3-D FDTD design simulation and experimental measurement of a Ka-band planar antipodal linearly-tapered slot antenna (ALTSA)

Three-dimensional (3-D) finite-difference time-domain (FDTD) simulation of a planar broadband Ka-band (25-35 GHz) antipodal linearly-tapered slot antenna (ALTSA) and the experimental measurements are presented. The Berenger perfectly matched layer (PML) absorbing boundary condition is used for the FDTD computation. A printed ALTSA has been realized by using the RT/Duroid PCB substrate. Good agreement between simulation and measurement were achieved.

I. Introduction

The broadband and high-gain natures of tapered slot antennas (TSAs) have been reported for years. Due to its coplanar structure, the TSA is easily integrated with microwave integrated Fig. 1. Geometry of an ALTSA and photograph of realized Ka-band printed ALTSAs on a RT/Duroid substrate circuits. In [1], some parameters that affect the performance of the TSA, such as the thickness of the substrates and the profile of the tapered slot, were presented by Yngvesson et al.R. Janaswamy and D. H. Schaubert [2] proposed a good-stepped approximation to analyze the TSA with exponential taper profiles, which are the general cases of TSAs. Nevertheless, the conventional feeding technologies applied in TSAs including CPW-to-slot transition, coax-to-slot transition, or even finline feeds, all face on difficulty of impedance matching. To surmount the impedance matching difficulty, TSA of antipodal geometry was introduced [3]. The antipodal linearly-tapered slot antenna (ALTSA) reported in [4], [5] describes the development and performance of a balanced antipodal Vivaldi antenna. It can produce an ultrawide bandwidth element for circuit integration. One of the advantages of the antipodal geometry is that no stubs are need on the PCB to achieve impedance matching.