Design of a Single Circular Radiator With Multiple Patterns for a UWB Three-Axis Monopulse System

This paper proposes a single radiator multiple patterns (SRMP) antenna that utilizes a single circular disc radiator to provide multiple radiation patterns that are suitable for ultra-wideband (UWB) direction-finding. The antenna design includes a circular disc and a ground structure for broadband characteristics and a slot structure to reduce mutual coupling. In addition, we simplify the UWB direction-finding system by employing a monopulse method that uses only sum and difference patterns rather than the sensitive phase difference of arrival (PDoA) method. The coordinates for conventional monopulse systems are converted into
$\alpha $
-,
$\beta $
-, and
$y$
-axes that are more suitable for the proposed SRMP antenna. Then, the monopulse ratios on each of the three axes, obtained using sum and difference patterns, are then compared to the simulation and ideal results. To verify the feasibility, the proposed SRMP antenna is fabricated, and antenna characteristics, such as reflection coefficients, mutual couplings, and radiation patterns are measured in a full anechoic chamber. To examine the direction of arrival (DoA) estimation using the proposed antenna, we use the monopulse ratios calculated based on the measured data in the
$z\alpha $
-,
$z\beta $
-, and zy-planes. The maximum RMS error is reduced to 0.105 using the three-axis monopulse system within the angle range from −15° to 15°. The results confirm that the proposed SRMP antenna is suitable for the UWB three-axis monopulse direction finding.