A new dual-polarized antenna loading frequency-selective surface (FSS) is proposed for 5G wireless local networks (WLANs) application. The antenna consists of two orthogonal bow-tie dipoles and a ground plane. A new wideband FSS is designed comprising ring-slot connecting rectangular slots. The reflection coefficient of wideband FSS is less than 0.9 from 4-6.5 GHz. The phase of reflection coefficient is -163°at 5.5 GHz. The novel cell analyzed by the equivalent circuit is given and simulated. The wideband FSS is employed as a superstrate layer for bandwidth enhancement and radiation gain improvement of the antenna. After loading wideband FSS, the measured bandwidth is 5.3-6.3 GHz (17.2%) with S₁₁ and S₂₂ both less than -10 dB, which cover various 5G WLAN bandwidths. The gain of the antenna is 12.1 dBi at 5.5 GHz. The bandwidth of antenna with FSS increases 40%, and gain improves 5.6 dBi. The simulated and measured results agree well.

A compact printed dual-band antenna for WiMAX/WLAN applications is proposed in this paper. The dual-band monopole antenna consists of a triangular patch and two folding arms shorted to the ground plane. The proposed antenna features a low profile and compact dimension. To avoid via process in the fabrication, the triangular patch. The two folding arms are separately constructed on the two sides of a FR4 substrate. By employing this structure, five different resonances can be yielded. The triangular patch provides two resonant modes (4.62 GHz and 7.05 GHz), two folding arms produces three resonances at 2.43 GHz, 3.43 GHz, and 6.59 GHz. A prototype of the dual-band antenna is experimentally fabricated and tested. The measured results shows good impedance bandwidth and radiation pattern.

By using some special passive structures and correction of boundary conditions, a novel method to improve the electromagnetic (EM) simulation accuracy is proposed. With this method, the substrate parameters, such as thickness, loss, dielectric constant, loss tangent, sheet resistance, square capacitance and conductivity of the metal, can be described more accurately, and a lot of high frequency effects caused by skin effects, parasitic effects, coupling between micro-strip lines and fluctuation from the sheet resistance, etc. can also be simulated more precisely. Then an accurately scalable small-signal model for millimeter-wave HEMTs is proposed and presented. Combined with distributed modeling, pulsed IV and S parameter measurements, this model can be made scalable freely. The measurements agree with simulated results very well, which also proves that this method applied to the scalable small-signal models has a good consistency and accuracy.

This paper describes the concept and the development of key components of a novel multiple-beam antenna for satellite applications. The antenna is designed to be used in a transparent high-rate data relay system that links several low earth orbit (LEO) satellites to a single ground station via a satellite positioned on a geostationary orbit (GEO). The proposed antenna is based on the concept of an array-fed reflector. The antenna can track LEO satellites by switching between different subarrays of a bigger multifeed array using a reconfigurable switch matrix based on radio frequency micro-electro-mechanical system (RF MEMS) switches. The radiation characteristic of the antenna is further improved by combining digital beamforming with beam switching. In order to validate the proposed antenna concept and to show its suitability for space applications a demonstrator has been built. Measurements of the antenna's key components and of the demonstration system are given.

This paper presents the simulation and fabrication of a new power divider/combiner based on a new waveguide H-plane folded magic-T structure. Measurements of the fabricated magic-T confirm the accuracy of the optimization algorithms existing in the CST software (Genetic algorithm, Particle Swarm Optimization algorithm PSO, etc.). The magic-T structure exhibits moderate bandwidth response in the frequency range of 8-10 GHz. Also, it shows that the return loss is better than -15 dB, the insertion loss about -3.4 dB, and the isolation between the two output ports better than -25 dB in the frequency range of 8.4-10 GHz, with good transmission phase characteristics. Based on this magic-T structure, a 1:4 power divider/combiner is simulated and tested. The measured results show that the insertion loss is about -6.5±0.25 dB, the return loss less than -15 dB, the isolation among the output ports less than -25 dB, the combining efficiency about 89%, and the transmission phase differences are about ±2° in the frequency range of 8-10 GHz.

The 2 × 2 multiple-input-multiple-output (MIMO) capacities of three types of colocated dual-polarized loop (DPL) antennas with different current distributions and isolations are investigated in the free space (FS) channel, the corridor with perfect electric conductor walls (PEC corridor) and the corridor with concrete walls (CON corridor), separately. Capacity results show strong dependences on both the structure and the position of the DPL antenna, in addition to the propagation conditions. For all the three propagation scenarios, the largest capacity can be reached is in the PEC corridor, employing the DPL antenna with a uniform current distribution and a high isolation. Specifically, for a 20 dB signal-to-noise ratio (SNR), the maximum dual-polarized MIMO capacity is 13.1 bps/Hz, which is 1.97 time of that obtained by the one-polarized loop. It is also noted that, the rich-multipath environment can increase the robustness of the DPL MIMO system and the difference of the MIMO capacity obtained by different antenna structures will get smaller with respect to that in the FS channel.

In this letter, a new image fusion methodology for integration of SAR and optical images using combined dictionary is proposed. The approach taken is based on sparse and redundant representations by employing a combined dictionary consisting of wavelets, shearlets and discrete cosine transform (DCT). Wavelets and shearlets provide pointlike and curvelike structures for the optical image, and DCT are taken as obtaining the best performance on SAR image. The experimental results demonstrate feasibility and effectiveness of the method.

A novel wideband balun filter based on a symmetric four-port balanced circuit is proposed in this paper. A pair of open coupled lines is used to realize DC suppression and in-band balance improvement for the balun bandpass filter. The bandwidth can be easily adjusted by changing the characteristic impedance of transmission lines in the balanced circuit. For the proposed balun bandpass filter, excellent in-band balance performance (amplitude and phase imbalance are less than 0.25 dB and 1.3˚ respectively) over the passband are achieved. A wideband balun bandpass filter prototype with center frequency 3.75 GHz and 3-dB bandwidth 33.8% is designed and fabricated. Good agreement can be observed between the measured results and theoretical expectations.

This paper presents the design, fabrication, and measurement of triple band metamaterial absorber at 8 GHz, 10 GHz and 12 GHz which are in the X-band frequency range. The unit cell of the metamaterial consists of three concentric copper rings at different radii, printed on 0.8 mm thick FR4 substrate in order to obtain triple resonant frequencies. The highly symmetrical ring structure in nature makes this absorber insensitive to any polarization state of incident electromagnetic (EM) waves for normal incident waves. The proposed structure is capable to operate at wide variations angle of incident wave. The simulated result shows that the triple-band metamaterial absorber achieves high absorbance for normal incident electromagnetic waves of 97.33%, 91.84% and 90.08% at 8 GHz, 10 GHz and 12 GHz respectively, when subjected to normal incident electromagnetic. With metamaterial absorber maintaining 50% of absorbance value, the corresponding full width half maximum (FWHM) are 5.61%, 2.90% and 2.33%. The operating angles in which the metamaterial structure can maintain 50% absorbance at TE mode and TM mode are 670 and 640 respectively. The experimental result verifies that the absorber is well performed at three different resonant frequencies with absorbance greater than 80%.

A pattern synthesis approach based on a modified alternating projection method in an affine coordinate system is proposed in this paper. The approach is suitable for large planar arrays with periodic parallelogram element layout. According to the affine transformation theory, the radiation pattern of the array with a periodic parallelogram element layout could be written down immediately from that of a conventional one with rectangle cells when a pattern invariant group is defined. Just as known, the conventional alternating projection method is sensitive to the starting point and easy to fall into local optimum; in this paper we introduce a modified alternating projection method with a variable projection operator. To verify the rationality of the proposed method, several examples have been performed on our personal computer. Results show that the method could quickly synthesize the array patterns to the required with high accuracy. In addition, if the array has a triangle or parallelogram element layout, the required antennas to fill up the aperture is reduced when compared with the conventional one with antennas arranged along a rectangle grid. In our examples, the maximum reduction is about 18.09%, which is quite beneficial to reduce the weight and cost of the array.

One of the most important aspects for body centric communication is the development of the textile antenna for on-body communication. Antennas for on-body environment usually suffer performance degradation caused by the human body. Apart from that, textile antenna gets easily bent, flexed, wrinkled or wet. This paper presents an investigation on three different designs and types of planar antennas, which are single band textile dipole antenna, fractal Koch multiband dipole antenna and monopole ultra wide band antennas. The performance of the antennas has been evaluated in terms of bending, wetness condition and on-body simulation. The results show that the bending effect is not critical in free space for the planar antennas, but the performance is notably degraded under wet condition while the antenna reflection coefficient is shifted when placed on the human body.

A coupled-line circuit structure is proposed in this paper to design a modified Schiffman phase shifter with short reference line. Based on the traditional transmission line theory and ABCD parameters, closed-form mathematical equations for electrical and scattering parameters are obtained. Obviously, this proposed coupled-line phase shifter has several advantages such as arbitrary phase difference, easy implementation, and analytical design method. Finally, two examples of microstrip coupled-line phase shifter, which have fractional bandwidth over 45%, are fabricated and measured. Good agreements between the simulated and measured results verify our design.

A compact ultrawideband (UWB) multiple-input-multiple-output (MIMO) antenna with a small size of 22×36 mm² is proposed for portable devices. The MIMO antenna consists of two symmetric slot antenna elements with back-to-back separation of 7 mm. Adjusting the open-ended stepped radiator and position of the microstrip line can realize UWB impedance matching. In order to achieve wideband and high isolation, a cross-shaped decoupling slot and connecting metal line are etched on the ground plane. The cross-shaped slot between the antenna elements is used to decrease the mutual coupling caused by near-field at middle and high bands. The connecting line can be interpreted as a neutralized line, which produces an additional current path for the coupling ground currents. Measured S-parameters show that the isolation is better than -16 dB across the UWB of 3.1-10.6 GHz. The radiation pattern, gain, and envelope correlation coefficient are also measured. The proposed antenna with a simple structure and compact size achieves good impedance matching and excellent port isolation simultaneously, and is a good candidate for UWB MIMO systems.

A miniaturized annular ring slot antenna is presented. The antenna consists of an annular ring slot structure and a novel folded matching structure. The annular ring slot structure is printed on a substrate and shorted concentrically with a set of conductive vias. The additional matching structure is a ring cavity attached to the back of the annular ring slot structure. Firstly, the diameter of the proposed antenna is reduced by using the folded matching structure comparing with traditional annular ring slot antennas. Secondly, the impedance matching of the proposed antenna is achieved by optimizing the size of the matching structure. A prototype of the proposed antenna with a height of 3.048 mm (0.03λ) and a radius of 47.2 mm (0.4λ) is designed, fabricated and measured. The antenna resonates at 2.67 GHz and has a monopole-like radiation pattern, which shows that the antenna is suitable for the applications of taking off, landing, and long distance communications for a small or mini UAV.

In this paper, a cross-slot-coupled dual-band circularly polarized (CP) hybrid dielectric resonator antenna (DRA) is presented. The design concept is based on using a cross-slot as both a feeding structure of the DRA and an effective radiator. Full wave simulation is used to verify the proposed design concept in this paper. A prototype antenna is designed, fabricated, and measured. Good agreement is obtained between the simulated and measured results.

This paper presents the development of an Ultra Wide Band (UWB) monopole antenna with dual band notch characteristics. Modified crown-square shaped fractal slots in the ground-plane are implemented to enhance the impedance bandwidth to around 58% as compared to conventional square monopole antenna without slots. Impedance bandwidth of the proposed antenna is approximately 114% with Voltage standing wave ratio (VSWR)<2. In addition to this, two omega-shaped (Ω) slots have been incorporated in the radiating patch to render band-notch characteristics centered at 5.5-GHz band assigned to IEEE802.11a and HIPERLAN/2 as well as X-band for satellite communication centered at 7.5-GHz band. Measured antenna gain is stable over the entire UWB region except at the notch bands. Radiation pattern of the antenna show that the proposed antenna exhibits nearly monopole like E plane radiation patterns and omni-directional H plane radiation patterns throughout the band. A fabricated prototype is developed with close agreement between simulated and measured results.

A novel broadband absorber using the fractal tree structure is presented in this paper, which consists of three metallic layers separated by two dielectric substrates. Five metallic vias connect these three layers which make the whole structure like a two order fractal tree. Simulated and measured results show that this absorber can provide a high absorptivity level from 4.98 to 12.58 GHz, equivalent to a relative absorption bandwidth about 87%. Further investigations show that this wideband absorption can be attributed to the multi-eigenmodes and lower quality factor of the fractal tree structure.

With the vast emergence of new mobile applications, multiband operation in a compact size is mandatory for market penetration. In this paper, a new mobile handset antenna suitable for both mobile and wireless LAN services is presented. The antenna operates for most of the mobile applications such as the GSM 900, DCS 1800, PCS 1900, UMTS 2100, and most of the LTE bands, especially the low frequency LTE 700 band at -10 dB. The antenna also supports the WIMAX, WLAN, and the ISM bands. The antenna not only has a compact size, but also supports a low SAR radiation at all the operating frequencies. The antenna consists of two concentric open rings that act as quarter wavelength monopoles. The inner ring radiates at 900 MHz, while the outer ring radiates at 700 MHz. The inner ring works as a monopole radiator as well as a slot radiator fed by another rectangular monopole. The advantage of the slot is that it supports a wide range of modes that by its role open the radiation band from 1.65 to 3.6 GHz. The antenna meets three challenging parameters: compact size, multiband operation including low frequency bands, and low SAR radiation. Good agreement is noticed between the experimental and simulated results.

This paper presents an optimized design of Litz-wire coil pair with ferrite substrates based on a set of analytical expressions and a 2-D finite-element analysis (FEA) in a way that the coupling coefficient is maximized. An investigation is made on key structure parameters of coils (e.g., structure of Litz-wire, number of turns, and number of layers) to determine their influence on self-inductance and mutual inductance respectively. The influence of ferrite substrate (e.g., relative permeability and thickness) is also considered. Different types of fabricated coils are used to verify all analytical expressions and optimization methods, and it is found that the theoretical predictions and simulations are in agreement with the measured results.

Wireless communication along the stairwell in a high rise building is important to ensure immediate response to take place via consistent relaying of necessary information or data in emergency situations. Thus, a good understanding of signal wave attenuation along the stairwell is necessary to allow a better wireless network planning. This paper presents empirical path loss prediction model for multi-floor stairwell environment. The proposed model is based on measurement in 4 different stairwells, at 900 MHz and 1800 MHz which are near public safety communication bands. The model incorporates the effect of different floor heights and unique path loss-to-distance relation on several stair flights observed during measurement campaign. The proposed model demonstrates higher accuracy than 3 standard path loss models at 2 other stairwells.