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A TWO PORT UWB-DUAL NARROWBAND ANTENNA FOR COGNITIVE RADIOS Sasmita Pahadsingh and Sudhakar Sahu School of Electronics Engineering, KIIT University, Bhubaneswar, Odisha, India; Corresponding author: ssahufet@kiit.ac.in Received 11 January 2016 ABSTRACT: A two port ultra wideband(UWB) and dual narrowband antenna for cognitive radio(CR) applications is reported. In this letter an elliptical patch is used as an UWB sensing antenna which is copla- nar waveguide (CPW)-fed transmission line with elliptically tapered ground plane. A rectangular slot is etched from the radiating patch to integrate the narrow band communication antenna where basically the surface current density is effectively low. Within the slot a triangular monopole with meander line LC (inductance–capacitance) resonator in the feed helps to realize dual narrowband (NB) communication antenna. This proposed antenna is a potential candidate for cognitive radio appli- cation where the elliptical patch antenna covers the UWB frequency range (3.1–10.6 GHz) with stable radiation patterns for spectrum sens- ing and the triangular monopole with meander lines LC resonator in the feed behaves as dual band communication antenna with first band oper- ating at WLAN 5.04 GHz (4.48–5.4 GHz) and second band operating at X band satellite communication at 7.6 GHz (7.4–7.76 GHz) with isola- tion less than 210 dB in the whole operating band between the two antenna ports. The prototype of the proposed antenna has been fabri- cated and its S-parameters in terms of S 11 , S 22 , S 21 as well as radiation patterns were measured that shows good agreement with simulated results. V C 2016 Wiley Periodicals, Inc. Microwave Opt Technol Lett 58:1973–1978, 2016; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.29951 Key words: cognitive radio; ultra wideband sensing antenna; narrow- band communication antenna 1. INTRODUCTION Electromagnetic radio spectrum is the natural resource and the efficient use of it as transmitter and receiver is being decided by the Government. The spectrum available is quite limited and has become more and more congested owing to the excessive growth of wireless communication. Aiming to such facts, design and development of smart communication system is highly essential which accommodate entire application in spite of lim- ited spectrum. So the most promising technology to enhance the spectrum efficiency is cognitive radio (CR) [1] came into pic- ture. Specifically, a CR system has the ability to sense the spec- trum usage and then allocate services to the unoccupied part of the spectrum without causing interference to the other users. On this context, two separate antennas are required namely a wide- band antenna feeding the receiver for scanning the spectrum and a narrowband communication antenna feeds the front end for communication at desired frequency bands [2]. Since then num- ber of integrated antennas have been developed [3–10] without much disruption of each antenna element. Therefore this is a challenging task for antenna designers to integrate both the sens- ing (UWB) and communication (NB) antenna on a limited space in the same volume. In this letter, a new integration technique is implemented where the large metallization space of one antenna is efficiently shared for the use of additional antenna. The pro- posed design is a dual port antenna system where Port 1 consists of a CPW [11] fed elliptically tapered radiating patch as first antenna performing UWB and Port 2 consists of a triangular monopole with meander lines LC resonator in its feed as second antenna performing dual purpose narrow band operation. Aiming to the region of low current concentration, a rectangular slot has been etched from the first antenna so that the overall UWB per- formance will not be affected. Within this slot the second antenna has been developed so that the first antenna (elliptical UWB patch) at Port 1 behaves as coplanar ground for second antenna (triangular dual narrowband) at Port 2. The first TABLE 1 Optimized Dimension of Proposed Antenna Parameters W L L 1 L 2 L 3 W 1 W 2 S Dimension (mm) 75.7 58.35 25 10 13 22 14 3 Parameters g L w L s L f h L r W r S 1 Dimension (mm) 0.35 26 10 10 1.5 4.5 0.4 3 DOI 10.1002/mop MICROWAVE AND OPTICAL TECHNOLOGY LETTERS / Vol. 58, No. 8, August 2016 1973