Because most people wouldn't respect the request "Wait, Mr. $criminal, I left my pistol at home; let me go get it and I'll be right back!"
Where I work there have been stories (all old from before I started, thankfully) of at-work violence (no, it's not the Post Office!). The little town I work in even had its own mass-murderer!
A firearm left out of arm's reach is a pretty paperwieght.
No, it means that all that money that the government borrowed to pay for its largess gets paid back. "National debt" is that which the government already owes. It has nothing to do with continuing services.
Islam bring us science, mathematics, philosophy, astronomy and humanism when we was in the dark age.
Too bad they didn't bring you grammar while they were at it.
Didn't the Greeks pioneera lot of what you're attributing to much later peoples? It is, after all, the Pythagorean theorem, no? We ponder Aristotle or Plato and read the works of Sophocles or Homer. Even the beloved concept of democracy is Greek in origin.
Beyond that, if you want to talk about important people, we must mention the Sumerians; they invented just about everything!
The key to fuel economy with internal intermittant combustion engines (like reciprocating gas engines found in cars) is to use them at their maximum power setting with as few combustion events per unit time as possible. In other words, wide open throttle and low RPMs (high manifold pressures). This car gets 128 miles per gallon at 35 MPH, and it's just a pure diesel engine.
Currently I think that the gas/electric hybrid is the best touring vehicle (as opposed to a commuting vehicle) platform, but I have yet to see one that I like. The Toyota Prius I got to look at closely a few weeks ago was very disappointing. A 1989 Honda Civic CRX gets better milage! The Toyota drive system is overly complicated with a gearbox that allows the wheels to be driven by either the electric motor and/or the gas engine. The added complexity and weight of the gearbox offset any efficiency gains of the electric system.
Lets look at it with the "Back To The Future analogy" (at her request I took my wife to go see Willard, starring Crispin Glover... who played George McFly in BttF) which goes something like this:
Biff = Saddam Hussien Marty McFly = George W. Bush. George McFly & other wimps = "rest of world"
Biff goes aound terrorizing (!) George, causing general havoc. George grows up cowing to Biff, and eventually goes to work for him. George grows old in fear of Biff. That is, until Marty goes back to 1955 and changes things.
Marty shows George that he can, and indeed must, stand up to Biff. At the end of the movie we see what a glass tiger Biff really is-- one punch from the underweight highschool loser George McFly knocks him cold.
Upon returning to "present day" 1985, Marty finds the world a very different place. His parents are no longer losers-- his dad cowering at biff and his mother an overweight chain smoker. Nope-- his parents in this alternate reality "grow up" to be vibrant, active and fearless. Biff, on the other hand, is given his come-uppance: he's outside waxing Marty's new truck!
The moral of the story: people never realize their true potential while cowering in the shadows of bullies. They must stand up to the bullies and defeat them in order to be all they can be.
Moore's law hasn't applied to RF and microwave circuits; the production volumes haven't been there. GPS is a relatively low frequency signal; where are the real microwave parts in true volume production? "10 GHz transistors clocked at 3 GHz?" That's not fast. Show me your 40 GHz processor! (there aren't any!) "Talking across circuit boards at 500 MHz?" That's not fast. I've done 40 GHz circuits.
No processor is even close to being able to handle a Ka band signal. I don't mean just digitize it. I mean process it. Half order of magnitude? Not in 2003, that's for sure.
There's not "wireless Ethernet" chip that can do what I've mentioned. What do you mean by "LNAs currently aren't great?" Poor return loss? Bad noise figure? No gain? All of those == "not an LNA." What's an "agile phase synthesizer?" I have no idea what that is.
As far as the Vivato antenna goes, it's not a "phased array" as much as a "switched beam array." (They even call it such!) It can't slew the main beam to any arbitrary direction in its scan volume; only certian pre-defined directions are supported. It has no ability for adaptive null steering for jammer rejection. It' can't effectively track a moving transmitter (airplane, satellite) between beam positions.
You can't filter noise. Noise is, by definition, not a band-limited signal. Furthermore, due to the nature of its generation, your filter will add noise to its output signal.
basically what your saying is this:
noise = rand();
rx_sig= desired_sig+noise;
therefore:
desired_sig= rx_sig-rand();
how does that work? You can't know in advance what the noise spectra is.
Digital beamforming != Software Defined Radio. Electronically Steered Phased Array != discrimination between two frequency-adjacent or -overlapping signals.
Remember- for digital beamforming you're not looking at a single signal at whatever the CW frequency is, you're looking at (# elements) signals: one from each of the antenna elements in the array. That means that for a 64-element array 1 MHz AM array (neglecting the fact that it would be HUGE!) would have only 7 instructions per RF cycle (per antenna element). Is that a useful number? (I don't know; I've never done DSP programming.)
Nobody wants a ESPA at those low frequencies; it's been at microwave and millimeter wave frequencies that people have wanted them: LiveTV for instance. Comm on the move(search for Harris) for another.
The original poster was writing about electronically steered antennas-- not signal processing. There's a fundamental difference between having a directional antenna pointing in different directions and discrimininating between two adjacent or overlapping signals.
I was replying to his idea that an electronically steered phased array isn't going to cost anywhere near what he thinks it is.
Furthermore, it's not "40 GBps." I was writing of the signal's 'carrier frequency,' the frequency that you'd receive if the modulation was turned off. You could put a 110 BPS signal on a 40 GHz carrier just fine. I don't deal with the signalling techniques too much; that's the modem guys. I just have to make sure the modulated signal gets spewed in the right direction! To me, generally speaking, everything's CW:).
To answer your question about post-processing: that only works for signals that are static in nature (radio astronomy?).
"Steering an array" means (for a receiver) to add delay between the individual antenna elements and the summing circuit as required to make the signal "appear" as if it's coming from right in front of the array ("at boresight"). The delayed signals are then summed together. Elements closer to the signal source get delayed more than those that are farther away.
For digital beamforming, the processing power required is multiplied by the number of elements (minus one). In other words, for a 64-element array, sixty three delay (phase shift) values would have to be calculated and applied. The delayed signals, now coherent, are added together to make the signal that is sent to the demodulator.
Other problems with ESPA include squint (the change in apparent apeture size with scan angle) and polarization purity (your CP antenna elements look more and more like LP at high scan angles, for instance).
Antenna beam width is inversely proportional to apeture size. Building several small antennas and hooking them together as an array (like the VLA and VLBA do) increases the apparent apeture size (although it has a very bad fill factor!), reducing the beamwidth of the composite antenna.
Furthermore, increasing the apeture size also increases sensitivity by increasing the total received power. If an antenna with an effective apeture of one square meter receives a signal of -100 dBm, using an antenna with an effective apeture of two square meters would double (+3 dB) the received power (to -97 dBm), all else being equal. Likewise a four-square-meter apeture would provide 6dB of gain relative to the 1 square-meter antenna.
Finally, it's easier and less expensive to build and use multiple smaller antennas than one big honkin' antenna. The dishes of the VLA are steerable; they can see more of the sky. Arecibo is not nearly as flexible.
The magic of SDR is not the ability to discern between two adjacent or overlapping signals, but to use one piece of hardware to recover a multitude of modulation schemes.
Instead of using separate hardware to recover AM, broadcast FM, broadcast TV (AM video, FM audio), etc., a SDR can be programmed to recover them all. (maybe not all at once:)
What I still dont understand is that unlike digital setups, frequencies are all analog. Instead of seeing noticable spikes in a "graphical signal", why not just encode data on much smaller deviations of the sine wave? In essence, more sensitive tramsnitter/receiver?
Simple answer: noise.Noise limits the ultimate sensitivity of ANY system.
n-QAM systems do just what you suggest: by using both AM and QPSK, n-QAM systems encode many bits on each symbol, increasing the spectral efficiency of the trasmission. Of course, that comes at the expense of noise immunity.
What you need is an antenna with multiple elements, and electric circuits that can combine the signals from the elements in arbitrary combinations.
$500? For an electronically steerable phased array? Can you tell me where? We've been trying to beat the six-figure-per-panel barrier for a while now. I've worked on several ESPA systems (X-band to Ka-band) over the past few years and NONE were even close to that price. That might be a good per element starting point, however.
Each element (individual antenna piece) in a receive-only ESPA requires its own amplifier and phase shifter or time delay circuit. A good LNA die can be had for maybe $25. A good phase shifter die could be $200. Now those have to be packaged. A special-purpose LTCC package for those dice could run $200. There's $425 and you've not even put them together yet. Or integrated them on the beamformer. Or installed the antenna element! Or included a radome. Or power supply. Or control circuits.
Now, let's say you have 64 elements (my X-band Rx array). That's 64x$425 = $27,200 just in LNAs, phase shifters and their packages! Want a two-beam system that can track two transmitters simultaneously? Double the packages and phase shifter counts (we'll share the first-stage LNA between the beams): $78,800.
These things are not cheap.
Software beamforming? They don't make DSP systems fast enough! Show me a DSP that can eat a Ka-band (20-40 GHz) signal. Want to mix it down? Fine: One mixer per element, plus LNAs= $$$$$$$!
As several people have noted, the hybrid seems to be the way that auto manufacturers are going for "reduced emissions" vehicles.
At a recent "Engineers' Week" party, the local Toyota dealer had a couple of Prius available for inspection and demonstration. I was unimpressed. The drive system is overly complicated and 50 MPG is pathetic for a "reduced emissions" vehicle that has economy as its main selling point. Granted, it's better than 20-30 MPG I get in my eight-year-old Firebird, but it's not impressive. A ten-year-old Honda Civic or Geo Metro can do that, and they're pure gasoline!
This car has it right. The most efficient way to run an internal combustion engine is to have it operate at high manifold pressures and low RPMs: Wide Open Throttle. By using a 17 horsepower (12.7 kW) diesel tractor engine and a tall final drive ratio allows this car to get around town at 35 miles per hour while achieving 128 miles per gallon. Of course, it has a top speed of only 65 miles per hour.
1a) Granted. 1b) When have "we" bombed a country for building a nuclear power plant?
2) Digging coal out of the ground is not gentle either. Even a small facility like Plant Wansley requires two train loads of coal per day. As a student at Georgia Tech I visited Wansley as part of my power & distribution class.
Power generating companies are already giving all kinds of credits for reducing use-- not because of nuclear energy, but because NO new generation facilities have been built anywhere in ages. Since "we" haven't allowed new generation facilities of any kind to be built, there has been increasing pressure on existing facilities as demand has increased. Why do you think your utility company keeps pressuring you, even offering cash, to dump that old AC unit for a new 14+ SEER heat pump?
I still maintain that nuclear is the most efficient power technology on a energy-per-pound-of-fuel scale available today, and the problems you mention are not insurmountable as long as "we" refrain from spreading FUD.
If recycling was really worth the effort, the recycling companies would be paying the city for the effort and we'd be getting credits on our utility bills! If recycling was really worth the effort, recycling companies wouldn't need government mandates and subsidies to stay in business.
Just what's wrong with fission, anyway? According to this list, nothing touches uranium for energy density. Nothing even comes close.
Coal has an energy density of a little less than 30 GJ/tonne (10^9 Joules per 1000 kg). Natural gas is almost 40 GJ/tonne. Kerosene and gasoline are about 45 GJ/tonne. Metallic uranium has a listed energy density of 560E3 GJ/tonne, twelve-thousand times as dense as gasoline!
In other words, to get as much energy from coal as we would from one metric ton of uranium metal, we'd have to burn nineteen thousand three hundred ten (19,310) metric tons of coal.
You'd think that finding a place to put the equivalent of a cube 37.4 cm on a side (actually smaller; the fission products would be lighter and smaller than the parent uranium!) would be easier for the environmentalists to handle than burning 19,310 metric tons of coal!
They are dropped onto enemy electric lines which shorts out the lines - and with a near 0 load, the generators spin out of control, and kill people in the powerplant when it busts open / bursts into flames.
Even power generating facilities have equipment protecting switchgear. Very large circuit breakers. They open within a cycle or two-- very quickly. There won't be any damage to generating equipment, but there won't be any power transmission either until the lines are cleared.
Slashdot Mirror
Because most people wouldn't respect the request "Wait, Mr. $criminal, I left my pistol at home; let me go get it and I'll be right back!"
Where I work there have been stories (all old from before I started, thankfully) of at-work violence (no, it's not the Post Office!). The little town I work in even had its own mass-murderer!
A firearm left out of arm's reach is a pretty paperwieght.
In Toronto, huh? Enjoy your high-speed internet connection while you can!
No, it means that all that money that the government borrowed to pay for its largess gets paid back. "National debt" is that which the government already owes. It has nothing to do with continuing services.
Too bad they didn't bring you grammar while they were at it.
Didn't the Greeks pioneer a lot of what you're attributing to much later peoples? It is, after all, the Pythagorean theorem, no? We ponder Aristotle or Plato and read the works of Sophocles or Homer. Even the beloved concept of democracy is Greek in origin.
Beyond that, if you want to talk about important people, we must mention the Sumerians; they invented just about everything!
Nope!
The key to fuel economy with internal intermittant combustion engines (like reciprocating gas engines found in cars) is to use them at their maximum power setting with as few combustion events per unit time as possible. In other words, wide open throttle and low RPMs (high manifold pressures). This car gets 128 miles per gallon at 35 MPH, and it's just a pure diesel engine.
Hydrogen is a losing proposition because there isn't any lying around free. It has to be made, and that takes energy. In fact, it takes more energy to make it than could ever be returned by burning it (Thermodynamics... increaing entropy...).
Currently I think that the gas/electric hybrid is the best touring vehicle (as opposed to a commuting vehicle) platform, but I have yet to see one that I like. The Toyota Prius I got to look at closely a few weeks ago was very disappointing. A 1989 Honda Civic CRX gets better milage! The Toyota drive system is overly complicated with a gearbox that allows the wheels to be driven by either the electric motor and/or the gas engine. The added complexity and weight of the gearbox offset any efficiency gains of the electric system.
Lets look at it with the "Back To The Future analogy" (at her request I took my wife to go see Willard, starring Crispin Glover... who played George McFly in BttF) which goes something like this:
Biff = Saddam Hussien
Marty McFly = George W. Bush.
George McFly & other wimps = "rest of world"
Biff goes aound terrorizing (!) George, causing general havoc. George grows up cowing to Biff, and eventually goes to work for him. George grows old in fear of Biff. That is, until Marty goes back to 1955 and changes things.
Marty shows George that he can, and indeed must, stand up to Biff. At the end of the movie we see what a glass tiger Biff really is-- one punch from the underweight highschool loser George McFly knocks him cold.
Upon returning to "present day" 1985, Marty finds the world a very different place. His parents are no longer losers-- his dad cowering at biff and his mother an overweight chain smoker. Nope-- his parents in this alternate reality "grow up" to be vibrant, active and fearless. Biff, on the other hand, is given his come-uppance: he's outside waxing Marty's new truck!
The moral of the story: people never realize their true potential while cowering in the shadows of bullies. They must stand up to the bullies and defeat them in order to be all they can be.
Have you thought about RULE?
Maybe you should read This link. Common sense and a little scientific method make the world a much less scary place!
"The dose makes the poison."
Everything is toxic in the proper amount.
Moore's law hasn't applied to RF and microwave circuits; the production volumes haven't been there. GPS is a relatively low frequency signal; where are the real microwave parts in true volume production? "10 GHz transistors clocked at 3 GHz?" That's not fast. Show me your 40 GHz processor! (there aren't any!) "Talking across circuit boards at 500 MHz?" That's not fast. I've done 40 GHz circuits.
No processor is even close to being able to handle a Ka band signal. I don't mean just digitize it. I mean process it. Half order of magnitude? Not in 2003, that's for sure.
There's not "wireless Ethernet" chip that can do what I've mentioned. What do you mean by "LNAs currently aren't great?" Poor return loss? Bad noise figure? No gain? All of those == "not an LNA." What's an "agile phase synthesizer?" I have no idea what that is.
As far as the Vivato antenna goes, it's not a "phased array" as much as a "switched beam array."
(They even call it such!) It can't slew the main beam to any arbitrary direction in its scan volume; only certian pre-defined directions are supported. It has no ability for adaptive null steering for jammer rejection. It' can't effectively track a moving transmitter (airplane, satellite) between beam positions.
You can't filter noise. Noise is, by definition, not a band-limited signal. Furthermore, due to the nature of its generation, your filter will add noise to its output signal.
basically what your saying is this:
noise = rand();
rx_sig= desired_sig+noise;
therefore:
desired_sig= rx_sig-rand();
how does that work? You can't know in advance what the noise spectra is.
Digital beamforming != Software Defined Radio.
Electronically Steered Phased Array != discrimination between two frequency-adjacent or -overlapping signals.
Remember- for digital beamforming you're not looking at a single signal at whatever the CW frequency is, you're looking at (# elements) signals: one from each of the antenna elements in the array. That means that for a 64-element array 1 MHz AM array (neglecting the fact that it would be HUGE!) would have only 7 instructions per RF cycle (per antenna element). Is that a useful number? (I don't know; I've never done DSP programming.)
Nobody wants a ESPA at those low frequencies; it's been at microwave and millimeter wave frequencies that people have wanted them: Live TV for instance. Comm on the move(search for Harris) for another.
The original poster was writing about electronically steered antennas-- not signal processing. There's a fundamental difference between having a directional antenna pointing in different directions and discrimininating between two adjacent or overlapping signals.
:) .
I was replying to his idea that an electronically steered phased array isn't going to cost anywhere near what he thinks it is.
Furthermore, it's not "40 GBps." I was writing of the signal's 'carrier frequency,' the frequency that you'd receive if the modulation was turned off. You could put a 110 BPS signal on a 40 GHz carrier just fine. I don't deal with the signalling techniques too much; that's the modem guys. I just have to make sure the modulated signal gets spewed in the right direction! To me, generally speaking, everything's CW
To answer your question about post-processing: that only works for signals that are static in nature (radio astronomy?).
"Steering an array" means (for a receiver) to add delay between the individual antenna elements and the summing circuit as required to make the signal "appear" as if it's coming from right in front of the array ("at boresight"). The delayed signals are then summed together. Elements closer to the signal source get delayed more than those that are farther away.
For digital beamforming, the processing power required is multiplied by the number of elements (minus one). In other words, for a 64-element array, sixty three delay (phase shift) values would have to be calculated and applied. The delayed signals, now coherent, are added together to make the signal that is sent to the demodulator.
Other problems with ESPA include squint (the change in apparent apeture size with scan angle) and polarization purity (your CP antenna elements look more and more like LP at high scan angles, for instance).
To clarify:
Antenna beam width is inversely proportional to apeture size. Building several small antennas and hooking them together as an array (like the VLA and VLBA do) increases the apparent apeture size (although it has a very bad fill factor!), reducing the beamwidth of the composite antenna.
Furthermore, increasing the apeture size also increases sensitivity by increasing the total received power. If an antenna with an effective apeture of one square meter receives a signal of -100 dBm, using an antenna with an effective apeture of two square meters would double (+3 dB) the received power (to -97 dBm), all else being equal. Likewise a four-square-meter apeture would provide 6dB of gain relative to the 1 square-meter antenna.
Finally, it's easier and less expensive to build and use multiple smaller antennas than one big honkin' antenna. The dishes of the VLA are steerable; they can see more of the sky. Arecibo is not nearly as flexible.
The magic of SDR is not the ability to discern between two adjacent or overlapping signals, but to use one piece of hardware to recover a multitude of modulation schemes.
:)
Instead of using separate hardware to recover AM, broadcast FM, broadcast TV (AM video, FM audio), etc., a SDR can be programmed to recover them all. (maybe not all at once
Simple answer: noise. Noise limits the ultimate sensitivity of ANY system.
n-QAM systems do just what you suggest: by using both AM and QPSK, n-QAM systems encode many bits on each symbol, increasing the spectral efficiency of the trasmission. Of course, that comes at the expense of noise immunity.
$500? For an electronically steerable phased array? Can you tell me where? We've been trying to beat the six-figure-per-panel barrier for a while now. I've worked on several ESPA systems (X-band to Ka-band) over the past few years and NONE were even close to that price. That might be a good per element starting point, however.
Each element (individual antenna piece) in a receive-only ESPA requires its own amplifier and phase shifter or time delay circuit. A good LNA die can be had for maybe $25. A good phase shifter die could be $200. Now those have to be packaged. A special-purpose LTCC package for those dice could run $200. There's $425 and you've not even put them together yet. Or integrated them on the beamformer. Or installed the antenna element! Or included a radome. Or power supply. Or control circuits.
Now, let's say you have 64 elements (my X-band Rx array). That's 64x$425 = $27,200 just in LNAs, phase shifters and their packages! Want a two-beam system that can track two transmitters simultaneously? Double the packages and phase shifter counts (we'll share the first-stage LNA between the beams): $78,800.
These things are not cheap.
Software beamforming? They don't make DSP systems fast enough! Show me a DSP that can eat a Ka-band (20-40 GHz) signal. Want to mix it down? Fine: One mixer per element, plus LNAs= $$$$$$$!
As several people have noted, the hybrid seems to be the way that auto manufacturers are going for "reduced emissions" vehicles.
At a recent "Engineers' Week" party, the local Toyota dealer had a couple of Prius available for inspection and demonstration. I was unimpressed. The drive system is overly complicated and 50 MPG is pathetic for a "reduced emissions" vehicle that has economy as its main selling point. Granted, it's better than 20-30 MPG I get in my eight-year-old Firebird, but it's not impressive. A ten-year-old Honda Civic or Geo Metro can do that, and they're pure gasoline!
This car has it right. The most efficient way to run an internal combustion engine is to have it operate at high manifold pressures and low RPMs: Wide Open Throttle. By using a 17 horsepower (12.7 kW) diesel tractor engine and a tall final drive ratio allows this car to get around town at 35 miles per hour while achieving 128 miles per gallon. Of course, it has a top speed of only 65 miles per hour.
1a) Granted.
1b) When have "we" bombed a country for building a nuclear power plant?
2) Digging coal out of the ground is not gentle either. Even a small facility like Plant Wansley requires two train loads of coal per day. As a student at Georgia Tech I visited Wansley as part of my power & distribution class.
3) I thought "we" did!
Power generating companies are already giving all kinds of credits for reducing use-- not because of nuclear energy, but because NO new generation facilities have been built anywhere in ages. Since "we" haven't allowed new generation facilities of any kind to be built, there has been increasing pressure on existing facilities as demand has increased. Why do you think your utility company keeps pressuring you, even offering cash, to dump that old AC unit for a new 14+ SEER heat pump?
I still maintain that nuclear is the most efficient power technology on a energy-per-pound-of-fuel scale available today, and the problems you mention are not insurmountable as long as "we" refrain from spreading FUD.
If you're a taxpayer, this isn't news. Here in Melbourne, Florida we have a mantitory waste recycling program for glass, plastic, metals and paper. Residents pay for the priveledge of sorting their junk and setting out FOUR refuse containers (three recycle bins plus their "to the landfill" bin).
If recycling was really worth the effort, the recycling companies would be paying the city for the effort and we'd be getting credits on our utility bills! If recycling was really worth the effort, recycling companies wouldn't need government mandates and subsidies to stay in business.
Just what's wrong with fission, anyway? According to this list, nothing touches uranium for energy density. Nothing even comes close.
Coal has an energy density of a little less than 30 GJ/tonne (10^9 Joules per 1000 kg). Natural gas is almost 40 GJ/tonne. Kerosene and gasoline are about 45 GJ/tonne. Metallic uranium has a listed energy density of 560E3 GJ/tonne, twelve-thousand times as dense as gasoline!
In other words, to get as much energy from coal as we would from one metric ton of uranium metal, we'd have to burn nineteen thousand three hundred ten (19,310) metric tons of coal.
You'd think that finding a place to put the equivalent of a cube 37.4 cm on a side (actually smaller; the fission products would be lighter and smaller than the parent uranium!) would be easier for the environmentalists to handle than burning 19,310 metric tons of coal!
Even power generating facilities have equipment protecting switchgear. Very large circuit breakers. They open within a cycle or two-- very quickly. There won't be any damage to generating equipment, but there won't be any power transmission either until the lines are cleared.
Funny, I've never seen *any* software that was Copyright Anonymous Coward.
Perhaps if had better contact information they could find you and secure persmission?
Just a question-- you mention Bill O'Reilly. What has he said that makes you think he's, in your words, eurocentric? I'm serious.