Performance Characterization of Four-Arm MAW Spiral Antennas for Digital Direction-of-Arrival Sensing

The characterization of four-arm modulated arm width (MAW) spiral antennas for linearly polarized direction-of-arrival (DOA) sensing with a directly connected coherent receiver and digital backend is discussed. The performance is assessed from the system level, with the achievable field of view (FOV) is used as the metric for the antenna, evaluated by means of the Cramer-Rao Lower Bound. The resulting antenna deviates from the previous MAW spiral designs, emphasizing system DOA performance over previous metrics, such as pattern quality. Simulation and measurement of this MAW spiral show that the antenna can sense the DOA with 1° rms error in azimuth and elevation over a ±30° elevation and 360° azimuth FOV across a 4.6:1 bandwidth. This antenna is then compared with a traditional MAW spiral and a conventional spiral, which in contrast achieve bandwidth less than 2:1.