Disc monopoles are popular low cost antennas which are typically used in modern wireless communication systems requiring wideband performance with low to medium gain. The Dielectrically loaded disc monopole has performance similar to that of a normal Circular disc monopole (CDM) with an almost 60% size reduction whilst maintaining almost 80% of the impedance bandwidth. As shown in the above image, an extra dielectric layer is added to improve the match between the inner dielectric and free space. This outer layer has a thickness of λ/4 and relative permittivity of √εr_inner.
The following graphs show typical performance of a Dielectrically loaded disc monopole designed with inner and outer dielectric materials, εr_inner = 9 and εr_outer = 3 respectively....Typical reflection coefficient versus frequency Total gain patterns - fmin ,1.5fmin, 2fmin and 2.5fmin