746 S. SHARMA, C. C. TRIPATHI, AN INTEGRATED FREQUENCY RECONFIGURABLE ANTENNA FOR COGNITIVE RADIO … DOI: 10.13164/re.2017.0746 ELECTROMAGNETICS An Integrated Frequency Reconfigurable Antenna for Cognitive Radio Application Sonia SHARMA, Chandra Charu TRIPATHI Dept. of Electronics and Communication Engineering, UIET, Kurukshetra University, Kurukshetra, India sonia990@gmail.com, tripathiuiet@gmail.com Submitted November 20, 2016 / Accepted May 22, 2017 Abstract. A novel integrated antenna that consists of spectrum sensing and frequency reconfigurable antenna, printed on a single substrate is presented here. The inte- gration of both antennas is based on the fact that reasona- bly large metallization area of UWB antenna can be used as a space for printing another narrowband antenna. Prominently, the second antenna should be placed on a region of large UWB antenna where there is less distri- bution of E field. The proposed antenna senses the spec- trum over a wide frequency range from 2 GHz to 12 GHz via a U shape monopole having partial ground structure. After sensing the spectrum condition, the slot antenna with reconfigurable feeding structure can switch its operating bands among six narrowbands: 5.65 GHz, 3.6 GHz, 5 GHz, 2.94 GHz, 4.5 GHz, 2.15 GHz and two dual bands at 2 GHz, 5.48 GHz and 1.7 GHz, 5 GHz. In addition to this, the proposed antenna can also reconfigure its frequency in wide-bandwidth using two ground stubs. Since wide band response for spectrum sensing and each of eight frequency state works independently, therefore, there is no interference among various signals. Keywords Cognitive radio, frequency reconfiguration, slot antenna, spectrum sensing, wideband antenna 1. Introduction The next generation smart systems should have capa- bility to automatically detect the spectrum condition and accordingly change the radio operating parameters to mod- ify system performance such as maximize throughput, mitigate interference, facilitate interoperability etc. In ad- dition, the physical size of these devices must follow the downsizing trend of the system unit. A smart Cognitive Radio (CR) compatible antenna with smaller physical size meets the essential requirement for these systems. Such antenna has a spectrum-sensing antenna for detecting the spectrum condition and reconfigurable antenna for com- municating purpose [1], [2]. Many antenna designs have been already reported in the literatures, which are compati- ble with CR [3–6]. Further to decrease the system size, these two antennas must be optimally design on a single substrate. Only a handful of techniques based on integra- tion concept of these antennas, on a single substrate are reported in literature [7–15]. In these techniques, small narrowband (NB) antenna are integrated in UWB antenna by using various topology viz. using large metallization area of UWB antenna as ground plane for a smaller antenna [7], [8], by utilizing the empty space in between the radi- ating element, and in between two tapered slots [9], by adding reconfigurable part in the feeding area of Vivaldi antenna [10], by adding reconfigurable band pass filter in feed line [11], by adding JK inverter in the switchable feed line structure [12], by placing the NB antenna at a point where electric field does not disturb the UWB antenna [13], by adding UWB antenna above the reconfigurable antenna [14], by reusing the printed area in different operating modes [14], etc. In all the above designs the numbers of frequency reconfiguration states are limited because of size constraint so there is underutilization of available area. Further up gradation of these antennas to increase the re- configuration states is quite challenging because of limited space constraints on board. This may compromise the goal of combining the wideband and reconfigurable antenna together for CR systems. Therefore, in the present work, UWB antenna and re- configurable antenna are integrated in such a way that they do not disturb the characteristics of each other. The chal- lenging goal in this work is to use the available space op- timally for multiple purposes. For space management, the Fig. 1. Layout of the proposed integrated antenna.