Using the far field equation that relates the dimension of the antenna structure and wavelength is the one used in contemporary antennas? So my question is if this formula applies to LCX(Leaky Coaxial antennas) also ? If so what is the dimension of the antenna: Is it the diameter of the cable (without jacket) or the length of the cable?
Dear Researcher Kelvin Okenye,
Another technique used to calculate the radiated E-field from a TL is the Hertzian dipole approximation method , which is to decompose a TL into many short Hertzian dipoles see the references [1,2]. According to Paul Clayton "The equation can be summarized as being the largest of 3λ or 2D ^ 2 / λ, where D is the largest dimension of the antenna. Typically the first criterion is used for “wire-type”.
[1] Y. S. Khee and M. Z. M. Jenu, “Magnetic and electric field radiation of
bent microstrip line using Hertzian dipole method, in Proc. IEEE Int. RF Microw. Conf., 2008, pp. 31–35.
[2] P. Taheri, B. Kordi, and A. M. Gole, “Electric field radiation from na overhead transmission line located above a lossy ground,” in Proc. IEEE 43rd Int. Univ. Power Eng. Conf., 2008, pp. 1–5. Dear Researcher Kelvin Okenye,
Please read the paper " A simple test for measuring the shielding effectiveness of coaxial cables and connectors" (Author Copy): A short dipole, the Eq. (28) can be used to calculate the electric field intensity in far field at a distance r from the source. It can be concluded from this work that common mode radiation is the main energy leakage phenomenon observed in defective shielding cables. The measurement and simulation showed that dielectric material differences with small variations in characteristic impedance do not impact significantly the resonance frequencies. The main element able to change resonance frequencies is the cable physical length. The proposed setup permits to test shielded cables in order to mitigate common mode currents through techniques increasing common mode impedance like RF chokes, connector uniform shielding avoiding pig tail and transformers decoupling common mode currents.
LCX radiation depends on the slot geometry, orientation, slot spacing, apart from the cable material type, geometry, dielectric, sheath, and other properties that affect the reflection, absorption and radiation. The antenna formula may not be applied directly, unless the LCX properties are modelled into an equivalent antenna. There are many papers available on radiation calculation for LCX (intended radiation) as well as through coax cable braids (unintended leakage).
LCX vendors would normally specify the power leak per unit length and radiation patterns, for engineering purpose.
Hope it helps.
The far-field condition uses the width of the part of the antenna that radiates, seen from the direction you are interested in, whatever the type of antenna is.
It is easy to prove this yourself. The far-field region is when contributions from different parts of the antenna are within 1/8 wavelength of the design far-field phase. The 2D squared over lambda formula comes directly from that.
Hey @Malcolm White ..What do you mean exactly by' when contributions from different parts of the antenna are within 1/8 wavelength of the design far-field phase '?
@Shiv Prasad thank you for the answer ..it's true the radiation is based on slot spacing and cable geometry but my question is based on the far field distance from the radiating slots of a LCX.. how far from the slots of the LCX is considered as the far field for this RC type cable?
Each part of the antenna radiates. They may be all at different distances from a distant point. In the far field you can work this out by working out the distance of each from any plane perpendicular to the line of sight. Usually they are phased so that in the peak direction the distance to this plane cancels out any phase differences in the feed, so at the plane they are all in phase. In the near field the distances to a point are different, because the point is now so close that the width of the antenna makes the distance to the edges further. Look up the definition of Far-field - there should be simple pictures.
Dear Researcher Kelvin Okenye,
Another technique used to calculate the radiated E-field from a TL is the Hertzian dipole approximation method , which is to decompose a TL into many short Hertzian dipoles see the references [1,2]. According to Paul Clayton "The equation can be summarized as being the largest of 3λ or 2D ^ 2 / λ, where D is the largest dimension of the antenna. Typically the first criterion is used for “wire-type”.
[1] Y. S. Khee and M. Z. M. Jenu, “Magnetic and electric field radiation of
bent microstrip line using Hertzian dipole method, in Proc. IEEE Int. RF Microw. Conf., 2008, pp. 31–35.
[2] P. Taheri, B. Kordi, and A. M. Gole, “Electric field radiation from na overhead transmission line located above a lossy ground,” in Proc. IEEE 43rd Int. Univ. Power Eng. Conf., 2008, pp. 1–5. Dear Researcher Kelvin Okenye,
Please read the paper " A simple test for measuring the shielding effectiveness of coaxial cables and connectors" (Author Copy): A short dipole, the Eq. (28) can be used to calculate the electric field intensity in far field at a distance r from the source. It can be concluded from this work that common mode radiation is the main energy leakage phenomenon observed in defective shielding cables. The measurement and simulation showed that dielectric material differences with small variations in characteristic impedance do not impact significantly the resonance frequencies. The main element able to change resonance frequencies is the cable physical length. The proposed setup permits to test shielded cables in order to mitigate common mode currents through techniques increasing common mode impedance like RF chokes, connector uniform shielding avoiding pig tail and transformers decoupling common mode currents.
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