Keywords

1 Introduction

Antennas play a crucial role in aerospace communication by transmitting and receiving radio signals between aircraft, satellites, and ground stations. A wide range of antennas, including semi-circular, L-shaped, triangular, multi-slot, and U-shaped antennas, are used in aerospace communication [1,2,3,4,5,6]. Techniques like changing the ground plane with parasitic elements, adding a small fractal component, U-shaped or circular slots, and circles are discussed to enhance their performance [7,8,9,10,11]. Polar radiation patterns can be created by altering the circular patch or by cutting a rectangular piece [12,13,14]. Previous research has shown that a wideband aerospace band can be created by changing a patch with a defective backside and semi-circular slots [15, 16]. As stated in references, altering the backside by modifying slots leads to a patch element with a defective plane [2, 17]. According to studies [18, 19], one method involved the use of a flexible antenna and “dumbbell-shaped” radiator. A long strip patch with cut rear slots is another design modification noted in reference [20], which improves current flow. The literature presents various design options for planar antennas. To generate balanced radiation patterns, one suggestion is to use a modified backside with precisely trimmed circular holes, as shown in references [21, 22]. The addition of a rectangular patch to the edges increases oscillations, as per reference [23, 24]. A fractal antenna design has been demonstrated to achieve high gain, as stated in reference [25]. Impedance matching reported through the design of multi-slots [26], The L-shaped design has been shown to reduce band resonance, as stated in reference [27]. More information on the antenna design, development, and simulated outcomes is provided in other sections of the paper.

2 Geometry and Design Principle

Figure 1 illustrates the geometry and concept for the design of an antenna. Substrate used in the antenna design is FR-4 inscribed on copper annealed with overall dimensions as 13 mm * 15 mm * 1.5 mm. The Ra and Rb represent the width and length of antenna, respectively. The parameter values for the design are displayed in Table 1 (given in mm). The length ‘Rq’ and width ‘Rv’ of the microstrip line are 2 mm and 1.5 mm, respectively, and are connected to the substrate's thickness, denoted by ‘Sg’. The front part of the antenna is created by parasitic circular rings, rectangular patch, T, and inverse T with microstrip line. The outer and inner diameters of circular parasitic circular ring are denoted by ‘Rc’ and ‘Rd’. The length and width of inner rectangular patch are defined as ‘Re’ and ‘Rf’. With a partial ground plane and a rectangular slot, the antenna's back portion has ‘Sd’ and ‘Sc’ as its length and width, respectively. Backside also consists of four horizontal strips arranged in increasing order with width as ‘Rx’, ‘Rz’, ‘Sa’, and ‘Sb’, respectively, with width denoted by ‘Ry’. Three parastic sring are placed on the top of the back plane and it is denoted by “Se” and “Sf” as outer and inner radii of the circular rings. Parasitic elements help to resonant the lower order band.

Fig. 1
A structure of the antenna. a. Front view has 4 rings horizontal strip at the top, below 2 T's facing each other with 2 L's placed in rectangle form on either side. b. The back view has 3 rings horizontal strip at the top, 4 increasing level strips, and 2 strips placed side by side. c. Long strip.

Proposed antenna structure

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Table 1 Comparison of published planar antennas
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3 Result and Discussion

Based on an analysis of their impacts on the S11 parameter and other simulated results, the proposed structure optimizes the result.

Figure 2 is showing simulated return loss of the proposed antenna. The antenna’s gain is another important parameter that indicates the strength of the transmitted signal. The maximum radiation effectiveness is shown within 3.3–5.2 GHz frequency range. The proposed design's simulated antenna efficiency and gain vs. frequency curve is depicted in Fig. 3. Peak gain, with a value of 4.81 dB, is seen at 4.5 GHz. Maximum radiation efficiency of antenna is observed at 4.25 GHz having a value of 0.82 or an efficiency of 82%. As the frequency rises, ohmic losses increase, leading to a gradual decline in antenna efficiency at higher frequencies.

Fig. 2
A line graph of the magnitude of S 11 versus frequency for return loss. The line plots a decreasing curve from (2.0, negative 5) to (4.0, negative 29) and plots an increasing curve to (6.0, negative 10), respectively.

Simulated return loss

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Fig. 3
A 2-line graph of gain and radiation efficiency versus frequency. The lines gain and radiation efficiency begin at 1.5 and 0.2 at 2.0, rise to 4.75 and 0.8 at 4.5, then to 4.25 and 0.8 at 5.5, and end at 4.75 and 0.8 at 6.0, respectively.

Gain and antenna efficiency curve

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Figure 4 displays an I/P impedance curve that reflects the frequency curve for the proposed design's simulated real and imaginary components. The behavior is inductive within the 3.2–4.2 GHz frequency range, followed by a capacitive behavior. The inductive behavior is represented by a positive polarity, whereas a negative polarity indicates capacitive behavior. The curve illustrates the impedance normalized to 50 Ω.

Fig. 4
A 2-line graph of input impedance versus frequency for real part and imaginary part. The real and imaginary parts begin at 15 and negative 60 at 2.0 rise to 75 at 4.5 and 20 at 4.0 and end at 40 and negative 15 at 6.0, respectively.

I/P impedance curve

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Figure 5 depicts the 5G antenna's 3.5 GHz polar pattern, in two orthogonal coordinates: both H- and E-plane patterns. The radiation pattern improves the ability to identify the radiation pattern at a specific frequency by displaying measured and simulated H- and E-plane radiation patterns. Two perpendicular planes depict the radiation pattern, one of which represents the E-field and is oriented at a 90-degree angle to the YOZ plane, and the other of which represents the H-field and is oriented at a 0-degree angle to the XOZ plane. The radiation pattern remains stable, and the antenna is coherent.

Fig. 5
A radiation pattern with a 360-degree angle and two perpendicular planes simulated H-plane and simulated E-plane. The H plate plots a circular plot, while the E-plane plots an eight-shaped figure.

Radiation pattern

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The current field distribution of the 5G antenna is presented in the paper. Figure 6 displays the current distributions from a front-to-rear perspective. The equivalent surface of the antenna represents its radiated current field and highlights its signal strengths, with the ability to generate both E-field and H-field, indicating significant signal strength in the design. Depicts the simulated radiation lobe pattern of the 5G antenna. The front plane of the structure and the frequency distribution of the 2D-vector surface current (at 3 GHz) are shown in Fig. 7. The radiated field will closely mirror the surface current of the original antenna by substituting similar surface currents for the antenna. This indicates that even in the absence of the main current source, the surface current can help to detect radiation.

Fig. 6
2 contour plots of surface current distribution. The distribution has a maximum at the top and a minimum at the bottom.

Surface current distribution

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Comparison table with previously published antenna is shown below, and our proposed TL-Shaped Circular Parasitic Compact planar antenna for 5G microwave applications is satisfy the requirement of all antenna parameters.

4 Conclusion

This research proposes a circular TL-shaped parasitic planar antenna for 5G applications. The proposed planar antenna has been measured, and the findings were subjected to a comprehensive analysis having dimensions of 13 * 15 * 1.5 mm3. Efficiency for the suggested radiator is 82% and a high gain of 4.81 dBi. Impedance bandwidth of design is 60.8%, a 4.5 GHz center frequency, and a 3.2–6 GHz frequency range. There is an intense radiation signal visible in the E-/H-field current distribution. Suggested design has totally stable radiation pattern. The distribution of surface currents shows a significant signal. This ‘TL’-shaped antenna is suitable for 5G microwave communication applications.