ULTRA WIDE BAND C SHAPED MONOPOLE ANTENNA FOR COGNITIVE...
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International Journal of Electrical, Electronics and Data Communication, ISSN (p): 2320-2084, Volume-1, Issue-2, April-2013 Ultra Wide Band C Shaped Monopole Antenna For Cognitive Radio Applications 12 ULTRA WIDE BAND C SHAPED MONOPOLE ANTENNA FOR COGNITIVE RADIO APPLICATIONS 1 M. S. NARLAWAR, 2 S. L. BADJATE, 3 VARSHA H. GOUR 1 Dept of Electronics and Telecommunication, Y.C.C.E, Wanadongri, Nagpur, India. 2 S.B.Jain College of Engineering,Nagpur, India 3 Dept of Electronics and Telecommunication, Y.C.C.E, Wanadongri, Nagpur, India Email: [email protected], [email protected], [email protected] Abstract— This paper presents an antenna scheme suitable for cognitive radio applications. The omni directional c-shaped monopole disc antenna is designed to achieve impedance matching for ultra wide band range The proposed antenna uses FR-4 substrate having thickness of 1.6mm and dielectric constant 4.4 The antenna achieves an enhanced impedance bandwidth of 121.36 % covering from 4.666 to 12 GHz with a stable radiation performance and omnidirectional radiation pattern. The radiated patch occupied a total volume of 50 x 60 x 1.6 mm. The antenna suitable for cognitive radio applications was designed and analyzed by means of an e.m. design tool cad-feko. Keywords : Ultra Wideband, circular monopole disc I. INTRODUCTION According to the Federal Communications Commission (FCC), a cognitive radio is “a radio that can change its transmitter parameters based on interaction with the environment in which it operates.” Thus, a cognitive radio should be able to recognize spectrum availability and reconfigure itself for more efficient communications and spectrum use [1]. The monitoring of the wireless spectrum is the key in cognitive radio since the spectrum can be idle for 90% of the time. Therefore, in such a system, we should differentiate between a primary user that owns the spectrum and a secondary user that wants to access the spectrum whenever it is idle [2]. With the advances realised in the wireless communications domain, the number of users is increasing rapidly, which will lead to the saturation of important parts of the spectrum. In addition, it has been shown that a large portion of the spectrum is not adequately used. One of the solutions to the spectrum saturation problem consists of the cognitive radio (CR) concept, where the radios have the capability of learning and adapting to the environment where they operate. One of these adaptations involves changing the operating frequency [3-5]. In the future, it is suggested that the spectrum will be deregulated and cognitive radios could operate in any frequency band within the available spectrum. To this end, CRs must sense the spectrum to find a suitable frequency band to operate in, and then use it to transmit and receive data. While there is no agreed scheme for the operation and the sensing modes in cognitive radios yet, one possibility involves having an antenna with its front-end used for continuous sensing and another antenna with its front-end for the operation. To make sensing of the whole spectrum quick, it is suggested that the sensing antenna could be very wideband and the front-end would perform the frequency subdivision, scanning and filtering to achieve a convenient noise level for measuring the interference. It is also suggested that the operation antenna should be narrowband to help filter out-of-band signals [6]. The basic RF architecture of a CR system comprises of a “sensing antenna” to continuously monitor the wireless channel and search for unused frequency bands and a “reconfigurable transmit/receive antenna” to perform the required communication within those unused frequency channels [8]. One possible implementation of a CR system is shown in Fig. 1. In such a system, we should have a sensing antenna that continuously scans the communication channel searching for spectrum holes. Two modules, the “Spectrum Sensing” and the “Spectrum Decision”, are required to determine the unused frequency bands and assign the appropriate frequency to the secondary users. Based on the output of the “Spectrum Decision” module, the “Switch Controller” will communicate with the switch activation circuit in order to change the physical/electrical structure of the reconfigurable antenna. The reconfigurable antenna should tune its operating frequency to the one determined by the “Spectrum Decision” module. The paper is divided as: section II presents’ Objective of the project, section III & IV presents the proposed antenna design & simulation results and finally section V presents the conclusion.
Transcript of ULTRA WIDE BAND C SHAPED MONOPOLE ANTENNA FOR COGNITIVE...
International Journal of Electrical, Electronics and Data Communication, ISSN (p): 2320-2084, Volume-1, Issue-2, April-2013
Ultra Wide Band C Shaped Monopole Antenna For Cognitive Radio Applications
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ULTRA WIDE BAND C SHAPED MONOPOLE ANTENNA FOR COGNITIVE RADIO APPLICATIONS
1M. S. NARLAWAR, 2S. L. BADJATE, 3VARSHA H. GOUR
1Dept of Electronics and Telecommunication, Y.C.C.E, Wanadongri, Nagpur, India. 2S.B.Jain College of
Engineering,Nagpur, India 3Dept of Electronics and Telecommunication, Y.C.C.E, Wanadongri, Nagpur, India
Email: [email protected], [email protected], [email protected]
Abstract— This paper presents an antenna scheme suitable for cognitive radio applications. The omni directional c-shaped monopole disc antenna is designed to achieve impedance matching for ultra wide band range The proposed antenna uses FR-4 substrate having thickness of 1.6mm and dielectric constant 4.4 The antenna achieves an enhanced impedance bandwidth of 121.36 % covering from 4.666 to 12 GHz with a stable radiation performance and omnidirectional radiation pattern. The radiated patch occupied a total volume of 50 x 60 x 1.6 mm. The antenna suitable for cognitive radio applications was designed and analyzed by means of an e.m. design tool cad-feko. Keywords : Ultra Wideband, circular monopole disc I. INTRODUCTION
According to the Federal Communications Commission (FCC), a cognitive radio is “a radio that can change its transmitter parameters based on interaction with the environment in which it operates.” Thus, a cognitive radio should be able to recognize spectrum availability and reconfigure itself for more efficient communications and spectrum use [1]. The monitoring of the wireless spectrum is the key in cognitive radio since the spectrum can be idle for 90% of the time. Therefore, in such a system, we should differentiate between a primary user that owns the spectrum and a secondary user that wants to access the spectrum whenever it is idle [2].
With the advances realised in the wireless
communications domain, the number of users is increasing rapidly, which will lead to the saturation of important parts of the spectrum. In addition, it has been shown that a large portion of the spectrum is not adequately used. One of the solutions to the spectrum saturation problem consists of the cognitive radio (CR) concept, where the radios have the capability of learning and adapting to the environment where they operate. One of these adaptations involves changing the operating frequency [3-5]. In the future, it is suggested that the spectrum will be deregulated and cognitive radios could operate in any frequency band within the available spectrum. To this end, CRs must sense the spectrum to find a suitable frequency band to operate in, and then use it to transmit and receive data. While there is no agreed scheme for the operation and the sensing modes in cognitive radios yet, one possibility involves having an antenna with its front-end used for continuous sensing and another antenna with its front-end for the operation. To make
sensing of the whole spectrum quick, it is suggested that the sensing antenna could be very wideband and the front-end would perform the frequency subdivision, scanning and filtering to achieve a convenient noise level for measuring the interference. It is also suggested that the operation antenna should be narrowband to help filter out-of-band signals [6].
The basic RF architecture of a CR system comprises of a “sensing antenna” to continuously monitor the wireless channel and search for unused frequency bands and a “reconfigurable transmit/receive antenna” to perform the required communication within those unused frequency channels [8]. One possible implementation of a CR system is shown in Fig. 1. In such a system, we should have a sensing antenna that continuously scans the communication channel searching for spectrum holes. Two modules, the “Spectrum Sensing” and the “Spectrum Decision”, are required to determine the unused frequency bands and assign the appropriate frequency to the secondary users. Based on the output of the “Spectrum Decision” module, the “Switch Controller” will communicate with the switch activation circuit in order to change the physical/electrical structure of the reconfigurable antenna. The reconfigurable antenna should tune its operating frequency to the one determined by the “Spectrum Decision” module.
The paper is divided as: section II presents’ Objective of the project, section III & IV presents the proposed antenna design & simulation results and finally section V presents the conclusion.
International Journal of Electrical, Electronics and Data Communication, ISSN (p): 2320-2084, Volume-1, Issue-2, April-2013
Ultra Wide Band C Shaped Monopole Antenna For Cognitive Radio Applications
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Fig. 1. A Cognitive radio system
II. OBJECTIVE
The objective is to design a sensing antenna for cognitive radio applications which should be wide band and omnidirectional and to evaluate performance of a compact size antenna that operates in ultra-wideband range.
Several factors need to be considered while designing the antenna, including bandwidth, directivity, polarization, power gain, radiation pattern and return loss.
Theoretically, it is expected that the fabricate antenna has VSWR in the range 1 < V < 2 Return loss less than -10dB Omni-directional radiation pattern Bandwidth large enough to span the entire
UWB range.
III. PROPOSED ANTENNA DESIGN
The presented C-shaped UWB radio antenna system has been evolved after subtracting a small arc from the circular disc monopole antenna with a radius of r and a 50 Ω microstrip feed line which is printed on the same side of the FR4 (Flame Resistant 4) substrate (the substrate has a thickness of H=1.6mm). L and W denote the length and the width of the substrate, respectively. The width of the microstrip feed line is fixed at W1=2.6mm to achieve 50 Ω impedance. On the other side of the substrate, the conducting ground plane with a length of L1=20mm only covers the section of the microstrip feed line. The design of the patch, the partial ground plane, the slots and the feed matching section guarantee a UWB response of the sensing antenna. [7]
Fig.2 The schematic of the proposed ultra wideband antenna. The proposed antenna dimensions are tabulated as:
Parameters Dimensions(mm) L(mm) 60 W(mm) 50 W1(mm) 2.6 L2(mm) 20 W2(mm) 50
r(mm) 12 r1(mm) 8
Table 1. Proposed antenna dimensions
IV. SIMULATION RESULTS
The proposed antenna has been simulated in CADFEKO software. Simulated parameters are visualized in the following figures. The impedance plot for proposed antenna is as shown in Fig 3 and Fig 4. It should match to 50 ohm to make antenna more perfect, but considering losses its value should around 50 ohm. At the resonant frequency 7.64 GHz of proposed antenna, the magnitude of impedance is around 50.3 ohm with little reactive impedance which is under consideration.
Fig. 3 Impedance real [ohm] verses frequency [GHz]
International Journal of Electrical, Electronics and Data Communication, ISSN (p): 2320-2084, Volume-1, Issue-2, April-2013
Ultra Wide Band C Shaped Monopole Antenna For Cognitive Radio Applications
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Fig. 4 Impedance imaginary [ohm] verses frequency [GHz]
The return loss plot showing interested band of frequencies and resonant frequency has been depicted in Fig 5. In Fig 5, there is four notches in frequency range 2 – 3 GHz, 4.5 – 6.5 GHz, 7 – 8 GHz and 10 – 12 GHz respectively. Since the proposed antenna is designed for the 7 – 8 GHz frequency band is considered for further work. The return loss plot for complete bandwidth from 4.666 GHz to 12 GHz is below -10dB. In respective band, the resonant frequency is found to be 7.64 GHz and return loss value is at -40.78 dB as shown in Fig 5.
Fig. 5 Reflection coefficient [dB] verses frequency [GHz] For proposed antenna, the VSWR plot is as shown in Fig 6. Its value should be in the range of 1 to 2. For proposed antenna, at the resonant frequency, 7.64GHz the value of VSWR is found to be 1.03.
Fig.6 VSWR verses frequency [GHz]
Gain is another important parameter which has been studied. The 3d view of gain for proposed antenna is shown in Fig 8. The value of gain is around 5.32dBi for proposed slotted circular monopole antenna.
Fig. 7. The polar plot
Fig. 8 The radiation pattern
International Journal of Electrical, Electronics and Data Communication, ISSN (p): 2320-2084, Volume-1, Issue-2, April-2013
Ultra Wide Band C Shaped Monopole Antenna For Cognitive Radio Applications
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The above results can be tabulated as,
Performance Parameters
Observed Value
Impedance
46.2 Ω at 2.686GHz 58.3 Ω at 6.043GHz 50.7 Ω at 7.644GHz
Return loss
-27.86dB at 2.686GHz
-20.14 at
6.043GHz
-40.78dB at 7.644GHz
Bandwidth 7.334GHz
VSWR 1.09 at 2.686GHz 1.22 at 6.043GHz 1.02 at 7.644GHz
Gain 5.47dBi at 7.644GHz
Table 2. Results
CONCLUSION
The antenna is simulated using the simulation tool CADFEKO®. The observed results are tabulated above and are found to be in close agreement with the theoretically expected values. The antenna can be used in Cognitive Radio applications. Its usability in Cognitive Radio systems can be enhanced by incorporating a narrowband antenna in the same antenna structure to serve the desired user.
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