  Graphene is an interesting debated topic between scientists because of its
unique properties such as tunable conductivity. Graphene conductivity can be
varied by either electrostatic or magnetostatic gating or via chemical doping,
which leads to design of various photonic and electronic devices. Among various
graphene-based structures, plasmonic graphene filters have attracted the
attention of many researchers because of their various applications in THz
frequencies. There are four main types of graphene filters proposed in the
literature, which are: 1- Circular filters, 2- Planar filters, 3- Periodic
filters, and 4- Other types of filters (which are not categorized in any of the
other three groups). This paper aims to study and investigate various types of
graphene-based filters published in the literature.
