Tightly Coupled Array Antennas for Ultra-Wideband Wireless Systems

Tightly coupled array (TCA) antenna has become a hot topic of research recently, due to its potential of enabling one single antenna array to operate over an extremely wide frequency range. Such an array antenna is promising for applications in numerous wideband/multi-band and multi-function wireless systems such as wideband high-resolution radars, 5G mobile communications, satellite communications, global navigation satellite systems, sensors, wireless power transmission, Internet of Things, and so on. Many papers on this topic have been published by researchers internationally. This paper provides a detailed review of the recent development on TCA that utilizes the capacitive coupling. The basic principles and the historical evolution of the TCAs are introduced first. Then, recent development in the analysis and design of TCAs, such as equivalent circuit analysis, bandwidth limitation analysis, array elements, feed structures, substrates/superstrates loading, and so on, are explained and discussed. The performances of the state-of-the-art TCAs are presented and a comparison amongst some TCAs reported recently is summarized and discussed. To illustrate the practical designs of TCA, one case study is provided, and the detailed design procedures of the TCA are explained so as to demonstrate the TCA design methodology. Simulated results including the VSWR at different angles of scanning, patterns, and antenna gain are shown and discussed. A conclusion and future work are given in the end.