Improved Multifunctional MIMO Cognitive Radio System for Integrated Interweave-Underlay Operations

摘要

This article presents the design of an integrated system involving multiple-input-multiple-output (MIMO) and cognitive radio (CR) technologies for sub-6 GHz applications. Two types of CR techniques, i.e., interweave and underlay CR, have been discussed in this article. The design model has a four-port multifunctional MIMO antenna system involving lumped elements for three selectable operation choices. Based on the switching conditions, the MIMO antenna system can operate as a wideband antenna (for sensing purpose), or narrowband frequency tunable antenna (for communicating purpose in interweave CR), or a wideband antenna with frequency tunable band notch (for communicating purpose in underlay CR). The sensing frequency range is 2.45-5.3 GHz. The interweave CR communicating antenna frequency tuning range is 3.6-4.2 GHz. To cover the entire desired spectrum range, i.e., from 2.5 to 4.2 GHz, another four-port narrowband MIMO antenna system with resonance frequency tuning from 2.5-3.6 is designed on the other/backside of the substrate. In the underlay CR communicating antenna, the stopband frequency tuning range is 3.1-3.85 GHz. The complete structure is having dimensions of 110 x 70 x 1.52 mm(3). The measurements are performed, and good matching is found between simulated and measured results.