Defense Electronics Highly Integrated GPS Receiver

and-held GPS receivers are used by soldiers to find their way in strange lands, especially at night. H GPS receivers are also used to find downed pilots and locate other strategic personnel. After the Gulf War, the U.S. Army announced it would install GPS in all armored vehicles to help minimize friendly fire incidents, which was a major source of casualties in Operation Desert Storm. Friendly fire incidents most often were caused by armored unit commanders who were lost in the featureless Iraqi desert or were out of position during ground attacks. It is clear from these experiences that the military would like to have GPS location capability on every person, vehicle and projectile. The projectiles do not stop at cruise missiles, but also include 155 mm Howitzers and 5-inch Navy deck guns with GPS guidance. These military GPS receivers must be able to receive the military version of the spread-spectrum code, and they must be antijamming receivers. The first requirement is so the military can dither or “scramble” the commercial code to prevent the enemy from using the GPS signal, but still allowing the full precision for the desired users. The second requirement, antijamming, surfaced in 2003, although it had been anticipated previously. “From the day we built GPS, we’ve been working on ways to overcome jamming,” said Lt. Col. John Carter, chief of space GPS is a navigational system that provides 3D geo-location using a constellation of 24 NAVSTAR medium earth orbit satellites at an altitude of 20,200 km while completing Figure 1. NAVSTAR GPS satellite. Photo courtesy NASA Figure 2. Artist’s concept of the GPS satellite constellation. Photo courtesy U.S. Department of Defense