Recently, the idea of reconfigurable antennas has made it feasible to design a single antenna that can support

multiple wireless standards while maintaining the same performance as multiple antennas. The integration of a

single antenna that can operate at multiple frequencies is required to enable multiple applications in a single

device. This paper presents a compact frequency-reconfigurable microstrip antenna designed to support multiple

wireless standards in modern communication devices. The proposed antenna, with dimensions of 30 × 15 × 1.52

mm³, is simulated using CST Studio Suite and achieves reconfigurability through the integration of PIN diodes

as switches within strategically placed slots on the radiating structure. By controlling the bias states of the two

dedicated radiators. This makes it highly suitable for integration into space-constrained devices such as

smartphones, laptops, tablets, IoT systems, and next-generation wireless networks. The proposed antenna

demonstrates versatile multiband/frequency agility compatible with WLAN, 5G, radio altimeters, military

radars, and weather radar applications, highlighting its potential to address the growing demand for efficient,

multifunctional antennas in emerging wireless ecosystems.

Reconfigurable antenna polarisations, radiation patterns, and operating frequencies are greatly desired due to the

explosive growth of wireless communications and the increasing need to integrate numerous wireless standards

onto a single platform [1]. Depending on the host system's operating needs, reconfigurable antennas alter their

[4] discusses various reconfigurable components that can be used on the antenna to change its structure and

function. Different possible mechanisms can be used for every possible reconfigurable process. Reconfigurable

antennas are utilized in various applications, including space and ground systems, for satellite communication

and mobile phone technologies, cognitive radio, and multiple-input–multiple-output (MIMO) systems. The re-

configurability can be obtained by a change in surface current distribution, feeding network, physical structure,

or radiating edges of the antenna, so a change in one parameter of the antenna can affect the other. Such antennas

are a solution to requirements like MIMO Applications, Direction finding, Cognitive Radio, Beam steering,

Radar command and Control. Therefore, more than one wireless standard can be accessed by using the

reconfigurable antennas.

A low-profile (0.21λg× 0.35λg× 0.02λg) and a simply-structured frequency-switchable antenna with eight

gain (>1.5 dBi in all modes) and reasonable efficiency (>82% in all modes) for each mode. Using a high-

frequency structure simulator (HFSS), the switchable antenna is designed and optimized. The fabricated model,

along with the PIN diode and biasing network, is tested experimentally to validate the simulation results. The

proposed antenna may also be combined in compact and heterogeneous radio frequency (RF) front-ends because

of its small geometry and efficient utilization of the frequency spectrum [15]

[17] A frequency reconfigurable Libra shape antenna has been presented to provide frequency reconfigurability.

Two PIN diodes are integrated into the designed antenna structure; thus, the antenna is operated in four different

modes. Each mode is characterised by specific resonant frequencies, reflection coefficients (S11), and

bandwidths, demonstrating the reconfigurability of the antenna. Between 26 and 40 GHz, the S11 values for the

operating in the S and C bands of the RF spectrum, which are overwhelmed by wireless applications.

Reconfiguration is achieved by using a single PIN diode on the ground plane. By varying the voltage applied to

the diode, three modes can emerge, exhibiting main resonant frequencies at 2.07, 4.63, and 6.22 GHz. Resonance

switching requires a voltage of less than 0.9 V. The antenna fabricated on an FR-4 substrate, with a volume of

70 x 60 x 1.5 mm3, has a radiating patch element of a rectangular ring shape. The proposed low-cost antenna is

easily implemented in a typical university lab-based environment. The total bandwidth for the three modes is

close to 1 GHz, while the voltage standing wave ratio (VSWR) of the fabricated version of the antenna does not

exceed 1.02, and the return loss is well below -40 dB for the three primary resonant frequencies.

[19] presents the design and evaluation of a compact-sized antenna targeting heterogeneous applications working

in the C-band, 5G-sub-6GHz, and the ISM band. The antenna offers frequency reconfigurability along with

wideband mode covering the C-band, Wi-Fi 6E, and the ISM band. Meanwhile, the multiband modes offer the

additional coverage of the LTE, LTE 4G, ISM lower band, and GSM band. The various performance parameters

are studied and compared with measured results to show the performance stability of the proposed reconfigurable

antenna. In addition, an in-depth literature review along with a comparison with the proposed antenna is

performed to show its potential for targeted applications. The utilisation of FR4 as a substrate of the antenna,

along with its compact size of 15 mm × 20 mm, while having multiband and multi-mode frequency

reconfigurability, makes it a strong candidate for present as well as for future smart devices and electronics.

[20] presents a frequency reconfigurable monopole antenna developed for UWB/Ku band applications. The

design employs a microstrip-fed Reuleaux-triangle-shaped patch with a defected ground structure. The antenna

exhibits a wide operating bandwidth achieved due to rectangular slits integrated into the Reuleaux-triangle patch.

Meanwhile, adding rectangular slots in the ground plane improves the return loss level. Frequency

with gains from 2.63 to 3.85 dBi. The antenna’s dynamic switching between UWB and Ku band operations

makes it suitable for applications such as satellite communications, health monitoring, 5G, aerospace, and remote

sensing.

while the patch and the ground plane are all designed using copper annealed. Table 1 lists all the antenna

parameters. The proposed antenna is fed using a coaxial feeding line method; it has a partial ground plane. The

antenna resonates at dual bands, 2.4 GHz and 6.3 GHz. The purpose of this design is to achieve dual band, to

operate on two distinct frequency bands simultaneously or selectively. This can be useful for improving network

performance, reducing interference, or expanding compatibility with different wireless standards.

Fig. 2 presents the same microstrip patch antenna which is designed in fig. 1, two slots with 1 x 2 mm width are

created in the radiating structure. The reason for creating the slot is to determine the position to put the PIN diode

switch. The proposed antenna is fed using a coaxial feeding line method and has a partial ground plane. Figure

1 presents the front and back view antenna. The purpose of this design is to identify the ideal position for placing

the slot in order achieve reconfigurability.

Fig. 4 present same microstrip patch antenna, which is designed using the same materials as in Figure 1, but the

slot in the patch of the antenna is replaced with a PIN diode switch in order to achieve frequency reconfiguration.

The purpose of this design is to facilitate frequency reconfiguration, allowing for the adjustment or modification

of frequencies as required. Figures below present the front and back view antenna.

Due to the commercial availability of the Rogers RO3003 substrate, the antenna design is now more viable and

inexpensive. Obtaining optimal gain, efficiency, and directivity is the antenna's advantage. For the antenna

excitation, a 50Ω microstrip line with a width of 5.5 mm is utilized. The antenna is excited via the waveguide

port that is designated for the feed line. As illustrated in Fig. 2, the radiating structure has two slots set aside for

the integration of vacuum switches, each measuring 1 mm in width. The suggested monopole antenna is 30 x 15

x 1.52 mm². The detailed dimensions of the suggested building are compiled in Table 1.

based switching enables dynamic frequency agility while preserving acceptable impedance matching and

radiation characteristics across the targeted reconfigurable modes.

Figure 9 illustrates the simulated far-field radiation patterns of the reference (non-reconfigurable) microstrip

patch antenna in its principal planes at the resonant frequencies of interest.

In the H-plane (typically the azimuthal plane, φ = 0° or 90° depending on orientation), the proposed antenna

exhibits a nearly omnidirectional radiation pattern. This characteristic indicates relatively uniform radiation

intensity in all in-plane directions, making the antenna well-suited for applications requiring broad azimuthal

coverage, such as indoor WLAN access points, mobile devices, or IoT nodes where signals may arrive from

These complementary radiation behaviors, omnidirectional in the H-plane and bidirectional in the E-plane

confirming the antenna’s balanced performance for typical dual-band WLAN and sub-6 GHz applications, where

both wide angular coverage in the horizontal plane and reasonable directivity in the vertical plane are desirable.

The patterns observed in Figure 9 serve as the baseline reference for assessing any modifications to the radiation

characteristics introduced by the slot perturbations, PIN-diode switching, and optional reflector in the

reconfigurable configurations discussed in subsequent sections.

Figure 9: Radiation Pattern of the antenna (a) E-Plane (b) H-Plane

Table 4 presents a comprehensive summary of the key performance metrics, reflection coefficient (S11), realized

gain, and radiation efficiency extracted from the simulation results shown in Figures 14, 15, and 16 for the

proposed frequency-reconfigurable microstrip patch antenna employing PIN diodes as switching elements. The

binary notation is adopted to describe the four switching configurations: 1 denotes the ON state (PIN diode

forward-biased, low impedance), 0 denotes the OFF state (PIN diode reverse-biased, high impedance), yielding

the combinations 00 (both OFF), 11 (both ON), 10 (first switch ON, second OFF), and 01 (first switch OFF,

second ON). A notable improvement is observed when a reflector plane is introduced beneath the antenna

structure: both the realized gain and radiation efficiency exhibit significant enhancements across all resonant

bands compared to the baseline configuration without the reflector, while maintaining |S11| ≤ –10 dB, thereby

as smartphones, tablets, and IoT systems. Using only a single antenna element (compared to 2–4 elements in

several references like [16], [17], and [20]), it achieves six operating bands (supporting frequencies from 2.4

GHz to 6.3 GHz across multiple single- and dual-band modes for WLAN, sub-6 GHz 5G, radio altimeters, and

radars), matching or exceeding the band count of most competitors (e.g., seven in [22] but over a narrower 1–5

GHz range, and six in [23] but limited to 2.3–2.68 GHz). Additionally, the realized gain range of 2.1–5.8 dBi is

competitive or superior to many reported values (e.g., 3.2 dBi in [15], 1.7–3.4 dBi in [16], and 2.6 dBi in [23]),

benefiting from the low-loss Rogers RO3003 substrate (which offers better efficiency, signal integrity, and

thermal stability compared to higher-loss FR-4 or PDMS substrates used in most references).

Overall, the proposed work provides an excellent size-bandwidth-gain trade-off through optimized slot-based

PIN-diode reconfigurability (only two switches) and strategic reflector integration, delivering greater operational

modes tailored to diverse wireless applications while maintaining a low-profile structure suitable for integration

into modern portable devices.

In the all-ON switch configuration, the antenna exhibits dual-band operation at 2.4 GHz (lower WLAN) and 5.6

GHz (higher WLAN). When both switches are OFF, it resonates in a single band at 4.2 GHz, supporting radio

altimeter systems. Selective switching Sw1 ON with Sw2 OFF enables single-band performance at 2.9 GHz for

military and meteorological radar applications, while Sw1 OFF with Sw2 ON provides dual-band coverage at

3.5 GHz (sub-6 GHz 5G) and 5.6 GHz (higher WLAN/5G). These configurations collectively enable

compatibility with WLAN standards, 5G communications, radio altimeters, military radars, and weather radar

systems, offering a versatile single-antenna solution for multifunctional wireless devices such as smartphones,

tablets, laptops, and IoT platforms.

performance metrics and confirm the efficacy of the slot-based switching approach for frequency agility. Future

efforts will focus on prototype fabrication, experimental validation through laboratory measurements, and

potential enhancements such as further miniaturization, incorporation of additional reconfigurability

mechanisms (e.g., pattern or polarization tuning), and real-world integration testing to bridge the gap toward

practical deployment in next-generation wireless systems.

In conclusion, the presented frequency-reconfigurable microstrip patch antenna represents an efficient, low-

complexity approach to addressing the increasing demand for multifunctional, compact radiators in emerging

wireless ecosystems, paving the way for more adaptive and integrated communication solutions.

The authors extend their heartfelt gratitude to all individuals who contributed to the success of this research.

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