Global Navigation Satellite System (GNSS) is a system that finds the location of a target using the navigation signal transmitted from the artificial satellite. There are GPS(Global Positioning System) devleoped in the US, GLONASS(GLObal NAvigation Satellite System) of Russia, Galileo of the European Union(EU), and BeiDou of China.

Jamming is a radio wave jamming technology that interferes with receiver performance and causes malfunction by emitting a strong signal in the frequency band where the satellite navigation signal is used. Since the navigation satellite signal is a radio wave from a satellite about 20,000 km away, when it reaches the ground, it is weak and vulnerable to jamming

Anti-jamming is a technology that cancels these disturbances to improve the survivability of the satellite navigation receiver and enables the device to operate normally for its intended purpose. As such, jamming and anti-jamming are constantly evolving in competition each other.

Recent anti-jamming technologies are largely divided into antenna steering technology (beam steering array, null steering array), band filter technology, AGC technology, digital signal processing technology, code/carrier tracking loop technology, and the like.

The GPS composite jamming active countermeasure device uses an array antenna used in various industrial fields such as communication, radar, and sonar. In order to increase the anti-jamming performance, the array antenna pattern must be precisely measured, and it must be measured in an anechoic chamber in the absence of interference signals.
WISTEK has developed a jamming location detection RF unit that actively responds to Jamming by identifying/detecting various jamming sugnals in GPS.