The back-up structure of a parabolic dish antenna, which supports its reflecting
surface, is formed in this invention by preloading its radial and circumferentially
placed straight structural members and hence it is termed as preloaded parabolic
dish antenna. Such a preloading results in considerable reduction in its weight
and also to the effort involved in its assembly. The back-up structure of the preloaded
parabolic dish antenna is made of a central hub, an assembly of a suitable number
of elastically bent radial structural members connected rigidly to the central
hub and to the same number of straight structural members which are connected to
the tips of the radial members at the outer rim of the dish and also to straight
bracing members placed circumferentially at intermediate locations, which are all
tensioned to specified prestress values in the absence of wind loading. The outermost
rim members placed at the periphery of the dish form the aperture of the dish.
The backup structure of the preloaded parabolic dish antenna is given the parabolic
shape by fixing the radial members at a suitable inclination angle and location
at the hub and by applying an appropriate force with a normal component at their
tips so as to bend the radial members elastically such that their curvature becomes
approximately the same as that of the parabolic curve between the hub and the peripheral
rim point. The invention incorporates a suitable rigid connection of the elastically
bent radial members and other structural members in order to store sufficient initial
elastic energy in the back-up structure of the dish for resisting gravitational
and static and dynamic wind forces on the parabolic dish antenna for the survival
wind condition at the antenna site. This configuration also reduces moment of the
wind forces and torques on the mounting tower and gear drive system of the dish
antenna. This invention is also applicable to structures of geometries other than
that of the parabolic dishes. The method of constructing the preloaded parabolic
dish and attaching reflector panels of lightweight is also disclosed.
The preloaded parabolic dish antennas are useful in microwave communication,
satellite communication, radar, radio telescope and other similar applications
for receiving and/or transmitting radio waves.
