In Firstly, a microstrip transmission line canIn Firstly, a microstrip transmission line can

In the past few years, the conventional
band stop filters just depended on the miniaturized scale strip technology with
the accumulation of inductors and capacitors and its computational verification
in the form of parallel-coupled micro strip lines.

Firstly, a microstrip transmission line
can be used for designing bandstop filters. A micro strip transmission line is
used in the transport of waves with relatively low frequency. The general
structure of a microstrip is illustrated in Fig. 1.1. The wave type propagating
in this transmission line is a quasi TEM wave. A conducting strip with a width
W and a thickness t is on the top of a dielectric substrate that has a relative
dielectric constant ?r and a thickness h, and the bottom of
the substrate is a ground conducting plane. The width of the strip along with
the dielectric constant and the thickness of the substrate determine the characteristic
impedance of the line 1.

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In this report, the principle goal is to
make the proposed filter achieve a significant size reduction, give high
performance results and most importantly acquire tunability. As wireless
applications nowadays are numerous, the filter is designed to operate at a
frequency ranging from 2.6 to 5.8 GHz to be used in a variety of wireless
applications.The design of a tunable and compact microstrip
bandstop filter in this structure is presented by making a full utilization of
the theories of microstrip technology. As stated in 1, when the longitudinal
components of the fields for the dominant mode of a microstrip line remain
smaller than the transverse components, they may be neglected. In this case,
the dominant mode then behaves like a TEM mode, therefore the TEM transmission
line theory is relevant for the microstrip line as well. This is called the
quasi-TEM approximation. A homogeneous dielectric material with an effective
dielectric permittivity is found instead of the dielectric air media of the
microstrip. Transmission characteristics of microstrips are described by two parameters,
the effective dielectric constant ?re and characteristic impedance
Zc, These parameters of microstrips are then determined as follows: