FUNCTION OF ANTENNA (cont) - Mismatch exist that is surrounding space as load.
- Since the two wires are closed together and in opposite direction (180°), therefore it is apparent that the radiation from one tip will cancelled that from the other.
- Figure 5.2 below, shows the energy transmitted into free space via an open ended λ/4 transmission line. The proportion of wave escaping the system is very small due
Figure 5.2
TYPES OF MICROWAVE ANTENNA - Horn / aperture antenna
- Parabolic / dish antenna
- Dipole antenna
- Slotted (leaky-wave) antenna
- Dielectric lens antenna
- Printed (patch or microstrip) antenna
- Phase Array antenna
- Like parabolic reflectors, HORN RADIATORS can use to obtain directive radiation at microwave frequencies
- Horn radiators are used with waveguides because they serve both as an impedance-matching device and as a directional radiator. Horn radiators may be fed by coaxial and other types of lines
Figure 5.3 : Horn antenna
Horn Antenna - Horn radiators are constructed in a variety of shapes, as illustrated in figure 5.4
- The shape of the horn determines the shape of the field pattern. The ratio of the horn length to the size of its mouth determines the beam angle and directivity. In general, the larger the mouth of the horn, the more directive is the field pattern.
Figure 5.4 : Horn radiator
DIFFERENT TYPES OF HORN ANTENNA - Horn antenna tapered / flared in one dimension only i.e in E-plane or H-plane (known as sectoral horn).
- Horn antenna tapered / flared in two dimension i.e in E-plane and H-plane (known as pyramidal horn).
- Conical taper / flares uniformly in all direction i.e in circular form.
THE DIFFERENCES BETWEEN THE E-, H-PLANE & PYRAMIDAL HORN SECTORAL ANTENNA
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