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In this paper, a wideband eight-element multiple-input multiple-output (MIMO) antenna array for 5G smartphone applications is presented. Each antenna is composed of a dual-arm tortuous monopole radiating element with a double-stub tuner and an open slot on the ground plane. Tuning stub microstrip lines are utilized to improve impedance matching. The operating bandwidth of the single antenna element is from 3200 to 6000 MHz with three resonant frequencies. The operating bandwidth covers the 5G new radio (NR) bands (n77/n78/n79) and the WLAN-5GHz band. The isolation of the proposed MIMO antenna array is above 10 dB in the entire operating band without any isolation elements. Furthermore, the proposed MIMO array was manufactured and measured. The measured results validate that the MIMO antenna array has a wide 6-dB impedance bandwidth from 3.2 to 6 GHz and the isolations are all more than 10 dB. The total efficiency ranges from 38% to 83%. The above results show that this MIMO antenna array can support 5G applications in smartphones.

A compact multi-bands antenna for the 4G mobile terminal applications is presented. The proposed antenna consists of a T shape feeding structure and an inverted F shape radiation structure. Among them, the T shape feeding structure covers the WLAN2.4-GHz and LTE2600 bands; the inverted F-shape antenna covers the GSM850/900, LTE1800. A prototype was fabricated and measured on a FR4 substrate with an overall size of 135 mm × 55 mm × 0.8 mm and the size of antenna only has 55 mm × 8 mm × 0.8 mm. The measured efficiencies are above 40% at all work bands.

This article proposes an uniplanar antenna operating in the LTE 900/1800/2600 and the WLAN-2.4/-5.2 bands for the laptop applications. The size of this antenna is 45 ×9 × 0.8 mm3 and it fabricated on a FR4 glass epoxy substrate. This antenna is mounted on the 260 × 200 × 0.1 mm3 copper sheet. The efficiency and peak gain are 31-81% and −0.05–5 dBi, respectively.

This study proposes a single-layer dual-broadband circularly polarised (CP) antenna that operates at 2.4, 5.2 and 5.8 GHz for wireless local area networks (WLAN) applications. An annular-slot antenna loaded with a lightning-shaped slot for achieving good CP radiation in the WLAN 2.4 GHz band is initially studied. To cover the WLAN 5.2 GHz band as well, the inner circular patch of the aforementioned design is modified as an inner ring patch loaded with a notch and a narrow U-shaped strip. By further embedding a crescent parasitic element into the circular slot of the inner ring patch, the upper CP band is significantly broadened to cover the WLAN 5.8 GHz. Accordingly, the final design can exhibit two wide 3 dB axial ratio bands of 13.3% (2.24-2.56 GHz) and 16.9% (5.01-5.94 GHz), and their corresponding 10 dB impedance bandwidths are 25.9% (2.21-2.86 GHz) and 25.9% (5.05-6.54 GHz). With the advantages of compact size, low-cost, easy integration and dual-broad CP bands, the proposed designs are very attractive for modern wireless communication systems, especially for WLAN applications.

A $1 \times 4$ antenna array with wideband and high gain is proposed for 60-GHz applications. The operating bandwidth is from 57 to 66 GHz. A superstrate above and an electromagnetic bandgap reflector below the array structure increase peak gain and decrease backward radiation, respectively. This paper elaborates the design guidelines. The slot stubs are designed appropriately to increase the bandwidth of square-slot antenna and maintain the radiation pattern. The simulated and measured impedance bandwidth ( $\vert S_{11}\vert \le -10$ dB) are 28.8% (52.6–69.9 GHz) and 23.2% (52.6–66.5 GHz), respectively. The peak antenna gain ranging from 57 to 66 GHz is simulated to be 14.2–12.4 dBi, while the measured peak gain at 57, 60, 63, and 66 GHz are 13.6, 13.4, 12.6, and 11.3 dBi, respectively. The above results can satisfy requirement of many commercial applications.

An aperture coupled microstrip-line fed patch antenna with circularly polarized (CP) radiation is initially studied. To achieve better CP radiation at lower frequency and meanwhile able to yield good frequency agility, the technique of loading an inverted C-shaped slit into the circular patch is proposed. Furthermore, frequency agility can also be attained by simply tuning the air-gap distance between the upper layer circular patch and the lower layer cross-slot feeding structure. Further analyses have shown that the proposed antenna can achieve good CP frequency agility across the desired UHF (ultra-high frequency) RFID operating band (902–928 MHz).

This paper proposes a uniplanar 2 × 2 MIMO (Multi-Input Multi-Output) antenna suitable for laptop computer applications. The proposed 2×2 MIMO antenna is composed of two identical antenna elements, and each antenna element is composed of a loop structure and a parasitic element. The size of each antenna element is 38 mm × 7 mm, and it has a small ground plane of size 38 mm × 6 mm. The 6-dB impedance bandwidths of each antenna element are able to cover 1677 — 1905 MHz, 2132 — 2587 MHz and 4860 — 6360 MHz, and the isolation between two antenna elements is greater than 17dB. Furthermore, the measured efficiency is more than 45%.

An ellipse-shaped circularly polarized (CP) monopole antenna is proposed in this paper. A slanted slot is added into the antenna to enhance 3-dB axial ratio bandwidth. The antenna operates at ultrahigh frequency (UHF) band for radio-frequency identification (RFID) reader applications. The measured bandwidth of standing wave ratio (SWR) < 2 is 535 MHz (553 MHz–1088 MHz) and the measured 3-dB axial ratio (AR) bandwidth 45MHz (900MHz–945MHz). The size of the radiating element is 137 mm × 122 mm.

The paper proposes multiband antennas for the smart watch applications. The size of the smart watch is 49 mm × 35 mm × 5 mm. These antennas are placed in the top side and bottom side of the smart watch and printed on a 0.4-mm thick FR-4 substrate. The sizes of these antennas in the top side and bottom side are the same 2 mm × 35 mm × 5 mm, and these two antennas are Invert-F antenna (IFA) type structure. The measured impedance bandwidths of these antennas are 1555–1680 MHz, 1705–1892 MHz and 2395–2485 MHz. The maximum of isolation of the measurement are −14.5 dB in GPS band, −12.2 dB in GSM1800 band and −18.1 dB in Wi-Fi band.

A compact, high gain and dual-polarization 2 × 4 patch antenna array for 802.11ac MIMO applications is proposed. The antenna size is compact with an area of 145 × 95 mm2 (2.42 λ 0 × 1.58 λ 0 ), which is very suitable for outdoor wireless products. The measured impedance bandwidth |S 11 | ≤ − 10 dB is at the 802.11ac band (5150 ∼ 5850 MHz) and isolation is above 15 dB, respectively. The antenna peak gain and efficiency are at least 12 dBi and 55 %, respectively.

This paper proposes a dualband metamaterial-radome which can improve the gain of circularly polarized antenna. The refractive index of the metaterial is designed to near zero. This feature can use to focus on the electromagnetic wave and increase the gain of antenna. This dualband metamaterial is placed in front of the antenna 6 mm. The gain of the circularly polarized antenna increases 1.47 dB and 1.05 dB at the 2.4GHz and 5GHz band respectively.

We develop a novel MIMO antenna with excellent broadband isolation performance in this communication. Metamaterial (MTM)-inspired resonators can function as insulators and are placed periodically into a compact MIMO antenna system for portable applications. These insulators only need a 0.18 wavelength. The broadband insulators can efficiently reduce the coupling of MIMO antennas. Isolation bandwidth under 20 dB can reach 8% with relative to the center frequency. Adding a T-shaped branch behind the insulators markedly improves the isolation bandwidth. An isolation bandwidth under 20 dB can achieve 19.3% relative to the center frequency. The effectiveness of the proposed insulators is validated by measurements.

This investigation presents axial ratio bandwidth enhancement for a quarter-wave polarizer composed of mutilayered uniaxial anisotropic media and chiral media using a genetic algorithm. In our design, the constitutive parameters of materials can be arbitrary. This broadband polarizer can be realized through the adjustment of the thickness of materials. The nearly optimal and suitable thickness of each cell is determined by using a genetic algorithm. Two numerical examples with three and five cells are presented to validate the design. The axial ratio bandwidths of about 84.1% and 92.8% can be achieved, more than the double of the maximum theoretical bandwidth for the case of the single uniaxial anisotropic slab

In this paper, a folded C-shaped monopole for WLAN/WiMAX USB dongle is proposed. The antenna is fabricated on FR4 substrate; the overall dimensions are 35 mm × 10 mm × 1.6 mm. The antenna portion is occupied by 10 mm × 10 mm, and the size of system ground is 25 mm × 10 mm. The C-shaped monopole consists of the left arm with longest length and the left arm. The left arm of the folded C-shaped generates the low band (2.4GHz) mode; the right arm produces the high band (5.2/5.8GHz), the both of folded C-shaped and the ground resonates the middle band (3.4GHz). From the results, the antenna is covering the bands of WLAN (2.4, 5.2, and 5.8GHz band ) and the band of WiMAX 3.5GHz. The antenna with small size and easy manufacturing is suitable for USB application.

This work presents a dual-band high-gain metamaterial radome which can increase antenna gain. This radome operates at the WiMAX (3.5GHz) band and the WiFi (5.8GHz) band. The refractive index of this radome is designed to near zero. The radiation beamwidth of antenna becomes small and the antenna gain is increasing. The size of this radome is 90 mm × 90 mm. This radome improves antenna gain 2.6 dB and 5.7 dB at 3.57GHz and 5.95 GHz respectively.

A circularly polarized (CP) patch antenna with parasitic square-ring is presented for UHF RFID reader. The operating frequency of the proposed antenna covers 877MHz to 945MHz with VSWR less than 2. The size of this antenna is 174 × 171 × 10 mm⁁3. A 3dB axial ratio is about 56MHz from 878MHz to 934MHz. The antenna gain is about 6.3–7.9dBic.

A high-gain aperture coupled antenna with superstrate structure for 60 GHz communication is proposed. Unprinted dielectric slab acts as superstrate is added above the antenna in order to increase the gain performance. Then, the effective radiated area and transmission line model are used to further enhance the gain. The maximum simulated gain of the antenna with superstrate structure can achieve 15.2 dBi at 60 GHz and is more than 13 dBi all over the 60 GHz band (from 57 to 66 GHz). From simulated results, the radiation patterns are found to be broadside all over the frequency band.

Metamaterial (MTM) unit-cells with a zero refractive index was developed, characterized and employed for gain enhancement of a Yagi antenna operating at 60 GHz. The unique property of the MTM gathers the wave radiated from the antenna and collimates it towards the normal direction when used as director. The proposed design provides a gain enhancement of 2.3 dB when the nearing zero-refractive-index MTM director is utilized. Simulation results show that the conventional Yagi antenna's director replaced by the proposed MTM directors can achieve a maximum gain of 8.18 dBi at 60 GHz.

A series of carbodiimide insertion products were prepared using various aluminum reagents (viz., AlR3 (R = Me, Et), AlX2Y (X = Cl, R; Y = Cl, NR‘2)) and 1,3-diisopropyl- and 1,3-di-tert-butylcarbod...

This paper presents a miniature implanted antenna operated at medical implant communication systems (MICS) band (402–405 MHz) with the dimension of 40×10×1.905 mm3 for biotelemetry. The antenna is fabricated on biocompatible Ceramic Alumina substrates. For simplicity three □ layer human tissues are adopted first. With the special arrangement of the antenna structure, a spiral □ like current distribution is excited and the corresponding electromagnetic wave can be radiated toward the outside of the human body. The antenna achieves a gain of −21.7 dBi, capable of extending the battery life. Furthermore, the frequency response is insensitive to the change of the implanted environment. Finally, a complete human model is used and the results are similar.

This paper presents a novel intelligent metamaterial (I-MTM) design for specific absorption rate (SAR) reduction. The I-MTM can distinguish whether the phantom is close to or far away from itself. In turn it will show different properties. In the SAR reduction mode, the peak SAR value can be reduced by around 56%. In the normal mode, the I-MTM will not affect the performance of an antenna.

A high gain patch antenna using more subwavelength hole metamaterial as radome operating at 3.5 GHz band is proposed in this work. We use a metamaterial superstrate, which is constructed by stacking three layers of Jerusalem cross structure. The structure can be applied to modify the radiation pattern and increase antenna gain. The proposed structure is made by three layers FR4 and the Jerusalem cross structure is printed on the front slab at each layer. This radome's refraction index approximately equals zero and increases the antenna gain at a frequency close to 3.5 GHz. In addition, we change the number of subwavelength holes in metamaterial radome to further enhance antenna gain. A patch antenna which is covered by the proposed metamaterial radome can achieve a maximum gain of 7.8 dBi.

Single negative metamaterial designed in MIMO antenna is suitable for portable applications. Metamaterials reduce the coupling at a separation distance of 0.18-wavelength for the MIMO system. Multi-layer metamaterials with different spiral length can improve the isolation bandwidth. In our design, it can cover whole WiMAX bands. And Ω-shape arrangement is also proposed; the isolation has 6dB improvement at 2.6GHz. This paper successfully shows that metamaterials can be used in MIMO antennas system to reduce correlation and size. And it is suitable for portable applications.

We find that using metamaterial antenna radome made by 90 degree rotational symmetric unit cell structure can enhance the gain of dual-polarized antenna. The Jerusalem cross structure is proposed for dual-polarized antenna radome and its refraction index is designed to be near zero. This radome is designed for the WiMAX applications. Simulation results show that this antenna radome can improve the gain of dual-polarized patch antenna.

The design of antenna radome utilizing the left-handed materials at a frequency close to 5 GHz for the first time for enhancing the antenna gain is presented. We make use of the multi-layered structure composed of two materials with left-handed materials and air. The two materials have an average index of refraction around zero. The simulation results show that the antenna gain and the radiation patterns are effectively enhanced. The beamwidth is reduced by 37.5% and the antenna gain is increased to about 6 dBi. The results can be used in applications such as point-to-point communications between the buildings.

When designing an uninterruptible power system, it is important to be able to predict the performance of the EMI filter accurately. In this paper, the effects of parasitic elements of the filter components and the noise impedance on the filter performance are evaluated. Methods to determine the values of the parasitic elements and the noise impedance are described. Based on the insertion loss, three situations are compared using two different filter topologies. It is shown that our approach can significantly reduce the discrepancy between the theoretical prediction and the measurement and thus is useful for the design of EMI filters.

It is important to be able to separate common-mode and differential-mode noises in the conducted emission. We propose new discriminators, which are low-cost, easily manufactured and are able to give exact noise readings without further adjustment. This diagnostic circuit is used in CAD of power line filters. To this end, we also propose a relatively cheap approach using an oscilloscope. The time-domain measurement is performed and transformed into frequency domain using FFT. A realistic design example is shown to give satisfactory results.

This work presents a new viewpoint to study polarization transformations. This concept is more convenient when dealing with polarization transformation problems in multiple layers. The anisotropic medium and the chiral medium can be regarded as circuit elements. Specifically, we show that anisotropic media can be seen as transformers and chiral media as transmission lines. Once the equivalent circuits are determined, the microwave network theory can be used to investigate the polarization transformation. An example is used to demonstrate the transformation from the horizontally polarized wave to the circularly polarized wave employing the equivalent circuit concept.

A compact dual-band insulator for multiple-input, multiple-output (MIMO) antennas is presented. The capacitively loaded loops are designed for different operating frequencies and printed on both sides of the substrate of the MIMO antenna of the portable devices. When the proposed insulators are inserted in between MIMO antennas, the isolation shows good improvement at both 2.6 and 3.5 GHz bands. The isolation is suppressed under −20 dB at the lower band of 2550–2730 MHz and at the upper band of 3390–3820 MHz. The proposed insulators are also validated through measurements.