Research of High Sensitivity GPS Receiver Anti-jamming Using LCMV and Minimum Norm Algorithms Based on Circular Antenna Array

A jammer is an intentional or unintentional signal that directly interferes within the L1 or L2 frequency bands. GPS signal which reaches the receiver is below the thermal noise power by about 30 dB. When the signal is masked by foliage or other man-made obstructions, the power of GPS signal is attenuated and comes to be even weaker. Although the GPS uses DSSS technique, it is vulnerable to high power jammers like CW, FM, pulse, and noise. Adaptive antenna is suitable to be used to cancel these types of jammers, and it utilizes the technique of cancellation based on determining the jammer directions like MUSIC algorithm or PI. The main purpose of adaptive antenna is to reduce the jammer signals up to a certain level so that the spread spectrum mechanism can extract the signals. As high sensitivity GPS uses weak signals, the jammer-to-signal ratio will be higher for the weaker signals and interference. It may cause loss of signal tracking or large measurement errors. In this sense, the main objective of this paper is to study the effect of low power GPS signal anti-jamming. In the present paper, a new model for suppressing jammers to the high sensitivity GPS receiver is proposed. Minimum norm algorithm can assign a deep null blindly to the jammers' incident direction, and it also doesn't introduce any false nulls like other algorithms do. So combining it with linearly constrained minimum variance (LCMV) algorithms give a structure capable of adjusting the weights of the antenna array in real time to respond to the signals coming from the desired directions while highly suppresses the jammers coming from the other directions. Circular antenna array can make accurate decisions on the coming directions of the jammer signals in two dimensional spaces. So, in the model, circular antenna array combining with minimum norm (min-norm) and LCMV algorithms have been used for signal anti-jamming. The paper will present the simulation results and the detailed method which is used in the simulation.