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qnach
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Suppose the performance of an antenna is calculated.
How about its complimentary antenna?
How about its complimentary antenna?
Could you please explain more about what you are asking? Are you asking about self-complimentary antennas?qnach said:Suppose the performance of an antenna is calculated.
How about its complimentary antenna?
berkeman said:Could you please explain more about what you are asking? Are you asking about self-complimentary antennas?
https://en.wikipedia.org/wiki/Self-complementary_antenna
tech99 said:An antenna and its complement are related by Babinet's Principle, which was originally devised for simple problems with light.
The input impedance, for instance, of the two antennas is related by 2 x SQRT(Z1 x Z2) = Zo, where Zo is 377 Ohms, the intrinsic impedance of free space. For instance, a strip dipole might have an input impedance of 70 Ohms. Its complement will be a slot having the same dimensions and cut in a large sheet of metal. The input impedance across the centre of the slot will be 507 Ohms.
The radiation pattern of one antenna in its E-plane should be the same as the other in its H-plane. However, there is a little uncertainty about this because a half wave slot does not seem to replicate a dipole pattern exactly.
In his book "Antennas", J D Kraus introduces the term "Magnetic Dipole" for antennas which are complementary to a dipole. By this he meant that the E plane pattern of a dipole resembles the H plane pattern of a slot or loop. Unfortunately, this has led to some confusion over the radiation mechanism of the two. For both classes of antenna, radiation is caused by the acceleration of electrons.
By performance, do you mean the drive impedance or the radiation pattern?qnach said:Suppose the performance of an antenna is calculated.
How about its complimentary antenna?
The radiation pattern of an array of elements is important. This becomes very important with arrays of slots in a waveguide, such as often used for marine radar antennas. Are you only interested in single elements and their complement?qnach said:Babinet's Principle seems more about diffraction pattern instead of antenna performance?
Baluncore said:By performance, do you mean the drive impedance or the radiation pattern?The radiation pattern of an array of elements is important. This becomes very important with arrays of slots in a waveguide, such as often used for marine radar antennas. Are you only interested in single elements and their complement?
There is an elegant design, halfway between the electric-dipole and it's complement, the magnetic-slot.
That special case is the self-complementary antenna, where the conductor and space are symmetric in pattern.
The self-complementary antenna has an input impedance of 376.73 / 2 = 188.365 ohm.
http://bbs.hwrf.com.cn/downrf/self-complementary Antenna.pdf
What other properties are there that you are interested in?qnach said:You mentioned impedance and the radiation pattern of such antenna. How about other properties?
Baluncore said:What other properties are there that you are interested in?
The near fields also seem to be complementary. For instance, if we approach a dipole along the equatorial plane, when we get closer than about lambda/6, the power flux density no longer grows with 1/D^2 but flattens off until we reach the antenna. The E-field remains uniform from lambda/6 until we almost touch the antenna, whilst the B field continues upward with 1/D. But for a slot antenna, the opposite happens; the E field grows with 1/D whilst the B field remains constant as the antenna is approached.qnach said:Everything we can calculated from an antenna.
The reciprocity idea seems hard to disprove. For instance, if I have two dipoles very close to one another, the loss between them is fixed at approx 3dB. As the antennas are identical, I measure 3dB whichever way round I do the test.sophiecentaur said:A bit of a nectar post but I have to wonder what fundamental laws are being used to lead one to expect that a 'similarity' is several respects (Kraus) should demand that there would be total equivalence. I know that this complementary idea is always taught in EM courses but that doesn't mean there should be any significant principle involved.
The principle of Reciprocity tells us that transmit and receive antennae could be interchanged and the loss over any path would be the same but reciprocity has to run out of steam once the antennae are near enough together. We also tend to analyse antennae as either Transmit or Receive, depending on which suits us and we assume the patterns will come out right.
For a slot to have the same pattern as a dipole requires the slot be cut in an infinite conductive sheet. But the sheet will not be truly infinite, so external peripheral currents will flow that distort the field. Likewise a wire dipole will not be in free space, so nearby conductive structures will distort the dipole's field in ways different to the periphery of a slot's actual conductive sheet.tech99 said:However, I have a nagging doubt about it as a slot does not seem to have exactly the same pattern as an equivalent dipole.
A complimentary antenna is a type of antenna that is used to enhance the performance of a primary antenna. It is designed to work together with the primary antenna to improve its reception and transmission capabilities.
The performance of a complimentary antenna can be affected by several factors, including its design, placement, and the materials used. The surrounding environment, such as buildings or other objects, can also impact its performance.
The performance of a complimentary antenna can be measured using various metrics, such as gain, radiation pattern, and standing wave ratio. These measurements can be taken using specialized equipment, such as an antenna analyzer or network analyzer.
Yes, a complimentary antenna can be used with any type of primary antenna, including dipole, yagi, or patch antennas. However, the design of the complimentary antenna may need to be adjusted to match the primary antenna's frequency and characteristics.
The use of a complimentary antenna can improve the overall performance of the primary antenna, resulting in better reception and transmission of signals. It can also help reduce interference and increase the range of the primary antenna.