Someone "invented" a previously unpublished military design.
Century means there is a factor of a hundred between lower and upper frequency that the antenna efficiently works on.
Decade means a factor of 10.
Bandwidth is typical the range of frequencies where the antenna is efficient.
Typically we categorise this by comparing it's gain at the centre frequency with how much you have to deviate before the gain drops some set amount.
Let's say it's resonant at 10GHz with a gain of 6dB. Typically we care about the range it's within 3dB of that.
Gain in this setting is less about amplification and more about concentrating the energy into a region of space rather than out in all directions.
If you go down to 3Ghz (probably 3.16GHz actually)and up to 30GHz( probably 31.6ghz)and it's still withing 3dB of 6dB, you have a decade bandwidth.
If you can do a century you're looking at 1 to 100GHz
An Octave is 1/sqrt(2) to sqrt(2) a decade is 1/sqrt(10) to sqrt(10) and a century is 1/sqrt(100) to sqrt(100) range.
So if you have an A4 note at 440Hz and you want a filter that captures an Octave with that A at its centre you would need a filter from 440/sqrt(2) =311 and 440×sqrt(2) = 622 which are d#4 and d#5. 6 semitones up from D#4 you get A4, another 6 and you have D#5. Musically it sounds like A4 is exactly between D#4 and D#5.
Here is a basic explanation and a comment on the patent issue the author is addressing:
1. Antennas are designed to either transmit or receive RF.
2. The antenna is like water spigot for RF energy. If you design the antenna right, you can maximize the amount of RF energy you can get through it. This is equivalent to minimizing the impedance.
3. But, antennas are resonant. In other words the amount of RF that gets through can be maximum at one frequency (or a small range or bandwidth of frequencies), but very bad outside of that range.
4. Antenna designers try all kinds of tricks and techniques--including shapes, elements, delays, etc.--to try to get the antenna to have a broader resonance. An analogy might be the design of a musical instrument like the saxophone.
5. The VSWR the author mentions is a way of charting the resonance of the antenna with respect to frequency, ie. the bandwidth of the antenna.
6. Typical antennas (like a rod or something) have a bandwidth of maybe 5-10% of the center frequency.
7. Fancier antennas like a discone have a fractional bandwidth of up to 10:1.
8. An antenna like the one described by the author claimed to be 100:1.
9. But...even though the antenna may have broad bandwidth...the other factor antenna designers care about is gain (or loss). And this just complicates the design process even more.
Now, what I find most interesting about the author's comments is their suggestion that people continue to reinvent the wheel and then patent it. I too have seen this happen (not necessarily patents, but with other "technology inventions") over the years. I used to work in radio direction finding and every five or ten years someone would claim to have a new way of locating signals--but it's always just the same ideas over and over again. In other words, physics is physics.
(2006)
Hope someone will explain this
Someone "invented" a previously unpublished military design.
Century means there is a factor of a hundred between lower and upper frequency that the antenna efficiently works on.
Decade means a factor of 10.
Bandwidth is typical the range of frequencies where the antenna is efficient.
Typically we categorise this by comparing it's gain at the centre frequency with how much you have to deviate before the gain drops some set amount.
Let's say it's resonant at 10GHz with a gain of 6dB. Typically we care about the range it's within 3dB of that. Gain in this setting is less about amplification and more about concentrating the energy into a region of space rather than out in all directions.
If you go down to 3Ghz (probably 3.16GHz actually)and up to 30GHz( probably 31.6ghz)and it's still withing 3dB of 6dB, you have a decade bandwidth.
If you can do a century you're looking at 1 to 100GHz
An Octave is 1/sqrt(2) to sqrt(2) a decade is 1/sqrt(10) to sqrt(10) and a century is 1/sqrt(100) to sqrt(100) range.
So if you have an A4 note at 440Hz and you want a filter that captures an Octave with that A at its centre you would need a filter from 440/sqrt(2) =311 and 440×sqrt(2) = 622 which are d#4 and d#5. 6 semitones up from D#4 you get A4, another 6 and you have D#5. Musically it sounds like A4 is exactly between D#4 and D#5.
Here is a basic explanation and a comment on the patent issue the author is addressing:
1. Antennas are designed to either transmit or receive RF.
2. The antenna is like water spigot for RF energy. If you design the antenna right, you can maximize the amount of RF energy you can get through it. This is equivalent to minimizing the impedance.
3. But, antennas are resonant. In other words the amount of RF that gets through can be maximum at one frequency (or a small range or bandwidth of frequencies), but very bad outside of that range.
4. Antenna designers try all kinds of tricks and techniques--including shapes, elements, delays, etc.--to try to get the antenna to have a broader resonance. An analogy might be the design of a musical instrument like the saxophone.
5. The VSWR the author mentions is a way of charting the resonance of the antenna with respect to frequency, ie. the bandwidth of the antenna.
6. Typical antennas (like a rod or something) have a bandwidth of maybe 5-10% of the center frequency.
7. Fancier antennas like a discone have a fractional bandwidth of up to 10:1.
8. An antenna like the one described by the author claimed to be 100:1.
9. But...even though the antenna may have broad bandwidth...the other factor antenna designers care about is gain (or loss). And this just complicates the design process even more.
Now, what I find most interesting about the author's comments is their suggestion that people continue to reinvent the wheel and then patent it. I too have seen this happen (not necessarily patents, but with other "technology inventions") over the years. I used to work in radio direction finding and every five or ten years someone would claim to have a new way of locating signals--but it's always just the same ideas over and over again. In other words, physics is physics.