Abstract
In this work, a switchable bandstop filter is used as a decoupling structure for developing a miniaturized reconfigurable multiple input multiple output (MIMO) antenna. Initially, a dual band ((2.43-2.60 GHz and 3.51-3.79 GHz)) single monopole antenna structure is developed on FR4 substrate. Then the single monopole antenna and its replica are accommodated in a small space with an edge to edge separation distance of 11 mm to form a 2 port MIMO antenna. Now, a switchable bandstop filter is used as a decoupling network between two closely spaced monopole antenna elements to prevent mutual coupling and reconfigure the antenna characteristics. The dual pole switchable bandstop filter is configured in such a way that one of its poles lies at 2.5 GHz in one state (Mode 1) and at 3.68 GHz in another state (Mode 2) under the switching action of two PIN diodes. Controlling the ON/OFF states of the PIN diodes in the bandstop filter, high isolation is achieved alternately in lower (2.43-2.60 GHz) and upper (3.51-3.79 GHz) frequency bands of the MIMO antenna. Also, stub network is used to improve impedance matching in the upper frequency band. The proposed isolation technique helps the antenna to yield high isolation (>30 dB), fair gain (>2.97 dBi), reasonable radiation efficiency (>86.8 %), low envelope correlation coefficient (< 0.16), high diversity gain (DG >9.88 dB), low Mean effective gain ratio (MEG 1/MEG 2 < 0.05 dB) and low channel capacity loss (CCL < 0.06 bits/s/Hz) for both the operating frequency bands. The overall dimension of the antenna is restricted to 44mm <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\times $ </tex-math></inline-formula> 22mm ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$0.36\lambda _{o}\,\,\times \,\,0.18\lambda _{o}$ </tex-math></inline-formula> ) for its easy integration in compact wireless devices. This type of reconfigurable MIMO antenna is best suited for cognitive radio communication, which promotes efficient spectrum utilization.
Highlights
B ECAUSE of the introduction of various multimedia services, todays modern wireless communication systems can accommodate higher data rates than previous systems
The upper (3.68 GHz) and lower (2.5 GHz) band multiple input multiple output (MIMO) operations can be controlled by the switching function of bandstop filter
In this work, a switchable bandstop filter is used as decoupling structure for developing miniaturised reconfigurable multiple input multiple output (MIMO) antenna
Summary
B ECAUSE of the introduction of various multimedia services, todays modern wireless communication systems can accommodate higher data rates than previous systems. Multi-element antennas, such as multiple-input multipleoutput (MIMO) antenna systems, are required for these multimedia services, as they are one of the most effective strategies for enhancing channel capacity and reliability [1]. In addition to the high data rate, modern communication systems require the ability to accommodate multiple communication standards integrated with a single antenna compact device. Reconfigurable MIMO systems which can support multiband communications with high data rates are in the prime focus of wireless communication research [2]. Reconfigurable MIMO systems require reconfigurable MIMO antennas for transmitting and receiving electromag-.
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