Receiving antenna apparatus for broadcast by satellite

摘要

A receiving antenna apparatus for receiving broadcast by satellite and adapted for mounting on a mobile body in which radio wave interruption tends to occur by obstacles, attains high-speed automatic tracking function capable of catching the satellite again in a short time just after cutting off of radio waves. In the receiving antenna apparatus, an incoming direction of radio waves is roughly detected to limit a search area and then a gain of the tuners is reduced to a value in the tracking control capable of detecting a peak and confirming a main lobe in accordance with power level of the received signal, so that a narrow and fine search may be made only in the limited search area. The antenna apparatus includes a gain setting device for varying gains of AGC of the tuners. Upon searching for the satellite, gains of the tuners are set to a first gain by the gain setting device to perform the rough search and the gains of the tuners are reduced to a second gain level lower than the first gain to perform the fine search. Thus, a time required to catch the satellite after cutting off of radio waves can be reduced.