Using GPS to Synthesize A Large Antenna Aperture When The Elements Are Mobile

This paper presents a design for a transmitting antenna array comprised of mobile antenna elements, where the Global Positioning System (GPS) is used to estimate the current location and velocity of those elements. GPS is also used to synchronize the clocks carried by the mobiles. With this information, a central algorithm can control the phase of the radio signal radiated from each element so that the multiple signals add constructively at the desired receiving site. The algorithm can also control the elemental phases to cause destructive interference at any undesired receiving site. In this way, GPS is used to synthesize an antenna aperture larger than any single robot or human could carry. This enhanced system is able to communicate over longer distances and have the capability to avoid communication to undesired listeners. To evaluate the results, the GPS-based array is compared to a more conventional adaptive antenna array. The latter array uses signal strength measurement feedback from the desired receiving direction and the undesired receiving direction. This conventional approach will be our baseline to evaluate the efficacy of GPS. When some of the mobile antenna elements are not reporting GPS, the two algorithms will be combined.