# Pattern Reconfigurable Antenna for VANET, Wi-Fi, and WiMAX Wireless Communication Systems

Authors: Rahmani Faouzi; Amar Touhami Naima; BelbachirKchairi Abdelmounaim; Aknin Noura; Taher Nihade
Journal: International Journal of Antennas and Propagation
 (2021)

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## Abstract

This work presents the design and analysis of a beam switching antenna for VANET, Wi-Fi, and WiMAX wireless communication systems. The proposed reconfigurable antenna is powered by a coaxial cable and consists of a circular patch, six fish-shaped radiating elements, and a circular planar ground. The antenna was constructed on a Rogers RT5880 substrate. Its dimensions are as follows: 0.81λ0 × 0.81λ0 × 0.03λ0. It performs six reconfigurable operating states, at the same frequency, by controlling the activation and deactivation of six PIN diodes to change the beam’s direction. A theoretical equivalent circuit model of the antenna is extracted. A progressive analysis of improving the antenna characteristic performances is provided. The bandwidth of the proposed antenna is 9.07% (measured), 9.62% (simulated), and 9.31% (theoretical). The designed antenna has a maximum gain of 9.57 dB for all pattern states and a superior efficiency ratio from 85% to 95% over the operating range (5.54 GHz–6.10 GHz). The proposed reconfigurable antenna is fabricated. Measured, simulated, and theoretical results are given and show good agreement, including reflection coefficient (S11) and radiation patterns.


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## Body

## 1. Introduction

In the last decade, wireless communication in different fields has been developed enormously due to the low cost and high performance of wireless devices. In the domain of antenna systems, the reconfigurable antenna design has gained a lot of attention [1–3]. Its versatility in frequency picking, polarization selectivity, and pattern reconfiguration makes it very suitable for various wireless communication systems, such as wireless WLAN systems. The reconfigurable pattern antenna can produce different radiation patterns on a physical aperture at the same operating frequency. This antenna concept can provide electrical adjustment mechanisms with multifunctional control of electromagnetic waves, such as adjusting the applied bias voltage.Typical active elements used in reconfigurable meta-surfaces [4, 5] include varactor diodes [6], radio-frequency micro-electromechanical systems (RF-MEMSs) [7], and PIN diodes [8], which have been used to achieve beam direction. Since they are not very costly, the PIN diodes are very effective and can easily combine with patch antennas [9–12].There are some key approaches and strategies in the literature to explain the reconfigurability of the pattern with enhanced radiation gain and efficiency [13–16]. By monitoring the condition of two PIN diodes between the feed line and patch components, the antenna in [17] achieved two states. The radiation pattern of the antenna in [18] would be reconfigured by steering the status of two PIN diodes in two modes in the azimuth plane based on a circular monopole patch and three ship-shaped parasitic patches. The antenna in [19] monitored the status of PIN diode switches in four operating states. We propose using six radiating cells to increase the antenna performance. The goal is to increase the bandwidth and also to improve antenna gain, in addition to the pattern reconfigurability.The novelty of the proposed design, compared to all our published works, is mainly the ability to improve the antenna performance such as gain, bandwidth, and efficiency [20–23]. A circular planar antenna with reconfigurable radiation pattern using parasitic patches was proposed in our previous study [20], but this kind of antenna was not be able to cover the whole azimuth plane. The antenna in [21] has only a bandwidth of 4.7% and a gain of 8.22 dB for four pattern states. In addition, a wideband reconfigurable antenna with beams switching has been proposed in [22], and it has a bandwidth of 26.75%, while the gain is less than 6 dB. A new reconfigurable antenna was proposed in [23] using eight hexagon-shaped radiation cells; the antenna has a bandwidth of 6.2% and gains of 8.46 dB.In this work, we propose a new antenna using six fish-shaped radiating cells with reconfigurable radiation patterns that operate either as a reflector(s) or director(s) and a circular planar ground according to the switch states. Using six PIN diodes, the radiation pattern can be modified into six states. By controlling the states (ON or OFF) of six Microsemi MPP4203 PIN diodes [24], the main beam of the antenna can be redirected in six directions in half an elevation plane. The proposed antenna may also alter the direction of the main lobe in the azimuth plane at specific steering angles. The proposed design guarantees the possibility that the antenna can radiate in all directions of the xy-plane. The simulated realized gains for all pattern states are about 9.57 dB. The designed reconfigurable antenna operates for VANET, Wi-Fi, and WiMAX wireless communication systems and has a simulated bandwidth of 9.62% from 5.54 GHz to 6.10 GHz.The content of this work is divided into three sections. Section1 is presented as a general introduction. In Section 2, we introduce the design principle used to realize the reconfigurability of radiation patterns, we present the parametric study of the proposed antenna that is used to obtain the optimal values and the best performance, and we discuss the obtained measurement and simulation results. Finally, the main conclusions of this study are given in Section 3.


## 2. Design Principle

Figure1represents the proposed antenna design evolution, with corresponding results of simulated reflection coefficient (S11) as shown in Figure2(a) and simulated realized gain of each step as shown in Figure 2(b). All proposed structures are engraved on h = 1.57 mm thick Rogers RT5880 substrate with a relative permittivity of 2.2 and a loss tangent of 0.0009. The antenna geometry must be chosen in such a way that the antenna can direct the main lobe in very precise directions. To cover the whole azimuth plane (xoy-plane), the feed line using coaxial cable is more adequate for the designed antenna. The proposed design is generally formed of some modified rectangular patch antennas distributed symmetrically around a coaxial feed line as shown in Figure 1(a). The antenna center frequency was designed as 5.8 GHz, and the rectangular patch physical parameters were calculated using the following equations used in the transmission line model [25].(1)W=c2f2εr+1,where c represents the electromagnetic wave speed in free space.(2)L=c2fεre−2ΔL,(3)εre=εr+12+εr−1211+12h/W,(4)ΔL=0,412hεre+0,3W/h+0,264εre−0,258W/h+0,8.Figure 1
The antenna design evolution: (a) Ant. 1, (b) Ant. 2, and (c) Ant. 3.
(a)(b)(c)Figure 2
Reflection coefficient (a) and gain (b) for different antennas.
(a)(b)Each radiating element is connected to the feed line via a PIN diode in the gap between them. By controlling the ON and the OFF states of the Microsemi MPP4203 PIN diodes, the distribution of the antenna surface current will be modified, so the antenna radiation direction will deviate. When a PIN diode is reverse biased, the radiating cell will act as a director, while in direct biased, the parasitic patch will act as a reflector. The initial step in the design of the proposed reconfigurable antenna is presented in Figure1(a). As can be seen from this figure, on the top side of the substrate, three symmetrical kite-shaped radiating elements are placed so that one is rotated from the other by 120°, and a circular-shaped patch located at the center of the antenna is connected to the coaxial cable inner pin. Using three PIN diodes, the radiating elements are connected to the central circular patch, which is connected to the inner pin of the coaxial cable. As shown in Figure 2(a), the initial antenna (Ant. 1) resonates at 5.8 GHz frequency, and the simulated S11 parameter value is not also below −12 dB. Note that the maximum simulated gain value does not exceed 7.14 dB as shown in Figure 2(b).In order to make the antenna more adapted for 5.8 GHz and to increase the antenna gain, a change in the shape of the radiating elements was implemented as shown in Figure1(b). In the second step geometry (Ant. 2), three fan-shaped coupling elements distributed symmetrically around the antenna center are added. As presented in Figure 2(a), a resonant frequency at 5.8 GHz is created with −10 dB impedance bandwidth that ranges from 5.74 to 5.86 GHz. Also, it can be seen that the maximum simulated gain value is 7.62 dB for Ant. 2, as presented in Figure 2(b).In order to improve the bandwidth and also to enhance the antenna gain, in addition to the pattern reconfigurability, a change in the number of the radiating cells and coupling elements was implemented as shown in Figure1(c). The final proposed antenna geometry is formed of three parts, as shown in Figure 3. The first part (yellow area) is a circular-shaped patch located at the center which is connected to the inner pin of the coaxial cable. The second part (blue area) comprises six fan-shaped coupling elements, which are connected by six PIN diodes with six fish-shaped radiating cells (red area) distributed around the antenna center symmetrically. The substrate size which has the circular-shaped is (Ø × H) = (80 mm × 1.57 mm).Figure 3
The designed reconfigurable antenna. (a) Top view. (b) Side view.
(a)(b)In order to design and to simulate the proposed antenna, Computer Simulation Technology Microwave Studio (CST MWS) software was used. Table1 represents the final optimized parameters values of the proposed antenna design. As given in Figure 2(a), the final proposed reconfigurable antenna operates in the band ranging from 5.54 GHz to 6.10 GHz with the center frequency at 5.82 GHz. As given in Figure 2(b), the final antenna has a maximum gain of 9.57 dB at 5.82 GHz, greater than that of the two previous antennas. The main reason for getting suddenly high gain of a proposed antenna (Ant. 3) compared with Ant.1 and Ant. 2 is the use, for each state, of three radiating cells as directors and three other radiating cells as reflectors.Table 1
Dimensions of antenna in Figure3.
ParameterLR1R2R3R4R5Dimension16 mm2.5 mm2.8 mm3.3 mm3.6 mm4.6 mmParameterW0DdθβαDimension0.4 mm4.1 mm1.2 mm80°45°90°The fish-shaped radiating elements are selectively powered by the circular patch through PIN diode biasing. According to the datasheet of the Microsemi MPP4203, the diode parameters areLD = 0.02 nH, RDS = 3 Ω, CT = 0.08 pF, and RDP = 25 KΩ. The RF equivalent circuit of the diode is shown in Figures 4(a) and 4(b) for both the ON and the OFF states, respectively [19, 21, 24]. A rectangular microstrip patch is analyzed and considered as a parallel combination of resistance (RP), inductance (LP), and capacitance (CP) as shown in Figure 4(c). Expressions for the lumped elements of RP, LP, and CP [26, 27] are given as(5)CP=ε0εreLW2hcos−2πYfL,(6)LP=1ωP2CP,(7)RP=QrωCP,where L = length of the patch, W = width of the patch, Yf = y coordinates of feed point, and h = thickness of the substrate material.Figure 4
Equivalent circuit model. (a) Forward bias of PIN diode (ON). (b) Reverse bias of PIN diode (OFF). (c) Rectangular patch antenna. (d) Proposed antenna.
(a)(b)(c)(d)(8)Qr=cεre4fh.Figured4(d) represents the equivalent circuit of the proposed antenna. The circular gap around the central circular patch, as represented in Figure 2(a), can be considered as a coupling by mutual inductance (coupling #1) characterized by the coupling coefficient k. Taking into account the inter-element couplings, the gap between each coupling element (blue area) and the neighboring fish-shaped radiating cell can be analyzed as a parasitic capacitance (C1) in parallel with the equivalent circuit of the PIN diode connected in this gap. The cumulative charges between the coupling elements and the ground can be considered as a parasitic capacitance (C2). In order to simulate the equivalent circuit of the proposed antenna, Advanced Design System (ADS) was used. The final optimized lumped parameters values are presented in Table 2.Table 2
Optimized lumped parameter values.
ParameterRP (Ω)LP (nH)CP (pF)C1 (pF)C2 (pF)kValue2450.411.710.040.0431


### 2.1. Parametric Study

A parametric study was conducted to comprehend the effect on the proposed antenna performance. In this section, we study the effects of the main geometric parameters on reflection coefficient (S11) and antenna gain. We present a parametric study of the proposed antenna that is used to obtain the optimal values and the best performance by tuning one parameter at a time while other parameters are left invariable. Concerning the parameters (R2, R3, R4, and W0), we took the optimal minimum values to fabricate the proposed antenna.


### 2.2. Effect of LengthL

The reflection coefficient (S11) and antenna gain for different values of length (L) of radiating patches are simulated and plotted in Figure 5. It can be seen that the impedance bandwidth of the proposed antenna remains stable and that the center frequency is shifted. As shown in Figure 5(a), when L = 16 mm, the band frequency is shifted to the desired center frequency value with better adaptation, while the antenna gain becomes maximum at 5.82 GHz when the length is L = 16 mm, as shown in Figure 5(b). So, the optimal value of length is L = 16 mm.Figure 5
Reflection coefficient (a) and gain (b) for different length (L) values.
(a)(b)


### 2.3. Effect of Angleβ

The antenna gain and the reflection coefficient (S11) are also simulated as a function of the different angle (β) values. As shown in Figure 6(a), the center frequency remains stable. As β increases, the frequency band reduces. In parallel, the antenna gain becomes maximum (9.57 dB) at a frequency of 5.82 GHz when the angle is β = 45°, as shown in Figure 6(b). We can see that the best result is obtained for an angle (β) equal to 45°.Figure 6
Reflection coefficient (a) and gain (b) for different angles (ß).
(a)(b)


### 2.4. Effect of Angleθ

The antenna gain and the S11 parameter are also simulated versus the different angle (θ)values. As shown in Figure 7(a), the center frequency remains stable. The desired frequency band is obtained for the angle θ = 80°. As illustrated in Figure 7(b), the antenna gain becomes maximum at the desired frequency when the angle is θ = 80°. We notice thereby that the best result is obtained for an angle (θ) equal to 80°.Figure 7
Reflection coefficient (a) and gain (b) for different angle values (θ).
(a)(b)


### 2.5. Effect of RadiusR1

In this section, we display the effect of the radius (R1) of the central patch on the S11 parameter and the antenna gain, while keeping the other dimensions invariable. From Figure 8(a), we show the curves of S11 parameter with different values of R1. As the radius R1 increases, the center frequency changes, and the frequency band moves to the desired value (5.54–6.10 GHz) for 2.5 mm of R1. The impedance bandwidths are about 560 MHz. On the other hand, Figure 8(b) illustrates the simulated gain versus frequency with different values of R1. We can see from this figure that the maximum gain value at 5.82 GHz is obtained for 2.5 mm of R1. So, the optimal value of radius R1 is 2.5 mm.Figure 8
Reflection coefficient (a) and gain (b) for different radius (R1) values.
(a)(b)


### 2.6. Experimental Results and Discussion

The antenna, which is shown in Figure3, is fabricated using a printed circuit board (PCB) milling machine (LPKF Protomat E33), as presented in Figure 9. The control of each PIN diode is done by two biasing lines: the first one is served as a direct current (DC) supply and the other is served as a ground. In each operating mode, three PIN diodes are forward biased while the other three PIN diodes are reverse biased. By changing the distribution of the antenna surface current, this will deflect the direction of the antenna radiation. Thus, simulation series were performed as given in Table 3. The fish-shaped radiating cell acts as a director when the PIN diode is reverse biased. Otherwise, it acts as a reflector. It shows that the proposed antenna has six operating states named as S1, S2, S3, S4, S5, and S6. Table 3 presents specific biasing requirement for these six operating states.Figure 9
Photograph of fabricated antenna.Table 3
Operating states of the proposed antenna.
Operating statesPIN diode statesCenter frequency (GHz)Simulated gain (dB)Beam directionD1D2D3D4D5D6xy-planexz-planeyz-planeState 1OFFOFFONONONOFF5.829.57ϕ = 0°θ = 20°θ = 0°State 2OFFOFFOFFONONON5.829.57ϕ = 60°θ = 16°θ = 19°State 3ONOFFOFFOFFONON5.829.57ϕ = 120°θ = -15°θ = 19°State 4ONONOFFOFFOFFON5.829.57ϕ = 180°θ = -20°θ = 0°State 5ONONONOFFOFFOFF5.829.57ϕ = 240°θ = -15°θ = -19°State 6OFFONONONOFFOFF5.829.57ϕ = 300°θ = 16°θ = -19°The S11 parameter of the proposed antenna is measured using “Rohde and Schwarz ZVB20 vector network analyzer” to verify obtained simulation results. Figure10(a) shows the comparison of S11 plot of measured, simulated, and theoretical results of the proposed antenna.  Thebandwidth of the measured result is 9.07% (from 5.58 to 6.11 GHz). While forthe simulated values, the bandwidth is 9.62% (from 5.54 to 6.10 GHz). Further,the theoretical value is 9.31% (from 5.53 to 6.07 GHz). It is observed that the results are in good agreement. The reasons behind this improved bandwidth are the employment of electronic switches with smaller capacities and the use of fan-shaped coupling elements as shown in Figure 3. The small disagreement between simulated and measured results can be ascribed to tolerances in fabrication process. All the results presented are given when the antenna is operating in state 1. The same results are obtained for the other operating states.Figure 10
(a) Simulated, theoretical, and measured S11 and (b) simulated antenna efficiency and gain.
(a)(b)The antenna efficiency increases from 85% to 95% with increasing frequency through the operating range (5.54–6.10 GHz), as shown in Figure10(b). The designed antenna has a maximum gain of 9.57 dB and a maximum directivity of 10.07 dB for all pattern states. The reasons behind such high efficiency and enhanced antenna gain in this work are the use, for each state, of three radiating cells as directors and three other radiating cells as reflectors and the use of a low loss dielectric of Rogers RT5880 with loss tangent of 0.0009.Far-field radiation patterns of the presented antenna are measured by an antenna measurement system of Geozondas Ltd. Figures11(a)–11(f) show the simulated and measured xz-plane (ϕ = 0°) radiation patterns. The antenna’s main beam can be steered to approximately 20° (right endfire), 16° (right endfire), −15° (left endfire), −20° (left endfire), −15° (left endfire), and 16° (right endfire), for State 1 to State 6, respectively.Figure 11
Simulated and measured radiation patterns of the proposed antenna in thexz-plane (ϕ = 0°) at 5.82 GHz: (a) State 1, (b) State 2, (c) State 3, (d) State 4, (e) State 5, and (f) State 6.
(a)(b)(c)(d)(e)(f)Figures12(a)–12(f) present the simulated and measured yz-plane (ϕ = 90°) radiation patterns. The antenna’s main beam can be steered to approximately 0° (boresight), 19° (right endfire), 19° (right endfire), 0° (boresight), −19° (left endfire), and −19° (left endfire), for State 1 to State 6, respectively. Far-field radiation patterns at frequency of 5.82 GHz in xz-plane and yz-plane show that proposed reconfigurable pattern antenna radiates in six different directions. The measured results agree well with the simulated predictions, which validate the antenna operation.Figure 12
Simulated and measured radiation patterns of the proposed antenna in theyz-plane (ϕ = 90°) at 5.82 GHz: (a) State 1, (b) State 2, (c) State 3, (d) State 4, (e) State 5, and (f) State 6.
(a)(b)(c)(d)(e)(f)Figure13 shows simulated 3D radiation patterns at 5.82 GHz. The antenna’s main beam can be steered in xy-plane (azimuth plane) to approximately 0°, 60°, 120°, 180°, 240°, and 300°, for State 1 to State 6, respectively. Far-field radiation patterns at frequency 5.82 GHz in the azimuth plane show that proposed antenna radiates in six different directions.Figure 13
Simulated 3D radiation patterns at 5.82 GHz.To validate the proposed design, Table4 displays a comparison between our reconfigurable antenna and other previously reported designs. The proposed antenna not only has pattern reconfigurability and enhanced gain but also possesses additional advantages, notably an improved impedance bandwidth, a smaller size, and a very high efficiency.Table 4
Comparison between the proposed reconfigurable antenna and several other reconfigurable antennas.
Year/RefNo. of layersSize (λ03)Frequency (GHz)Impedance BW (%)GainEfficiency (%)2017/[19]21.17 × 1.17 × 0.083.45.65.4–8.31 dBiNG2017/[28]11.37 × 1.37 × 0.025.918.66–6.5 dBi762018/[29]30.79 × 0.79 × 0.282.49.3–12.66.5 dBi852019/[30]11,48 × 1,48 × 0,0082.3410.255.9 dBiNG2020/[31]10.91 × 0.85 × 0.023.654.15.7–6.9 dBi892020/[32]41.39 × 1.39 × 0.062.4512.247.0–8.9 dBiNGThis work10.81 × 0.81 × 0.035.829.629.57 dBi95λ0 is the wavelength of the free space.


## 2.1. Parametric Study

A parametric study was conducted to comprehend the effect on the proposed antenna performance. In this section, we study the effects of the main geometric parameters on reflection coefficient (S11) and antenna gain. We present a parametric study of the proposed antenna that is used to obtain the optimal values and the best performance by tuning one parameter at a time while other parameters are left invariable. Concerning the parameters (R2, R3, R4, and W0), we took the optimal minimum values to fabricate the proposed antenna.


## 2.2. Effect of LengthL

The reflection coefficient (S11) and antenna gain for different values of length (L) of radiating patches are simulated and plotted in Figure 5. It can be seen that the impedance bandwidth of the proposed antenna remains stable and that the center frequency is shifted. As shown in Figure 5(a), when L = 16 mm, the band frequency is shifted to the desired center frequency value with better adaptation, while the antenna gain becomes maximum at 5.82 GHz when the length is L = 16 mm, as shown in Figure 5(b). So, the optimal value of length is L = 16 mm.Figure 5
Reflection coefficient (a) and gain (b) for different length (L) values.
(a)(b)


## 2.3. Effect of Angleβ

The antenna gain and the reflection coefficient (S11) are also simulated as a function of the different angle (β) values. As shown in Figure 6(a), the center frequency remains stable. As β increases, the frequency band reduces. In parallel, the antenna gain becomes maximum (9.57 dB) at a frequency of 5.82 GHz when the angle is β = 45°, as shown in Figure 6(b). We can see that the best result is obtained for an angle (β) equal to 45°.Figure 6
Reflection coefficient (a) and gain (b) for different angles (ß).
(a)(b)


## 2.4. Effect of Angleθ

The antenna gain and the S11 parameter are also simulated versus the different angle (θ)values. As shown in Figure 7(a), the center frequency remains stable. The desired frequency band is obtained for the angle θ = 80°. As illustrated in Figure 7(b), the antenna gain becomes maximum at the desired frequency when the angle is θ = 80°. We notice thereby that the best result is obtained for an angle (θ) equal to 80°.Figure 7
Reflection coefficient (a) and gain (b) for different angle values (θ).
(a)(b)


## 2.5. Effect of RadiusR1

In this section, we display the effect of the radius (R1) of the central patch on the S11 parameter and the antenna gain, while keeping the other dimensions invariable. From Figure 8(a), we show the curves of S11 parameter with different values of R1. As the radius R1 increases, the center frequency changes, and the frequency band moves to the desired value (5.54–6.10 GHz) for 2.5 mm of R1. The impedance bandwidths are about 560 MHz. On the other hand, Figure 8(b) illustrates the simulated gain versus frequency with different values of R1. We can see from this figure that the maximum gain value at 5.82 GHz is obtained for 2.5 mm of R1. So, the optimal value of radius R1 is 2.5 mm.Figure 8
Reflection coefficient (a) and gain (b) for different radius (R1) values.
(a)(b)


## 2.6. Experimental Results and Discussion

The antenna, which is shown in Figure3, is fabricated using a printed circuit board (PCB) milling machine (LPKF Protomat E33), as presented in Figure 9. The control of each PIN diode is done by two biasing lines: the first one is served as a direct current (DC) supply and the other is served as a ground. In each operating mode, three PIN diodes are forward biased while the other three PIN diodes are reverse biased. By changing the distribution of the antenna surface current, this will deflect the direction of the antenna radiation. Thus, simulation series were performed as given in Table 3. The fish-shaped radiating cell acts as a director when the PIN diode is reverse biased. Otherwise, it acts as a reflector. It shows that the proposed antenna has six operating states named as S1, S2, S3, S4, S5, and S6. Table 3 presents specific biasing requirement for these six operating states.Figure 9
Photograph of fabricated antenna.Table 3
Operating states of the proposed antenna.
Operating statesPIN diode statesCenter frequency (GHz)Simulated gain (dB)Beam directionD1D2D3D4D5D6xy-planexz-planeyz-planeState 1OFFOFFONONONOFF5.829.57ϕ = 0°θ = 20°θ = 0°State 2OFFOFFOFFONONON5.829.57ϕ = 60°θ = 16°θ = 19°State 3ONOFFOFFOFFONON5.829.57ϕ = 120°θ = -15°θ = 19°State 4ONONOFFOFFOFFON5.829.57ϕ = 180°θ = -20°θ = 0°State 5ONONONOFFOFFOFF5.829.57ϕ = 240°θ = -15°θ = -19°State 6OFFONONONOFFOFF5.829.57ϕ = 300°θ = 16°θ = -19°The S11 parameter of the proposed antenna is measured using “Rohde and Schwarz ZVB20 vector network analyzer” to verify obtained simulation results. Figure10(a) shows the comparison of S11 plot of measured, simulated, and theoretical results of the proposed antenna.  Thebandwidth of the measured result is 9.07% (from 5.58 to 6.11 GHz). While forthe simulated values, the bandwidth is 9.62% (from 5.54 to 6.10 GHz). Further,the theoretical value is 9.31% (from 5.53 to 6.07 GHz). It is observed that the results are in good agreement. The reasons behind this improved bandwidth are the employment of electronic switches with smaller capacities and the use of fan-shaped coupling elements as shown in Figure 3. The small disagreement between simulated and measured results can be ascribed to tolerances in fabrication process. All the results presented are given when the antenna is operating in state 1. The same results are obtained for the other operating states.Figure 10
(a) Simulated, theoretical, and measured S11 and (b) simulated antenna efficiency and gain.
(a)(b)The antenna efficiency increases from 85% to 95% with increasing frequency through the operating range (5.54–6.10 GHz), as shown in Figure10(b). The designed antenna has a maximum gain of 9.57 dB and a maximum directivity of 10.07 dB for all pattern states. The reasons behind such high efficiency and enhanced antenna gain in this work are the use, for each state, of three radiating cells as directors and three other radiating cells as reflectors and the use of a low loss dielectric of Rogers RT5880 with loss tangent of 0.0009.Far-field radiation patterns of the presented antenna are measured by an antenna measurement system of Geozondas Ltd. Figures11(a)–11(f) show the simulated and measured xz-plane (ϕ = 0°) radiation patterns. The antenna’s main beam can be steered to approximately 20° (right endfire), 16° (right endfire), −15° (left endfire), −20° (left endfire), −15° (left endfire), and 16° (right endfire), for State 1 to State 6, respectively.Figure 11
Simulated and measured radiation patterns of the proposed antenna in thexz-plane (ϕ = 0°) at 5.82 GHz: (a) State 1, (b) State 2, (c) State 3, (d) State 4, (e) State 5, and (f) State 6.
(a)(b)(c)(d)(e)(f)Figures12(a)–12(f) present the simulated and measured yz-plane (ϕ = 90°) radiation patterns. The antenna’s main beam can be steered to approximately 0° (boresight), 19° (right endfire), 19° (right endfire), 0° (boresight), −19° (left endfire), and −19° (left endfire), for State 1 to State 6, respectively. Far-field radiation patterns at frequency of 5.82 GHz in xz-plane and yz-plane show that proposed reconfigurable pattern antenna radiates in six different directions. The measured results agree well with the simulated predictions, which validate the antenna operation.Figure 12
Simulated and measured radiation patterns of the proposed antenna in theyz-plane (ϕ = 90°) at 5.82 GHz: (a) State 1, (b) State 2, (c) State 3, (d) State 4, (e) State 5, and (f) State 6.
(a)(b)(c)(d)(e)(f)Figure13 shows simulated 3D radiation patterns at 5.82 GHz. The antenna’s main beam can be steered in xy-plane (azimuth plane) to approximately 0°, 60°, 120°, 180°, 240°, and 300°, for State 1 to State 6, respectively. Far-field radiation patterns at frequency 5.82 GHz in the azimuth plane show that proposed antenna radiates in six different directions.Figure 13
Simulated 3D radiation patterns at 5.82 GHz.To validate the proposed design, Table4 displays a comparison between our reconfigurable antenna and other previously reported designs. The proposed antenna not only has pattern reconfigurability and enhanced gain but also possesses additional advantages, notably an improved impedance bandwidth, a smaller size, and a very high efficiency.Table 4
Comparison between the proposed reconfigurable antenna and several other reconfigurable antennas.
Year/RefNo. of layersSize (λ03)Frequency (GHz)Impedance BW (%)GainEfficiency (%)2017/[19]21.17 × 1.17 × 0.083.45.65.4–8.31 dBiNG2017/[28]11.37 × 1.37 × 0.025.918.66–6.5 dBi762018/[29]30.79 × 0.79 × 0.282.49.3–12.66.5 dBi852019/[30]11,48 × 1,48 × 0,0082.3410.255.9 dBiNG2020/[31]10.91 × 0.85 × 0.023.654.15.7–6.9 dBi892020/[32]41.39 × 1.39 × 0.062.4512.247.0–8.9 dBiNGThis work10.81 × 0.81 × 0.035.829.629.57 dBi95λ0 is the wavelength of the free space.


## 3. Conclusion

In this work, a new antenna with reconfigurable radiation pattern using six fish-shaped radiation cells is simulated, measured, and investigated. Based on the PIN diode switch biasing, the proposed reconfigurable antenna can function at six basic different states and attain radiation pattern reconfigurable characteristic. Changing the distribution of the antenna surface current will deflect the direction of the antenna radiation in six different directions in elevation plane. It indicates that this novel antenna can cover the whole azimuth plane. The designed reconfigurable antenna can provide a wideband ranging from 5.54 GHz to 6.10 GHz centered on 5.82 GHz, a maximum gain of 9.57 dB, and a very good efficiency of 95%. It is known that this band is accurately reserved for VANET, Wi-Fi, and WiMAX wireless communication systems. Thus, the proposed antenna achieves the goal of this work perfectly.



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*Source: 9973839-2021-10-31.xml*