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

This work proposes the direction finding antenna system in two axis (θ 1 , θ 2 ) in X band using sum (Σ) and difference (Δ) patterns of received signal. Direction finding system is constructed by implementing the microstrip patch antenna array and 180° hybrid rat race ring coupler which generates Σ and Δ patterns of received RF signal. Initially, direction of arrival (DOA) is obtained in one axis, (θ 1 ), vertical direction, using the Σ–Δ patterns of antenna array of two elements. Using the equations of Σ and Δ of two input signals, radiation patterns at different θ values have been observed in simulation and compared with measured pattern values of constructed circuit. By taking the ratio of Δ to Σ patterns, DOA has been estimated of designed circuit. Another circuit similar to first circuit, oriented at 90° (horizontal direction) has been implemented to estimate the DOA (θ 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°, DOA has been observed with rms error of less than 5° 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. © 2015 Wiley Periodicals, Inc. Microwave Opt Technol Lett 57:2085–2092, 2015