1-D and 2-D Direction of Arrival Estimation in a Conical Conformal Array: Design and Implementation

Area of Science:

• Electromagnetics and Antenna Theory
• Signal Processing
• Array Signal Processing

Background:

• Direction of Arrival (DOA) estimation for conformal arrays faces challenges from non-omnidirectional element patterns and shadow effects.
• Conical Conformal Arrays (CCAs) mitigate shadow effects at small elevation angles, enabling azimuth and elevation DOA estimation.
• Conventional methods struggle with CCA element pattern determination and suffer reduced array degrees of freedom (DOF) at large elevation angles due to shadowing.

Purpose of the Study:

• To establish an accurate CCA radiation pattern model in a local coordinate system using 2-D coordinate transformation.
• To address the reduced array DOF in CCAs at large elevation angles by introducing the difference coarray method.
• To propose an improved propagator method for 2-D DOA estimation in CCAs, enhancing accuracy and reducing computational complexity.

Main Methods:

• Developed a 2-D coordinate transformation to establish the CCA radiation pattern in a local system.
• Introduced the difference coarray method to increase array DOF, compensating for shadowing at large elevation angles.
• Proposed a novel propagator method for 2-D DOA estimation, utilizing a new propagation matrix and linear computations, avoiding eigenvalue decomposition and spectral search.

Main Results:

• The established CCA model accurately represents the designed antenna.
• The proposed algorithms effectively handle CCA angle detection requirements.
• The new propagator method reduces estimation error and computational complexity compared to traditional techniques.
• Simulations and experiments validate the performance, showing estimation accuracy of approximately 5 degrees with 12 array elements.

Conclusions:

• The developed CCA radiation pattern model and proposed DOA estimation algorithms are effective for conical conformal arrays.
• The difference coarray and propagator methods significantly improve DOA estimation accuracy and efficiency, particularly in challenging scenarios with shadowing.
• The findings demonstrate the practical applicability and performance benefits of the proposed methods for CCA systems.