Analysis of series-fed slot antenna arrays transversely coupled to a microstrip line including mutual coupling effects

Microstrip line fed slot antenna arrays (Figure 1)are low profile structures that are easy to manufacture with low cost and they can be easily integrated with the feed network and/or the microwave front end circuits. Due to these features they are widely used in various applications. It is well known that a slot antenna positioned perpendicular to the microstrip feed line can be modeled by a series impedance whose value is determined by the offset (x) and the length of the slot (l). For the characterization of the slot impedance in terms of these two parameters two different approaches can be found in literature [1,2]. In the classical paper of Pozar [1], the full-wave analysis of the slot antenna is performed by the spectral domain Method of Moments (MoM) technique and the impedance value is obtained via reciprocity theorem. A similar analysis technique is also applied in [3] and the variation of slot impedance with the thickness and permittivity of the dielectric substrate is studied. On the other hand, in [2] the slot characterization is done experimentally by utilizing the TRL calibration technique and an 8 element linear array is designed through the use of the transmission line theory with each slot modeled as a series impedance.