“…In addition, the feeding structure can affect the antenna overall performance, changing its main parameters such as resonant frequency, bandwidth, radiation pattern, and radiation efficiency [1], [9]. Several impedance matching techniques have been developed for microstrip line and coaxial cable printed antenna excitation, such as λ/4 impedance transformers [10], [11], stubs [12], [13], inset-feed [14], [15], and probe feed [16], as shown in Fig. 2.…”