1. Field of the Invention
The subject invention relates generally to an antenna system having a radiation pattern that is steerable. Specifically, the radiation pattern is steerable based on geographic location to receive a signal from a satellite, such as a digital radio satellite.
2. Description of the Related Art
Antenna systems for receiving signals from a satellite, such as Satellite Digital Audio Radio Service (SDARS) signals, are well known in the art. Typically, these antenna systems provide a radiation pattern with an unchanging geometry to receive the SDARS signals. This can lead to poor performance of the antenna system in some geographic locations where the geometry of the radiation pattern and an angle between the satellite and the antenna system are less than optimal.
Antenna systems for receiving SDARS signals are routinely carried on vehicles for use with the vehicle's radio receiver. Typically, these antenna systems are roof-mounted and have a bulky appearance which is not aesthetically pleasing. However, vehicle manufacturers have been cautious in integrating SDARS antenna systems with windows of the vehicle, due to the potential obstruction of view caused by the antenna to the driver. Therefore, it is typically a requirement that the antenna occupy less than a certain surface area, or “footprint”, when integrated with the window.
Some prior art antenna systems utilize multiple radiating elements, i.e., an antenna array, where each radiating element produces a different radiation pattern. These systems involve complex switching and/or signal processing techniques to select the radiating element with the most favorable radiation pattern. Unfortunately, these systems can be expensive due to the number of radiating elements and the complex circuitry utilized. Moreover, it is difficult to dispose multiple radiating elements on a window of a vehicle, due to the obstruction of view they cause.
Therefore, there remains an opportunity for a cost efficient and non-obstructive antenna system with a radiation pattern that is steerable based on geographic location.