Abstract
A single-port uniplanar antenna with a built-in tunable filter is presented for operation in multiple LTE bands for cognitive femtocell applications. The antenna is based on a monopole microstrip patch fed by coplanar waveguide. The frequency reconfigurability is achieved by using two PIN diodes to couple or decouple a ring slot resonator filter from the antenna feed line. By switching the PIN diodes, the proposed design can operate in either wideband or narrowband modes. When the antenna operates in the narrowband state, two varactor diodes are used to continuously tune the narrowband frequency from 2.55 to 3.2 GHz, while the wideband state is obtained over the 1.35–6.2 GHz band. The diodes and their biasing networks have nearly no severe effect on the antenna characteristics. Prototypes of the proposed structure using ideal and real switches, with and without varactors, are fabricated and tested. Measured and simulated results are in good agreement, thus verifying the good performance of the proposed design. The obtained results show that the proposed antenna is very suitable for cognitive radio applications, in which the wideband mode is used for spectrum sensing and the narrowband mode for transmission at different frequency bands.
Highlights
A “data tsunami” has resulted from the emergence of data-hungry wireless applications
UWB to narrowband reconfiguration is achieved by employing two PIN diodes that couple or decouple the RSR filter from the antenna feed line, thereby making the filtenna work either in sensing or communication modes
The basic design of the filtenna consists of monopole antenna fed by CPW with a built-in RSR filter in the ground plane
Summary
A “data tsunami” has resulted from the emergence of data-hungry wireless applications. Femtocells are considered as a promising solution to overcome the indoor coverage issue and to achieve higher data rates by shorting the communication range and a better frequency reuse capability [6, 7]. Frequency reuse is a practical solution to overcome the spectrum scarcity [8], which is due principally to the increasing demand for more bandwidth versus the fact that all frequency bands are already allocated by the Federal Communications Commission (FCC). Another promising technology to meet the high data rate requirements and overcome the frequency scarcity is the cognitive radio (CR) paradigm [9]. The reconfigurable antennas are Reference [15] [23] [24] [25] [26] [27] Proposed filtenna
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