This law when used along with a parabola, helps the beam focus. The law of reflection states that the angle of incidence and the angle of reflection are equal. The ratio of focal length to aperture size (ie., f/D) known as “f over D ratio” is an important parameter of parabolic reflector. The reflected wave forms a colllimated wave front, out of the parabolic shape. Hence, as per the above definition, the distance between F and L lie constant with respect to the waves being focussed. PQ are the reflected rays where L represents the line directrix on which the reflected points lie (to say that they are being collinear). The line joining F and V is the axis of symmetry. The point F is the focus (feed is given) and V is the vertex. The following figure shows the geometry of parabolic reflector. The standard definition of a parabola is - Locus of a point, which moves in such a way that its distance from the fixed point (called focus) plus its distance from a straight line (called directrix) is constant. These antennas are widely used for radio and wireless applications. The frequency range used for the application of Parabolic reflector antennas is above 1MHz. For better understanding of these antennas, the concept of parabolic reflector has to be discussed. Parabolic Reflectors are Microwave antennas.
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