This paper presents the design and analysis of a compact eight-port multiband multiple-input–multiple-output (MIMO) antenna for 5G smartphones. The proposed antenna structure is designed using meandering elements, as radiator, on the FR4 substrate of 150 × 80 × 0.8 mm with loss tangent (tan δ) of 0.02 and relative permittivity (εr) of 4.4. The proposed antenna resonates at 2.4, 3.5, and 5.5 GHz, and it covers the bandwidth of 2%, 6.28%, and 2.53%, respectively. The measured results provide an omnidirectional radiation pattern with 58%–78% of efficiency in all operating bands. The eight-port multiband MIMO design provides a high isolation of 17.5 dB, envelope correlation coefficient < 0.04, diversity gain of 9.98 dB, total active reflection coefficient < −10 dB, and channel capacity loss of <0.25 bits/s/Hz. Also, the hand phantom is designed to analyze the reflection coefficients and efficiency of the proposed antenna.

This paper introduces a tri-band stacked elliptical patch antenna featuring a right-handed circular polarized, designed to operate at the L2, L5, and L1 Global Navigation Satellite System bands. Initially, an elliptic patch is constructed and fed by a probe feed to generate TM110 and TM210 modes at resonance frequencies calculated using Mathieu functions. The probe position is precisely adjusted to excite the quasi-orthogonal mode of TM110 to generate circularly polarized (CP) waves at the L2 and L5 bands. Subsequently, an eye-shaped aperture is engraved into the elliptical patch to enhance the axial ratio (AR) beamwidth in the L2 and L5 bands and stimulate the orthogonal mode of TM210 to produce CP waves at the L1 band. Lastly, a stacked partially elliptical parasitic element is placed beneath the upper slotted elliptical patch to enhance the orthogonality of TM210 surface current versions and thus improve the AR beamwidth at the L1 band. The proposed antenna shows low reflection coefficient values at 1.12–1.33 (L2/L5), and 1.5–1.66 GHz (L1). The AR beamwidths are 133/213∘, 167/163∘, and 36/103∘ at two orthogonal cutplanes at L5, L2, and L1 bands, respectively. The antenna also has decent gains of 6–6.9 dBic across the three bands.

The increasing demand for wireless communication has emphasized the need for multiband antennas. This study presents a novel design for a multiband antenna with reduced specific absorption rate (SAR), high gain, and improved front-to-back ratio (FBR) achieved through the integration with a 4 × 4 artificial magnetic conductor (AMC) surface. The proposed antenna covers a wide range of wireless frequency bands, including Industrial, Scientific, and Medical, Wireless Local Area Network, Worldwide Interoperability for Microwave Access, Wi-Fi 6E, and 7, with resonating frequencies at 2.4, 3.2, 5.5, 7.5, and 10 GHz. The AMC unit cell creates four zero-degree reflection phases with double negative properties at 2.5, 3.8, 5.5, and 7.5 GHz. The compact design measures 0.23λ0 × 0.296λ0 × 0.0128λ0 and placed 0.104λ0 above an AMC surface of size 0.512λ0 × 0.512λ0 × 0.1296λ0. This structure enhances the gain by up to 8.55dBi at 6.01 GHz. The proposed antenna has −10 dB impedance bandwidth for these corresponding frequencies viz 2.34–2.43 GHz (3.77%), 2.81–3.83 GHz (30.72%), 4.82–6.21 GHz (25.20%), 7–7.65 GHz (8.87%), and 8.06–10.31 GHz (24.5%). An overall average percentage reduction value of SAR taken at these frequencies has been found to be 96.11% with AMC structure. The antenna sample was successfully fabricated, and the experimental results have been found to match well with the simulation results. This integrated design offers a promising solution for wearable off-body communication devices.

In this paper, a new method based on a genetic algorithm and Minkowski Island fractal is proposed for multiband antennas. Three-antenna configurations are chosen to validate the proposed optimization procedure. The first configuration is a wide-band antenna, operating in the WLAN (wireless local area network) UNII-2C band. The second configuration is a dual-band antenna, operating in the WLAN UNII-2 and UNII-2C bands. In contrast, the third is a tri-band antenna operating in the UNII-2, UNII-2C, and UNII-3 bands. The optimization process is accelerated by using the Computer Simulation Technology (CST) Application Programming Interface which allows all genetic operators to be performed in MATLAB while the numerical calculations are running in the internal CST Finite-Difference Time-Domain -solver using parallel computing with GPU acceleration. All three designed configurations are manufactured using a $\textstyle0.8\;\text{mm}$ thick FR4 epoxy substrate with a relative dielectric constant of $4.8$. The return loss and the radiation pattern’s measurements agree well with the simulation results. Further, the methodology presented can be very effective in terms of size reduction; the designed antennas are $24 \times 24 \times 0.8\;{\textrm{m}}{{\textrm{m}}^3}$ ($460\;{\textrm{m}}{{\textrm{m}}^3}$).

A small-size multiband antenna with 14 bands is presented in this paper for wireless applications. The studied antenna mainly consists of a folded monopole antenna and an M-shaped structure. Furthermore, the antenna has a simple design with a compact dimension of 26.8 × 10.8 mm2. The studied antenna is printed on FR4 substrate with a depth of 0.8 mm and fed by a coaxial cable. The −10 dB bandwidths measured are 210 MHz (1200–1410 MHz), 100 MHz (2200–2300 MHz), 193 MHz (3000–3193 MHz), 180 MHz (3330–3510 MHz), 390 MHz (4110–4500 MHz), 4971 MHz, 577 MHz (5300–5877 MHz), and 700 MHz (7100–7800 MHz), which can cover 3G/4G/5G/Wi-Fi/WiMAX, C, and S bands. The gain and efficiency of the presented antenna are 1.3–4.00 dBi and 46%–60.2%, respectively.

In this paper, a novel multiband implantable planar inverted-F antenna (PIFA) antenna based on Gosper curve fractal geometry is designed for biomedical telemetry applications. The antenna has covered four dedicated frequency bands; medical implant communication system band (MICS 402–405 MHz), industrial, scientific, and medical bands (ISM 902–928 MHz and 2.4–2.5 GHz), and wireless medical telemetry services (WMTS 1395–1400 and 1429–1432 MHz). The proposed antenna is designed on Rogers RO 3010 substrate of thickness 25 mil and volume equal to 153.67 mm3. The reflection coefficient and the radiation pattern are measured inside muscle-mimicking liquid tissue phantom. The antenna has achieved the impedance bandwidth of 126, 406, 168, and 175 MHz at MICS (403 MHz), ISM (915 MHz), WMTS (1400 MHz), and ISM (2.45 GHz) with maximum gain value −33.6, −21.04, −15.48, and −10.25 dBi, respectively. The data link range between the implantable antenna and off body antenna has been performed with −16 dBm input power. Additionally, the obtained specific absorption rate with the input of 25 μW power has also been obtained within the safety limit and hence ensures the reliability of the proposed antenna.

This paper presents a comprehensive review of symmetrically shaped antennas in terms of antenna size, dielectric materials, resonating band, peak gain, radiation pattern, simulating tools, and their applications. In this article, flower shape, leaf shape, tree shape, fan shape, Pi shape, butterfly shape, bat shape, wearable, multiband, monopole, and fractal antennas are discussed. Further, a survey of previously reported bandwidth enhancement techniques of microstrip patch antenna like introduction of thick and lower permittivity substrate, multilayer substrate, parasitic elements, slots and notches, shorting wall, shorting pin, defected ground structure, metamaterial-based split ring resonator structure, fractal geometry, and composite right-hand/left-handed transmission line approach is presented. The physics of these techniques has been discussed in detail which is supported by circuit theory model approach.

A quad band antenna with good gain and omni-directional pattern is proposed in this paper. The antenna design is based on loading a conventional monopole antenna by three different resonators. The resonators are inspired from the shunt branch of composite right-/left-handed cell. The resonators have a simple structure and compact size. The control of the frequency bands can be achieved arbitrarily and hence the suggested design methodology can be generalized to any required bands. The fabricated antenna prototype is operating at 2.6, 3.35, 5.15, and 6.1 GHz with bandwidth wider than 100 MHz for each band. The antenna's operating principle and design procedures with the aid of electromagnetic full wave simulation are presented. Finally, the experimental results exhibit good agreement with the simulated ones which confirm the proposed designed methodology. The proposed monopole antenna has a patch size of 13.5 mm × 6.5 mm and the whole antenna size (including the feed line) is 35 mm × 32 mm. Compared to conventional single-band microstrip patch radiator size, the proposed quad band radiator has the size of 9, 15, 37.5, and 72.5% at relevant frequency bands.

The design and analysis of meta-material inspired loaded monopole antenna for multiband operation are reported. The proposed antenna consists of multi resonators inspired from half mode composite right/left handed cells, which has a simple structure, compact size, and provides multiband functionalities. As a proof of concept, a triple band antenna covering all possible WiMAX operating bands, has been designed, fabricated, and characterized. The hosting monopole patch itself generates resonance for 3.3–3.8 GHz band, whereas the loaded metamaterial cells add extra resonance frequencies. The loading of two resonator cells introduces two extra resonances for 2.5–2.7 GHz and 5.3–5.9 GHz bands, respectively. The antenna's operating principle and design procedures with the aid of electromagnetic full wave simulation and experimental measurements are presented. The antenna has good omnidirectional patterns at all three bands. The monopole patch size is 13.5 × 6.5 mm2 and the whole antenna size (including the feed line) is 35 × 32 mm2. Compared with conventional single band microstrip patch radiator, the radiator size of this antenna is only 8.5% at 2.5 GHz, 17% at 3.5 GHz, and 37% at 5.5 GHz.

Fractals have unique properties such as self-similarity and space-filling. The use of fractal geometry in antenna design provides a good method for achieving the desired miniaturization, multi-band, and wideband properties. In this communication, novel fractal geometry is proposed based on which a multiband antenna is designed. The proposed antenna has fractal patches which are shaped as different iterations of an eight-pointed star. The multiband behavior is in the frequency range from 4.50 to 17.00 GHz. The proposed antenna is designed on a dielectric substrate Roggers RO4003 lossy with a dielectric constant of εr = 3.55. The antenna has applications in commercial and military communication system.

This paper of lettering reveals about a modified Koch snowflake fractal multiband antenna for cognitive radio applications. Multiband antennas can be employed for spectrum sensing in cognitive radio. This new microstrip-modified Koch fractal antenna exhibits multiple actions in four dissimilar resonant frequencies at 3.2, 5.2, 6, and 9.5 GHz correspondingly that covers the frequency bands such as S, C, and X bands. Its multiband behavior was analyzed by designing and simulating in ADS EMDS software. Three iterations were carried out to study the performance of modified Koch snowflake fractal antenna. The outer ring and a small rectangular slot in the center of the antenna are used for 50 Ω impedance matching and to increase the number of resonant frequencies. The fractal antenna parameters such as gain, directivity, and its radiation pattern are also analyzed in this paper. The measured results show good agreement with the simulated results.

A compact asymmetric coplanar strip fed Sinc shaped monopole antenna suitable for multifrequency operations is proposed for portable wireless devices. The proposed Sinc shaped monopole antenna with truncated half ground plane operates at three frequency bands, 2110–2380, 4180–4600, and 5200–5678 MHz, showing fractional impedance bandwidths of 12, 9, and 8.8%, respectively, suitable for Universal Mobile Telecommunications System, Long Term Evolution handheld devices, Worldwide Interoperability for Microwave Access, Wireless Local Area Network, Hyperlan-2, and aeronautical navigation applications. Proposed antenna shows a dual mode of polarization. Finally a prototype model is developed for a typical configuration and the simulated results are validated experimentally.

A dual wideband design of Sierpinski carpet fractal-shaped planar monopole antenna with a coplanar waveguide (CPW) feed is proposed in this letter. Wide impedance bandwidth of 22% at lower resonance from 4.88 to 6.08 GHz and 41.7% at higher one, which ranges from 9.5 to 14.5 GHz, is obtained. Measured realized antenna gain is around 5 dBi at the lower band centered around 5.5 GHz and are around 4.5 dBi at the higher band. A fabricated prototype is developed with good agreement between simulation and measurement.