Evolution of Compact Slot Antennas

Abstract

In purely physical terms a slot etched into a plane conducting screen is a remarkably simple structure. Nevertheless if appropriately fed with a source of electromagnetic waves, it has led to the evolution of a wide range of significant antenna types ranging from compact embodiments for communication systems to large phased arrays for radar. Initial research on the so called slot radiator can be traced back to before the Second World War. It was strenuously propelled by military pressures to advance the detection capabilities of radar. As a consequence of this early ‘baptism’ the literature is comprehensive and extensive, requiring patient time-consuming study by antenna designers, and by research engineers, with a need to claim mastery of the topic. Recent progress has been largely triggered by the burgeoning of modern communications techniques demanding increasingly compact, lighter, and more mobile antennas, offering large bandwidth to the user. Due diligence requires a thorough sifting of this literature, which is inevitably time consuming and expensive when it is so extensive. This chapter aims to identify the primary threads in the historical evolution of antennas influenced by the elemental slot, while at the same time providing a resource which short-circuits the tedious knowledge gathering process for budding innovators.