According to one embodiment of the invention, an antenna system includes a substrate, a plurality of antennas formed on the substrate, a plurality of photodiodes formed on the substrate and coupled to respective ones of the antennas, and a plurality of optical fibers coupled to the substrate and coupled to respective ones of the photodiodes. The first lens group includes cemented lens elements having a positive lens element and a negative lens element. The mobile computer system is coupled to a GPS receiver that acquires vehicle information related to at least one of the geographic coordinates, orientation, and speed of the feedlot vehicle. The face component is composed of a metal material, and the aft-body is composed of a non-metal material such as a composite material or a thermoplastic material. This configuration effectively reduces rise and fall time of the output signal for high-frequency transmission. A barrier layer is disposed on the first and second walls and the tubular member.