Two axis direction finding antenna system using sum-difference patterns in X band

Official URL: http://dx.doi.org/10.1002/mop.29269

This work proposes the direction finding antenna system in two axis ((1), (2)) in X band using sum (sigma) and difference () patterns of received signal. Direction finding system is constructed by implementing the microstrip patch antenna array and 180 degrees hybrid rat race ring coupler which generates sigma and patterns of received RF signal. Initially, direction of arrival (DOA) is obtained in one axis, ((1)), vertical direction, using the sigma- patterns of antenna array of two elements. Using the equations of sigma and of two input signals, radiation patterns at different values have been observed in simulation and compared with measured pattern values of constructed circuit. By taking the ratio of to sigma patterns, DOA has been estimated of designed circuit. Another circuit similar to first circuit, oriented at 90 degrees (horizontal direction) has been implemented to estimate the DOA ((2)) in other axis. By taking the 3D radiation patterns of each circuit in anechoic chamber, both circuits are measured for performance; and from 0 to +/- 40 degrees, DOA has been observed with rms error of less than 5 degrees in both axis. At 10 GHz operating frequency, experimental results, using material RT Duroid 5880, show that satisfactory performance can be achieved with proposed setup.