4. Compact filtennas with enhanced bandwidth

Two filtennas are proposed by a design strategy with the merits of both a compact structure and enhanced bandwidth. The reliability of the filtennas is verified though simulations and analysis of a compact NFRP filtenna which is proposed and fabricated. The reported design employs a Rogers 4350B substrate with relative permittivity ε<sup>r</sup> = 3.48, relative permeability μ<sup>r</sup> = 1.0, and dielectric loss tangent tan σ = 0.0037.

#### 4.1 Design of compact filtennas

A well-designed compact NFRP antenna is selected as the radiator [19, 20]. Then a compact NFRP antenna is designed, which consists of a traditional monopole and a rectangular microstrip capacitively loaded loop (CLL)-based band-pass filter [21, 22].
