no clue what you are talking about. The reflected power (if it happens to exist in this case...which it doesn't because these transmitters are designed quite well and usually include a circulator or isolator at the output of the amplifier to ensure an excellent match) does not go back into the amplifier, because if it did the amplifier would not work as it was designed and would either oscillate or produce extremely poor waveform quality at the output.
Now, if you can bypass the circulator/isolator I mentioned above (which is what I gather they are trying to do in this article) then that is one less place power can be lost on the way to the antenna.
No, "cellphone antennas" are not "power efficient". I assume you actually mean the radio (antennas [the antenna itself, not the other components you are incorrectly referencing] are generally passive...they do have a radiating efficiency, but they generally don't consume power in the classical sense). Cellular transmitters (base station and mobiles) are usually only in the 25-35% range of efficiencies. This is the result of high peak to average ratios in the signal which require the amplifier to be oversized by as much as 10x to ensure the FCC and other similar bodies will certify the equipment. In general, if your mobile is actually transmitting lets say 50 mW (the power reaching the antenna), the transmit chain would likely be consuming at least 150 mW (likely more).
Yes. Every connector, isolator, circulator, switch, filter, duplexer, wire, conductor, etc. contributes to the losses in the circuit.
As much as half your power can be lost after the final power amplifier (more than that and you need lessons in radio design, or you need to adjust your requirements).
Umm, dude...just because you shield a component doesn't mean it stops radiating. Shielding inhibits EM fields which are already present. To reduced radiated losses, you need to either improve the fundamental design of the circuit or make it radiate so well that you build an antenna instead.
They can't plagiarize your work if you don't give it to them. If someone asks for your solution/paper/answers, just tell them to screw off and figure it out for themselves.
because sometimes there are people that have too much money, and this is one way to legally steal from idiots that will spend whatever they can just to get some specific name.
Except that step 2 only works if they actually disconnect the hard drive or flash drive from the computer each time. Otherwise the backup data is just as easily wiped as the original data.
Slashdot Mirror
And while "baud rate" is now tacitly accepted as a term, baud already includes the unit of time. Saying "baud rate" is like saying "symbols/time/time" as if the data rate is accelerating. 2400 baud is already equivalent to 2400 symbols/second. /pedant
(re-reading your post, I think you understand this but I think the distinction is important)
And they charge $0.99 for shipping
Any system will stop working when the battery dies. The point of saying POTS lasting through outages is because Telcos have to adhere (or should) to strict standards regarding availability of service and they maintain their centralized battery backup much better than a consumer does (or can).
I don't have any experience with VOIP, so I don't know how long their batteries last. However, given that people tend to use their smart phones for everything (GPS, video, audio, etc.) how much of a battery buffer is left at the end of the day to last a 24 hour outage (since power outages are generally unplanned). I know the smart phones I've used can handle a couple hours of GPS, video, audio, etc. and there usually isn't much battery left for voice or standby.
All I'm saying is that while centralization provides a single point of failure, it also provides a single point of maintenance and allows much larger battery backup than would otherwise be possible. Not to mention that it is much easier to restore power to every CO in the city to restore phone service than it is to restore power to the entire city (much like how blocks on the same grid as a fire station are usually the first to have power restored).
Also:
-you included your Cisco ID at the beginning, but removed it at the end.
-a few inconsistencies regarding punctuation at the end of bullet points.
-1 Wrong.
Gigabits per siemens?
correlation does not...awe forget it...
+1 Funny. Honestly. Thank you.
Damn, my mod points expired.
As another EE (who does all their work at about 3GHz), I must say you need to be modded to oblivion for that comment.
Please, just stop.
I don't find ultra "realistic" or difficult games fun to play. As a casual gamer, I want to play a game to pass the time and enjoy a sense of accomplishment. If I can't make any progress in what I feel to be a reasonable time, I drop the game and move to something else.
If you're doing anything non-trivial, why would you be working in Word to begin with? Word is just a little WYSIWYG word processor for student papers and unimportant documents. It's not capable of real typesetting or controlled document structure. For anything serious, more specialized software is absolutely necessary.
This is just plane ignorance on your part. Word has a powerful set of features for document and styles management. Sure, it is no LaTeX for scientific or mathematical papers, but I personally have reviewed thousand page proposals for various defense organizations that had made extensive use of Words advanced features. Your statement clearly shows that you have no such experience.
Not necessarily. Given that this is an apartment, the user will be in close proximity to his AP and many others. It is possible that boosting his power (in the presence of other interference) could simply overdrive the Wifi receiver in the laptop (driving it into compression). This creates an even higher noise floor (resulting from third order intermods) which desensitizes the receiver (and will of course reduce throughput). This will happen to even the most linear, low noise amplifier if you drive it hard enough. A properly designed receiver should have enough analog attenuator range to prevent this, but it could be a crappy/low cost design.
Don't worry though...Bono will save them!
Well done :) Parenthesis have their place in technical writing for the non-technical. They allow you to set off portions of text as "tid-bits" which may help in the understanding but is not required for the technical reader.
I agree though...far too many of them!
Oh please, another software engineer? Amplifiers are by their very nature non linear devices as a whole (they just happen to have a linear region which we can make use of). The amplifiers in question are operated within their linear region as much as possible where possible, but certain requirements like efficiency force the designers to drive the transistor partly into its non-linear region (closer to P1dB). Some non-linearity is tolerated and is dictated by the FCC, ETSI or CRTC in the form of emissions masks or by the wireless standard in the form of modulation quality. The only way to ensure the amplifier is always inside the linear region under all conditions would be to back off from P1dB by so much that your efficiency tanks. But that is entirely not feasible for cellular design...consumers like long battery life and carriers like low operating costs.
Now, getting back to your comments. "As long as the mismatch is within spec, the only problem will be reduced efficiency". Amplifiers (or to be more specific, the transistors used in amplifiers) do not have real imput and output impedances. The real (resistive) component will generally not have the desired characteristic impedance (usually 50 ohms) and can be quite small (sometimes a few ohms or even tenths of an ohm). The imaginary (reactive) component will also be non-zero (which is undesirable, but a fact of life) which will tell whether the output (or input) is capacitive or inductive (depending on the sign of the reactive element). Real "high power" amplifiers (I say "high power" to describe the condition where the amplifier is operated towards the upper bounds of the linear region) are not simply matched for maximum power transfer and your done (the input is often matched this way since you would like to ensure any power available to the transistor will actually be taken into the device to be amplified...this is different for low noise amplifiers). This is called conjugate matching (where you set the real parts equal, and negate the reactive part).
On the output a different set of techniques is used. Loadpull is one technique which allows you to design your output matching network not only for linearity, but also efficiency or any other characteristic you can measure. The output matching network that produces the best efficiency (which is what we are talking about here) is most likely not the same as the one that produces the best P1dB or linearity. Also note that conjugate matching or other types of matching do not mean zero reflection (or VSWR=1). By the nature of the networks, the resulting VSWR (albeit low VSWR) is actually part of the desired characteristics of certain matching networks. Put another way, having the best VSWR response (i.e. zero reflection) will not get you the best efficiency (this is the aspect of your post that I take issue with). Reactive components do not dissipate energy (well, if you cosider the small resistive component they do, but this is orders of magnitude smaller than the other resistive components).
All this being said, another way to look at it is that if the reflections occur as part of the matching network, these can be tolerated since they are an inherent part of the design. Reflections after you have reached 50 ohms (i.e. between the matching network and the antenna) can be devastating to an amplifier. This is why they place a circulator or isolator directly after the matching network in most cases...this allows the output of the matching network to see a 20 dB match at least (depending on the circulator) regardless of what happens after (the antenna breaks, cable breaks, etc.). This prevents potentially devastating power from returning to the amplifier.
I am fully aware of how antennas are designed. Tuning the resonant frequency of an antenna should go without saying (though given the other posts on this story, I appreciate the fact that you spoke of what you knew, and limited yourself to just that).
My comment played off the OPs comment about a cantenna (which achieves its performance by increasing directivity). However, while tuning to your carrier frequency is generally accepted as the most basic guideline, you should take it one step further to include the radiation pattern in your overall design (and will ensure other performance characteristics are considered).
Also, true omnidirectional antennas don't exist...
The problem is that if you make the antenna too directive, you may miss out on certain cell sites entirely (as you mention in the example with your pringles can). You may also notice that your pringles cantenna is highly symetrical about a few axes. You also provide a substantial ground plane which results in a design that better approaches theoretical design guidelines.
Cell phone designers have a lot to deal with, your big head, your hand, buildings, etc...in reality, a highly directive antenna on a mobile (that is truly mobile, unlike your cantenna) would be catastrophic in terms of being able to make a call.
Oh my god. Please not another "informative" post. I really wish you people would stop commenting on these articles when you clearly have no clue what you are talking about. The reflected power (if it happens to exist in this case...which it doesn't because these transmitters are designed quite well and usually include a circulator or isolator at the output of the amplifier to ensure an excellent match) does not go back into the amplifier, because if it did the amplifier would not work as it was designed and would either oscillate or produce extremely poor waveform quality at the output.
Now, if you can bypass the circulator/isolator I mentioned above (which is what I gather they are trying to do in this article) then that is one less place power can be lost on the way to the antenna.
No, "cellphone antennas" are not "power efficient". I assume you actually mean the radio (antennas [the antenna itself, not the other components you are incorrectly referencing] are generally passive...they do have a radiating efficiency, but they generally don't consume power in the classical sense). Cellular transmitters (base station and mobiles) are usually only in the 25-35% range of efficiencies. This is the result of high peak to average ratios in the signal which require the amplifier to be oversized by as much as 10x to ensure the FCC and other similar bodies will certify the equipment. In general, if your mobile is actually transmitting lets say 50 mW (the power reaching the antenna), the transmit chain would likely be consuming at least 150 mW (likely more).
Yes. Every connector, isolator, circulator, switch, filter, duplexer, wire, conductor, etc. contributes to the losses in the circuit. As much as half your power can be lost after the final power amplifier (more than that and you need lessons in radio design, or you need to adjust your requirements).
Umm, dude...just because you shield a component doesn't mean it stops radiating. Shielding inhibits EM fields which are already present. To reduced radiated losses, you need to either improve the fundamental design of the circuit or make it radiate so well that you build an antenna instead.
They can't plagiarize your work if you don't give it to them. If someone asks for your solution/paper/answers, just tell them to screw off and figure it out for themselves.
because sometimes there are people that have too much money, and this is one way to legally steal from idiots that will spend whatever they can just to get some specific name.
Except that is the very reason why viruses WOULD go past the boot drive. Security by obscurity doesn't work, remember?
Except that step 2 only works if they actually disconnect the hard drive or flash drive from the computer each time. Otherwise the backup data is just as easily wiped as the original data.