A Compact Monopole Wideband Antenna Based on DGS

Abstract

This paper presents a compact monopole wideband antenna based on DGS. The ultimate geometry of the designed antenna is obtained after many design modifications and optimizations. A commercially available Taconic TLY substrate with a dielectric constant (ε_r) = 2.2, loss tangent (tan δ) = 0.0009, and thickness (h) of 1.524 mm is used. The dimension of the substrate is 34 mm × 28 mm. A 50Ω microstrip transmission line of size 12 mm × 3 mm is used to feed the antenna. Simulation results demonstrate a bandwidth from 4.08 to 18.92 GHz, a percentage bandwidth of 129% for S11 < −10 dB, and a peak gain of 7.4 dB. The DGS slots are embedded into the ground plane to enhance the antenna’s bandwidth, impedance matching, gain, and efficiency. For verification, the proposed antenna is fabricated and measured. Good agreement between measured and simulated results is observed. Thus, this antenna is appropriate for various modern wireless communication systems.

1. Introduction

Monopole patch antennas have gained significant attention in recent years due to their compact size, ease of fabrication, and versatility in various communication applications. The introduction of defected ground structures (DGSs) has further enhanced the performance of these antennas by improving bandwidth and reducing electromagnetic interference. This study focuses on the design and simulation of a DGS-based monopole patch antenna. The choice of Taconic TLY substrate, characterized by a low dielectric constant and minimal loss tangent, supports efficient radiation characteristics. The incorporation of L-slot and circular slot segment configurations in the ground plane allows for effective ground defection, which is critical in enhancing the antenna’s performance metrics.

There are different bandwidth enhancement techniques for monopole patch antennas, such as integrating DGS with air-loaded patches, DGS with fractal patch structures, modifying the patch and/or applying slots and using partial ground plane or DGS, frequency reconfiguration using pin diodes, DGS-based monopole patch, using different feed techniques such as using tapered feed with tapered patches and coplanar waveguide (CPW) feed. These have been suggested by antenna designers in order to achieve wider bandwidth.

In [1], a wide-bandwidth antenna DGS-integrated air-loaded wideband microstrip antenna for X- and KU-band is presented. The enhanced bandwidth is achieved by a simple and completely planar air-gap-loaded rectangular microstrip antenna integrated with a single shorting post and defected ground structures. This design has an impedance bandwidth ratio of 8.3–15.2 GHz. The suggested antenna’s gain ranges from 5 to 6.5 dBi. By modifying and applying optimized slots to patch and partial grounding or using DGS, it results in increased bandwidth. For example, special shapes with rounded structures and various optimized slots in partial grounds, which play a major role in producing desired wideband characteristics [2]. This antenna has a bandwidth of 1.73 to 12.73 GHz and a gain of 4.47 dBi. By increasing the size of the patch and the DGS in it, it is possible to have a wideband antenna [3]. A miniaturized planar antenna with optimized slots and DGS is designed [4]. This antenna has a range of bandwidth from 5.75 to 12.86 GHz and a peak gain of 5.4 dB. In a similar manner, a circular patch antenna with rectangular slots and DGS for UWB multiband applications [5] has a dual bandwidth from 4.98 to 8.08 GHz and 11.49–20 GHz and a gain of 6.9 dBi. The other technique is by using a modified plus-shaped microstrip patch antenna with DGS for UWB applications [6]. By incorporating DGS, the ultra-wideband (UWB) is achieved with a bandwidth of 8.85 GHz 6.39 to 14.73 GHz, and the peak gain obtained is 3.79 dBi at 7.1 GHz and 5.75 dBi at 12.8 GHz. A slotted monopole patch antenna design for UWB wireless applications [7] is presented. This multi-slot patch antenna that is designed, optimized, and analyzed with a partially slotted ground plane for UWB wireless applications has a bandwidth of 3.15 to 10.79 GHz and a gain of 3.22 dBi. Wideband monopole patch antennas can be designed by slotting the patch [8,9,10]. DGS-based Koch fractal antennae for S- and C-band applications are designed for wide bandwidths [11]. In this antenna the radiator is miniaturized by using the fractal technique, and wideband is achieved with the help of the defected ground structure technique, and it has a bandwidth from 1.76 to 4.29 GHz and a peak gain of 4.06 dB. A compact 8-state frequency reconfigurable UWB antenna with a bandwidth of 2.82 GHz to 13.25 GHz and a gain of 5 dBi in [12]. Here, three PIN diodes are connected across the C-slots and inverted U-slot, and by controlling the on/off state of PIN diodes, realize notch reconfiguration. Defected ground structure-based monopole patch antennas are common to design wider band antennas [13,14,15,16,17,18,19,20]. A unique patch of octagon shape connected to a 50 Ω microstrip feed line on a top plane in addition to the partial ground on the bottom plane. The patch tapering results in bandwidth improvement [21]. It has simulation results as bandwidth from 2.8–13 GHz and a gain of 4.64 dBi. Particle swarm optimization (PSO) is involved in determining the distribution of control points both on the radiator and ground plane. The antenna configuration that uses a straight CPW feedline is then changed by applying a tapered CPW feedline to suppress the notch response that occurred, thereby yielding a single wide bandwidth response to accommodate UWB applications [22]. This shows bandwidth is from 1.76 to 20 GHz.

This study presents a compact monopole wideband antenna based on DGS, designed to enhance communication efficiency through a compact form, increased bandwidth, and improved impedance matching. The design process encompasses three key stages: reconfiguration, characterization, and evolution. Initially, the conventional rectangular radiator was reconfigured into asymmetric U-shaped and G-shaped designs. Characterization of these designs identified the G-shaped antenna as superior due to its wider bandwidth and better impedance matching. In the evolution stage, DGS was incorporated to further enhance performance by strategically adding an L-slot and a semi-circular slot, resulting in a bandwidth increase from 2.71 to 14.84 GHz. The novelty of this antenna lies in its dual-slot configuration that effectively defects the ground plane, enabling multi-frequency operations suitable for modern wireless communication systems. With overall dimensions of 34 mm × 28 mm, this compact design can be seamlessly integrated into various portable devices. The iterative design process, illustrated in the accompanying figures, showcases significant enhancements and systematic improvements in the antenna’s performance. The detailed evolution performance analysis presented in

Table 1. Performance analysis of a compact monopole wideband antenna based on DGS evolution.

Stages of Evolution	Type of Shaped Slots to DGS	Obtained Frequencies (GHz)	3D Gain Plot (dBi)	Bandwidth (GHz)	Total Bandwidth (GHz)	Total Bandwidth (%)
1	Standard ground plane	8.85	6.8	8.79–8.93	2.71	20.5
		15.57		15.03–17.60
2	L-slot	6.77	4.32	4.18–7.64	9.35	77.8
		8.2		8.12–8.37
		13.57		12.9–17.45
		19.51		18.77–19.86
3	Semi-circular segment	16.90	4.18	4.08–18.92	14.84	129.04

highlights various design stages and their outcomes, showcasing the systematic approach towards enhancing the antenna’s characteristics based on the DGS methodology.

The remainder of this paper is organized as follows: Section 2 presents antenna design methodology and optimization process; Section 3 discusses the simulation results and analysis; Section 4 presents fabrication measurements and a comparison of the antenna with previous works; and Section 5 summarizes the paper.

2. Antenna Design Methodology and Optimization Process

2.1. Initial Antenna Design

The antenna is constructed on a Taconic TLY dielectric substrate with a dielectric constant of ε_r = 2.2, a loss tangent of (tan δ) = 0.0009, and a thickness of 1.524 mm. A 50 Ω microstrip line is connected to excite the antenna and to reduce incident wave rejection. The center frequency was set to 11.5 GHz. Equations (1)–(7), Ref. [23] are used to determine the initial dimensions of the antenna radiators’ width (w) and length (L). In this design we used half of the center frequency to calculate the width and length of the patch or ground plane by considering the DGS. Here also L_S is used as W_S and vice versa for the substrate or ground plane for convenience of the design.

Patch width (w) and effective permittivity (ε_reff):

$$\mathrm{w}={\displaystyle \frac{c}{2f_c}}\sqrt{{\displaystyle \frac{2}{{\epsilon }_r+1}}}$$

(1)

$${\mathsf{\epsilon }}_{\mathrm{reff}}= {\displaystyle \frac{{\mathsf{\epsilon }}_r+1}{2}}+{\displaystyle \frac{{\mathsf{\epsilon }}_r-1}{2}}{\left[1+12{\displaystyle \frac{h}{w}}\right]}^{-1/2}$$

(2)

Patch length (L) and length for fringing fields, ΔL is written as follows:

L = L_eff − 2ΔL

(3)

$${\mathrm{L}}_{\mathrm{eff}}={\displaystyle \frac{c}{ 2f_{c\sqrt{{\mathsf{\epsilon }}_{reff}}}}}$$

(4)

$$\mathrm{\Delta }\mathrm{L}=0.421\mathrm{h}{\displaystyle \frac{\left({\mathsf{\epsilon }}_{reff}+0.3\right)}{{(\mathsf{\epsilon }}_{reff}-0.258)}}{\displaystyle \frac{\left(\frac{w}{h}-0.246\right)}{\left(\frac{w}{h}-0.813\right)}}$$

(5)

Substrate dimension is calculated as follows:

L_S = L + 6h

(6)

W_S = W + 6h

(7)

where W refers to the patch width, c refers to the vacuum light speed, fc is the center frequency, ε_r is the relative dielectric permittivity, ε_reff is the effective permittivity of the substrate, h is the substrate height, and L is the patch length. It is important to consider the transmission line width (W_f) when calculating radiation intensity because it directly impacts the signal’s bandwidth. By plugging in values for the desired impedance (Z₀), thickness of copper (t), dielectric thickness (h), and relative dielectric constant (ε_r), the fundamental Equation (8) can be used to calculate the width of the microstrip line [23].

$$W_f={\displaystyle \frac{7.48\times \mathrm{h}}{e^{\frac{z_0\times \sqrt{{\mathsf{\epsilon }}_r\times 1.41}}{87}}}}-1.25\times \mathrm{t}$$

(8)

In accordance with the fundamental equation, the width of the transmission line was calculated to be 4 mm when the impedance is 50 Ω, copper thickness is 0.035 mm, dielectric thickness is 1.524 mm, and dielectric constant is 2.2.

By using the basic monopole antenna Equations (1)–(7), the antenna’s initially optimized dimensions were derived at the beginning of the design as W = 23 mm, L = 20 mm, L_S = 28 mm, and W_S = 34 mm (Figure 1a). Afterward, we analyzed the next better antenna from the asymmetric U-shaped antenna and G-shaped antenna through antenna characterization and then finally developed the proposed antenna using the antenna evolution method.

2.2. Reconfiguration and Characterization of Antenna

To enhance radiation performance and achieve a compact size, the conventional rectangular patch antenna, Figure 1a, was reconfigured into asymmetric U-shaped and G-shaped designs. The total area of the original antenna was 20 × 23 mm². To obtain the G-shaped antenna involved removing 23.70% (109 mm²) of the total area, while the asymmetric U-shaped antenna reduced the total area by 18.04% (83 mm²), Figure 1b. The dimensions of the U-shaped patch, L-slot, and semi-circular slot of the G-shaped patch are obtained by the trial-and-error method.

Characterization was performed on both reconfigured designs mounted on a substrate-sized ground plane of 28 × 34 mm² with a 50 Ω impedance-matched stepped feed line. The simulated reflection coefficient (S11) plots are shown in Figure 2d. The G-shaped antenna exhibited notch bands at 8.79–8.93 GHz and 15.03–17.60 GHz, resulting in a total bandwidth of 2.71 GHz. In contrast, the asymmetric U-shaped patch displayed bands at 6.50–6.65 GHz, 16.37–16.63 GHz, and 19.83–20.48 GHz, with a total bandwidth of 1.06 GHz.

Based on these results, the G-shaped patch is preferred for further characterization and evolution due to its superior impedance matching and wider bandwidth. The use of a DGS was then explored to enhance bandwidth and gain. The DGS geometry incorporates two slots (L-slot and semi-circle slot), improving antenna performance by altering surface current distribution and modifying transmission line characteristics, including inductance and capacitance. The proposed antenna with a conventional ground plane and optimized DGS is illustrated in Figure 3a–c. The S₁₁ responses for both configurations are presented in Figure 3d, highlighting the transformation of notched bands into a passband, which is essential for achieving wideband characteristics. Thus, the parametric analysis will focus on the DGS structure evolution.

Using DGS in the ground plane alters the surface current distribution in a microstrip antenna, leading to a wider operating frequency band. This disturbance affects transmission line characteristics by modifying parameters such as inductance, capacitance, and resistance between the feed line and the slot. Specifically, having a DGS beneath the feed line changes its effective capacitance and inductance due to the added slot effects. Consequently, the resonance frequency of a DGS-based antenna differs from that of a standard ground plane. Notably, the effective capacitance is inversely related to the DGS slot area, while the effective inductance is directly proportional to it.

2.3. Evolution of the Proposed Antenna Design

The design evolution of the proposed antenna begins with a G-shaped radiator and a conventional rectangular ground plane on a 1.524 mm thick Taconic TYL substrate, referred to as antenna-1 (stage-1), as shown in Figure 4a. This configuration yields two notch bands: 8.79–8.93 GHz and 15.03–17.60 GHz, resulting in a total bandwidth of 2.71 GHz. In the second stage, antenna-2 (stage-2) introduces an L-slot with an area of 404.43 mm² at the center of the ground plane (Figure 4b). This modification enhances performance, producing four notch bands: 4.18–7.64 GHz, 8.12–8.37 GHz, 12.9–17.45 GHz, and 18.77–19.86 GHz, with a total bandwidth of 9.35 GHz, significantly improving upon antenna-1. The final design, antenna-3 (stage-3), features a semi-circular slot across the horizontal of the L-slot with a radius (R_S = 2.6 mm), transforming the notch bands into a passband (Figure 4c). Note that for all three stages, the top patch is kept constant, while the lower or ground patch is modified at three different stages. This results in a wideband antenna with a bandwidth of 14.84 GHz (4.08–18.92 GHz) at S₁₁ < −10 dB, achieving maximum gains of 4.18 dBi at 16.90 GHz and a peak realized gain of 7.4 dB at 15.5 GHz. In summary, the evolution from stopband to passband involved iterative design improvements aimed at enhancing performance across a broader frequency range. The introduction of the L-slot and semi-circular slot significantly shaped the radiation pattern, minimized unwanted reflections, and increased bandwidth, ultimately optimizing the antenna’s overall performance as depicted in Figure 5, resulting in a much better reflection coefficients observed than previous stages.

2.4. The Proposed Antenna Designs

Various modifications at Figure 1, Figure 2 and Figure 4 were made to achieve the proposed antenna suitable for wireless networks, satellite systems, and/or IoT applications. The final dimension of the proposed design was the same as the initial antenna for characterization except for the reduction in thickness of the feed line from 4 mm to 3 mm. The proposed antenna geometric layout is depicted in Figure 6, featuring a simpler stepped-fed patch and L-slot inserted at the center region of the patch, and a major semi-circle is embedded adjacent to the bottom of the L-slot along the feed line on the ground plane. The area and dimensions of the DGS slots are optimized by parametric analysis.

The antenna’s overall dimension is 34 × 28 × 1.524 mm³. The size of the optimized feedline is 3 × 12 mm².

Table 2. Dimensions of the proposed antenna.

Symbol	Dimension (mm)	Symbol	Dimension (mm)	Symbol	Dimension (mm)	Symbol	Dimension (mm)
Ls	34	d	9	Lt	4	T	11
Ws	28	a	1	LVS	24	S	17.13
f1	3	b	1	c	1	U	13
Lf1	10	K	6	e	6	WVS	8.87
f2	4.5	Pv	20	Q	8	Hp	23
f3	6	VW	6	RS	2.6	m	1

contains all the optimized design parameters of the proposed antenna. The 2022 high-frequency structure simulation (HFSS) was used to achieve optimal bandwidth, gain, and performance.

2.5. Parametric Analysis

The antenna’s performance is influenced by key electrical and geometric parameters, including radiator dimensions, DGS features, feed gap, feed type, and substrate dielectric constant. A parametric analysis was conducted on the DGS dimensions to assess their impact on surface current distribution, which alters the feed line’s inductance and capacitance. Introducing rectangular and circular defects enhances effective inductance and fringing electric fields, increasing parasitic capacitance and improving bandwidth through better coupling between the ground and feed. In this study, by using Figure 3b, one parameter was varied at a time while keeping others fixed, optimizing the antenna’s ground to a DGS-based partial ground plane. The analysis focused on the effects of varying dimensions on essential performance metrics, specifically bandwidth and reflection coefficient (S₁₁). Key findings included length of L-slot vertical (L_VS), width of L-slot vertical (W_VS), spacing of L-slot horizontal (S), thickness of L-slot horizontal (T), and radius of semi-circular slot (R_S).

2.5.1. Effect of Length of L-Slot Vertical (Lvs)

Varying Lvs at 18, 20, and 24 mm revealed a maximum bandwidth of 4.08–18.92 GHz and optimal impedance matching at Lvs = 24 mm. The simulated S₁₁ for various Lvs values is shown in Figure 7a. The lower the length of Lvs, the shorter the bandwidth coverage of the antenna, and this resulted in generating a dual-band response.

2.5.2. Effect of Width of L-Slot Vertical (W_VS)

The Adjusting W_VS to 3.87, 8.87, and 10.87 mm showed that W_VS = 8.87 mm provides better impedance matching and a bandwidth of 14.84 GHz. The simulated S₁₁ for various Wvs values is shown in Figure 7b, while other values resulted in reduced bandwidth. It offers reduced bandwidth and impedance matching with a change in resonance frequency.

2.5.3. Effect of Spacing of L-Slot Horizontal (S)

Changing S to 12.13, 15.13, and 17.13 mm achieved maximum bandwidth and improved impedance matching at S = 17.13 mm. The simulated S₁₁ for various S values is shown in Figure 7c. Smaller spacings led to decreased bandwidth.

2.5.4. Effect of Thickness of L-Slot Horizontal (T)

Varying T at 8, 11, and 14 mm indicated that T = 11 mm yielded the best performance. The simulated S₁₁ for various T values is shown in Figure 7d, while other values resulted in reduced bandwidth.

2.5.5. Effect of Radius of Semi-Circular Slot (R_S)

Finally, the analysis of R_S at 1.6, 2.6, and 3.6 mm revealed that R_S = 2.6 mm optimizes bandwidth and impedance matching. The simulated S₁₁ for various R_S values is shown in Figure 7e, while other radii produce less favorable results. As a conclusion, the parametric analysis underscores the sensitivity of the DGS-based monopole patch antenna to variations in design dimensions, which are crucial for enhancing performance metrics like bandwidth and reflection coefficient. Each parameter significantly affects these metrics, emphasizing the need for careful optimization.

3. Simulation Results and Analysis

3.1. Reflection Coefficient (S₁₁) and Voltage Standing Wave Ratio (VSWR)

Figure 8a shows the reflection coefficient graph with a significant null at 16.90 GHz, where the S₁₁ value is −48.59 dB. This low S₁₁ confirms that the antenna is well-tuned, reflecting minimal power. The graph also displays multiple resonant peaks and valleys across the 4.08 GHz to 18.92 GHz range, indicating a broad operational bandwidth for effective performance. Figure 8b presents the VSWR graph, showing a value of 1.01 at 16.90 GHz, which signifies exceptional impedance matching and efficient power transmission with negligible standing waves. Together, the analyses of S₁₁ and VSWR highlight the antenna’s excellent performance. The deep null in S₁₁ corresponds with the low VSWR, confirming efficient operation at this frequency. The multiple resonances suggest versatility across a wide range, with the VSWR indicating minimal power loss.

Design modifications, including slots in the ground plane, have enhanced the antenna’s low reflection and high efficiency. Overall, the combined analysis demonstrates that the antenna is optimized for performance, making it a reliable choice for various wireless communication applications.

3.2. Surface Current Distribution

The antenna shows distinct characteristics due to the L-slot and semi-circular slot defects in the ground plane. Analyzing the surface current distribution at frequencies of 2.5 GHz, 7.5 GHz, 12.5 GHz, and 17.5 GHz, Figure 9a–d offers insights into the antenna’s performance. At low frequency (2.5 GHz), the surface current is mainly concentrated at the edges of the patch, indicating strong coupling with the ground. The L-slot has minimal impact on current distribution, with most current remaining within the patch. At mid frequency (7.5 GHz), as frequency increases, the surface current patterns become more complex. The current spreads more uniformly across the patch while maintaining significant edge currents. The L-slot enhances impedance matching and bandwidth, while the semi-circular slot improves radiation characteristics. Near center frequency (12.5 GHz); at this frequency, the current distribution is well-balanced, with strong currents in the patch and around the slots. Ground plane defects enhance radiation efficiency, resulting in a low S₁₁ parameter (−48.59 dB) and low VSWR (1.01). This reflects optimal antenna performance and effective energy radiation. At high frequency (17.5 GHz), the current distribution indicates operation in a higher order mode, with currents concentrated towards the center of the patch. The slots enable a unique distribution that supports higher frequency operation, achieving a peak gain of about 7.4 dB. This shift in distribution affects radiation patterns and overall gain. Overall, the surface current distribution analysis reveals key insights into the patch antenna’s performance. The L-slot and semi-circular slot effectively optimize current flow, enhancing bandwidth and gain. As frequency increases, the current distribution becomes more complex, leading to improved radiation efficiency at the target frequency of 11.5 GHz. This analysis underscores the importance of ground plane modifications in achieving desired antenna characteristics.

3.3. Peak Gain

The peak gain analysis of the antenna, shown in Figure 10a, reveals key characteristics. Operating from approximately 4.08 GHz to 18.92 GHz, the DGS technique, featuring L-shaped and semi-circular slots, facilitates this broad range. A maximum gain of about 7.4 dB occurs at 15.5 GHz, demonstrating the design’s effectiveness at higher frequencies. Although gain fluctuates across the spectrum, it remains above 4 dB for most of the bandwidth, ensuring reliable performance. At 5.5 GHz, the gain is approximately 4.1 dB, indicating successful optimization for the intended application. Overall, the DGS design enhances gain characteristics and operational capabilities, making it suitable for various wireless communication applications. The maximum gain of the antenna was measured at 0⁰ elevation.

3.4. Total Efficiency

The total efficiency graph at Figure 10b illustrates the antenna performance across frequencies, showing values from 63% to 92%. Most frequencies maintain high efficiency (above 78%), with a notable dip to around 63% at certain points. This indicates strong radiation efficiency with minimal losses. The drop-in efficiency may relate to specific resonances or bandwidth limitations from the ground plane slots. Overall, the antenna generally performs well, though some frequencies warrant further investigation. Overall, the design effectively supports the intended frequency range, and DGS enhances performance through improved impedance matching and radiation characteristics.

3.5. Radiation Pattern

The radiation pattern analysis of the designed patch antenna at frequencies of 6 GHz, 7.5 GHz, 9.5 GHz, and 11 GHz (Figure 11 and Figure 12) provides insights into its performance characteristics, including directivity, gain, and overall efficiency. At 6 GHz, the radiation pattern exhibits a broad main lobe, suggesting effective energy distribution. Sidelobes are minimal, indicating good directivity and reduced unwanted radiation, which enhances the antenna’s performance for applications in this frequency range. At 7.5 GHz, the main lobe remains pronounced, with a slight shift in direction compared to the 6 GHz pattern. The overall gain appears to increase, reflecting improved efficiency in energy radiation, which is beneficial for communication applications. At 9.5 GHz, the radiation pattern becomes more concentrated, with a narrower main lobe indicating enhanced directivity. This change likely results from the optimal operation of the slots in the ground plane, which affects the current distribution and improves performance. At 11 GHz, the pattern shows a well-defined main lobe, indicating strong performance at the antenna’s center frequency.

Further minimization of sidelobes suggests excellent radiation efficiency and directivity, confirming that the antenna is effectively tuned for this frequency. Overall, the analysis of the simulated radiation patterns from 6 GHz to 11 GHz demonstrates that the antenna maintains good performance across the tested frequencies. The presence of the L-slot and circular slot significantly enhances the radiation characteristics, contributing to improved directivity and overall gain. The patterns indicate that the antenna is well-suited for dual-band operation, showcasing effective energy radiation and minimal sidelobe interference, confirming its applicability for various wireless communication applications. The theta and phi of the 2D and the 3D are obtained at (0$\le \theta \le \pi$), and phi ranges from ($0\le \phi \le 2\pi$).

3.6. Parametric Analysis on G-Shaped Patch Antenna

Parametric optimization and analysis were conducted to assess the effects of the dimensions of the G-shaped patch antenna’s performance. Various parameters controlling the resonant characteristics and bandwidth were adjusted. This subsection presents key parameters influencing the antenna’s overall performance. In this study, one parameter was varied at a time while keeping others fixed to optimize the antenna structure. The analysis focused on the width of Lt, VW, and K of the G-shaped patch antenna to investigate their effects on key performance metrics, including reflection coefficient (S11) and bandwidth.

3.6.1. Effect of Variation of Lt

A parametric analysis was conducted on the length (Lt) of the G-shaped patch antenna to improve impedance matching and bandwidth, as shown in Figure 13a. Adjusting Lt from 3 mm to 5 mm in 1 mm increments revealed that Lt significantly impacts antenna performance. The simulated S11 values indicate optimal impedance matching and bandwidth at 4 mm length, while variations above or below 4 mm lead to dual-band behavior and higher S₁₁ values.

3.6.2. Effect of Variation of V_W

Adjusting the feed width of the G-shaped patch antenna to 5, 6, and 7 mm indicated that 6 mm provides optimal impedance matching and maximum bandwidth. When Vw deviates from 6 mm, the antenna exhibits higher S₁₁ values, demonstrating both dual-band and narrow frequency range (Figure 13b).

3.6.3. Variation of K

A parametric analysis was conducted on the dimension K to improve impedance matching and bandwidth, as shown in Figure 13c. Adjusting K from 5 mm to 7 mm in 1 mm increments revealed that K significantly affects antenna performance. The simulated S₁₁ values indicate optimal impedance matching and bandwidth at 6 mm length. The antenna illustrates less optimal bandwidth and impedance match for dimensions above and below 6 mm.

4. Fabrication, Measurements, and Comparison

The proposed fabricated antenna was shown in Figure 14a, while the measurement setup in the chamber room is provided in Figure 14b. The suggested prototype was fabricated on a Taconic TLY substrate (ε_r = 2.2, tan δ = 0.0009, h = 1.524 mm) and is tested using a vector network analyzer (VNA). The comparison of S₁₁ values between simulated and measured results (Figure 15) shows that the fabricated antenna achieves dual-band frequencies of 4.115–13.115 GHz and 15.32–18.425 GHz, with a total bandwidth of 12.1 GHz at VSWR < 2. In contrast, the simulated antenna has a bandwidth of 4.08–18.92 GHz. Limitations in the fabricated antenna’s bandwidth and S₁₁ values are attributed to fabrication tolerances, discrepancies between actual and nominal dielectric constants, dielectric losses, environmental influences, impedance matching issues, and the transition effects between the SMA connector and microstrip. Despite these differences, the overall consistency between simulated and measured results confirms the antenna’s suitability for various wireless communication applications. Future designs should focus on minimizing these discrepancies through improved fabrication processes and material selection.

4.1. The Measured Radiation Patterns

The measured 2D radiation patterns of the antenna at 6 GHz, 7.5 GHz, 9.5 GHz, and 11 GHz reveal its radiation characteristics and performance (Figure 16a–d). The wideband operation and ground plane slots significantly shape these patterns. At 6 GHz, Figure 16a, the pattern features a broad main lobe, indicating effective energy distribution and good directivity with low sidelobes. At 7.5 GHz, in Figure 16b, the main lobe is prominent but slightly shifted, showing increased gain and improved radiation efficiency. At 9.5 GHz, in Figure 16c, the pattern is more defined with a narrower main lobe, suggesting enhanced directivity due to optimal slot operation. At 11 GHz, Figure 16d, the well-focused main lobe indicates strong performance at the center frequency, with minimized sidelobes for excellent radiation efficiency. Overall, the analysis shows that the antenna performs well across the tested frequencies. The L-slot and circular slot enhance radiation characteristics, contributing to better directivity and gain, validating the design choices and ground plane modifications.

4.2. The Impedance Plot Analysis of the Antenna

The impedance plot illustrates the frequency-dependent behavior of the antenna’s input impedance, Figure 16. The impedance is represented as a complex quantity:

$$Z_{in}\left(f\right)=R\left(f\right)+jx\left(f\right)$$

(9)

where

$R\left(f\right)$ is the resistive component;

$jx\left(f\right)$ is the reactive component;

$f$ is the frequency in GHz.

The ideal impedance for most RF systems is 50 Ω (purely resistive). A good impedance match ensures maximum power transfer and minimal reflection.

The ideal input impedance for most RF systems is 50 Ω (purely resistive). A good impedance match ensures maximum power transfer and minimal reflection. The impedance plot confirms the effectiveness of the patch antenna design in achieving wideband impedance matching. The low S₁₁ value, near-ideal VSWR, and broad frequency coverage are a testament to the design enhancements provided by the L-slot and semi-circular slot on the ground plane. This design approach successfully meets the requirements for high-performance broadband antenna applications (Figure 17). The wide bandwidth is attributed to the introduction of the L-slot and circular slot, which create multiple resonant modes and improve current distribution. The impedance plot indicates an efficient radiation across a broad frequency range and a stable impedance matching, which will consequently minimize return losses.

4.3. Performance Comparison of the Antenna

Table 3. Comparison of this antenna with latest published related works in the references.

Reference	Antenna Size (mm3)	Bandwidth (GHz)	Gain dB	Year
[1]	60 × 60 × 1.575	8.3–15.2	5–6.5	2020
[2]	36 × 30 × 1.6	1.73–12.73	4.47	2020
[3]	50 × 30 × 3.2	1.3086	5.366	2023
[6]	38 × 48 × 1.6	6.39–14.73	5.75	2023
[11]	58 × 38 × 1.6	1.76–4.29	4.06	2023
[12]	22 ×13 × 0.8	2.82–13.25	5	2021
[13]	45 × 45 × 1.575	2.5–14	6.82	2021
[14]	34 × 38 × 1.6	2.68–10.39	(0.5–4.5)	2023
[15]	50 × 50 × 1.5	2.94–6.96	3.93	2021
[18]	43 × 33 × 1.6	2.45–11.3	3.96	2023
[20]	38 × 48 × 1.6	2.5–10.6	8.3	2021
[23]	73.84 × 64.6 × 1.6	1.3–3.7	6.15	2022
Proposed antenna	34 × 28 × 1.524	4.08–18.92	7.4	2025

summarizes the main performance of the proposed antenna with the parameters including size, impedance bandwidth, and gain. A comparison with other previous state-of-the-art wideband and UWB antennas is as shown. This antenna is compact in size and far better in bandwidth and gain. Thus, this broadband antenna is better in all parameters and appropriate for various wireless communication applications.

5. Conclusions

The compact monopole wideband antenna utilizing DGS with a Taconic TLY dielectric substrate exhibits excellent wideband performance, high gain, and effective impedance matching. The integration of L-shaped and semi-circular slots in the ground plane significantly contributes to these attributes. Comparative analysis with existing designs highlights the superiority of the proposed structure. Experimental results validate the close consistency between simulated and measured outcomes. The antenna achieves a wide bandwidth of 4.08–18.92 GHz, with a 3D gain of 4.18 dBi and peak gain of 7.4 dB at 16.90 GHz and 15.5 GHz, respectively. These results indicate efficient radiation and signal transmission, making it a promising candidate for wireless applications, including satellite communication, radar systems, and UWB systems.