An accurate model of a wide-band microstrip feed for slot antenna arrays

Tapered slot antennas (TSAs) are well suited for phased array applications where a wide frequency band and/or large scan range are of prime importance. The use of accurate modeling techniques is essential for predicting the impedance and radiation characteristics of TSA arrays well. Often, a computationally intensive full-wave analysis is performed for both the TSA array and its microwave feeding network. However, since no direct mutual interaction between the feed network and antenna exists (except at the transition), the computational burden can be relaxed by separating the microwave modeling of the feed from the electromagnetic modeling of the TSA array. In the past, difficulties have been encountered when also developing a circuit model for the (circular) cavity of the TSA and consider it as part of the feed. It has been found that such models do not enable us to perform a quantitative analysis for TSA arrays. This paper describes a systematic method to model the feed network and antenna array separately, which not only leads to an accurate prediction of the behavior of a single TSA, but also for arrays of TSAs. The accuracy of the total model will be demonstrated through the measurements of a practical TSA array.