Constant Niamien

Compact Expressions for Efficiency and Bandwidth of Patch Antennas Over Lossy Magneto-Dielectric Materials

Closed-form formulas for calculating the radiation efficiency and bandwidth of patch antennas over lossy magneto-dielectric materials are proposed by using the cavity model. These expressions agree well with simulations. It is well known that the bandwidth of microstrip antennas is enhanced when the dielectric substrate is replaced by a magnetic one. Here, we confirm more generally that not only the bandwidth, but also the radiation efficiency, can be improved when the permeability (μr) is greater than the permittivity (εr).

Surface wave loss and material loss in printed antennas over magneto-dielectric materials

Since many years, investigations on microstrip antennas have received renewed attention due to many advantages they offer as low cost, ease of production, compact size, etc… The use of dielectric materials with high permittivity in microstrip antennas leads to size reduction but at the same time the efficiency and the bandwidth are significantly reduced [1], [2]. However, with magneto-dielectric materials, this limitation seems to be overcome since such materials give a larger bandwidth compared to dielectric materials [3]-[5]. But, available magneto-dielectric materials are very lossy in microwave frequency ranges and the substrate under the conductor line is usually extended beyond the line limits (not truncated substrate) which can excite surface waves [6], [7]. So, as for dielectric materials [8]-[13], the use of magneto-dielectric materials also means that losses can be generated either by the propagation of surface waves for non truncated substrates or by the inherent material loss tangents.