Junsheng Yu

Novel Compact Multiband MIMO Antenna for Mobile Terminal

A novel compact MIMO antenna for personal digital assistant (PDA) and pad computer is proposed. The proposed antenna is composed by two multipatch monopole antennas which are placed 90° apart for orthogonal radiation. To strengthen the isolation, a T-shaped ground branch with proper dimension is used to generate an additional coupling path to lower the mutual coupling (below −15 dB), especially at GSM850/900 band. The proposed MIMO antenna is fabricated and tested, both the simulated and the measured results are presented, and some parametric studies are also demonstrated. In addition, there are some advantages about the proposed antenna such as simple structure, easy fabrication, and low cost.

Tetraband Small-Size Printed Strip MIMO Antenna for Mobile Handset Application

A compact printed multiple-input multiple-output (MIMO) antenna for tetraband (GSM900/1800/1900/UMTS) mobile handset application is presented. The proposed MIMO antenna, which consists of two coupled-fed loop antennas with symmetrical configuration, was printed on a 120 * 60 * 0.8 mm3 Fr-4 substrate of relative permittivity of 4.4, loss tangent 0.02. Each element antenna requires only a small area of 22.5 * 25 mm2 on the circuit board. The edge-to-edge spacing between the two elements is only of 920 MHz. A slot and a dual-inverted-L-shaped ground branch were added in the ground plane to decrease the mature coupling between the antenna elements. The measured isolation of the proposed antenna is better than 15 dB among the four operating frequency bands. The simulated 3D radiation patterns at 900 MHz and 1900 MHz of both antenna elements show that two loop antennas in general cover complementary space regions with good diversity performance. Detailed antenna impedance matching performance comparisons were done to evaluate the benefit of using different decoupling technology. The envelop correlation coefficient is calculated to represent the diversity performance of the MIMO antenna.

Novel Diversity/MIMO PIFA Antenna With Broadband Circular Polarization for Multimode Satellite Navigation

A broadband circular polarized two-element planar inverted-F antenna (PIFA) with pattern diversity and high isolation for multimode satellite navigation is reported. Circular polarization characteristic of the proposed antenna is achieved by introducing a cross branch at its corner of the ground. The modified PIFA structure gives the antenna a broadband impedance bandwidth characteristic. A prototype is fabricated and measured. The results show that this circular polarized antenna with compact dimension has broadband from 1.1 to 1.7 GHz and good isolation of 14 dB between the two elements over the whole band, which makes the antenna suitable for handheld terminal application of multimode satellite navigation.

Multiband Planar Monopole Antenna for LTE MIMO Systems

A novel multiband-printed planar monopole antenna for LTE multi-input and multi-output (MIMO) application is proposed. A meandering microstrip line-loaded monopole antenna with multiband characteristic is presented. The proposed antenna provides five frequency bands for LTE application, covering 0.7, 1.7, 2.1, 2.3, and 2.5 GHz. In order to provide low mutual coupling and envelope correlation, two of the antennas are combined with orthogonal polarizations. The mutual coupling of the antenna is lower than −13 dB across the operation bands. Both the simulated and measured results are shown to illustrate the performances of the proposed antenna.

Radiofrequency heating of nanomaterials for cancer treatment: Progress, controversies, and future development

In recent years, the application of nanomaterials to biological and biomedicine areas has attracted intensive interest. One of the hot topics is the nanomaterial mediated radiofrequency (RF) hyperthermia or ablation, i.e., using RF fields/waves to heat tumor tissues treated with nanomaterials to destroy cancerous cells while minimizing the side-heating effect. However, there are currently many contradictive results reported concerning the heating effect of nanomaterials under a RF field. This paper provided a comprehensive review to nanomaterial mediated RF ablation from both experimental and theoretical aspects. Three heating mechanisms were discussed, i.e., laser heating, magnetic field heating, and electric field heating in RF spectrum, with the focus on the last one. The results showed that while diluted pure metallic nanoparticles could be heated significantly by a laser through the surface plasmon resonance, they cannot be easily heated by a RF electric field. Further studies are proposed focusing on nanoparticle structure and morphology, electromagnetic frequency and localized heating effect to pave the way for future development.

RFID Technology and Applications

RFID is emerging as one of most fundamental technologies to Internet of Things due to its attractive features such as good reading ranges, high data rates, and low cost. RFID has achieved a widespread success in various applications, ranging from asset tracking, highway toll collection, supply chain management, animal identification to surveillance systems. Moreover, there has been a wide scope of development in RFID standards, protocols, and middleware. However, a series of challenging issues should be properly addressed before a massive adaptation of RFID technology. In this special issue, we have received 24 paper submissions and accepted 9 papers finally according to the reviewers’ comment and associate editors’ suggestion. These accepted papers include RFID reader antenna design, RFID tag antenna design, RFID passive transponders, tag collision algorithm, and RFID application systems. B. Lee et al. from Kwangwoon University of Korea proposed a novel structure of an NFC loop antenna for mobile handset applications by improving the performance of an NFC loop antenna when a ferrite-polymer composite is attached between the embedded NFC loop antenna and the phone battery. The proposed loop antenna gives better performance than that of a conventional NFC loop antenna. L. X. Zheng et al. from South China University of Technology proposed a compact RFID reader antenna for UHF near-field and far-field operations. The structure of the antenna is a novel folded-dipole loop and is formed by a concentric metal ring with a split. It can provide uniform magnetic near-field distribution and available farfield gain. Y. Yao et al. from Beijing University of Posts and Telecommunications also proposed a novel RFID reader antenna. This antenna was fabricated using indium tin oxide film; thus, it has optically transparent characteristic.This kind of antenna can be used in clothing stores. P. Jankowski-Mihulowicz et al. from Rzeszów University of Technology proposed novel RFID passive transponders with additional energy harvester. They can recover energy from the electromagnetic field of read device and the harvested energy was utilized to supply a microprocessor acquisition block for developed LTCC pressure sensor. C. Wang et al. from Beijing University of Posts and Telecommunications proposed an advanced dynamic framed-slotted ALOHA algorithm based on Bayesian estimation and probability response to solve the tag collision problem of RFID system. The simulation results show that the proposed algorithm has better performance. We sincerely hope that this special issue can further help the readers to understand RFID antenna design and applications and explore the future development of the system.

Analysis and Design of a Novel Circularly Polarized Antipodal Linearly Tapered Slot Antenna

This paper presents and characterizes a novel antipodal linearly tapered slot antenna for generating the circularly polarized (CP) field. By introducing two symmetrical slots on the top and bottom layers of a rectangular WR-15 waveguide, we could obtain circular polarization with an axial ratio bandwidth of 34.1%. The waveguide was used to feed the proposed antenna with very wideband impedance matching. The antenna can achieve impedance bandwidth of 40% for S(1,1) <;-15 dB from 50 to 75 GHz. The simulation and measurement results show that the antenna can produce very good radiation patterns, with stable gain of 9.8 dBi ± 1.24 dBi, low back radiation, and narrow beamwidth over the operating frequency range. The working principle of this CP antenna is explained, using theoretical equations and explicit current distributions. The proposed antenna is easy to manufacture and is a compact candidate for high performance CP millimeter-wave antenna.

Planar antenna for RFID tags on metal platform

In this paper, a planar RFID tag antenna in the UHF band that can be stuck to metallic objects is designed. The proposed tag antenna consists of a slotted radiating patch and a grounded microstrip line, which serves as an impedance matching stub between the radiator and a tag chip. The fractional return loss bandwidth for S11<−10dB is about 9%. When the antenna is placed on the large metal platforms, the impedance matching remains almost unchanged while the reading range is increasing as the size of the metal platform is increasing.

Pattern-Reconfigurable Dual-Polarized Dielectric Resonator Antenna

We present a portable pattern-reconfigurable dual-polarized dielectric resonator antenna (DRA). Low-cost gallium arsenide (GaAs) single-pole, double-throw (SPDT) switches are utilized to select one of the feedline paths of the DRA, giving a boresight or cardioid pattern electronically. The measured results verify the proposed antenna switches its radiation patterns between cardioid and boresight shape, without significantly affecting its matching in the operating frequency range of 5-6 GHz. Results also confirm that the pattern configuration in one port with one polarization does not affect the RF characteristics of the other port with alternative polarization of the antenna. This two-port configuration makes the proposed antenna a suitable candidate for IEEE 802.11ac multi-user multiple-input-multiple-output (MU-MIMO) applications.

Electromagnetic heating effect of aggregated gold nanoparticle colloids

Gold nanoparticles (GNPs) have been recently investigated intensively for potential hyperthermia treatment of malignant cancer cells in combination with radiofrequency (RF) electromagnetic (EM) fields/waves. However, many controversial results have been reported on whether GNPs can be heated by EM fields. It has been suggested that aggregated GNPs may be heated significantly by a RF field, which however has not been examined experimentally. This work proposes a novel electric treatment of mono-dispersed particles to create aggregated GNPs, and conducts an investigation of their bulk heating behavior under a 655 nm laser and a 13.56 MHz RF electric field. It is revealed that the heating rates of aggregated colloids are significantly higher than those of mono-dispersed GNPs for the 655 nm laser, whereas at 13.56 MHz, the heating effects are barely noticeable for both aggregated and mono-dispersed colloids. Various possible reasons are discussed and the negligible electric field enhancement is believed to be responsible at 13.56 MHz.