An Improved Method to Measure, Characterize, and Model Microstrip Antennas in the W Band

The rapid evolution of wireless technology demands an ever-growing number of connected devices, and hence, a greater availability of antennas for a gamut of applications in different frequency ranges [1]–[3]. The size, materials, and geometry of antennas, however, depend on the application as well as on important considerations, including resonant frequency, bandwidth, gain, efficiency, shape of the radiation pattern, input impedance, and many more [4]. Hence, a universal measuring technique for antennas cannot be derived, and in general, each case requires that it be treated individually. In addition, as frequency of measurement increases, more effects must be taken into account when interpreting data; one of relevance is that introduced by the surface roughness at the interface between the printed circuit board (PCB) substrate and the metal foil that serves as a conductor [5]–[6]. In fact, the surface roughness of the copper foil is necessary to achieve good adherence to the dielectric substrate, and thus, it is voluntarily included in the manufacturing process. Unfortunately, the variation of the metal surface from the ideal smooth case increases the resistance of the foil at microwave frequencies. In consequence, it negatively impacts the electrical performance of structures and should be considered when assessing the response of antennas on PCB.