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Parametric study on effect of solar-cell position on the performance of transparent DRA transmitarray
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ARTICLE IN PRESS Int. J. Electron. Commun. (AEÜ) xxx (2016) xxx–xxx
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International Journal of Electronics and Communications (AEÜ) journal homepage: www.elsevier.com/locate/aeue
Parametric study on effect of solar-cell position on the performance of transparent DRA transmitarray Noha A. Al-Shalaby a,∗ , Shaymaa M. Gaber b a b
Faculty of Engineering, Kafer Elshekh University, Egypt Faculty of Engineering, Egyptian Russian University, Egypt
a r t i c l e
i n f o
Article history: Received 12 May 2015 Accepted 9 January 2016 Keywords: Transmitarray Solar cell Dielectric resonator antenna FIT
a b s t r a c t Linearly polarized transparent dielectric resonator antenna (TDRA) transmitarray is designed and investigated for 12 GHz applications. A parametric study on the effect of solar-cell position on the radiation characteristics of the TDRA transmitarray. The unit cell consists of two TDRAs arranged back-to-back with one on either side of a perfect transparent conducting ground plane. The waveguide model is used to calculate the required compensation phase of each cell in the transmitarray. The radiation characteristics of a 9 × 9 linearly polarized transparent transmitarray antenna are investigated in different positions of solar-cell with respect to the DRA. The peak gain is 20.22 dB with a 1-dB gain bandwidth is more than 2 GHz (16.67%) for the TDRA transmitarray without solar-cell. The solar-cell is integrated with TDRA transmitarray with different positions for small satellite applications. The radiation characteristics of the transmitarray are simulated and calculated using the finite integral technique (FIT). © 2016 Elsevier GmbH. All rights reserved.
1. Introduction The small satellites have a limited surface area. The satellite surface area is occupied by the solar-cells, test instruments, and antennas which affect the overall size and weight of the satellites. An important challenge for a small satellite is to make use of the limited surface area and save cost [1,2]. The design of small satellite antenna includes some limitations such as limited surface area, limited antenna mounting positions, and deployed mechanism [3]. The integration of antennas with solar-cell offers a wide range of advantages as small surface coverage, light weight, low costs and improving the economic viability of renewable energy [4–7]. Solar powered communication systems have advantages that operate without the necessity of an electrical grid connection. There are two types of photovoltaic-antenna integration techniques used in communication systems. The first technique used the solar-cells as an independent power source operating separately from the antennas [8]. The solar-cells are separated from the antennas by a certain distance to ensure that the cells do not effect on the RF characteristics of the antennas [9,10]. The second technique is the full integration of photovoltaics with microwave antennas in a compact communication system, which used the solar-cells as
∗ Corresponding author. Tel.: +20 1091537813. E-mail addresses: [email protected] (N.A. Al-Shalaby), [email protected] (S.M. Gaber).
a part of RF operation [8]. Recently, transparent antennas can be integrated with solar-cells to save surface area of small satellites [3]. Transparent conductive films allow the transmission of electric currents and keep optical transparency of the film, which is more suitable for antennas integrated with solar-cells [7]. The conventional high-gain antennas are parabolic reflectors. The parabolic dish transforms a spherical wave into a planar one and vice versa. Some of the drawbacks of the parabolic reflector are weighted, fabrication complexity, and large overall size [11,12]. The phased arrays offer several advantages over the parabolic antennas, such as electronic steering capability, light-weight and ease of production [13,14], but losses arise from both the physical length of line and from radiation produced at the feed network junctions. The reflectarray is a good choice for the intended satellite-based application since it combines the light weight and low profile while emulating the electrical performance of a phased array or parabolic dish. The reflectarray still requires an offset feed to avoid blockage losses [15]. The offset geometry destroys the symmetry of an antenna aperture and increases the angle of the incident wave, thus reducing the reflector’s gain, decreasing efficiency and complicating the design [16–21]. The transmitarray is similar to the reflectarray where, the feed signal is not reflected, but passes through the structure as it is collimated into a plane wave. Consequently, the feed horn cannot interfere with the transmitted and received waves, and there is no blockage loss [22–24]. The DRA is used for transmitarray to increase the bandwidth, compared to earlier transmitarrays which have been designed using patch elements [25], or using
http://dx.doi.org/10.1016/j.aeue.2016.01.006 1434-8411/© 2016 Elsevier GmbH. All rights reserved.
Please cite this article in press as: Al-Shalaby NA, Gaber SM. Parametric study on effect of solar-cell position on the performance of transparent DRA transmitarray. Int J Electron Commun (AEÜ) (2016), http://dx.doi.org/10.1016/j.aeue.2016.01.006
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2
Fig. 1. The structure of the transmitarray.
Fig. 4. DRA transmitarray structure.
3. Numerical result 3.1. Design of the first unit-cell
Fig. 2. (a) The side view of the unit cell and (b) 3D-view of the unit cell.
cross-dipole elements as done by Chaharmir et al. [26]. DRAs offer many advantages, such as low-profile, low-cost, and high radiation efficiency and high power-handling capability [27–30]. In this paper, 9 × 9 linearly polarized TDRA transmitarray integrated with solar-cell have been introduced. The effect of solar-cell position relative to the TDRA on the radiation characteristics of the transmitarray had been investigated. The TDRA transmitarray is designed and simulated using the finite integral technique (FIT) [31]. 2. Theory Considering the array on the x–y plane illuminated by a feed horn, the required phase distribution ϕij , at each element of the array to collimate a beam in the ( o , ϕo ) direction is determined from ϕij = krij − k(xi sin o cos ϕo + yj sin o sin ϕo )
3.2. The transparent DRA transmitarray The configuration of the transmitarray and feed horn is shown in Fig. 4. The transmitarray is composed of 9 × 9 cell elements and is covering an area of 126 mm × 126 mm. The feed is a linearly polarized pyramidal horn. The dimensions of the horn are 60 mm × 30 mm × 50 mm. The F/D ratio is set to 1. The E-plane and H-plane patterns for the transmitarrays at 12 GHz are shown in Fig. 5. The radiation pattern in E-plane is different from that in
360
0
300
- 0.5
transmited magnitude (dB)
transmitted phase (degrees)
where ko is the propagation constant in vacuum, rij is the distance from the feed horn (xf , yf , zf ) to the element ij of the array and (xi , yj ) are the coordinates of the cell element ij as shown in Fig. 1.
The transmitarray cell element consists of two transparent rectangular dielectric resonators arranged back-to-back with one on either side of a perfect transparent conducting ground plane as shown in Fig. 2. The two RDRA are coupled by a rectangular slot (6 mm × 2 mm) in the ground plane. Each rectangular DRA cell element has a width W = 3 mm, a height h = 4 mm and a variable length L, the relative dielectric constant is εr = 12. The variation of the length of the transparent rectangular DRA changes the resonant frequency of the DRA which yields a change in transmission coefficient phase at the 12 GHz operating frequency. The DRA is mounted on (14 mm × 14 mm) transparent conducting ground plane thickness hs = 0.1 mm with = 5 × 105 S/m. This RDRA cell element is designed to operate at 12 GHz. Fig. 3 shows the phase and the magnitude of the transmission coefficient of RDRA cell element as a function of RDRA length for normal incident plane wave. The results are obtained by applying the FIT technique. The minimum value of the transmission magnitude through the unit cell is lower than −3 dB, and the element achieves a phase tuning range of 360◦ .
240 180 120 60 0 4.5
5.5
6.5
7.5 8.5 9.5 Length (mm)
(a)
10 0.5 11.5
-1 - 1.5
-2 - 2.5
-3
5
6
7
8
9
10
11
Length (mm)
(b)
Fig. 3. (a) Transmission coefficient phase variation versus DR length. (b) Transmission coefficient magnitude variation versus DR length.
Please cite this article in press as: Al-Shalaby NA, Gaber SM. Parametric study on effect of solar-cell position on the performance of transparent DRA transmitarray. Int J Electron Commun (AEÜ) (2016), http://dx.doi.org/10.1016/j.aeue.2016.01.006
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Fig. 5. The gain patterns of 9 × 9 DR transmitarray at 12 GHz.
H-plane due to the rectangular shape of the horn aperture. A peak gain of 20.2 dBi was calculated at 12 GHz. The symmetrical gain patterns for the broadside fed transmitarray at 12 GHz in E-plane and H-plane are obtained due to the symmetry of the array about the x-axis and y-axis. The first side lobe levels (SLLs) in the E-plane and H-planes are approximately 12.13 dBi and 15.6 dBi below the main peaks, respectively. The gain versus the frequency is shown in Fig. 6. The beamwidth in the H-plane is narrower than the beamwidth in the E-plane due to the rectangular shape of the horn aperture. The 1-dB gain bandwidth is approximately 16.67% (more than 2 GHz).
Gain (dB)
23
0 10.5
11
11.5 5
12
12.5
13
13.5
Frequency(GHz) Fig. 6. Gain versus frequency of the DR transmitarray.
Fig. 7. (a) The side view of the transparent unit cell. (b) 3D-view of the transparent unit cell.
3.3. Solar cell over the top transparent DRA transmitarray (case 1) The unit cell is the same as in the first structure but the solar cell is added at the top of the TDRA cell as shown in Fig. 7. The solar cell has thickness hs = 0.057 mm and with εr = 1.5. Again the variation in the length of the RDRA is used to adjust the needed phase shift at each element. The configuration of the proposed unit cell is designed at 12 GHz. The magnitude and phase responses of the unit cell are calculated using FIT technique as shown in Fig. 8. The minimum value of the transmission magnitude experienced by the structure is −3 dB, while the reflection phase covers approximately 360◦ in total. Fig. 9 shows the radiation patterns in H-plane and E-plane of the 9 × 9 RDRA transmitarray at 12 GHz. The first side lobe level (SLL) in the H- and E-planes is approximately 12.23 dBi and 12.34 dBi, respectively below the main beam. The peak gain is 18.47 dBi. The −1 dB gain bandwidth is 9.6% (1.15 GHz) as shown in Fig. 10.
0
transmitted magnitude (dB)
transmitted phase (degrees)
360
300
240
180
120
60
0 4.5
-0.5
-1
-1.5
-2
-2.5
-3 5.5
6.5
7.5
8.5
Length (mm)
9.5
10.5
11.5
6
8
10
Length (mm)
Fig. 8. (a) Transmission coefficient phase variation versus DR length. (b) Transmission coefficient magnitude variation versus DR length.
Please cite this article in press as: Al-Shalaby NA, Gaber SM. Parametric study on effect of solar-cell position on the performance of transparent DRA transmitarray. Int J Electron Commun (AEÜ) (2016), http://dx.doi.org/10.1016/j.aeue.2016.01.006
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25
20
Case1 Case2 Case3 Case4
15
15
Gain P attern (dB i)
Gain Pattern (dBi)
10 5 0 -5 -10
10 5 0 -5 -10
Ph=900
-15 -20 -45
Case1 Case2 Case3 Case4
20
-35
-25
-15
-5
5
Ph=00
-15 15
25
35
Evaluation angles(Degrees)
(a) E- plane.
45
-20 -45 -35 -25
-15
-5
5
15
25
35
45
Evaluation angles(Degrees) (b) H -plane.
Fig. 9. The gain patterns for 9 × 9 DRA transmitarray at 12 GHz.
25
G a in (d B i)
20 15 10
Case1 Case2 Case3 Case4
5 0 10.5
11
11.5 12 12.5 Frequency(GHz)
13
13.5
Fig. 10. Gain versus frequency of the DRA transmitarray.
Fig. 11. (a) The side view of the transparent unit cell. (b) 3D-view of the transparent unit cell.
3.4. Solar cell over the bottom transparent DRA transmitarray (case 2) The unit cell is the same as in the first structure but the solar cell is added over the bottom TDRA cell as shown in Fig. 11. Again the variation in the length of the RDRA is used to adjust the needed phase shift at each element. Shows the radiation patterns in E-plane and H-plane compared with that calculated in case I, respectively. It is clear from Fig. 9. The first side lobe level (SLL) in the H- and Eplanes is approximately 12.4 dBi and 12 dBi, respectively below the main beam. The peak gain is 18.7 dBi. The gain versus the frequency is shown in Fig. 10. The 1-dB gain bandwidth is approximately 12.5% (1.5 GHz).
Fig. 12. (a) The side view of the transparent unit cell. (b) 3D-view of the transparent unit cell.
3.5. Solar cell between the top TDRA and the ground plane layer (case 3) The unit cell is the same as in the second structure but the solar cell is added between top TDRA and the ground plane layer as shown in Fig. 12. The simulation results have achieved a 360◦ of phase variation with less than 3 dB of variation in transmission magnitude throughout the tuning range as shown in Fig. 13. Computed radiation patterns of the transmitarray in E-plane and H-plane at f = 12 GHz are shown in Fig. 9, respectively. The symmetrical gain patterns for the transmitarray at 12 GHz in E-plane and H-plane are obtained due to the symmetry of the arrays about the x-axis and y-axis. At the design frequency 12 GHz, the transmitarray has maximum gain of 13.97 dBi with the first SLL 9.6 dBi in the H-plane and 4.5 dBi in the E-plane below the main beam. Fig. 10 shows the gain as function of the frequency. Broadband transmitarray was shown to achieve a maximum 1 dB gain bandwidth close to 3% (0.352 GHz). 3.6. Solar cell between the bottom TDRA and the ground plane layer (case 4) The unit cell is the same as in the third structure but the solar cell is added between the bottom TDRA and the ground plane layer as shown in Fig. 14. The computed radiation patterns of the transmitarray in E-plane and H-plane at f = 12 GHz are shown in Fig. 9. The side lobe levels (SLL) in the E- and H-planes are approximately 12.45 dB and 11.3 dB, respectively. The gain of the transmitarray against the frequency is shown in Fig. 10. The peak gain is 17.5 dB. The 1 dB gain bandwidth is 11.25% (1.35 GHz). The comparison
Please cite this article in press as: Al-Shalaby NA, Gaber SM. Parametric study on effect of solar-cell position on the performance of transparent DRA transmitarray. Int J Electron Commun (AEÜ) (2016), http://dx.doi.org/10.1016/j.aeue.2016.01.006
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transmitted magnitude (dB)
transmitted phase (degrees)
0 360 300 240
180 120 60
0 4.5
5.5
6.5
7.5
8 .5
9.5
10. 5 11.5
-0..5 -1 -1..5 -2 -2..5 -3 -3..5
Length ((mm)
6
8
10
Length (mm m)
(a)
(b)
Fig. 13. (a) Transmission coefficient phase variation versus DR length. (b) Transmission coefficient magnitude variation versus DR length.
solar cell. A solar cell is integrated with the optically transparent transmitarray have been introduced and reached that by putting the solar cell on the back side of the transmitarray is the best position of solar cell. The solar-cell integration with the transmitarray reduces the maximum gain by about 1.52 dB due to the increase in the magnitude of the transmission coefficient.
Fig. 14. (a) The side view of the transparent unit cell. (b) 3D-view of the transparent unit cell. Table 1 Comparison between TDRA and the four position of solar cell. Case
Gain
B.W.
Highest SLL
TDRA only Case 1 Case 2 Case 3 Case 4
20.22 dB 18.47 dB 18.7 dB 13.97 dB 17.5 dB
More than 2 GHz 1.15 GHz 1.5 GHz 0.352 GHz 1.35 GHz
12.13 dB/15.6 dB 12.23/12.34 dB 12.4/12 dB 9.6/4.5 dB 12.45/11.3 dB
between the TDRA transmitarray and the four cases of solar cell integrated TDRA transmitarray presented in Table 1. 4. Conclusion The paper introduces the radiation characteristics of a transparent DRA transmitarray antenna for satellite applications at 12 GHz. The unit cell is two transparent rectangular dielectric resonators arranged back-to-back with one on either side of a perfect transparent conducting ground plane. A studying the effect of integrated the solar cell with the transmitarray at different positions has been introduced. The magnitude of the transmission coefficient achieves 0 dB nearly with 360◦ transmission coefficient phase varied by varying the transparent DRA’s length, from 4.5 mm to 11.5 mm. The radiation characteristics of a 9 × 9 linearly polarized transparent transmitarray antenna are investigated. A linearly polarized horn antenna is utilized to feed the transmitarray. The peak gain is 20.22 dB with a 1-dB gain bandwidth is more than 2 GHz (16.67%) for the transparent DRA transmitarray, when TDRA transmitarray integrated with solar-cell the peak gain variable from 18.7 dBi to13.97 dBi with a 1-dB gain bandwidth of 1.5 GHz (12.5%) to 0.35 GHz (3%) according to the poison of a solar cell with respect to TDRA and the feeding horn. A decrease in the optical transparent DRA transmitarray gains bandwidth due to varying the position of
References [1] Pointer M, Sweeting MN. Antennas for modern small satellites. IEEE Antenna Propag Mag 2009;51(August):21. [2] Mahmoud N, Mahmoud A (Thesis submitted in partial fulfillment of the requirements for the degree of Master of Science) Integrated solar panel antennas for cube satellites. Logan, Utah: Utah State University; 2010. [3] Dreyer P, Morales-Masis M, Nicolay S, Ballif C, Perruisseau-Carrier J. Copper and transparent-conductor reflectarray elements on thin-film solar-cell panels; 2013. p. 83 (This work was supported by the Swiss National Science Foundation SNSF) under grant no 1335). [4] Roos Ons MJ (doctoral thesis) Integration of antennas and solar-cells for autonomous communication systems. Dublin: Dublin Institute of Technology; 2010. [5] Roo-Ons MJ, Shynu SV, Ammann MJ, McCormack SJ, Norton B. Transparent patch antenna on a-Si thin-film glass solar module. Electron Lett 2011;47(January (2)):85–6. [6] Turpin TW, Baktur R. Meshed patch antennas integrated on solar cells. Antennas Wirel Propag Lett IEEE 2009;8:693–6, http://dx.doi.org/10.1109/ LAWP.2009.2025522. [7] Azini AS, Kamarudin MR, Rahman TA, Rahim SKA, Rani MSA. Transparent antenna design for wireless access point application. In: PIERS proceedings. Johor, Malaysia: Wireless Communication Centre (WCC), Faculty of Electrical Engineering Universiti Teknologi Malaysia, UTM Skudai; 2013. p. 910–3. [8] Yurduseven O, Smith D, Pearsall N, Forbes I. A solar-cell stacked slot-loaded suspended microstrip patch antenna with multiband resonance characteristics for WLAN and WiMAX systems. Prog Electromagn Res 2013;142:321–32. [9] Shynu SV, Ons MJR, McEvoy P, Ammann MJ, McCormack SJ, Norton B. Integration of microstrip patch antenna with polycrystalline silicon solar cell. IEEE Trans Antennas Propag 2009;57(December (12)):3969–72. [10] Shynu SV, Ammann MJ, Norton B. Quarter-wave metal plate solar antenna. Electron Lett 2008;44(April (9)):570–1. [11] Galindo V. Design of dual-reflector antennas with arbitrary phase and amplitude distributions. IEEE Trans Antennas Propag 1964;12(July (7)):403–8. [12] Rudge AW. Offset-parabolic-reflector antennas: a review. Proc IEEE 1978;66(December (12)):1592–618. [13] Allen JL. On surface wave coupling between elements of large arrays. IEEE Trans Antennas Propag 1965;13(July (7)):638–9. [14] Trinh PD, Yegnanarayanan S, Coppinger F, Jalali B. Silicon-on-insulator (SOI) phased-array wavelength multi/demultiplexer with extremely lowpolarization sensitivity. IEEE Photonics Technol Lett 1997;9(July (7)):940–2. [15] Huang J, Encinar JA. Reflectarray antennas. Hoboken, NJ, USA: John Wiley & Sons, Inc.; 2007. [16] Mcgrath DT. Planar three dimensional constrained lenses. IEEE Trans Antennas Propag 1986;34(January (1)):46–50. [17] Ravishankar S, Biswagar P. Spherical modal analysis of shaped dielectric lens antennas for mobile broadband applications. In: Antennas Propag Soc Int Symp. 2005. p. 454–547.
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ARTICLE IN PRESS Int. J. Electron. Commun. (AEÜ) xxx (2016) xxx–xxx
Contents lists available at ScienceDirect
International Journal of Electronics and Communications (AEÜ) journal homepage: www.elsevier.com/locate/aeue
Parametric study on effect of solar-cell position on the performance of transparent DRA transmitarray Noha A. Al-Shalaby a,∗ , Shaymaa M. Gaber b a b
Faculty of Engineering, Kafer Elshekh University, Egypt Faculty of Engineering, Egyptian Russian University, Egypt
a r t i c l e
i n f o
Article history: Received 12 May 2015 Accepted 9 January 2016 Keywords: Transmitarray Solar cell Dielectric resonator antenna FIT
a b s t r a c t Linearly polarized transparent dielectric resonator antenna (TDRA) transmitarray is designed and investigated for 12 GHz applications. A parametric study on the effect of solar-cell position on the radiation characteristics of the TDRA transmitarray. The unit cell consists of two TDRAs arranged back-to-back with one on either side of a perfect transparent conducting ground plane. The waveguide model is used to calculate the required compensation phase of each cell in the transmitarray. The radiation characteristics of a 9 × 9 linearly polarized transparent transmitarray antenna are investigated in different positions of solar-cell with respect to the DRA. The peak gain is 20.22 dB with a 1-dB gain bandwidth is more than 2 GHz (16.67%) for the TDRA transmitarray without solar-cell. The solar-cell is integrated with TDRA transmitarray with different positions for small satellite applications. The radiation characteristics of the transmitarray are simulated and calculated using the finite integral technique (FIT). © 2016 Elsevier GmbH. All rights reserved.
1. Introduction The small satellites have a limited surface area. The satellite surface area is occupied by the solar-cells, test instruments, and antennas which affect the overall size and weight of the satellites. An important challenge for a small satellite is to make use of the limited surface area and save cost [1,2]. The design of small satellite antenna includes some limitations such as limited surface area, limited antenna mounting positions, and deployed mechanism [3]. The integration of antennas with solar-cell offers a wide range of advantages as small surface coverage, light weight, low costs and improving the economic viability of renewable energy [4–7]. Solar powered communication systems have advantages that operate without the necessity of an electrical grid connection. There are two types of photovoltaic-antenna integration techniques used in communication systems. The first technique used the solar-cells as an independent power source operating separately from the antennas [8]. The solar-cells are separated from the antennas by a certain distance to ensure that the cells do not effect on the RF characteristics of the antennas [9,10]. The second technique is the full integration of photovoltaics with microwave antennas in a compact communication system, which used the solar-cells as
∗ Corresponding author. Tel.: +20 1091537813. E-mail addresses: [email protected] (N.A. Al-Shalaby), [email protected] (S.M. Gaber).
a part of RF operation [8]. Recently, transparent antennas can be integrated with solar-cells to save surface area of small satellites [3]. Transparent conductive films allow the transmission of electric currents and keep optical transparency of the film, which is more suitable for antennas integrated with solar-cells [7]. The conventional high-gain antennas are parabolic reflectors. The parabolic dish transforms a spherical wave into a planar one and vice versa. Some of the drawbacks of the parabolic reflector are weighted, fabrication complexity, and large overall size [11,12]. The phased arrays offer several advantages over the parabolic antennas, such as electronic steering capability, light-weight and ease of production [13,14], but losses arise from both the physical length of line and from radiation produced at the feed network junctions. The reflectarray is a good choice for the intended satellite-based application since it combines the light weight and low profile while emulating the electrical performance of a phased array or parabolic dish. The reflectarray still requires an offset feed to avoid blockage losses [15]. The offset geometry destroys the symmetry of an antenna aperture and increases the angle of the incident wave, thus reducing the reflector’s gain, decreasing efficiency and complicating the design [16–21]. The transmitarray is similar to the reflectarray where, the feed signal is not reflected, but passes through the structure as it is collimated into a plane wave. Consequently, the feed horn cannot interfere with the transmitted and received waves, and there is no blockage loss [22–24]. The DRA is used for transmitarray to increase the bandwidth, compared to earlier transmitarrays which have been designed using patch elements [25], or using
http://dx.doi.org/10.1016/j.aeue.2016.01.006 1434-8411/© 2016 Elsevier GmbH. All rights reserved.
Please cite this article in press as: Al-Shalaby NA, Gaber SM. Parametric study on effect of solar-cell position on the performance of transparent DRA transmitarray. Int J Electron Commun (AEÜ) (2016), http://dx.doi.org/10.1016/j.aeue.2016.01.006
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2
Fig. 1. The structure of the transmitarray.
Fig. 4. DRA transmitarray structure.
3. Numerical result 3.1. Design of the first unit-cell
Fig. 2. (a) The side view of the unit cell and (b) 3D-view of the unit cell.
cross-dipole elements as done by Chaharmir et al. [26]. DRAs offer many advantages, such as low-profile, low-cost, and high radiation efficiency and high power-handling capability [27–30]. In this paper, 9 × 9 linearly polarized TDRA transmitarray integrated with solar-cell have been introduced. The effect of solar-cell position relative to the TDRA on the radiation characteristics of the transmitarray had been investigated. The TDRA transmitarray is designed and simulated using the finite integral technique (FIT) [31]. 2. Theory Considering the array on the x–y plane illuminated by a feed horn, the required phase distribution ϕij , at each element of the array to collimate a beam in the ( o , ϕo ) direction is determined from ϕij = krij − k(xi sin o cos ϕo + yj sin o sin ϕo )
3.2. The transparent DRA transmitarray The configuration of the transmitarray and feed horn is shown in Fig. 4. The transmitarray is composed of 9 × 9 cell elements and is covering an area of 126 mm × 126 mm. The feed is a linearly polarized pyramidal horn. The dimensions of the horn are 60 mm × 30 mm × 50 mm. The F/D ratio is set to 1. The E-plane and H-plane patterns for the transmitarrays at 12 GHz are shown in Fig. 5. The radiation pattern in E-plane is different from that in
360
0
300
- 0.5
transmited magnitude (dB)
transmitted phase (degrees)
where ko is the propagation constant in vacuum, rij is the distance from the feed horn (xf , yf , zf ) to the element ij of the array and (xi , yj ) are the coordinates of the cell element ij as shown in Fig. 1.
The transmitarray cell element consists of two transparent rectangular dielectric resonators arranged back-to-back with one on either side of a perfect transparent conducting ground plane as shown in Fig. 2. The two RDRA are coupled by a rectangular slot (6 mm × 2 mm) in the ground plane. Each rectangular DRA cell element has a width W = 3 mm, a height h = 4 mm and a variable length L, the relative dielectric constant is εr = 12. The variation of the length of the transparent rectangular DRA changes the resonant frequency of the DRA which yields a change in transmission coefficient phase at the 12 GHz operating frequency. The DRA is mounted on (14 mm × 14 mm) transparent conducting ground plane thickness hs = 0.1 mm with = 5 × 105 S/m. This RDRA cell element is designed to operate at 12 GHz. Fig. 3 shows the phase and the magnitude of the transmission coefficient of RDRA cell element as a function of RDRA length for normal incident plane wave. The results are obtained by applying the FIT technique. The minimum value of the transmission magnitude through the unit cell is lower than −3 dB, and the element achieves a phase tuning range of 360◦ .
240 180 120 60 0 4.5
5.5
6.5
7.5 8.5 9.5 Length (mm)
(a)
10 0.5 11.5
-1 - 1.5
-2 - 2.5
-3
5
6
7
8
9
10
11
Length (mm)
(b)
Fig. 3. (a) Transmission coefficient phase variation versus DR length. (b) Transmission coefficient magnitude variation versus DR length.
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Fig. 5. The gain patterns of 9 × 9 DR transmitarray at 12 GHz.
H-plane due to the rectangular shape of the horn aperture. A peak gain of 20.2 dBi was calculated at 12 GHz. The symmetrical gain patterns for the broadside fed transmitarray at 12 GHz in E-plane and H-plane are obtained due to the symmetry of the array about the x-axis and y-axis. The first side lobe levels (SLLs) in the E-plane and H-planes are approximately 12.13 dBi and 15.6 dBi below the main peaks, respectively. The gain versus the frequency is shown in Fig. 6. The beamwidth in the H-plane is narrower than the beamwidth in the E-plane due to the rectangular shape of the horn aperture. The 1-dB gain bandwidth is approximately 16.67% (more than 2 GHz).
Gain (dB)
23
0 10.5
11
11.5 5
12
12.5
13
13.5
Frequency(GHz) Fig. 6. Gain versus frequency of the DR transmitarray.
Fig. 7. (a) The side view of the transparent unit cell. (b) 3D-view of the transparent unit cell.
3.3. Solar cell over the top transparent DRA transmitarray (case 1) The unit cell is the same as in the first structure but the solar cell is added at the top of the TDRA cell as shown in Fig. 7. The solar cell has thickness hs = 0.057 mm and with εr = 1.5. Again the variation in the length of the RDRA is used to adjust the needed phase shift at each element. The configuration of the proposed unit cell is designed at 12 GHz. The magnitude and phase responses of the unit cell are calculated using FIT technique as shown in Fig. 8. The minimum value of the transmission magnitude experienced by the structure is −3 dB, while the reflection phase covers approximately 360◦ in total. Fig. 9 shows the radiation patterns in H-plane and E-plane of the 9 × 9 RDRA transmitarray at 12 GHz. The first side lobe level (SLL) in the H- and E-planes is approximately 12.23 dBi and 12.34 dBi, respectively below the main beam. The peak gain is 18.47 dBi. The −1 dB gain bandwidth is 9.6% (1.15 GHz) as shown in Fig. 10.
0
transmitted magnitude (dB)
transmitted phase (degrees)
360
300
240
180
120
60
0 4.5
-0.5
-1
-1.5
-2
-2.5
-3 5.5
6.5
7.5
8.5
Length (mm)
9.5
10.5
11.5
6
8
10
Length (mm)
Fig. 8. (a) Transmission coefficient phase variation versus DR length. (b) Transmission coefficient magnitude variation versus DR length.
Please cite this article in press as: Al-Shalaby NA, Gaber SM. Parametric study on effect of solar-cell position on the performance of transparent DRA transmitarray. Int J Electron Commun (AEÜ) (2016), http://dx.doi.org/10.1016/j.aeue.2016.01.006
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20
Case1 Case2 Case3 Case4
15
15
Gain P attern (dB i)
Gain Pattern (dBi)
10 5 0 -5 -10
10 5 0 -5 -10
Ph=900
-15 -20 -45
Case1 Case2 Case3 Case4
20
-35
-25
-15
-5
5
Ph=00
-15 15
25
35
Evaluation angles(Degrees)
(a) E- plane.
45
-20 -45 -35 -25
-15
-5
5
15
25
35
45
Evaluation angles(Degrees) (b) H -plane.
Fig. 9. The gain patterns for 9 × 9 DRA transmitarray at 12 GHz.
25
G a in (d B i)
20 15 10
Case1 Case2 Case3 Case4
5 0 10.5
11
11.5 12 12.5 Frequency(GHz)
13
13.5
Fig. 10. Gain versus frequency of the DRA transmitarray.
Fig. 11. (a) The side view of the transparent unit cell. (b) 3D-view of the transparent unit cell.
3.4. Solar cell over the bottom transparent DRA transmitarray (case 2) The unit cell is the same as in the first structure but the solar cell is added over the bottom TDRA cell as shown in Fig. 11. Again the variation in the length of the RDRA is used to adjust the needed phase shift at each element. Shows the radiation patterns in E-plane and H-plane compared with that calculated in case I, respectively. It is clear from Fig. 9. The first side lobe level (SLL) in the H- and Eplanes is approximately 12.4 dBi and 12 dBi, respectively below the main beam. The peak gain is 18.7 dBi. The gain versus the frequency is shown in Fig. 10. The 1-dB gain bandwidth is approximately 12.5% (1.5 GHz).
Fig. 12. (a) The side view of the transparent unit cell. (b) 3D-view of the transparent unit cell.
3.5. Solar cell between the top TDRA and the ground plane layer (case 3) The unit cell is the same as in the second structure but the solar cell is added between top TDRA and the ground plane layer as shown in Fig. 12. The simulation results have achieved a 360◦ of phase variation with less than 3 dB of variation in transmission magnitude throughout the tuning range as shown in Fig. 13. Computed radiation patterns of the transmitarray in E-plane and H-plane at f = 12 GHz are shown in Fig. 9, respectively. The symmetrical gain patterns for the transmitarray at 12 GHz in E-plane and H-plane are obtained due to the symmetry of the arrays about the x-axis and y-axis. At the design frequency 12 GHz, the transmitarray has maximum gain of 13.97 dBi with the first SLL 9.6 dBi in the H-plane and 4.5 dBi in the E-plane below the main beam. Fig. 10 shows the gain as function of the frequency. Broadband transmitarray was shown to achieve a maximum 1 dB gain bandwidth close to 3% (0.352 GHz). 3.6. Solar cell between the bottom TDRA and the ground plane layer (case 4) The unit cell is the same as in the third structure but the solar cell is added between the bottom TDRA and the ground plane layer as shown in Fig. 14. The computed radiation patterns of the transmitarray in E-plane and H-plane at f = 12 GHz are shown in Fig. 9. The side lobe levels (SLL) in the E- and H-planes are approximately 12.45 dB and 11.3 dB, respectively. The gain of the transmitarray against the frequency is shown in Fig. 10. The peak gain is 17.5 dB. The 1 dB gain bandwidth is 11.25% (1.35 GHz). The comparison
Please cite this article in press as: Al-Shalaby NA, Gaber SM. Parametric study on effect of solar-cell position on the performance of transparent DRA transmitarray. Int J Electron Commun (AEÜ) (2016), http://dx.doi.org/10.1016/j.aeue.2016.01.006
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transmitted magnitude (dB)
transmitted phase (degrees)
0 360 300 240
180 120 60
0 4.5
5.5
6.5
7.5
8 .5
9.5
10. 5 11.5
-0..5 -1 -1..5 -2 -2..5 -3 -3..5
Length ((mm)
6
8
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Length (mm m)
(a)
(b)
Fig. 13. (a) Transmission coefficient phase variation versus DR length. (b) Transmission coefficient magnitude variation versus DR length.
solar cell. A solar cell is integrated with the optically transparent transmitarray have been introduced and reached that by putting the solar cell on the back side of the transmitarray is the best position of solar cell. The solar-cell integration with the transmitarray reduces the maximum gain by about 1.52 dB due to the increase in the magnitude of the transmission coefficient.
Fig. 14. (a) The side view of the transparent unit cell. (b) 3D-view of the transparent unit cell. Table 1 Comparison between TDRA and the four position of solar cell. Case
Gain
B.W.
Highest SLL
TDRA only Case 1 Case 2 Case 3 Case 4
20.22 dB 18.47 dB 18.7 dB 13.97 dB 17.5 dB
More than 2 GHz 1.15 GHz 1.5 GHz 0.352 GHz 1.35 GHz
12.13 dB/15.6 dB 12.23/12.34 dB 12.4/12 dB 9.6/4.5 dB 12.45/11.3 dB
between the TDRA transmitarray and the four cases of solar cell integrated TDRA transmitarray presented in Table 1. 4. Conclusion The paper introduces the radiation characteristics of a transparent DRA transmitarray antenna for satellite applications at 12 GHz. The unit cell is two transparent rectangular dielectric resonators arranged back-to-back with one on either side of a perfect transparent conducting ground plane. A studying the effect of integrated the solar cell with the transmitarray at different positions has been introduced. The magnitude of the transmission coefficient achieves 0 dB nearly with 360◦ transmission coefficient phase varied by varying the transparent DRA’s length, from 4.5 mm to 11.5 mm. The radiation characteristics of a 9 × 9 linearly polarized transparent transmitarray antenna are investigated. A linearly polarized horn antenna is utilized to feed the transmitarray. The peak gain is 20.22 dB with a 1-dB gain bandwidth is more than 2 GHz (16.67%) for the transparent DRA transmitarray, when TDRA transmitarray integrated with solar-cell the peak gain variable from 18.7 dBi to13.97 dBi with a 1-dB gain bandwidth of 1.5 GHz (12.5%) to 0.35 GHz (3%) according to the poison of a solar cell with respect to TDRA and the feeding horn. A decrease in the optical transparent DRA transmitarray gains bandwidth due to varying the position of
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