- Email: [email protected]
Measurement of a metamaterial antenna angular power reception performance utilizing Software Defined Radio
Accepted Manuscript Regular paper Measurement of a Metamaterial Antenna Angular Power Reception Performance Utilizing Software Defined Radio Huseyin Akcelik, Yilmaz Durna, Safak Saraydemir, Hasan Kocer PII: DOI: Reference:
S1434-8411(16)30245-X http://dx.doi.org/10.1016/j.aeue.2017.03.013 AEUE 51819
To appear in:
International Journal of Electronics and Communications
Received Date: Revised Date: Accepted Date:
13 June 2016 6 February 2017 15 March 2017
Please cite this article as: H. Akcelik, Y. Durna, S. Saraydemir, H. Kocer, Measurement of a Metamaterial Antenna Angular Power Reception Performance Utilizing Software Defined Radio, International Journal of Electronics and Communications (2017), doi: http://dx.doi.org/10.1016/j.aeue.2017.03.013
This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
Measurement of a Metamaterial Antenna Angular Power Reception Performance Utilizing Software Defined Radio Huseyin Akcelik, Yilmaz Durna, Safak Saraydemir and Hasan Kocer
Mr. Huseyin Akcelik Affiliation: Defense Sciences Institute, Turkish Military Academy, 06654 Ankara, Turkey. Degree: MSc in Military Electronic Systems e-mail: [email protected]
Mr. Yilmaz Durna Affiliation: Department of Electronics Engineering, Turkish Military Academy, 06654 Ankara, Turkey. Degree: MSc in Electronics Engineering e-mail: [email protected]
Dr. Safak Saraydemir Affiliation: Department of Electronics Engineering, Turkish Military Academy, 06654 Ankara, Turkey. Degree: PhD in Electronics Engineering e-mail: [email protected]
Assoc.Prof. Hasan Kocer Affiliation: Department of Electronics Engineering, Turkish Military Academy, 06654 Ankara, Turkey. Degree: PhD in Electronics Engineering e-mail: [email protected]
1
Measurement of a Metamaterial Antenna Angular Power Reception Performance Utilizing Software Defined Radio Huseyin Akcelik1,*, Yilmaz Durna2, Safak Saraydemir2 and Hasan Kocer2,* 1
Defense Sciences Institute, Turkish Military Academy, 06654 Ankara, Turkey,
[email protected] 2
Department of Electronics Engineering, Turkish Military Academy, 06654 Ankara,
Turkey, [email protected], [email protected], [email protected] * Corresponding authors ABSTRACT
In wireless communication systems, angular positioning is an important aspect affecting the behavior of an antenna reception performance. In this study, a broadband, high gain rectangular microstrip patch antenna using planar-patterned metamaterial concept and its measured angular power reception performance are presented. The metamaterial antenna’s -10 dB bandwidth is achieved as 2.42 GHz in the frequency range of 2.89 – 5.31 GHz with the peak gain of 5.56 dBi. Angular power reception performance of the proposed antenna is measured for different selected intervals in indoor and outdoor environments with the help of Software Defined Radio. The antenna is orientated vertically / horizontally and rotated in the azimuth Ø plane from 0o to 360o with angular resolution of ∆Ø= 45 o. The measured received power distributions are shown at angle versus distance and compared.
Keywords: Angular power reception, broadband, metamaterial, patch antenna, software defined radio (SDR).
2
1. INTRODUCTION The demand for small, compact, low cost and wideband antennas has increased rapidly over the past years, due to the need for reduced size and enhanced bandwidth antenna for many applications in both military and industry. In that respect, compact size, lightweight, low cost and broadened bandwidth are now quite important challenges to be accomplished by the designers of wireless communication systems. It is believed that the microstrip patch antennas are the most commonly utilized printed antennas which offer attractive features, such as simple structure, small size, easy integration to planar and nonplanar surfaces, aesthetic appearance, ease of fabrication and mechanically robust when mounted on rigid surfaces [1]. However, these antennas have some disadvantages such as narrow frequency bandwidth and low gain. In recent years, many techniques have been investigated to overcome these drawbacks especially for narrowband. These techniques are mainly augmentation of the substrate thickness [2, 3], handling discrete shaped splits or propagating patches [4], placing unlike propagating elements to the antenna sideways [5, 6], utilizing magneto dielectric and aperture-coupled substrates [7, 8], and trying to change the ground plane with electromagnetic band gap materials [9, 10]. Metamaterial (MTM) or left-handed material (LHM) which had been studied theoretically by Veselago in 1960s [11] has become immensely popular because of their unconventional electromagnetic properties. Metamaterials are described as artificially engineered materials exposing unique or unusual properties that cannot be found when using natural materials [12]. The main properties of conventional materials existing in nature are having positive permittivity (є) and permeability (µ). But MTM presents negative є and / or µ [11]. In 2001, Shelby et al. showed that these materials have negative refractive index which is a reversal of Snell’s law [13]. These attractive features of MTM aroused the researchers’ desire. Scientists and designers have experimented different techniques to bring these MTMs
3
into practical applications, especially into antennas to enhance their gain, directivity and bandwidth [14-24]. While modern wireless communication systems have been developing quickly in years, an antenna as an integral part of a wireless system is required to have good radiation performances besides its bandwidth. A well-designed antenna is crucial for system performance. A wide band antenna design requires particular modeling of its power performance as a part of the communications link especially for its angular power distribution [25]. In this paper, a broadband and high gain rectangular patch metamaterial antenna (MMA) is proposed by deploying the planar patterned designs directly to the top patch and ground plane of the dielectric substrate (FR-4). This approach is different from similar previous study given in [14]. The suggested antenna, with a bandwidth of 2.42 GHz, ranges between 2.89 to 5.31 GHz ( |S11|<−10 dB ) and its dimensions are 44.8 × 54.87 × 1.6 mm 3. We present experimental results of the angular power distribution in different realistic propagation conditions at 2.8 GHz frequency. The measurements were performed using a wide-band MMA as a test-antenna and an omnidirectional antenna as a reference antenna which is connected to the Software Defined Radio (SDR). 2. DESIGN, SIMULATION AND FABRICATION OF ANTENNA A microstrip patch antenna is normally placed on one side of a dielectric substrate and the other side is covered with a conductive ground plane. In the proposed study, a planar LHM design is etched on the radiating patch to increase horizontal radiation of the antenna. The conducting ground plane is shaped to widen its bandwidth. On the surface of the patch, periodic apertures are used and shaped like separated mini triangular patterns, as shown in Fig. 1(a), while on the conductive part, periodically deployed intersecting straight line spaces are formed, as shown in Fig. 1(b). Geometrical parameters of MMA are also given in 4
Fig. 1(a, b). The left-handed features of these designs were represented in [26]. In the propagation mechanism of the antenna, the radiating upper patch and conductive bottom plane are coupled to model an inductive-capacitive (L-C) equivalent circuit. In this way, it leads to backward wave which propagates throughout the surface of the antenna [27]. Therefore, the direction of the radiation throughout the surface of the antenna is greatly increased. The metallic surfaces are used as conductive copper with 17 µm in thickness and its frequency independent conductivity is 5.8x10 7 S/m. As a dielectric substrate, epoxy glass cloth laminate (FR4) is used with 1.6 mm in thickness, its relative dielectric permittivity is 4.6 and the loss tangent is 0.025 [28]. To decide the optimum parameters and figure out the physical mechanisms of the antenna, the CST Microwave Studio simulation software with its transient solver is used. The parameters of the antenna are examined by shifting one at a time, while fixing the others. The MMA is fabricated using the printed circuit board (PCB) technique shown in Fig. 1 (c,d).
5
Fig. 1. Simulated antenna (a) top view and parameters (b) bottom view and parameters; fabricated antenna (c) top view (d) bottom view. 3. RESULTS AND DISCUSSIONS In the measurement setup (Fig. 2), a spectrum analyzer (Rohde & Schwarz, 9 KHz - 7 GHz), a transmitter (SDR, NI-USRP 2922, 400 MHz - 4.4 GHz), a transmitter antenna (VERT2450, omnidirectional) and a receiver antenna (proposed MMA) are used. The distance (R) is changed from 1 to 3 m with 25 cm intervals for indoor and from 1 to 8 m with 50 cm intervals for outdoor setup. The transmitting antenna is fixed at one position while the receiving antenna is placed on a man-controlled turntable and rotated in the azimuth Ø plane from 0o to 360o with angular
6
resolution of ∆Ø= 45 o. The MMA antenna is connected to the spectrum analyzer with two different positions in order to measure the received powers. The fabricated MMA’s reception performance is measured with two different cases. In the first case, the MMA is located on the xy plane perpendicularly and rotated with angle Ø around the z-axis. The Ø is the sweeping angle between x-axis and the front surface normal (N). In the second case, the MMA is positioned perpendicular to the xz plane and rotated around y-axis with angle Ø. Transmitter antenna (VERT 2450) is attached to SDR with an angle of 90 o. The SDR transceiver is connected to a host computer via ethernet cable. In the host computer, we use Labview software which provides an optimum way to interface with SDR hardware for the development of communication algorithms that process and synthesize the signals for transmission. The output powers (Pt1, Pt2) of the SDR are controlled on the host computer by changing the internal gain function in the Labview software interface. Gain function zero corresponds to Pt1 and the gain function twenty corresponds to Pt2. Pt1 and Pt2 are the power levels measured by connecting the output connector of the SDR device to the spectrum analyzer with an almost lossless RF cable without using the antenna. In this way, Pt1 and Pt2 are measured to be 7 dBm and 18.65 dBm, respectively. The operating signal is 2.8 GHz generated by SDR. In the experiment, a sinusoidal wave (f(t)) which has components of inphase and quadrature-phase is transmitted where = , = . The magnitude of the vector r is equal to + . The phase of the vector is θ which is equal to ⁄. The transmitted signal waveform is = − . These two components are perpendicular to each other and hence they do not interfere [29].
7
Fig. 2. Measurement setup block diagram for angular reception performance of the MMA. 3.1 Antenna Results The proposed MMA’s -10 dB bandwidth which is stated as a norm for engineering implementations ranges from 2.89 and 5.31 GHz with 2.42 GHz in bandwidth. Measured and simulated results of S11 values are compared in Fig. 3(a). S11 values in Fig. 3 (a, b) are measured using a vector network analyzer (Rohde&Schwarz ZNB, 9 KHz-8.5GHz). In general, the measured S11 result (Fig. 3(a)) nearly match the simulated one. In Fig. 3 (a, b, d), frequency axes are chosen between 2.5 – 4.5 GHz because the MMA and the SDR working bandwidths are overlapped in this range. The SDR antenna (VERT2450) is connected to vector network analyzer in order to measure S11 value as shown in Fig. 3 (b). The SDR antenna radiates omnidirectionally with 3 dBi gain [30]. Unlike the conventional patch antennas, the MMA propagates the effectual radiation horizontally. With respect to the simulated results, the three dimensional (3D) radiation pattern at 2.8 GHz is shown in Fig. 3(c).
8
The simulated gain of the MMA is shown in Fig. 3(d). The MMA’s realized gain is mostly over 3.4 dBi with maximum value of 5.56 dBi.
Fig. 3. (a) Measured and simulated S11 results of MMA (b) measured S11 result of SDR antenna (c) three dimensional (3D) radiation pattern of MMA at 2.8 GHz (d) simulated gain of MMA. 3.2 Reception Model of the Antenna The MMA received power is calculated by Friis Transmission Equation which is widely used in the design of wireless systems and antenna theory [1]. If the two antennas, as shown in Fig 4 (a), do not have matched reflection and polarization, the Friis Equation is given by [1] = . . . 1 − |# |. 1 − |# | . $
%&'(
9
) . * , , . * , , . |-. . -. |
(1)
Fig. 4. (a) Geometric position of two antennas for Friis Equation (b) calculated received powers for Pt1, Pt2. Here, is the received power of the antenna, is the output power of the transmitter, is conduction-dielectric losses (radiation efficiency), # is reflection efficiency (impedancematch), c is the speed of the electromagnetic wave in vacuum, f is the frequency, / is the distance between the antennas, * , ∅ is the directivity, -. is polarization efficiency of the antennas. If the two antennas match for impedance and polarization, (1) reduces to
= . 1 . 1 . $%&'( ) 2
(2)
where 1 is the gain of the transmitting antenna, 1 is the gain of the receiving antenna. If the gains and powers have units of dBi and dBm, respectively, (2) is altered to a more convenient form as
10
= + 1 + 1 + 20 5 67 $
%&'(
) 89:
(3)
In the calculations of (1)-(3), atmospheric attenuation is neglected because of the working frequency which is under 10 GHz frequency [31]. In the experimental setup, we assumed that the antennas are positioned for maximum directional radiation and reception. Therefore, we used (2) and (3) in order to theoretically calculate the received powers between 1 to 8 m with 50 cm intervals, as shown in Fig 4 (b). 3.3 Vertical MMA Angular Power Reception Results In this part, the MMA is positioned vertically to the earth surface under indoor conditions in order to get received powers, as seen in Fig. 5(a). The measurements are made in distance between 1-3 m with 25 cm intervals because of the indoor restrictions. The antenna is rotated with 45° intervals around the z-axis manually.
Fig. 5. (a) Measurement setup block diagram of vertical MMA for angular power reception performance at indoor (b) Outdoor measurement setup. 11
On the other hand, the outdoor measurements are executed in distance between 1-8 m with 50 cm intervals, as shown in Fig. 5(b). The measured results of vertical MMA’s angular received powers are shown in Fig. 6. It is obvious that when the transceiver power Pt1 is increased to Pt2, the received power of MMA is improved at all angles for indoor and outdoor. Therefore, the indoor results are not comparable because of the scattering from indoor clutter and oblique reflections from the walls, as shown in Fig. 6 (a, c). But the outdoor results are clear that the received power is related with the angle Ø. In particular, the received power is much higher between 0-90o and 270-360o, as shown in Fig 6 (b, d). Moreover, some power downfalls occurred between 135225 o, especially at 180o independent from distance. The received power is decreasing with distance as expected except for R=6 m which may become stronger because of the unwanted reflections. Eventually, the received power performance of vertical proposed antenna is higher approximately 15 % for angles 0 to 90o and 270 to 360 o.
Fig. 6. Measured angular received powers of vertical MMA for output power of Pt1 at (a) indoor and (b) outdoor; for output power of Pt2 at (c) indoor and (d) outdoor. 12
3.4 Horizontal MMA Angular Power Reception Results In this part, the MMA is positioned horizontally to the earth surface at outdoor in order to capture the received powers, as seen on Fig. 7 (a, b). The antenna is rotated at 45o intervals around the y-axis manually. The other conditions for measurement are similar with the previous case as mentioned above.
Fig. 7. (a) Measurement setup block diagram of horizontal MMA for angular power reception performance at outdoor (b) Outdoor measurement setup. The outdoor measured results of horizontal MMA’s angular received powers are shown in Fig. 8. The power concentration is more pronounced around 45 o, 180 o and 315o, as seen on Fig 8 (b). Thus, the received power performance of horizontal proposed antenna is higher approximately 32 % for these angles. Unlike the first case, the horizontal received power of
13
the proposed antenna for 180 o is increased substantially. Also, the average received power performance is increased approximately 15 % for all angles.
Fig. 8. Measured angular received powers of horizontal MMA for output power of (a) Pt1 and (b) Pt2 at outdoor. 4. CONCLUSION This study gives qualitative information about adesign of a broad-bandwidth, high gain metamaterial antenna and its angular received power performance utilizing Software Defined Radio under uncontrolled indoor and outdoor conditions for two different output powers. The measured results show that the received powers have been concentrated at specific angles for vertical and horizontal positions of the proposed antenna. The metamaterial antenna offers good reception performance at almost all angles, especially horizontal case compared with vertical position to the earth surface. This kind of metamaterial antenna finds its use in many practical applications that works in the microwave spectrum such as wideband wireless communication systems on moving platforms.
14
Acnowledgements Authors would like to thank Dr. Yucedag, Mr. Genc, 3rd AFMSC and Ankara University staff for their contributions to design, fabrication and measurement process of the antenna. References [1] Balanis C. A. Antenna Theory Analysis and Design. 3rd ed. New Jersey: John Wiley & Sons; 2005. [2] Manteghi M. Wideband microstrip patch antenna on a thick substrate. 2008 IEEE Antennas and Propagation Society International Symposium. p. 1-4. [3] Kovitz JM, Samii YR. Using thick substrates and capacitive probe compensation to enhance the bandwidth of traditional CP patch antennas. IEEE Trans Antennas Propag. 2014; 62(10): 4970–9. [4] Lao J, Jin R, Geng J, Wu Q. An ultra-wideband microstrip elliptical slot antenna excited by a circular patch. Microw Opt Technol Lett. 2008; 50(4): 845–6. [5] Ooi BL, Qin S, Leong MS. Novel design of broad-band stacked patch antenna. IEEE Trans Antennas Propag. 2002; 50(10):1391–5. [6] Matin MA, Sharif BS, Tsimenidis BS. Probe fed stacked patch antenna for wideband applications. IEEE Trans Antennas Propag. 2007; 55(8): 2385–8. [7] Namin F, Spence TG, Werner TH, Semouchkina E. Broadband, miniaturized stackedpatch antenna for L-band operation based on magneto-dielectric substrates. IEEE Trans Antennas Propag. 2010; 58(9): 2817–22. [8] Targonski SD, Waterhouse RB, Pozar DM. Design of wide-band apeerture-stacked patch microstrip antennas. IEEE Trans Antennas Propag. 1998; 46(9):1245–51. [9] Engheta N, Ziolkowski RW. Metamaterials: Physics and Engineering Explorations. New Jersey: John Wiley & Sons; 2006. [10] Akhoondzadeh L, Kern DC, Hall PS, Werner DH. Wideband dipoles on electromagnetic bandgap ground planes. IEEE Trans Antennas Propag. 2007; 55(9): 2426–34. [11] Veselago VG. The electrodynamics of substances with simultaneously negative values of ε and µ. Sov Phys Usp. 1968; 10(4): 509–14.
15
[12] Bilotti F, Sevgi L. Metamaterials: definitions, properties, applications, and FDTDbased modeling and simulation. Int J RF and Microwave Com Aid Eng. 2012; 22(4): 422-38. [13] Shelby RA, Smith DR, Schultz S. Experimental verification of negative index of refraction. Science. 2001; 292(5514): 77–9. [14] Li LW, Li YN, Yeo TS, Mosig JR, Martin OJF. A broadband and high-gain metamaterial microstrip antenna. Appl Phys Lett. 2010; 96(16):164101. [15] Xiong H, Hong JS, Tan MT, Li B. Compact microstrip antenna with metamaterial for wideband applications. Turk J Elec Eng & Comp Sci. 2013; 21: 2233–8. [16] Tang L, Zhang Z. Ultrawide bandwidth rectangular patch antenna over artificial magnetic conductor. 2102 Int Conf on Microwave and Millimeter Wave Technology (ICMMT). p. 1–3. [17] Pandey GK, Singh HS, Bharti BK, Meshram MK. Metamaterial-based UWB antenna. Electron Lett. 2014; 50(18): 1266–8. [18] Xu HX, Wang G.M, Tao Z, Cui TJ. (2014). High-directivity emissions with flexible beam numbers and beam directions using gradient-refractive-index fractal metamaterial. Sci Rep. 2014; 4: 5744. [19] Xu HX, Wang GM, Cai T. Miniaturization of 3-D anistropic zero-refractive-index metamaterials with application to directive emissions. IEEE Trans Antennas Propag. 2014; 62(6): 3141-3149. [20] Xu HX, Wang, GM, Liang JG, Qi MQ, Gao X. (2013). Compact circularly polarized antennas combining meta-surfaces and strong space-filling meta-resonators. IEEE Trans. Antennas Propag. 2013; 61(7): 3442-3450. [21] Cheng YZ, Jin J, Li WL, Chen JF, Wang B, Gong RZ. Indefinite-permeability metamaterial lens with finite size for miniaturized wireless power transfer system, AEU-Int J Electron Commun. 2016; 70(9): 1282-1287. [22] Upadhyaya TK, Kosta SP, Jyoti R, Palandoken M. Negative refractive index material inspired 90-deg electrically tilted ultra wideband resonator. Opt Eng. 2014; 53(10): 107104. [23] Upadhyaya TK, Kosta SP, Jyoti R, Palandöken M. Novel stacked µ-negative materialloaded antenna for satellite applications. Int J Microw Wirel T. 2016; 8(2): 229-235.
16
[24] Merih Palandöken (2011). Artificial Materials based Microstrip Antenna Design, Microstrip Antennas, Prof. Nasimuddin Nasimuddin (Ed.), InTech, DOI: 10.5772/14908. Available from: http://www.intechopen.com/books/microstrip-antennas/artificialmaterials-based-microstrip-antenna-design. [25] Malik WQ, Edwards DJ, Stevens CJ. Angular-spectral antenna effects in ultrawideband communications links. IEE Proc-Commun. 2006; 153(1): 99–106. [26] Matsunaga N, Sanada A, Kubo H. Novel two dimensional planar negative refractive index structure. IEICE Trans Electron. 2006; E89C(9): 1276–82. [27] Caloz C, Itoh T. Electromagnetic metamaterials: transmission line theory and microwave applications. New Jersey: John Wiley & Sons; 2006. [28] Hartley R. Base materials for high speed, high frequency PC boards. PCB&A West Conf. 2002. [29] National Instruments Corp. [Internet]. Austin: I / Q Data; [cited 2016 June 8]. Available from: http://www.ni.com/tutorial/1720/en/ [30] National Instruments Corp. [Internet]. Austin: VERT2450 Antenna; [cited 2016 June 8] Available from: http://www.ettus.com/product/details/VERT2450 [31]
Joseph G. Fundamentals of remote sensing. 2nd ed. India: Universities Press; 2005.
17
18
S1434-8411(16)30245-X http://dx.doi.org/10.1016/j.aeue.2017.03.013 AEUE 51819
To appear in:
International Journal of Electronics and Communications
Received Date: Revised Date: Accepted Date:
13 June 2016 6 February 2017 15 March 2017
Please cite this article as: H. Akcelik, Y. Durna, S. Saraydemir, H. Kocer, Measurement of a Metamaterial Antenna Angular Power Reception Performance Utilizing Software Defined Radio, International Journal of Electronics and Communications (2017), doi: http://dx.doi.org/10.1016/j.aeue.2017.03.013
This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
Measurement of a Metamaterial Antenna Angular Power Reception Performance Utilizing Software Defined Radio Huseyin Akcelik, Yilmaz Durna, Safak Saraydemir and Hasan Kocer
Mr. Huseyin Akcelik Affiliation: Defense Sciences Institute, Turkish Military Academy, 06654 Ankara, Turkey. Degree: MSc in Military Electronic Systems e-mail: [email protected]
Mr. Yilmaz Durna Affiliation: Department of Electronics Engineering, Turkish Military Academy, 06654 Ankara, Turkey. Degree: MSc in Electronics Engineering e-mail: [email protected]
Dr. Safak Saraydemir Affiliation: Department of Electronics Engineering, Turkish Military Academy, 06654 Ankara, Turkey. Degree: PhD in Electronics Engineering e-mail: [email protected]
Assoc.Prof. Hasan Kocer Affiliation: Department of Electronics Engineering, Turkish Military Academy, 06654 Ankara, Turkey. Degree: PhD in Electronics Engineering e-mail: [email protected]
1
Measurement of a Metamaterial Antenna Angular Power Reception Performance Utilizing Software Defined Radio Huseyin Akcelik1,*, Yilmaz Durna2, Safak Saraydemir2 and Hasan Kocer2,* 1
Defense Sciences Institute, Turkish Military Academy, 06654 Ankara, Turkey,
[email protected] 2
Department of Electronics Engineering, Turkish Military Academy, 06654 Ankara,
Turkey, [email protected], [email protected], [email protected] * Corresponding authors ABSTRACT
In wireless communication systems, angular positioning is an important aspect affecting the behavior of an antenna reception performance. In this study, a broadband, high gain rectangular microstrip patch antenna using planar-patterned metamaterial concept and its measured angular power reception performance are presented. The metamaterial antenna’s -10 dB bandwidth is achieved as 2.42 GHz in the frequency range of 2.89 – 5.31 GHz with the peak gain of 5.56 dBi. Angular power reception performance of the proposed antenna is measured for different selected intervals in indoor and outdoor environments with the help of Software Defined Radio. The antenna is orientated vertically / horizontally and rotated in the azimuth Ø plane from 0o to 360o with angular resolution of ∆Ø= 45 o. The measured received power distributions are shown at angle versus distance and compared.
Keywords: Angular power reception, broadband, metamaterial, patch antenna, software defined radio (SDR).
2
1. INTRODUCTION The demand for small, compact, low cost and wideband antennas has increased rapidly over the past years, due to the need for reduced size and enhanced bandwidth antenna for many applications in both military and industry. In that respect, compact size, lightweight, low cost and broadened bandwidth are now quite important challenges to be accomplished by the designers of wireless communication systems. It is believed that the microstrip patch antennas are the most commonly utilized printed antennas which offer attractive features, such as simple structure, small size, easy integration to planar and nonplanar surfaces, aesthetic appearance, ease of fabrication and mechanically robust when mounted on rigid surfaces [1]. However, these antennas have some disadvantages such as narrow frequency bandwidth and low gain. In recent years, many techniques have been investigated to overcome these drawbacks especially for narrowband. These techniques are mainly augmentation of the substrate thickness [2, 3], handling discrete shaped splits or propagating patches [4], placing unlike propagating elements to the antenna sideways [5, 6], utilizing magneto dielectric and aperture-coupled substrates [7, 8], and trying to change the ground plane with electromagnetic band gap materials [9, 10]. Metamaterial (MTM) or left-handed material (LHM) which had been studied theoretically by Veselago in 1960s [11] has become immensely popular because of their unconventional electromagnetic properties. Metamaterials are described as artificially engineered materials exposing unique or unusual properties that cannot be found when using natural materials [12]. The main properties of conventional materials existing in nature are having positive permittivity (є) and permeability (µ). But MTM presents negative є and / or µ [11]. In 2001, Shelby et al. showed that these materials have negative refractive index which is a reversal of Snell’s law [13]. These attractive features of MTM aroused the researchers’ desire. Scientists and designers have experimented different techniques to bring these MTMs
3
into practical applications, especially into antennas to enhance their gain, directivity and bandwidth [14-24]. While modern wireless communication systems have been developing quickly in years, an antenna as an integral part of a wireless system is required to have good radiation performances besides its bandwidth. A well-designed antenna is crucial for system performance. A wide band antenna design requires particular modeling of its power performance as a part of the communications link especially for its angular power distribution [25]. In this paper, a broadband and high gain rectangular patch metamaterial antenna (MMA) is proposed by deploying the planar patterned designs directly to the top patch and ground plane of the dielectric substrate (FR-4). This approach is different from similar previous study given in [14]. The suggested antenna, with a bandwidth of 2.42 GHz, ranges between 2.89 to 5.31 GHz ( |S11|<−10 dB ) and its dimensions are 44.8 × 54.87 × 1.6 mm 3. We present experimental results of the angular power distribution in different realistic propagation conditions at 2.8 GHz frequency. The measurements were performed using a wide-band MMA as a test-antenna and an omnidirectional antenna as a reference antenna which is connected to the Software Defined Radio (SDR). 2. DESIGN, SIMULATION AND FABRICATION OF ANTENNA A microstrip patch antenna is normally placed on one side of a dielectric substrate and the other side is covered with a conductive ground plane. In the proposed study, a planar LHM design is etched on the radiating patch to increase horizontal radiation of the antenna. The conducting ground plane is shaped to widen its bandwidth. On the surface of the patch, periodic apertures are used and shaped like separated mini triangular patterns, as shown in Fig. 1(a), while on the conductive part, periodically deployed intersecting straight line spaces are formed, as shown in Fig. 1(b). Geometrical parameters of MMA are also given in 4
Fig. 1(a, b). The left-handed features of these designs were represented in [26]. In the propagation mechanism of the antenna, the radiating upper patch and conductive bottom plane are coupled to model an inductive-capacitive (L-C) equivalent circuit. In this way, it leads to backward wave which propagates throughout the surface of the antenna [27]. Therefore, the direction of the radiation throughout the surface of the antenna is greatly increased. The metallic surfaces are used as conductive copper with 17 µm in thickness and its frequency independent conductivity is 5.8x10 7 S/m. As a dielectric substrate, epoxy glass cloth laminate (FR4) is used with 1.6 mm in thickness, its relative dielectric permittivity is 4.6 and the loss tangent is 0.025 [28]. To decide the optimum parameters and figure out the physical mechanisms of the antenna, the CST Microwave Studio simulation software with its transient solver is used. The parameters of the antenna are examined by shifting one at a time, while fixing the others. The MMA is fabricated using the printed circuit board (PCB) technique shown in Fig. 1 (c,d).
5
Fig. 1. Simulated antenna (a) top view and parameters (b) bottom view and parameters; fabricated antenna (c) top view (d) bottom view. 3. RESULTS AND DISCUSSIONS In the measurement setup (Fig. 2), a spectrum analyzer (Rohde & Schwarz, 9 KHz - 7 GHz), a transmitter (SDR, NI-USRP 2922, 400 MHz - 4.4 GHz), a transmitter antenna (VERT2450, omnidirectional) and a receiver antenna (proposed MMA) are used. The distance (R) is changed from 1 to 3 m with 25 cm intervals for indoor and from 1 to 8 m with 50 cm intervals for outdoor setup. The transmitting antenna is fixed at one position while the receiving antenna is placed on a man-controlled turntable and rotated in the azimuth Ø plane from 0o to 360o with angular
6
resolution of ∆Ø= 45 o. The MMA antenna is connected to the spectrum analyzer with two different positions in order to measure the received powers. The fabricated MMA’s reception performance is measured with two different cases. In the first case, the MMA is located on the xy plane perpendicularly and rotated with angle Ø around the z-axis. The Ø is the sweeping angle between x-axis and the front surface normal (N). In the second case, the MMA is positioned perpendicular to the xz plane and rotated around y-axis with angle Ø. Transmitter antenna (VERT 2450) is attached to SDR with an angle of 90 o. The SDR transceiver is connected to a host computer via ethernet cable. In the host computer, we use Labview software which provides an optimum way to interface with SDR hardware for the development of communication algorithms that process and synthesize the signals for transmission. The output powers (Pt1, Pt2) of the SDR are controlled on the host computer by changing the internal gain function in the Labview software interface. Gain function zero corresponds to Pt1 and the gain function twenty corresponds to Pt2. Pt1 and Pt2 are the power levels measured by connecting the output connector of the SDR device to the spectrum analyzer with an almost lossless RF cable without using the antenna. In this way, Pt1 and Pt2 are measured to be 7 dBm and 18.65 dBm, respectively. The operating signal is 2.8 GHz generated by SDR. In the experiment, a sinusoidal wave (f(t)) which has components of inphase and quadrature-phase is transmitted where = , = . The magnitude of the vector r is equal to + . The phase of the vector is θ which is equal to ⁄. The transmitted signal waveform is = − . These two components are perpendicular to each other and hence they do not interfere [29].
7
Fig. 2. Measurement setup block diagram for angular reception performance of the MMA. 3.1 Antenna Results The proposed MMA’s -10 dB bandwidth which is stated as a norm for engineering implementations ranges from 2.89 and 5.31 GHz with 2.42 GHz in bandwidth. Measured and simulated results of S11 values are compared in Fig. 3(a). S11 values in Fig. 3 (a, b) are measured using a vector network analyzer (Rohde&Schwarz ZNB, 9 KHz-8.5GHz). In general, the measured S11 result (Fig. 3(a)) nearly match the simulated one. In Fig. 3 (a, b, d), frequency axes are chosen between 2.5 – 4.5 GHz because the MMA and the SDR working bandwidths are overlapped in this range. The SDR antenna (VERT2450) is connected to vector network analyzer in order to measure S11 value as shown in Fig. 3 (b). The SDR antenna radiates omnidirectionally with 3 dBi gain [30]. Unlike the conventional patch antennas, the MMA propagates the effectual radiation horizontally. With respect to the simulated results, the three dimensional (3D) radiation pattern at 2.8 GHz is shown in Fig. 3(c).
8
The simulated gain of the MMA is shown in Fig. 3(d). The MMA’s realized gain is mostly over 3.4 dBi with maximum value of 5.56 dBi.
Fig. 3. (a) Measured and simulated S11 results of MMA (b) measured S11 result of SDR antenna (c) three dimensional (3D) radiation pattern of MMA at 2.8 GHz (d) simulated gain of MMA. 3.2 Reception Model of the Antenna The MMA received power is calculated by Friis Transmission Equation which is widely used in the design of wireless systems and antenna theory [1]. If the two antennas, as shown in Fig 4 (a), do not have matched reflection and polarization, the Friis Equation is given by [1] = . . . 1 − |# |. 1 − |# | . $
%&'(
9
) . * , , . * , , . |-. . -. |
(1)
Fig. 4. (a) Geometric position of two antennas for Friis Equation (b) calculated received powers for Pt1, Pt2. Here, is the received power of the antenna, is the output power of the transmitter, is conduction-dielectric losses (radiation efficiency), # is reflection efficiency (impedancematch), c is the speed of the electromagnetic wave in vacuum, f is the frequency, / is the distance between the antennas, * , ∅ is the directivity, -. is polarization efficiency of the antennas. If the two antennas match for impedance and polarization, (1) reduces to
= . 1 . 1 . $%&'( ) 2
(2)
where 1 is the gain of the transmitting antenna, 1 is the gain of the receiving antenna. If the gains and powers have units of dBi and dBm, respectively, (2) is altered to a more convenient form as
10
= + 1 + 1 + 20 5 67 $
%&'(
) 89:
(3)
In the calculations of (1)-(3), atmospheric attenuation is neglected because of the working frequency which is under 10 GHz frequency [31]. In the experimental setup, we assumed that the antennas are positioned for maximum directional radiation and reception. Therefore, we used (2) and (3) in order to theoretically calculate the received powers between 1 to 8 m with 50 cm intervals, as shown in Fig 4 (b). 3.3 Vertical MMA Angular Power Reception Results In this part, the MMA is positioned vertically to the earth surface under indoor conditions in order to get received powers, as seen in Fig. 5(a). The measurements are made in distance between 1-3 m with 25 cm intervals because of the indoor restrictions. The antenna is rotated with 45° intervals around the z-axis manually.
Fig. 5. (a) Measurement setup block diagram of vertical MMA for angular power reception performance at indoor (b) Outdoor measurement setup. 11
On the other hand, the outdoor measurements are executed in distance between 1-8 m with 50 cm intervals, as shown in Fig. 5(b). The measured results of vertical MMA’s angular received powers are shown in Fig. 6. It is obvious that when the transceiver power Pt1 is increased to Pt2, the received power of MMA is improved at all angles for indoor and outdoor. Therefore, the indoor results are not comparable because of the scattering from indoor clutter and oblique reflections from the walls, as shown in Fig. 6 (a, c). But the outdoor results are clear that the received power is related with the angle Ø. In particular, the received power is much higher between 0-90o and 270-360o, as shown in Fig 6 (b, d). Moreover, some power downfalls occurred between 135225 o, especially at 180o independent from distance. The received power is decreasing with distance as expected except for R=6 m which may become stronger because of the unwanted reflections. Eventually, the received power performance of vertical proposed antenna is higher approximately 15 % for angles 0 to 90o and 270 to 360 o.
Fig. 6. Measured angular received powers of vertical MMA for output power of Pt1 at (a) indoor and (b) outdoor; for output power of Pt2 at (c) indoor and (d) outdoor. 12
3.4 Horizontal MMA Angular Power Reception Results In this part, the MMA is positioned horizontally to the earth surface at outdoor in order to capture the received powers, as seen on Fig. 7 (a, b). The antenna is rotated at 45o intervals around the y-axis manually. The other conditions for measurement are similar with the previous case as mentioned above.
Fig. 7. (a) Measurement setup block diagram of horizontal MMA for angular power reception performance at outdoor (b) Outdoor measurement setup. The outdoor measured results of horizontal MMA’s angular received powers are shown in Fig. 8. The power concentration is more pronounced around 45 o, 180 o and 315o, as seen on Fig 8 (b). Thus, the received power performance of horizontal proposed antenna is higher approximately 32 % for these angles. Unlike the first case, the horizontal received power of
13
the proposed antenna for 180 o is increased substantially. Also, the average received power performance is increased approximately 15 % for all angles.
Fig. 8. Measured angular received powers of horizontal MMA for output power of (a) Pt1 and (b) Pt2 at outdoor. 4. CONCLUSION This study gives qualitative information about adesign of a broad-bandwidth, high gain metamaterial antenna and its angular received power performance utilizing Software Defined Radio under uncontrolled indoor and outdoor conditions for two different output powers. The measured results show that the received powers have been concentrated at specific angles for vertical and horizontal positions of the proposed antenna. The metamaterial antenna offers good reception performance at almost all angles, especially horizontal case compared with vertical position to the earth surface. This kind of metamaterial antenna finds its use in many practical applications that works in the microwave spectrum such as wideband wireless communication systems on moving platforms.
14
Acnowledgements Authors would like to thank Dr. Yucedag, Mr. Genc, 3rd AFMSC and Ankara University staff for their contributions to design, fabrication and measurement process of the antenna. References [1] Balanis C. A. Antenna Theory Analysis and Design. 3rd ed. New Jersey: John Wiley & Sons; 2005. [2] Manteghi M. Wideband microstrip patch antenna on a thick substrate. 2008 IEEE Antennas and Propagation Society International Symposium. p. 1-4. [3] Kovitz JM, Samii YR. Using thick substrates and capacitive probe compensation to enhance the bandwidth of traditional CP patch antennas. IEEE Trans Antennas Propag. 2014; 62(10): 4970–9. [4] Lao J, Jin R, Geng J, Wu Q. An ultra-wideband microstrip elliptical slot antenna excited by a circular patch. Microw Opt Technol Lett. 2008; 50(4): 845–6. [5] Ooi BL, Qin S, Leong MS. Novel design of broad-band stacked patch antenna. IEEE Trans Antennas Propag. 2002; 50(10):1391–5. [6] Matin MA, Sharif BS, Tsimenidis BS. Probe fed stacked patch antenna for wideband applications. IEEE Trans Antennas Propag. 2007; 55(8): 2385–8. [7] Namin F, Spence TG, Werner TH, Semouchkina E. Broadband, miniaturized stackedpatch antenna for L-band operation based on magneto-dielectric substrates. IEEE Trans Antennas Propag. 2010; 58(9): 2817–22. [8] Targonski SD, Waterhouse RB, Pozar DM. Design of wide-band apeerture-stacked patch microstrip antennas. IEEE Trans Antennas Propag. 1998; 46(9):1245–51. [9] Engheta N, Ziolkowski RW. Metamaterials: Physics and Engineering Explorations. New Jersey: John Wiley & Sons; 2006. [10] Akhoondzadeh L, Kern DC, Hall PS, Werner DH. Wideband dipoles on electromagnetic bandgap ground planes. IEEE Trans Antennas Propag. 2007; 55(9): 2426–34. [11] Veselago VG. The electrodynamics of substances with simultaneously negative values of ε and µ. Sov Phys Usp. 1968; 10(4): 509–14.
15
[12] Bilotti F, Sevgi L. Metamaterials: definitions, properties, applications, and FDTDbased modeling and simulation. Int J RF and Microwave Com Aid Eng. 2012; 22(4): 422-38. [13] Shelby RA, Smith DR, Schultz S. Experimental verification of negative index of refraction. Science. 2001; 292(5514): 77–9. [14] Li LW, Li YN, Yeo TS, Mosig JR, Martin OJF. A broadband and high-gain metamaterial microstrip antenna. Appl Phys Lett. 2010; 96(16):164101. [15] Xiong H, Hong JS, Tan MT, Li B. Compact microstrip antenna with metamaterial for wideband applications. Turk J Elec Eng & Comp Sci. 2013; 21: 2233–8. [16] Tang L, Zhang Z. Ultrawide bandwidth rectangular patch antenna over artificial magnetic conductor. 2102 Int Conf on Microwave and Millimeter Wave Technology (ICMMT). p. 1–3. [17] Pandey GK, Singh HS, Bharti BK, Meshram MK. Metamaterial-based UWB antenna. Electron Lett. 2014; 50(18): 1266–8. [18] Xu HX, Wang G.M, Tao Z, Cui TJ. (2014). High-directivity emissions with flexible beam numbers and beam directions using gradient-refractive-index fractal metamaterial. Sci Rep. 2014; 4: 5744. [19] Xu HX, Wang GM, Cai T. Miniaturization of 3-D anistropic zero-refractive-index metamaterials with application to directive emissions. IEEE Trans Antennas Propag. 2014; 62(6): 3141-3149. [20] Xu HX, Wang, GM, Liang JG, Qi MQ, Gao X. (2013). Compact circularly polarized antennas combining meta-surfaces and strong space-filling meta-resonators. IEEE Trans. Antennas Propag. 2013; 61(7): 3442-3450. [21] Cheng YZ, Jin J, Li WL, Chen JF, Wang B, Gong RZ. Indefinite-permeability metamaterial lens with finite size for miniaturized wireless power transfer system, AEU-Int J Electron Commun. 2016; 70(9): 1282-1287. [22] Upadhyaya TK, Kosta SP, Jyoti R, Palandoken M. Negative refractive index material inspired 90-deg electrically tilted ultra wideband resonator. Opt Eng. 2014; 53(10): 107104. [23] Upadhyaya TK, Kosta SP, Jyoti R, Palandöken M. Novel stacked µ-negative materialloaded antenna for satellite applications. Int J Microw Wirel T. 2016; 8(2): 229-235.
16
[24] Merih Palandöken (2011). Artificial Materials based Microstrip Antenna Design, Microstrip Antennas, Prof. Nasimuddin Nasimuddin (Ed.), InTech, DOI: 10.5772/14908. Available from: http://www.intechopen.com/books/microstrip-antennas/artificialmaterials-based-microstrip-antenna-design. [25] Malik WQ, Edwards DJ, Stevens CJ. Angular-spectral antenna effects in ultrawideband communications links. IEE Proc-Commun. 2006; 153(1): 99–106. [26] Matsunaga N, Sanada A, Kubo H. Novel two dimensional planar negative refractive index structure. IEICE Trans Electron. 2006; E89C(9): 1276–82. [27] Caloz C, Itoh T. Electromagnetic metamaterials: transmission line theory and microwave applications. New Jersey: John Wiley & Sons; 2006. [28] Hartley R. Base materials for high speed, high frequency PC boards. PCB&A West Conf. 2002. [29] National Instruments Corp. [Internet]. Austin: I / Q Data; [cited 2016 June 8]. Available from: http://www.ni.com/tutorial/1720/en/ [30] National Instruments Corp. [Internet]. Austin: VERT2450 Antenna; [cited 2016 June 8] Available from: http://www.ettus.com/product/details/VERT2450 [31]
Joseph G. Fundamentals of remote sensing. 2nd ed. India: Universities Press; 2005.
17
18