The title say’s “ Radiated Efficiency : a true measure of antenna performance ”
This is an interesting paper and deserves further thought, in any measure, it is always a comparison between two values, where one may be an accepted standard. In this article I have not seen any agreement to the later as being accepted as a value, in theory, antennas of the same configuration in terms of electrical and physical, will exhibit very close if not identical performance values, setting this aside, but not completely losing sight of it, a focus on determining what the title says, I agree that the amount of efficiency for an antenna is the ratio of how it efficiently radiates the power delivered to its feed point, thus a reference antenna would have to be conceived for this purpose, one that has a material superior above all others, and a physical configuration that will represent a true Omni radiation pattern, specifically under laboratory conditions.
Theoretically an isotropic reference antenna would fill this spot, however in that theory it did not mention the material that will exhibits such characteristics, thus in the real world, no two isotropic antenna of two material, of the same physical shape produce the same radiation characteristics efficiency. Gain is an element of physical configuration, thus for any specific applications where miniaturization and aesthetics are an issue, the unit gain will be compromised.
Jouni - just looking at the diagram on page 3 (of the PDF)- it appears that even in the direction of maximum radiation a dipole has very little gain over an isotropic antenna - one dB or so at the most??
Txema: From the article: "Antenna absolute gain is defined as the ratio
of the radiation intensity in a given direction to the radiation intensity that would be obtained if
the power accepted by the antenna were radiated evenly to all directions of surrounding space
Makes sense to me. Also it's important to distinguish between gain relative to a dipole or relative to a (hypothetical) isotropic antenna Hence the dBi used in the diagram on Page 4 (of the PDF).
Some antennas (eg the quoted "monopoles with parasitic elements") may radiate in a pattern that is equally strong in all HORIZONTAL directions. So you might get a radiation pattern that is like a much flatter doughnut than that shown on Page 3 (again of the PDF).
Jouni - could you say that antenna efficiency is the ratio of the actual radiated power in the direction of interest (usually that of max. radiation) divided by the theoretical predicted radiated power in that direction? and what sort of figures would you find in practice?
Great article - thanks!
(and RF ed - thanks for the PDF link)
The gain provides a single fiqure which determines antennas capability to radiate towards some specific direction and thus it doesn't tell whether the radiation is equally distributed towards all directions or not.
If the signal is equally strong in all directions, the radiation pattern is omnidirectional. In practice such antenna has some gain value less than 0dB. An isotropic antenna is an hypothetical lossless antenna having equal radiation in all directions. Such lossless antennas exists only in theory.
This is quite true that Radiated Efficiency is the true measure of the Antenna but in case of the Handhelds and Notebooks it is better if consumer can come to know about the property of the antenna, but generally they never come to know about this.
Even the laptops does not come with the reception pattern or radiation pattern of the antenna.
"Even if the signal is equally strong in all directions, gain doesn’t provide a measure to determine that"...confusing... if the signal is equally strong in all directions, then it is an isotropic pattern, and gain should be 0dB...
Or am I misunderstanding something?
I asked Pulse for the text of this white paper because it is a good, general description of important performance parameters.The original can be downloaded here. http://www.pulseelectronics.com/file.php?id=3720