A frequency domain implementation of the Butler Matrix direction finder

The Adcock-Butler Matrix (ABM) antenna array is a common direction finder but has the drawback of requiring complex analogue components such as hybrids, phase shifters and phase comparators. This paper presents a new direction finder which is a digital, frequency domain version of ABM. It obtains bearing estimation at each frequency bin and combines them to give a weighted average. Bias reduction and interference nulling are easy to incorporate into the scheme. Simulation studies show that this new direction finder has much lower estimation errors than the ABM, and can easily null out a sinusoidal interference