C- SLOTTED (LEAKY-WAVE) ANTENNA - Can be fabricated from a length of a waveguide. They are simple to fabricate, have low-loss (high efficiency) and radiate linear polarization with low cross-polarization.
- Slotted antenna arrays used with waveguides are a popular antenna in navigation, radar and other high-frequency systems. These antennas are often used in aircraft applications because they can be made to conform to the surface on which they are mounted. The slots are typically thin (< 0.1 ʎ) and 0.5 ʎ (at the center frequency of operation).
- What is SLOT Antenna:-
A slot antenna consists of a metal surface, usually a flat plate, with a hole or slot cut out. When the plate is driven as an antenna by a driving frequency, the slot radiates electromagnetic waves in similar way to a dipole antenna. The shape and size of the slot, as well as the driving frequency, determine the radiation distribution pattern.
Figure 5.8 : Slot antenna.
SLOTTED (LEAKY-WAVE) ANTENNA (CONT) - The slots on the waveguide will assumed to have a narrow width. Increasing the width increases the bandwidth (recall that a fatter antenna often has an increased bandwidth); the expense of a larger width is a higher degree of cross-polarization. The Fractional Bandwidth for thin slots can be as low as 3-5%; wide slots can have a FBW on the order of 75%.
- An example of a slotted waveguide array is shown in Figure 5.9 (dimensions given by length a and width b)
Figure 5.9 : slot waveguide with dimensions given by length a and width b.
SLOTTED (LEAKY-WAVE) ANTENNA (CONT) - As in the cavity-backed slot antenna, each slot could be independently fed with a voltage source across the slot. This would be very difficult to construct especially for large arrays. The waveguide is used as the transmission line to feed the elements.
- The position, shape and orientation of the slots will determine how (or if) they radiate. In addition, the shape of the waveguide and frequency of operation will play a major role.
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