Emerging applications such as modern wireless communications are often met only by high performance and compact filtering structures. Several of such filters have been reported using generic structures called the defected-ground structures (DGS). Since DGS cells have inherently resonant properties, they have been used in filtering circuits to improve the stop and passband characteristics. In recent years, periodic or non periodic arrays such defected ground structure (DGS) for planar transmission lines can be applied to wide frequency ranges including the microwave frequencies. The transmission lines combined with the periodic structures have a finite pass and rejection band like low pass filters (LPF), while the standard transmission lines show only the simple transmission characteristics over broadband. DGS[1], are realized by etching a few dumb-bell shaped patterns on the backside metallic ground plane, which give rise to increasing the effective capacitance and inductance of a transmission line, respectively. Thus, a parallel LC equivalent circuit can represent the proposed arrowhead-slot unit [2]. In this paper, we present a 5th order compact hi-lo DGS lowpass filter, using two low impedance capacitive sections and three DGS slots instead of the conventional high impedance inductive elements. A new technique is proposed in order to be able to carry out an equivalent Arrowhead-slot with the given circuit model. Changing the physical dimensions of the etched DGS can easily control the effective inductance. In order to improve its characteristics, we fabricated the proposed DGS-LPF. The simulations and measurements for the proposed LPF shows excellent agreement.
展开▼
