Optimized Differential TCDA (D-TCDA) With Novel Differential Feed Structure

Alexander D. Johnson,John L. Volakis,Satheesh Bojja Venkatakrishnan,Vignesh Manohar

doi:10.1109/ojap.2021.3067373

Alexander D. Johnson, John L. Volakis + Show 2 more

Open Access

https://doi.org/10.1109/ojap.2021.3067373

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Abstract

Modern phased arrays require large instantaneous bandwidths, wide fields of view, and low profiles to conduct multiple functions. Many of these phased arrays rely on emerging high speed ADCs and advanced balanced transceivers. The benefits of balanced front-ends include improved linearity, dynamic range, isolation, and noise resilience. The application of a differential phased array in such a system removes extraneous losses caused by baluns, though the issue of feed-borne E-plane scan resonances must be considered. We address the E-plane scan resonance issue through an improved Balanced Wideband Impedance Transformer (BWIT) feed for the ultra-wideband (UWB) Tightly Coupled Dipole Array (TCDA). This BWIT feed has already demonstrated mitigated common-modes over a 3:1 bandwidth ratio while scanning to low angles. Here, our differential TCDA (D-TCDA) is developed for the L-C band ( viz. 1.0 GHz to 6.1 GHz) with emphasis on resonance-free wide-angle scanning. Rigorous EM model and circuit analysis is included to verify the BWIT performance. Under a VSWR $8\times 8$ single-polarized prototype.

Highlights

M ODERN phased arrays are required to be low volume, high gain, multifunctional, and capable of large fields of view [1]
We present a differential Tightly Coupled Dipole Array (TCDA) (D-TCDA) alternative to TCDA designs include integrated balun (TCDA-IB) that allows balanced feeding without common-mode resonances, complex coupling shields, or intentional losses
TIGHTLY COUPLED DIPOLE ELEMENT DESIGN The presented D-TCDA unit cell employs half-wave dipoles with capacitive overlaps as in previous TCDA

Summary

INTRODUCTION

M ODERN phased arrays are required to be low volume, high gain, multifunctional, and capable of large fields of view [1]. The balanced antennas in [11], [12], [13], [14] all exposed the occurrence of common modes in their feeds, which caused efficiency-disastrous resonances These common modes are present at frequencies and scan angles (typically mid-band and >45◦) where mutual coupling between co-polarized array elements introduces a phase imbalance on the feed [15], [16]. Often, these feeds are perpendicular to the ground plane to incur image theory’s aid at a distance H. The BWIT feed can be integrated into a fully differential TCDA (D-TCDA) to suppress common mode resonances and improve matching

TIGHTLY COUPLED DIPOLE ELEMENT DESIGN

CONCLUSION