Introduction

Ultra-wideband (UWB) technology has garnered significant interest in due to its wide range of applications, including short-range communication and radar systems, particularly in the fields of biomedical imaging, Internet of Things (IoT), and intelligent wireless networks. UWB technology offers advantages such as high temporal resolution, low power consumption, and minimal interference with narrowband systems. However, challenges such as multipath interference, signal distortion due to environmental scattering, and electromagnetic compatibility with existing systems remain key obstacles to overcome in practical deployments. One of the most critical aspects in designing UWB antennas is the ability to reject specific interfering frequency bands on demand, including WiMAX (3.4–3.69 GHz and 5.25–5.825 GHz), C-band (3.7–4.2 GHz and 5.925–6.425 GHz), and WLAN (5.15–5.35 GHz and 5.725–5.825 GHz), without degrading the antenna’s broadband performance1,2. To address these issues, UWB antennas with frequency stop-band capabilities have been developed. However, fixed stop-bands can limit spectrum utilization when interference is absent3,4,5,6. Moreover, as the number of wireless nodes increases dramatically in IoT and smart city applications, there is a growing need for antennas that can dynamically adapt their frequency or radiation characteristics. Reconfigurable antennas offer a viable solution to these requirements by enabling dynamic control of parameters such as operating band, polarization, and radiation pattern. However, many reconfigurable designs suffer from drawbacks such as increased complexity, large size, or slow switching speed. Several techniques, including PIN diodes, varactors, and intelligent metasurface, have been proposed to address these issues. For instance, the recent study in7 demonstrated a metasurface-based antenna with pattern and beam reconfigurability for IoT applications, offering flexibility through unit-cell-level control. Despite these advancements, achieving compact, low-cost, and highly adaptive UWB antennas with reliable performance across various scenarios remains a pressing research challenges.

To address this challenge, researchers have proposed adjustable stop-band antennas, which allow selective switching of rejection bands to improve spectrum utilization and mitigate interference from coexisting narrowband systems. Several techniques have been employed to achieve reconfigurability in UWB antennas, including the use of PIN diodes2, Varactor diodes8, and RF-MEMS switches9. Each approach presents its own advantages and limitations. RF-MEMS offer high isolation and low insertion loss, making them suitable for high-performance applications; However, their fabrication is complex, expensive, and incompatible with standard PCB processes. Varactor diodes provide continuous tuning of the notch frequency by varying the bias voltage, which enables fine frequency control, but they suffer from nonlinearity, limited tuning range, and increased circuit complexity. In contrast, PIN diodes offer a simple, low-cost, and reliable method for implementing reconfigurable notches. Their binary ON/OFF switching capability is particularly effective for creating discrete operational states in microstrip monopole antennas, enabling wide tuning across multiple frequency bands without requiring bulky structures or specialized materials10. Furthermore, PIN diodes are compatible with standard PCB manufacturing processes and consume relatively low DC power. Adjustable antennas based on PIN diodes have been widely explored, demonstrating selective rejection of WiMAX, WLAN, and other interfering bands10,20. Nevertheless, challenges such as achieving multi-band rejection without increasing antenna size or compromising radiation characteristics still persist. Despite these challenges, the balance of simplicity, efficiency, and scalability makes PIN diodes one of the most practical and widely adopted solutions for reconfigurable UWB antennas.

In10, adjustability is achieved through the strategic placement of three PIN diodes, enabling eight operational modes. Reference11 uses five PIN diodes to provide three modes at UWB, WiMAX, or WLAN bands by adjusting the diode states, resulting in three distinct antenna configurations. In12, four diodes are used on T-strips and stubs, enabling independent control of the notch bands for WiMAX and WLAN. Likewise13, achieves dual-band adjustability for WiMAX and X-band by activating two diodes placed on C-shaped slots. Reference14 presents a triple-band frequency-adjustable monopole antenna for long-range IoT applications using two RF PIN diodes. In15, a triple-band notch is realized with U-shaped slots and three PIN diode switches, providing eight adjustable states within the UWB spectrum. Reference16 introduces adjustability through a PIN diode in a Slot-Type Split-Ring Resonator (ST-SRR) structure. In17, single, dual, and triple-band notch functions are made adjustable via switch modes on slots, while18 employs a square-shaped metallic loop in the upper ground plane with a PIN diode for switching notched bands. Reference19 demonstrates a frequency- adjustable antenna that can switch between UWB, narrowband, and dual-band modes using a switchable slotted structure. Lastly20, achieves adjustable band-notched performance by placing two PIN diodes in slots for notch band switching. Despite these improvements, most of the existing designs can’t completely eliminate all typical interference bands, including WiMAX, WLAN, and C-band, while also providing independent switchability. Furthermore, achieving adjustability frequently results in larger antenna dimensions. Recently, several compact reconfigurable UWB antennas have been proposed to overcome some of these limitations. In21, a miniaturized UWB antenna (15 × 20 × 1.6 mm³) integrates two PIN diodes to enable switching between UWB mode and single/dual-notch modes, demonstrating a compact structure and moderate gain performance. In22, a flexible PDMS-based antenna employs PIN diodes to transition between UWB and narrowband modes using a built-in filter, making it suitable for wearable devices. A highly selective stop-band UWB antenna with reconfigurable quasi-perfect notches using EBGs and PIN diodes is introduced in23, offering sharp rejection bands and dynamic switching among several operational modes. Moreover24, presents a compact MIMO antenna based on a staircase-shaped quasi-fractal design with a parasitic patch and integrated notch band, specifically designed for on-body and WBAN application.

Wireless Body Area Networks (WBANs) are widely used in healthcare, public safety, and defense for monitoring and communication. They are categorized into wearable and implantable systems, with wearable systems further divided into on-body, in-body, and off-body communication links25. This study focuses on in-body wearable systems. Breast cancer remains a major global concern, necessitating antennas for microwave imaging. Key challenges include size, gain, efficiency, and impedance bandwidth. While various wideband antennas have been developed, printed monopole antennas are preferred for their compact design and broad frequency coverage. To ensure human safety, the Specific Absorption Rate (SAR) is a critical parameter in wireless devices, with regulations requiring SAR levels below 1.6 W/kg (FCC) or 2 W/kg (ICNIRP). Various techniques have been employed to meet these standards. Given these requirements, a novel compact UWB printed antenna with dual-band-stop capabilities offers great potential for breast cancer detection25-27.

To address the limitations of conventional UWB antennas in interference rejection and system compatibility, this paper presents a novel in-body adjustable UWB monopole antenna that integrates triple-band notch capabilities and improved impedance bandwidth performance using an innovative arrangement of multiple PIN diodes and optimized slot geometries, specifically for advanced biomedical and body-centric wireless applications. The proposed structure distinguishes itself from prior works through a hybrid symmetrical and asymmetrical diode-switching configuration that enables 16 distinct operational modes, allowing adaptive interference suppression across WiMAX, WLAN, and C-band satellite communication bands. Bandwidth enhancement is achieved by incorporating two modified L-shaped slots in the ground plane, while the reconfigurable notch functionality is realized using two PIN diodes embedded in a modified W-shaped slit, two Γ-shaped slits, each integrated with PIN diodes, on the radiating patch, and a T-shaped stub in the ground. Simulation results demonstrate a wide impedance bandwidth (VSWR < 2) spanning from 3 GHz to beyond 17 GHz, along with configurable notch bands at 3.85–4.8 GHz, 5.15–5.75 GHz, and 5.95–7 GHz. This versatility renders the design highly suitable for reconfigurable biomedical implants, wearable devices, and smart body-centric wireless communication systems. The proposed approach offers compactness, flexible notch generation, and suitability for in-body environments, which collectively distinguish this design from prior works.

Antenna design and dimensions

The design of the proposed adjustable triple-band rejection ultra-wideband printed monopole antenna is shown in Fig. 1. This antenna is constructed on an FR4 substrate measuring 18 mm × 12 mm × 0.8 mm, with a relative dielectric constant of 4.4. To ensure a characteristic impedance of 50 Ω across the operational frequency range of 3–17 GHz, the width (Wf) is set at 1.5 mm. The impedance of this feed line can be determined4:

$${Z_c}=\frac{{120\pi }}{{\sqrt {{\varepsilon _{reff}}} \,\,[\frac{{{W_f}}}{h}+1.393+0.667\ln (\frac{{{W_f}}}{h}+1.444)]}}$$
(1)

.

where h is the height of the substrate. εreff is the effective dielectric constant and is given by:

$${\varepsilon _{reff}} = {\text{ }}\left( {{\varepsilon _r} + {\text{ }}1} \right)/2$$
(2)

For a characteristic impedance (ZC) of 50 Ω, a substrate dielectric constant (εr) of 4.4, and a substrate height of 0.8 mm, the width (Wf) has been determined as 1.5 mm. The design incorporates switching elements, including microstrip patches designated as D1, D2, D3, and D4, which are integrated into the resonant structure to facilitate switchable multi-band-stop functionalities. Also, initial values for length of the patch (L) and width of the patch (W) are chosen to determine the dimensions of the designed radiating patch, as outlined below:

$$W=\frac{{{\nu _0}}}{{2{f_{center}}}}\sqrt {\frac{2}{{{\varepsilon _r}+1}}},\quad L={{{\lambda _{lower}}} \mathord{\left/ {\vphantom {{{\lambda _{lower}}} 4}} \right. \kern-0pt} 4}$$
(3)

where λlower, and fcenter are the lower bandwidth wavelength and center of operating frequencies, respectively28.

The incorporation of two specially designed L-shaped slots in the ground plane significantly enhances the antenna’s broadband performance. These slots alter the electromagnetic interaction between the patch and the ground plane, resulting in the creation of additional resonances at higher frequencies. This design enhances the impedance bandwidth without necessitating an increase in size or cost. Additionally, the design of the ground plane affects the inductive and capacitive properties of the input impedance, consequently modifying the bandwidth characteristics3.

This research establishes adjustable triple-band rejection features centered at 4.3 GHz, 5.6 GHz, and 6.5 GHz by integrating four PIN diodes into a W-shaped slit and two Γ-shaped slits within the radiation patch. These configurations also affect the input impedance’s inductance and capacitance, which in turn influences the overall bandwidth. The antenna is designed with longitudinal symmetry in mind. The optimized dimensions of the antenna are detailed as follows: Lsub = 18 mm, Wsub = 12 mm, Lf = 7 mm, Wf = 1.5 mm, Lb = 7 mm, Wa = 2 mm, Wc = 2.25 mm, La = 7 mm, WT = 4 mm, Ld = 4.5 mm, Lc = 3 mm, WL = 4.5 mm, Lgnd=4 mm, Wr=3.25 mm, Wp=4.25 mm, Lm = 4.5 mm and Wb = 1.8 mm.

Results and discussions

This section explores various aspects of the constructed antenna structure, offering insights into the behavior of each parameter and helping to identify their optimal values. The geometry analysis is conducted using Ansoft HFSS™ software. The antenna design incorporates two uniquely configured L-shaped slots in the ground plane, which are intended to optimize impedance matching, increase bandwidth, and promote resonance at elevated frequencies.

Figure 2 illustrates the simulation process for the antenna’s multi-resonance and multi-stop-band performance. Figure 3 compares the impedance matching effects of the two adapted L-shaped slots against an identical antenna configuration without these slots. As shown, a simple monopole antenna (structure 1) demonstrates poor impedance matching beyond 10.3 GHz for VSWR < 2. Conversely, the addition of the two modified L-shaped slots increases the impedance bandwidth from 3 GHz to over 18 GHz by introducing additional resonant modes. Moreover, Fig. 3 demonstrates the impact of the modified structures, which consist of a W-shaped slit, adjusted Γ-shaped slits in the radiating patch, and a redesigned T-shaped stub in the ground plane (filter structures). By incorporating a redesigned T-shaped stub with optimized dimensions in the ground plane (structure 3), a stop-band is achieved near 6.2 GHz. Additionally, the addition of a pair of modified Γ-shaped slits in the radiating patch generates another band-stop around 5.1 GHz, resulting in two stop-bands (5.1 GHz and 6.3 GHz) in structure 4. The addition of a modified W-shaped slit to structure 4 creates an additional band-stop around 4.3 GHz, yielding triple-band-stop characteristics (4.3 GHz, 5.6 GHz, and 6.4 GHz) in structure 5, as shown in Fig. 3. It is important to note that all the results presented in Fig. 3 are for the case where all the diodes in Fig. 1 are assumed to be in the OFF state, allowing the number of displayed states to be represented in a single figure.

Fig. 1
figure 1

Configuration and parameters of the proposed triple-band rejection antenna (blue lines are metal).

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Fig. 2
figure 2

The step-by-step development of the antenna used for multi resonance and rejection-band performances.

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To gain a better understanding of the physical mechanisms that enhance the impedance bandwidth and facilitate the triple band-stop characteristics of the proposed printed monopole antenna, the simulated current distributions for the structures shown in Fig. 2 are presented in Fig. 4. For structure 2, the current distributions on the ground plane at frequencies of 9.6 GHz and 16.2 GHz are illustrated in Fig. 4(a) and (b), where a significant concentration of current is observed along the edges of the modified symmetrical L-shaped slots. This concentration improves the antenna’s impedance at these specific frequencies by leveraging the resonant properties of the symmetrical L-slot. Furthermore, Figs. 4(c), (d), and (e) illustrate the current distributions for structures at the center of the band-stop frequencies (6.2 GHz for structure 3, 5.8 GHz for structure 4, and 4.3 GHz for structure 5). Here, currents primarily circulate around the band-stop structures, exhibiting opposite flow directions on the outer and inner edges. This counter flow results in the cancellation of radiation fields, allowing for the targeted high attenuation at the specified band-stop frequencies. Changes in the surface current account for the variations observed in the stop bands. The electrical length of the antenna is influenced by the ON or OFF states of the diodes, with the switching of the PIN diodes having a substantial effect on the antenna’s stop bands.

The length of the resonant slot, which is a multiple of quarter-wavelength, can be approximately determined as \(\:{L}_{total}\cong\:n{\lambda\:}_{g}/4\)4. To obtain the desired band-stop frequency, the wavelength is determined by\(\:{\lambda\:}_{g}=\lambda\:/\sqrt{{\epsilon\:}_{reff}}\). In our designed scheme, an effective starting point for the length (Lnotch1) is set at 4.3 GHz, with a guided wavelength (λgnotch1) of 42.45 mm. The equivalent stub length for the first notch band frequency is determined as:

$${L_{notch1}} = {\text{ }}0.5{\text{ }}mm + {L_a} + {\text{ }}(1{\text{ }}mm + 2.2{\text{ }}mm + {\text{ }}1{\text{ }}mm){\text{ }} + {L_a} + {\text{ }}0.5{\text{ }}mm = 19.2{\text{ }}mm\;$$
(4)

This length is approximately half of the corresponding guided wavelength (λgnotch1/2 = 21.22 mm). The second notch band length, Lnotch2, is set at 5.8 GHz, with a guided wavelength (λgnotch2) of 31.48 mm. Similarly, the equivalent length for the second notch band frequency can be calculated as:

$${L_{notch2}} = {W_a} + Lm + \left( {1{\text{ }}mm + 1.5{\text{ }}mm + 0.5{\text{ }}mm} \right){\text{ }} + {L_d} = {\text{ }}14{\text{ }}mm\;\;$$
(5)

This length is roughly half of the corresponding guided wavelength (λgnotch2/2 = 15.74 mm). The third notch band length, Lnotch3, is set at 6.2 GHz, with a guided wavelength (λgnotch3) of 29.45 mm. Similarly, the equivalent length for the third notch band frequency can be calculated as:

$${L_{notch3}} = {\text{ }}0.5{\text{ }}mm + {W_b} + {\text{ }}({L_{gnd}} - 0.5{\text{ }}mm){\text{ }} + {W_T} = 9.8{\text{ }}mm$$
(6)

This length is one-third of the corresponding guided wavelength (λgnotch3/3 = 9.81 mm). The required lengths for each notch band are determined using Eqs. (4), (5) and (6) and integrated into the antenna design. These lengths are then refined through optimization in HFSS software to improve performance.

Fig. 3
figure 3

Simulated VSWR characteristics of the various structures shown in Fig. 2 (All diodes are in the OFF state).

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Fig. 4
figure 4

Surface current curves for the structures depicted in Fig. 2: (a) Structure 2 at 9.6 GHz, (b) Structure 2 at 16.2 GHz, (c) Structure 3 at 6.2 GHz, (d) Structure 4 at 5.8 GHz, and (e) Structure 5 at 4.3 GHz.

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To analyze the effect of critical design parameters on the performance and bandwidth of the proposed antenna, a parametric study is conducted. In Fig. 5, the influence of the parameter WL pertaining to the structure 2 shown in Fig. 2 is investigated. The parameter WL was varied from 4 mm to 4.8 mm, and the optimal value of 4.5 mm was selected based on the observed results. For WL = 4.5 mm, a new resonance emerges around 16.2 GHz, contributing to an improved impedance bandwidth. For values of WL smaller than 4.5 mm, the impedance matching deteriorates at higher frequencies, leading to reduced overall performance. Conversely, for values greater than 4.5 mm, a new resonance occurs near 14 GHz, which, compared to the optimal case, results in a narrower impedance bandwidth. This parametric analysis highlights the critical role of WL in controlling the antenna’s bandwidth and ensuring its optimal operation in the desired frequency ranges. Figure 6 illustrates the VSWR variations with respect to changes in the parameter WT. As depicted in this figure, WT is varied from 2 mm to 6 mm to analyze its impact on the antenna’s performance. This analysis corresponds to the structure 3 shown in Fig. 2. Additionally, as the WT parameter changes from 7.9 GHz to 5.3 GHz, the stop-band changes. Increasing this parameter to 6 millimeters disrupts impedance matching at higher frequencies. Therefore, the optimal dimension for this parameter is 4 millimeters. Figure 7 shows the changes in the parameter Wb for Structure 3. This figure illustrates that varying the Wb parameter from 1.2 mm to 1.8 mm shifts the stop-band from 6.5 GHz to 5.9 GHz. Additionally, as the parameter exceeds 1.8 mm, impedance matching at higher frequencies is disrupted, leading to a reduction in the impedance bandwidth. Therefore, the optimal dimension for this parameter is 1.8 mm.

Fig. 5
figure 5

Simulated VSWR characteristic of the proposed antenna for various WL.

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Fig. 6
figure 6

Simulated VSWR characteristic of the proposed antenna for various WT.

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Fig. 7
figure 7

Simulated VSWR characteristic of the proposed antenna for various Wb.

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While the antenna can function in 16 different configurations due to the presence of four PIN diodes, we concentrate on four distinct operating modes because D1 and D2 are symmetrical, as are D3 and D4. These modes are outlined in Table 1, and Fig. 8(a) presents the simulated VSWR results for each. The ability to switch between stop bands at different frequencies is apparent in these four modes, although this may lead to an asymmetrical design of the antenna. The first four symmetric switching states offer distinct practical advantages: State 1 (all diodes OFF) is ideal for general UWB applications requiring full-spectrum interference suppression; State 2 (all diodes ON) effectively mitigates lower-frequency WiMAX and early 5G interferences in urban areas; State 3 (D1 and D2 ON, D3 and D4 OFF) targets WiMAX and partial WLAN bands, making it suitable for dual-mode wearable devices; and State 4 (D1 and D2 OFF, D3 and D4 ON) offers dual-band rejection with reduced power consumption, optimized for low-power WBAN sensor nodes.

In addition to the four symmetric operating modes, five asymmetric switching configurations were also analyzed to further demonstrate the flexibility of the proposed antenna. The VSWR results for these five asymmetric states are shown in Fig. 8(b). These configurations correspond to partial ON/OFF combinations of the four PIN diodes, creating selective band-notch behavior adapted to specific practical needs. The corresponding switching conditions and resulting rejection bands are summarized in the Table 1, too. This extended study highlights the ability of the antenna to finely tune its frequency response depending on the required interference mitigation scenario, making it highly adaptable for dynamic UWB environments and WBAN applications.

For the proposed design, we utilized MACOM MA4P123-000 PIN diodes, which are recognized for their low capacitance and compact dimensions. These diodes exhibit a series inductance of 0.45 nH, a resistance of 1.5 Ω when in the ON state, and a parallel capacitance of 0.1 pF paired with a resistance of 10 kΩ in the OFF state29.

Table 1 Operative symmetric and some asymmetric states of proposed antenna.
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Experimental validation

Figures 9 (a) and (b) illustrate the simulated and measured VSWR curves for the UWB antenna featuring switchable triple band-stop characteristics, as well as the fabricated structure of the antenna. This antenna design supports operation in 16 different modes based on the diode states (ON or OFF). However, we focus on four primary operating modes: all diodes ON, all diodes OFF, D1 and D2 ON with D3 and D4 OFF, and D3 and D4 ON with D1 and D2 OFF. The results demonstrate a strong correlation with the simulated data, with only minor discrepancies likely due to fabrication tolerances and connector effects. The measurement results indicate that when all diodes are in the ON state, the antenna exhibits three stop bands at frequencies of 2.95–3.4 GHz, 4.3–4.85 GHz, and 5.75–6.75 GHz. Conversely, when all diodes are OFF, the stop bands shift to 3.85–4.58 GHz, 5.2–5.55 GHz, and 6–6.9 GHz. In the configuration where D1 and D2 are OFF while D3 and D4 are ON, two stop bands are observed at 3.8–4.55 GHz and 5.65–6.7 GHz. On the other hand, when D1 and D2 are ON and D3 and D4 are OFF, three stop bands are noted at 3.03–3.47 GHz, 4.45–5.38 GHz, and 5.85–6.7 GHz. Regardless of the diode state, the antenna design maintains UWB functionality, spanning a frequency range from 2 GHz to 17 GHz.

Fig. 8
figure 8

(a) Simulated VSWR for symmetric operating modes of PIN diodes, (b) Simulated VSWR for various asymmetric operating modes of PIN diodes.

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To characterize the radiation pattern of the fabricated antenna, two principal planes were selected: the yz-plane (E-plane) and the xz-plane (H-plane). Figure 10 illustrates the measured and simulated radiation patterns in both planes at frequencies of 4 GHz, 8 GHz, and 12 GHz. The xz-plane patterns demonstrate nearly omnidirectional characteristics across all three frequencies, while the yz-plane patterns display a distinct dumbbell shape. Additionally, Fig. 11 presents the simulated and measured peak antenna gain for two operating states: all diodes OFF and all diodes ON. As indicated, there is a noticeable reduction in gain at the stop-band frequencies of 4.3 GHz, 5.6 GHz, and 6.4 GHz when all diodes are OFF. In contrast, when all diodes are ON, a significant drop in gain occurs at the stopband frequencies of 3 GHz, 4.7 GHz, and 6.3 GHz. Outside these stopbands, the gain remains relatively stable, with variations of less than 2 dBi, confirming that the antenna maintains consistent performance across the operating band and validating the stopband characteristics of the design.

The Specific Absorption Rate (SAR) is a crucial parameter used to evaluate the safety of in-body antennas, as elevated SAR levels can have harmful effects on biological systems. SAR10g measurements are performed to ensure that the antenna operates within the safety limits, with international standards setting the SAR threshold at 2 W/kg, averaged over 10 g of tissue. In this study, a simple skin tissue model was used to assess the antenna’s effect on tissue, taking into account the conductivity and permittivity properties of the tissue, as shown in Fig. 12. The simulation results, presented in Figs. 13 and 14, show the highest SAR values for the antenna in skin and breast tissues. The maximum SAR value for the antenna is 1.475 W/kg, which is well within the limits set by both the FCC and ICNIRP guidelines. Additionally, as depicted in Figs. 13 and 14, increasing the distance d between the phantom and the antenna leads to a noticeable reduction in the maximum SAR value. This confirms that the designed antenna exhibits SAR values that are acceptable and comply with the established safety standards for in-body applications. All the SAR values shown in Figs. 13 and 14 are based on the antenna design with all diodes in the OFF state. These plots represent the SAR results for the OFF diode configuration.

It is worth noting that while the distance between the antenna and the tissue phantom has a noticeable effect on SAR values—as demonstrated in Figs. 13 and 14—the maximum SAR remains well below international safety limits even at the shortest tested distance. Specifically, the highest observed SAR10g value was 1.475 W/kg, which is within the ICNIRP guideline of 2 W/kg and the FCC limit of 1.6 W/kg. Therefore, no additional SAR reduction techniques, such as electromagnetic bandgap (EBG) structures or shielding layers, were necessary. The antenna’s geometry was carefully optimized to distribute current and field intensity in a manner that inherently limits SAR. This makes the design not only compact and high-performing but also safe for in-body applications without the need for external suppression structures.

Table 2 provides a comparison between the proposed antenna and other recent designs. The data shows that the proposed antenna is particularly compact, offering multimode switchable bands while maintaining a smaller footprint and wider impedance bandwidth compared to earlier UWB antenna designs. Moreover, it demonstrates satisfactory peak gain levels.

Fig. 9
figure 9

Photograph of the fabricated prototype, along with the measured and simulated results for the designed structure.

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Fig. 10
figure 10

Measured and simulated gain for the ON and OFF states of PIN diodes.

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Fig. 11
figure 11

Measured and simulated gain for the ON and OFF states of PIN diodes.

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Fig. 12
figure 12

Configuration of the compressed breast model with skin and breast tissue.

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Fig. 13
figure 13

SAR10g results at various frequencies for different distances in skin tissue.

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Fig. 14
figure 14

SAR10g results at various frequencies for different distances in breast tissue.

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Table 2 Comparison of designed antenna with the prior designs.
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Conclusion

This study presents a novel, compact, and reconfigurable UWB printed monopole antenna with enhanced impedance bandwidth and tunable triple-band notch characteristics. The antenna integrates a hybrid diode-switching mechanism comprising two PIN diodes in a modified W-shaped slit and two more in Γ-shaped slits, along with a T-shaped stub and dual L-shaped ground slots for performance optimization. A total of nine switching states—four symmetric and five asymmetric—were analyzed to demonstrate the antenna’s flexibility in dynamically suppressing interference in WiMAX, WLAN, and C-band satellite communication ranges. Analytical formulations for determining notch frequencies were also provided to support the design methodology. The antenna exhibits omnidirectional H-plane radiation patterns, compact dimensions, and excellent frequency agility while maintaining acceptable SAR levels for in-body biomedical applications. Comparative analysis with recent state-of-the-art designs highlights the antenna’s competitive advantages in terms of miniaturization, reconfigurability, and operational versatility. The simulated performance near a breast phantom further confirms the antenna’s suitability for wearable and in-body microwave imaging and WBAN environment.