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Frequencies from 100 GHz to 3 THz are promising bands for the next generation of wireless communication systems because of the wide swaths of unused and unexplored spectrum. These frequencies also offer the potential for revolutionary applications that will be made possible by new thinking, and advances in devices, circuits, software, signal processing, and systems. This paper describes many of the technical challenges and opportunities for wireless communication and sensing applications above 100 GHz, and presents a number of promising discoveries, novel approaches, and recent results that will aid in the development and implementation of the sixth generation (6G) of wireless networks, and beyond. This paper shows recent regulatory and standard body rulings that are anticipating wireless products and services above 100 GHz and illustrates the viability of wireless cognition, hyper-accurate position location, sensing, and imaging. This paper also presents approaches and results that show how long distance mobile communications will be supported to above 800 GHz since the antenna gains are able to overcome air-induced attenuation, and present methods that reduce the computational complexity and simplify the signal processing used in adaptive antenna arrays, by exploiting the Special Theory of Relativity to create a cone of silence in over-sampled antenna arrays that improve performance for digital phased array antennas. Also, new results that give insights into power efficient beam steering algorithms, and new propagation and partition loss models above 100 GHz are given, and promising imaging, array processing, and position location results are presented. The implementation of spatial consistency at THz frequencies, an important component of channel modeling that considers minute changes and correlations over space, is also discussed. This paper offers the first in-depth look at the vast applications of THz wireless products and applications and provides approaches for how to reduce power and increase performance across several problem domains, giving early evidence that THz techniques are compelling and available for future wireless communications.

This paper presents a multifeed antenna structure that synthesizes the desired far-field radiation characteristics with on-antenna power combining and increases the total radiated power of a wireless transmitter. The driving signals at the multiple antenna feeds are scaled properly in amplitude and phase, so that they collectively synthesize the desired on-antenna current/voltage distribution and achieve the resulting desired far-field radiation pattern. The proposed multifeed antenna offers flexibility to optimize the antenna driving impedances based on the locations of the feeds. It also simplifies the passive impedance matching and power-combining networks between the antenna feeds and the transmitter outputs, substantially increasing the total transmitter power efficiency. Most importantly, the proposed multifeed antenna achieves on-antenna low-loss power combining, which, compared with antenna array-based spatial power combining, does not suffer from narrowed beamwidth or enlarged antenna panel size. As proof of concept, multifeed slot antennas and a multifeed square loop antenna are designed and characterized at 10.3 GHz. Conventional single-feed slot antennas and a single-feed square loop antenna are also implemented as reference designs. Well matched antenna gains and radiation patterns between the proposed multifeed antennas and the conventional single-feed antennas are achieved in the measurements, demonstrating the on-antenna power combining of the proposed multifeed antennas without distorting the far-field radiation patterns.

© 1963-2012 IEEE. A novel design of boresight and conical pattern reconfigurable antenna with the capability of 360° polarization scanning is presented in this paper. At boresight mode, the antenna produces a continuously reconfigurable polarization over 360° in the azimuth plane, which provides adaptive-polarization reception between a transmitter and a receiver. The antenna is analyzed in terms of the electric field with an explanation of the generation of TM11 and TM02 resonant modes, which provides an innovative method of designing pattern reconfigurable antennas for the WLAN applications. The proposed method is validated by a good agreement between simulation and experimental results for an antenna designed to provide boresight and conical pattern switching at 2.4 GHz. The gain of 6.05 dBi and efficiency of 86.7% are measured in the boresight mode, corresponding to 4.39 dBi and 82.4% at conical mode.

This paper presents a novel and simple ultrawideband (UWB) printed rectangular monopole antenna (PRMA) for body-centric wireless communications. The design is based on etching a Q-slot on a rectangular radiator, and is optimized to produce the largest bandwidth in free space and close to the human body. We analyze the design of the proposed antenna and assess its performance in terms of bandwidth, gain, efficiency, and radiation patterns. We also characterize the antenna in the time-domain by calculating its fidelity factor. Our results show that the Q-slot antenna maintains its bandwidth when placed in close contact with the human body, or in contact with breast-mimicking tissue phantoms. The very good agreement between calculated and measured antenna performance in free space and on body suggests that the antenna is immune to variations in the human tissue, and is also robust to fabrication tolerances.

A monostatic dual-polarized simultaneous transmit and receive (STAR) antenna system with high isolation is introduced. A beamforming network (BFN) producing 0°, ±90°, ±180°, and ±270° phase progression is used to feed TX and RX ports of four dual-polarized antenna elements arranged in a sequential rotation array (SRA). Due to the phase progression and geometrical symmetry of SRA, the coupling from TX to RX ports is canceled at the RX port of the BFN; therefore, infinite system isolation is theoretically obtained. Full-wave simulations are used to verify the theory and study effects of element spacing and BFN imbalances. An additional cancelation layer is designed and used to compensate for the imbalances by the BFN and nearby scatterers. The proposed STAR antenna system is prototyped and tested in the 2.4–2.5 GHz industrial, scientific, and medical band where the measured isolation and return loss are above 47 and 22 dB, respectively. A dual circularly polarized antenna performance with realized gains above 7 dBic, broadside axial ratio

In this paper, we propose an ultrawide band design for the double ridged horn (DRH) antenna to be used behind the obstacle radar (BOR) applications such as ground penetrating radar (GPR) and through the wall radar (TWR) imaging. The design is developed and optimized by the help of full electromagnetic simulator code; CST. The design parameters such as frequencies of operation and the half power beam width (HPBW) are taken into account by considering the BOR application requirements. The design double ridged horn antenna provides a frequency bandwidth between 1.5 GHz and 7 GHz and HPBW around 30° around the center frequency that are very suitable for GPR and TWR applications. The final optimized design that is formed by CST is physically manufactured and measured. The prototyped DRH antenna’s measurement antenna parameter results are in good agreement with the simulated ones.

In this paper, a novel reconfigurable open slot antenna has been proposed for LTE smartphone applications to cover a wide bandwidth of 698–960 and 1710–2690 MHz. The antenna is located at the bottom portion of the mobile phone and is integrated with metal rim, thereby occupying a small space and providing mechanical stability to the mobile phone. Varactor diode is used to cover the lower band frequencies, so as to achieve a good frequency coverage and antenna miniaturization. The operational principles of the antenna are studied and the final design is optimized, fabricated, and tested. It has achieved the desired impedance bandwidth and the total efficiency of minimum 50% in free space throughout the required bands. The antenna performance with mobile phone components and human hand is also been studied. Furthermore, the SAR in a human head is investigated and is found to be within allowable SAR limits. Finally a multiple-input multiple-output antenna configuration with high isolation is proposed; it has an identical reconfigurable open slot antenna integrated at the top edge of the mobile phone acting as the secondary antenna for 698–960 and 1710–2690 MHz. Thus the proposed antenna is an excellent candidate for LTE smartphones and mobile devices.

An antenna system for high resolution airborne synthetic aperture radar (SAR) is developed at X-band. Basic specifications of the antenna are obtained from the swath and azimuth footprint requirements of the SAR system. Series-fed printed antenna is developed to achieve these specifications. To meet stringent requirement of isolation between the transmitting and receiving antenna, an optimized ground plane with horn flares is designed. Complete antenna system is simulated and measured for return loss, mutual coupling and radiation patterns. Measured results are in agreement with the simulated results as well as the requirements of the system. Achieved isolation between the transmitting and receiving antennas is better than 64 dB at the operating frequency.

In this paper, a four-port ultrawideband antenna design is proposed. The antenna is suitable for installation in pavements. The main application of this antenna is in the reuse of the existing manholes for radio equipment and antenna installation. Equally important is its application in dense network deployment as a result of its capability to alleviate intercell interference. The antenna can support up to $4\times 4$ multiple-input and multiple-output (MIMO) systems. The isolation between different ports exceed 28 dB over the commercial long term evolution bands 3 and 7. The multiport matching bandwidth of the antenna (>-0.3 dB) extends over 1700–3000 MHz range. The antenna is mechanically robust and can withstand a weight of 40 ton. MIMO performance of this antenna is verified by virtue of field measurements. A comparative study between the proposed antenna and a classic half-wavelength dipole antenna is presented highlighting the advantages of the proposed antenna. Finally, its compliance with the exposure limits for nonionizing radiation is also demonstrated.

Full-dimensional multiple-input multiple-output (FD-MIMO) systems, whereby each base station is equipped with a uniformly spaced rectangular antenna array (URA), provides a practical means of realizing massive MIMO systems. However, the spectral efficiency of URA is considerably lower than that of its uniformly spaced linear array counterpart having the same number of antenna elements. In this paper, we first introduce a discrete angular resolution metric for quantifying the low resolution of URA in the antenna-elevation domain. This motivates us to propose a novel antenna device design, referred to as the structured non-uniformly spaced rectangular array (NURA), in which the antenna elements are non-uniformly distributed in the elevation-angle domain. Specifically, we conceive a structured NURA device for which the nonuniform distribution of the elevation-domain antenna elements is controlled by a single parameter. The design of the optimally structured NURA for the given nonlinear antenna-element-positioning function then becomes a single parameter optimization, namely, that of maximizing the spectral efficiency of the FD-MIMO system, which can be solved efficiently. Our simulation results demonstrate that our structured NURA design significantly outperforms the standard URA in terms of achievable spectral efficiency. Our proposed structured NURA design therefore offers an effective practical framework for enhancing the achievable performance of FD-MIMO systems.

In this communication, a frequency and pattern reconfigurable V–shaped printed antenna is presented. The proposed structure operates at two different frequency bands. The variation in the frequency of operation is achieved by individually extending the length of each of the two antenna arms. The directional behavior of the proposed antenna structure is improved through the incorporation of a triangular parasitic element within the empty space between the two antenna arms. More specifically, the antenna is able to steer its gain pattern to either the left or right directions based on which arm of the V–shaped printed structure is fed. A prototype structure is fabricated and tested to validate the proposed approach in achieving directional behavior over two distinct frequency bands.

In multi-user beamforming systems, the inter-user interference are controlled by spatial filtering. Since the implementation of digital beamforming is difficult due to high hardware cost of large array system, the analog beamforming system with one phase shifter at each antenna element is considered with antenna selection scheme. However, the beamwidth is not sufficiently narrow to perfectly remove the interference due to limited size of antenna arrays. To mitigate the interference, we propose the random antenna selection system in millimeter wave channel. The random antenna selection expands the effective array size so that the beamwidth becomes narrow. We compare the beamwidth of conventional fixed antenna selection with random antenna selection and analyze the amount of interference for each selection scheme. Theoretical analysis and bit error rate simulation results indicate that the beamforming with random antenna selection can take advantage of large array.

TCAS/ACAS (Traffic/Aircraft Collision Avoidance System) is an airborne system designed to increase cockpit awareness of nearby aircraft and to service as a last defense against mid-air collisions between the aircrafts. In the existing system, four monopole stub elements are used as TCAS directional antenna and one blade type element is used as TCAS Omni-directional antenna. The transmission and reception frequencies of the TCAS antenna are 1.03G Hz and 1.09G Hz respectively. The existing TCAS antenna has some drawbacks such as low gain, large beamwidth, frequency and beam tuning/scanning issues etc. Antenna issues like unwanted signals reception may create difficulties in identifying the possible threats. In this paper, the focus is on the design and development of a novel Microstrip Antenna Array which can be used for TCAS/ACAS application. Two proposed antenna models are presented here – a Unit Element Dual Feed Microstrip Dual Patch Slotted Antenna and a Compact Microstrip Antenna Array. These are designed in CST tool to meet the current needs of aircraft Collision Avoidance System and to overcome the possible limitations associated with the existing techniques. The performance and other antenna characteristics have been explored from the simulation results followed by the antenna fabrication and measurement. A good Reflection Coefficient and VSWR with proper 50 Ω Impedance Matching, narrow Beamwidth, perfect Directional Radiation Pattern, high Gain and Directivity at the operating frequencies make this proposed antenna a good candidate for TCAS application. The proposed antenna would be expected to meet the requirements of the advanced avionics standards in terms of design simplicity, lightweight and high performance.

In this paper, a frequency reconfigurable antenna system with a directional selectivity is presented. The reconfiguration of the antenna's radiation characteristics is wirelessly controlled through a mobile phone and a microcontroller. The antenna system is a multi-element radiator composed of four monopoles on top of a hexagonal ground plane, in addition to four rectangular microstrip two-elements antenna arrays. The monopoles and the microstrip arrays are designed to contribute to the communication requirements of the complete system. The position, orientation, and topology of the various antennas are optimized to achieve the required frequency reconfigurability in addition to the variable selective directivity performance. The whole system is fabricated and integrated in a single compact unit controlled by a microcontroller, four servo motors, and a Bluetooth module. The antenna system is tested and the measured results confirm the validity of the proposed design.

© 2017 IEEE. A truncated circular cone slot array antenna that radiates a circularly polarized (CP) conical beam is presented. The direction into which the conical beam radiates depends mainly on the tilt angle of the outer conductor as well as the proper arrangement of the positions of its two slot arrays. The CP property is realized by introducing quasi-perpendicular slots that are cut into the outer conductor of a truncated circular cone. To illustrate the performance characteristics of this CP conical beam antenna, the tilt angle is set to 45° and the beam angle is pointed at 45° from boresight within the operating band. A prototype was fabricated and tested. The measured results demonstrate that its-10 dB impedance bandwidth ($\vert S-{{11}}{\rm{\vert \,< \,-10}}$ dB) is 720 MHz, from 5.05 to 5.77 GHz; and its 3 dB axial-ratio (AR) bandwidth is 500 MHz, from 5.5 to 6.0 GHz. Its realized gain over this AR bandwidth ranges from 4.84 to 5.8 dB. The designed beam direction can be easily changed to meet specific application requirements. Moreover, it can be readily reconfigured to be a conformal antenna mounted on the top of a high-speed mobile platform.

Multiple-input-multiple-output (MIMO) radars show improved angular resolution compared to traditional phased-array radar systems. Exploiting the advantages of MIMO radars could thus significantly improve the performances of the next generation of automotive radar sensors. The placement and the characteristics of the antenna arrays affect the performance of the MIMO system. For such applications, different metrics like the ambiguity function of the antenna system must be accurately evaluated. This letter presents a detailed characterization of an MIMO antenna configuration at millimeter-wave frequencies. To prove the effectiveness of this method, a five-element nonuniform antenna configuration based on cavity antenna arrays has been designed and tested., acceptedVersion

A modified microstrip Franklin array antenna (MFAA) is proposed for short-range radar applications in vehicle blind spot information systems (BLIS). It is shown that the radiating performance [i.e., absolute gain value and half-power beamwidth (HPBW) angle] can be improved by increasing the number of radiators in the MFAA structure and assigning appropriate values to the antenna geometry parameters. The MFAA possesses a high absolute gain value (>10 dB), good directivity (HPBW 80°) in the H-plane at an operating frequency of 24 GHz. Moreover, the 10-dB impedance bandwidth of the proposed antenna is around 250 MHz. The MFAA is, thus, an ideal candidate for automotive BLIS applications.

This paper theoretically analyzes the impact of the antenna sub-reflector focus excursion technique on the antenna pattern. First, we derive relevant formulas and analyze pattern variation based on the focus excursion. On this base, this paper then proposes a novel structure of antenna sub-surface focus excursion and investigates the concrete engineering realization. Experimental results based on the test-bed of the antenna show that the proposed focus excursion scanning technique improves the system performance and thus has a high-practical engineering value.

This letter proposes a novel toroidal plasma lens with circular polarization, as an alternative solution for electronic warfare antennas. The aim of the proposed solution is to reduce the antenna profile and the radar cross section, thus minimizing the probability of target detection. The results compare the performance of the proposed antenna to a conical horn and to a spherical/elliptical lens. The toroidal plasma lens achieved equivalent gain, with reduced antenna profile and reduced near-field backscattering from the plasma toroid, thus maximizing the true power delivered to the far-field region.

Horn antenna is flaring of open end of the waveguide. It is most widely used antenna at UHF and at microwave range. These are widely used transmitting and receiving antenna in the laboratory. Horn antenna provides a gradual transition of EM energy to the free space and prevent reflection of energy. The horn antennas are not always of small size, the world’s largest conical horn antenna is about 14 feet.In this review paper, various techniques of antenna have been proposed. This paper is a review for optimization of gain performance of an antenna. The different type of material has different effects on horn antenna. The Particle Swarm Optimization technique is also discussed here to optimize the results.

Massive multiple input and multiple output (MIMO) has attracted significant interests in both academia and industry. It has been considered as one of most promising technologies for 5G wireless systems. The large-scale antenna array for base stations naturally becomes the key to deploy the Massive MIMO technologies. In this communication, we present a dual-polarized antenna array with 144 ports for Massive MIMO operating at 3.7 GHz. The proposed array consists of 18 low profile subarrays. Each subarray consists of four single units. Each single antenna unit consists of one vertically polarized port and one horizontally polarized port connected to power splitters, which serve as a feeding network. A stacked patch design is used to construct the single unit with the feeding network, which gives higher gain and lower mutual coupling within the size of a conversional dual-port patch antenna. Simulation results of the proposed single antenna unit, sub-array, and Massive MIMO array are verified by measurement.

simple configuration omnidirectional microstrip planar antenna with agile features of frequency is paper is presented. The prototype design has the rectangular shaped radiating patch, which has four orthogonal slots. Where substrate dielectric constant value is 4.3, FR4-material for suppression of electric lines, Antenna is excited by the proximity feeding strip. Aim of paper to design a antenna reducing the size and to achieve symmetric broadside omnidirectional radiation pattern. The proposed antenna provides a solution for size reduction of the radiating patch while maintaining good broadside radiation pattern. Obtained results illustrate that the proposed radiating element is very effective in reducing the Antenna size. Good results of ReturnLoss-S11, gain, VSWR and radiation pattern can be achieved. The letter shows the novel smaller size proximity coupled single band for the application of C-Band microstrip antenna for 7.8 GHz frequency. Keywordsantenna, single and, proximity coupled, Gain, impedance.

A novel dual-mode triple-band communication terminal antenna is proposed in terms of the quadrifilar helix antenna and the BeiDou satellite navigation system. First, the folded arms are introduced, and at the top of the quadrifilar helix antenna, the folded arms are connected to the helix arms by the series capacitors. Second, the above quadrifilar helix antenna is applied to coaxially collocate with an ultrahigh-frequency monopole antenna. Furthermore, to solve the electromagnetic compatibility issues, a sleeve is coaxially collocated around the monopole antenna within the quadrifilar helix antenna, and the sleeve structure dimension parameters are optimized. Third, the above quadrifilar helix antenna collocated with the ultrahigh-frequency sleeve monopole antenna is designed to the B1 and B3 bands, based on the BeiDou satellite navigation system, and the military reserved ultrahigh-frequency communication frequency band is also supported, which satisfies the performance requirements of the multi-function antenna system in the communication terminal of soldier combat system to support navigation service. Finally, some numerical and experiment examples are provided to illustrate the performance of the proposed communication terminal antenna. And it shows that the proposed antenna system can easily be integrated with the existing soldier combat system device which reduced the maintenance costs.

This work analyzes planar antenna conformable to chair arm shaped surfaces for WLAN application. Closed form expressions for its radiation pattern are developed and validated using measurements on prototype and commercial EM code at 2.4 GHz.

A triple-band multibeam multiple-input multiple-output (MIMO) antenna is investigated for access points (APs). The triple-band antenna covers 2.4–2.5, 3.4–3.7, and 5.1–5.9 GHz frequency bands with high gains and directional radiation patterns for WLAN/WiMAX applications. The MIMO antenna consists of four triple-band antenna elements rotated around a circle for space and polarization diversities. The multibeam antenna is composed of four MIMO antenna units for the coverage of a conical area. The triple-band multibeam MIMO antenna is designed and the MIMO performance is evaluated. It is shown that low capacity loss and high diversity gain can be obtained with the low correlation and low branch power ratio between the MIMO antenna units. It is found that the four-beam MIMO antenna is suitable for large public places with high density clients where enhanced frequency reusability and reduced maintenance efforts are preferred.

A low-profile antenna installed on the road surface for RFID-enabled vehicle communication is presented. The antenna in this application operates as on-road sensor for vehicles identification. To that end, the antenna is required to have an elevated toroid-shaped radiation, so that the reader can easily interrogate an RFID-enabled vehicle license. The antenna is designed using a capacitive-loaded inverted-F radiator, which has an omnidirectional radiation in the azimuth plane. To adjust the radiation pattern to the required elevation above the road surface, and isolate the radiation from the effects of variable road conditions, a corrugated ground plane with perturbed surface impedance is used underneath the radiator. The antenna’s configuration is verified by full-wave finite difference time domain simulations with various road surface conditions. A prototype antenna is then developed and tested in realistic field scenarios as on-road sensor for vehicles identification. The results show that the antenna possess more than 15 dB return loss, more than 1.5 dBi gain, vertical polarization, and desirable radiation pattern from 880 to 960 MHz, which is the standard band licensed for RFID-enabled plates. The antenna also successfully communicates with an RFID-enabled vehicle registration plate.

A novel compact four-port reconfigurable multiple-input multiple-output (MIMO) antenna design for IEEE 802.11 applications is proposed. In one configuration, the antenna provides four ports operating from 4.9 to 5.725 GHz with isolation between antennas greater than 14 dB. In the second configuration, it provides a two-port antenna operating at 2.4–2.5 GHz together with another two-port antenna operating at 4.9–5.725 GHz all with isolations greater than 18 dB. The structure consists of four-slot antennas, and two of the slots are made reconfigurable by including MEMS switches in the slots. The overall antenna size is compact and occupies $46\times20\times1.6\;{\rm mm}^{3}$ and is printed on FR-4 printed-circuit-board. The proposed antenna is investigated by simulation and measurement, and results include radiation patterns, S-parameters, and signal correlations and branch power ratio (BPR) between ports. These show that in typical wireless environments’ envelope, cross correlations of less than 0.2 between the ports are obtained. The effect of the RF MEMS switches on the antenna performance is also addressed.

An interpolation method to reconstruct the 3-D directive antenna pattern is presented. The proposed method is based on the prior knowledge of the original antenna's principal planes patterns, to which a specific weighting method is applied to obtain an approximate 3-D antenna pattern. The performance of the proposed interpolation method is evaluated against 3-D antenna patterns from three typical directional antennas, extracted from appropriate electromagnetic simulation. Finally, a comparative analysis between the proposed method and current interpolation methods present in the literature is presented.

An active reconfigurable radar absorbing structure (RAS) with the pin diode was proposed to reduce the radar cross section (RCS) of antenna. The operating states of the RAS reflector can be switched by using the pin diode. For ON-state and OFF-state diodes, the reflection coefficients of the RAS reflector were less than −25 dB and more than −0.8 dB around 8.3 GHz, respectively. The RAS reflector with ON-state diodes can be used as a dipole antenna reflector and has the same radiation performance as a dipole with a metal reflector, while the RAS reflector with OFF-state diodes can be used as a radar absorber for RCS reduction. Meanwhile, chessboard-like geometry RAS reflector was proposed to achieve wideband RCS reduction. The RCS reduction band covers the working band and is extended to 5-18 GHz. The results show that the reconfigurable RAS reflector can contribute to the antenna RCS reduction at working frequency without loss of radiation performance of dipole antenna. With the detection and stealth technology developing rapidly, radar cross section (RCS) reduction (1-4) has been a serious problem in military applications and has attracted significant attention recently. Since the scattering of the antennas has contributed a lot to the total RCS for low observable platforms, more and more attention has been paid to antenna scattering. Shaping, coating with radar absorbing materials (RAM) and using passive and active cancellation technology are basic methods in stealth technology (5-7). Furthermore, a number of new structures and materials are applied to the RCS reduction of antenna, such as artificial magnetic conductor (AMC), radar absorbing structure (RAS), frequency selective surface (FSS), etc. (8-11). However, these structures and materials cannot be used for stealth in the working band. When RAS is used, the gain of the antenna has a large degeneration (12), and the application of AMC will increase the profile of the antenna. All of them greatly deteriorate the stealth performance and application of radar system or other platform. In early years, antennas did not need to work in airborne or missile borne systems continuously. To realize the stealth of antenna, the radar was opened in close proximity to the target and shut down through the dangerous area. This method has the advantages of simple, feasible, and good stealth characteristic. In addition, the radiation performance of the antenna is preserved. However, this method can only reduce the antenna mode scattering, and the structural mode scattering still exists. Meanwhile, general metamaterials are completely passive structures, and the properties of these metamaterials cannot be changed. Therefore, in the complex electromagnetic environment, these metamaterials cannot be able to quickly adapt to the changes in the external electromagnetic environment and reduce its effect. In order to overcome these problems, reconfigurable RAS is put forward as a new concept. Reconfigurable technology has been successfully applied to antenna design. Early research focused on changing the current distribution by adjusting the radiator structure, which made the frequency, pattern, polarization or impedance of antenna changed. Currently, the reconfigurable metamaterial is

In this communication, a reconfigurable feeding network is proposed for the design of a quad-polarization-agile antenna. By switching the PIN diodes, the four transmission modes with selected phase differences can be electrically tuned at two output ports. For each mode, the measured insertion loss of the feeding network is less than 0.8 dB at the operating frequency. Because of its compact size, the proposed feeding network can be further integrated with a dual-polarized aperture-coupled antenna, which can exhibit two orthogonal linear polarizations and two orthogonal circular polarizations. Measured results of the polarization-agile antenna are shown in detail, which verify its performance.

In the development of inter-vehicle communication systems for the prevention of car crashes, it is important to know radio propagation characteristics at blind intersections. In field experiments and numerical simulations to investigate radio propagation characteristics, a half wavelength dipole antenna is assumed to be the wave source in many cases. However, a directivity of car antenna is changed by the effect of both car body and antenna position on car. In this paper, path loss characteristics considering antenna positions on car body at a blind intersection in urban area for inter-vehicle communications using 700MHz band are investigated. Additionally, simplified car models are proposed for the efficient analysis of radio propagation. Here, the hybrid method using both FDTD and ray-tracing methods is used for the radio propagation analysis.

This article focuses on modeling of different options of antenna system including and in particular an antenna for the capsule endoscope (transmitter antenna) of the capsule endoscopic complex “Landish”. A helical antenna is reviewed for the transmitter, as well as a patch antenna on a curved substrate, and a quarter-wave monopole vibrator and a ceramic antenna. An experiment was conducted in order to compare the gain of the antennas at a fixed position in the space of the transmitting antennas, and the impact of the human body on the features of antennas. Recommendations on the choice of antenna systems in accordance with the simulation results are provided.

This letter introduces an antenna array calibration method that uses the channel response with known subject direction so as to accurately estimate living-body directions in multipath environments for elderly monitoring. Said calibration is extracted from the known living-body direction information using the Fourier transformed channel matrix. An experiment shows that the proposed method offers successful antenna array calibration even in indoor environments. Living-body directions are successfully estimated within acceptable error proving that the proposed method is effective in calibrating living-body radars.

A novel antenna design for implantable pacemakers is proposed. The housing of a pacemaker is utilized as an antenna to cover both the 402–405 MHz Medical Implant Communication Service band and the 433-MHz Industrial, Scientific and Medical band. This is achieved by exploiting radiating characteristic current modes of the housing case. These modes are excited using a capacitive coupling element with the help of a matching circuit. The radiation pattern of this antenna is optimized to be in a desirable direction away from the body (off-body direction). The ability of the proposed antenna for communications is demonstrated using a transceiver and a base station at 433 MHz. A communication range of 1 m is established when a transmitter with the proposed antenna is implanted in a rabbit and the power fed by the transceiver to the antenna is $25~\mu \text{W}$ . A longer range of up to 19 m can be established with the maximum allowable transmit power within the safety limits. Furthermore, the far field wireless power transfer through the proposed antenna is investigated by experiment. A received power of up to $22.38~\mu \text{W}$ by the proposed antenna is demonstrated when an equivalent isotropically radiated power of 140 mW is transmitted 1 m away from a transmitting antenna. From the same transmitting antenna in the same distance, a power of 4 mW can be received when the transmit power is within safety limits. This power can be used to recharge a small battery or a capacitor, which can potentially cover the communication power consumption of the pacemaker and hence extend the life span of the primary battery.

In this paper, a novel dual-band, dual-polarized, miniaturized and low-profile base station antenna operating in the frequency bands of 820–960 and 1710–2170 MHz is designed. Elements are arranged such that high-frequency elements are embedded in low frequency elements to reduce volume. A baffle is used to reflect the transmitted power density in the forward direction and also improve isolation between elements. Therefore, surrounding isolation baffles and rectangular baffles are appended around high-frequency elements and low-frequency elements, respectively. The diameter of the proposed antenna cover is only 200 mm, which is smaller than the existing antenna diameter of 280 mm. Compared with the other commonly used antennas, the proposed antenna also has some advantages such as concealment and low profile using a tubular form of radome, which can easily integrate the proposed antenna with the surrounding environment. The measured results verify that the proposed antenna meets the stringent design requirements: voltage standing wave ratio (VSWR) is less than 1.3, the isolation is greater than 30 dB, and the pattern parameters also meet telecommunications industry standards.

Antenna for the 88-108MHz Very high frequency (VHF) broadcast audio frequency-modulation (FM) band. The antenna is intended tofit in the flat area inside the head-band of an over ear hearing-protector headset. The space for the antenna is limited by an existing head-band design, where the unused internal area is the space studied in this thesis. A genetic algorithm is described for the multiple objective optimization of the antenna matching and radiation pattern optimization. The results of multiple genetic algorithm evaluations are described, and possible further improvements outlined. Progress is made on the development of the antenna. The antenna radiation pattern is evolved in desirable way, but a difficulty in solving the antenna matching problem is identified. Research for resolving the antenna matching problem is described in this paper

A simple U-shaped decoupling and matching network (DMN) with port pattern-shaping capability is presented for two closely spaced antennas. When the antennas are identical and symmetrically positioned, we prove that the port pattern remains unchanged, although an infinite number of U-shaped DMNs can be designed. Subsequently, two methods are proposed to enable port pattern-shaping capability without changing the antennas, i.e., changing the impedance matrix by adding a cross network between the antennas, and by introducing asymmetry to the U-shaped DMNs. These methods offer more freedom to the compact antenna system design especially in terms of pattern shaping.

An Antenna is one of the essential parts for microwave communication. Since it help both transmitting and receiving the information. An antenna is a device that is made to efficiently radiate and receive the radiated electromagnetic waves. The microstrip antennas have attractive features such as low profile, small size and weight, low cost, printed directly on circuit board and easy to analysis and fabricate. For reduction of return loss, stacked patch and Double U- slot on patch of microstrip antenna concept is used. A rectangular microstrip patch antenna has been investigated and its performance has been analyzed with the aid of Ansoft HFSS version 13.microstrip patch antenna, stacked patch microstrip antenna and double U- slot stacked patch microstrip antenna have been designed for S- band to reduce return loss of antenna.

This paper presents the design of a wideband microstrip patch antenna for LTE-A. The bandwidth of the conventional patch is enlarged by using etched slots at the antenna patch. The designed antenna has been fabricated by using thin film and photolithographic technique and has been measured by using the Vector Network Analyzer. The simulated and measured results were found to have good match with each other. Then, by using the designed single element antenna, a four-element MIMO antenna system has been built employing orthogonal polarization diversity. Isolation between the microstrip elements is increased by placing metal structure between antenna elements. For more isolation between antenna elements, Slotted Ground Plane SGP is utilized. It is found, by using commercial software CST Microwave Studio and measurement, that the designed planar MIMO antenna system has sufficiently high return loss and low mutual coupling at the required bandwidth of 70 MHz. It is found also that the developed antenna system meets the requirements for LTEAdvanced (2500 – 2570 MHz) band “CA-B7” as of today‟s standard based on 36.101 Table 5.5-1 (March 2012) .

This letter is concerned with the array design of a fixed point-to-point millimeter wave (MMW) communication system consisting of two paths between the transmitter and receiver. We assume uniform linear antenna arrays (ULAs) at both the transmitter and receiver and focus on the optimization of antenna deployment to maximize the system capacity with uniform power allocation. We analytically show that, at high signal-to-noise ratios (SNRs), the channel capacity depends on the spatial correlations between the two paths at both link ends. The optimal antenna array deployment that maximizes the channel capacity is derived. Numerical results show that the optimized antenna array deployment considerably improves the channel capacity, compared to the non-optimized deployment.

The large wavelength of decameter wave brings a lot of practical difficulties to the design of shipboard antennas in high-frequency (HF) band. How to design conformal or even platform-embedded HF antennas raises us a new challenging topic. This paper proposes an approach to address such challenging problem through the combination of the characteristic mode (CM) theory with the structural antenna concept. 1) The CMs are solved to understand the resonant behavior of the ship platform. 2) We synthesize the radiating currents for designated radiation pattern by making use of the CMs of the ship platform. It allows the dominant radiating currents to locally distribute on the superstructure of the ship. Consequently, the superstructure becomes the main radiator. The modal solutions in CM theory ensure the efficiency of the synthesis procedure. 3) Nonprotruding slits are proposed to excite the synthesized currents. As the resultant HF shipboard antenna has no protruding elements around the ship, this design can be considered as either platform-conformal or platform-embedded. As an example, HF antenna on a realistic ship with broadside radiation pattern is designed. Simulation and experimental results on a 1:400 scale model demonstrate the effectiveness of the proposed approach in HF shipboard antenna designs.

A dual-band antenna is designed for a fall-detection radar and telemetry system. The radar is designed based on the stepped frequency continuous wave (SFCW) concept, which requires Ultra Wideband (UWB) operation, low inter-element coupling and a directive radiation pattern with low backlobe. The telemetry system uses the 2.45 GHz band to enable signal transmission/reception in an indoor environment and the 6-7.5 GHz band for radar sensing part. A main dual-band radiator with a slotted patch is used as the basis for the antenna design: the patch resonates at 2.45 GHz whereas the antenna slot enables a wide band operation for the radar system. To enable a low-profile, an artificial magnetic conductor (AMC) structure is integrated into the antenna. It works as a perfect magnetic conductor (PMC) plane from 6 to 7.5 GHz and can be located close to the slot antenna functioning as a reflector. Both numerical and experimental results indicate a satisfactory antenna performance in terms of reflection coefficient and radiation pattern. The antenna was also integrated into the radar system and tested in a real environment on three subjects at fixed distances. A fall-detection up to 6 meters was achieved.

The present paper analyses and documents the merits of incorporating fractal design in microstrip antenna intended to be mounted on and integrated into the design of smart vehicles. A novel design is proposed for a compact tri-band hexagonal microstrip antenna to be integrated with the body of a smart vehicle for short range communication purpose in an Intelligent Transport System (ITS). This antenna can be used at 1.575 GHz of GPS L1 band for vehicle to roadside communication, at 3.71 GHz of mobile WiMAX band (IEEE 802.16e-2005) for blind spot detection and at 5.9 GHz of DSRC band (IEEE 802.11p) for vehicle to vehicle communication. At 3.71 GHz, the two major lobes of the antenna radiation beam, tilted by 35 ◦ on both sides from its broadside direction, help the vehicle to detect blind spots efficiently. The largest dimension of the proposed antenna corresponds to the lowest resonating frequency, 1.575 GHz. Compared to the conventional hexagonal patch, the modified Sierpinski fractal proposed herein reduces the overall area, at 1.575 GHz, by 75%, with 5.2 dBi gain. In comparison with other popular fractals, the proposed fractal structure achieves demonstrably better antenna miniaturization. When the antenna is mounted on the vehicle, considered an electromagnetically larger object, the simulated and on-vehicle experimental results show antenna gains of more than 5.5 dBi at 1.575 GHz, 8 dBi at 3.71 GHz and 9 dBi at 5.9 GHz in the desired direction with negligible amount of electromagnetic interference inside the car.