Antenna Size Research Articles

Review of Antennas for Railway Communications

This paper presents a review of the state-of-the-art antennas for the railway communications. There are various aspects that one should consider when designing an antenna, such as antenna size and directivity. While size constraints on railway antennas are not as critical as for mobile consumer counterparts, a radome structure is required to cover the antenna to minimize the aerodynamic resistance antenna. This paper reviews aerodynamic simulations to account for the drag coefficient of the antenna. In a low-frequency band (<5 GHz), railway antennas used to be omnidirectional in the horizontal plane. As the communication scheme advances toward 5G technology, high directivity is required for the railway antenna to compensate for the high path loss at high-frequency bands, i.e., 28-GHz band. We review recent studies of railway antennas over various frequency bands, such as LTE-R, LTE, and the lower and upper 5G bands. To accommodate multiple frequency bands with a single antenna, along with the aerodynamic radome cover, design techniques allowing multiple frequency bands are reviewed in this paper.

Development of a Triple Band Notched UWB Antenna

In this paper, a microstrip line-fed rectangular-shaped ultra-wideband (UWB) antenna offering triple-band notch characteristics is proposed. The notching was done primarily to provide rejection for Wi-Max (3.3-3.7 GHz), WLAN2 (5.15-5.825 GHz), and ITU (8.025-8.4 GHz) through the combination of slots and a modified electromagnetic band gap (M-EBG). The antenna was simulated using HFSS and CST modelling tools. The antenna was able to notch three frequencies from narrow band communication systems (Wi-Max, WLAN2, and ITU), causing interference within the UWB band. The gain of the system over the operating frequency, the current distributions, and the impedance covered were studied to assess the effectiveness of the antenna. The proposed antenna is simple and compact, with a total antenna size of 19 mm by 24 mm and a wide bandwidth (3.2 to 12.5 GHz). Satisfactory results have been obtained when its performance was analyzed. A stable radiation characteristic is observed with a radiation efficiency of 94% when operating at a UWB resonant frequency of 6.85 GHz with a total gain between -10 dB and 5 dB within the range of the frequency band of 3.2 to 12.3 GHz.

Parachute shape ultra‐wideband wearable antenna for remote health care monitoring

SummaryWireless body area networks (WBAN) is used to measure patients' health conditions continuously. Different kinds of sensors are required to measure health conditions. When such types of antennas are used on the human body, they are flexible with the movements. The usage of wearable devices is currently increasing in the biomedical field. The presented wearable antenna is suitable for biomedical applications. The presented ultra‐wideband (UWB) flexible parachute shape wearable antenna is fabricated on a jeans textile substrate. The prototype antenna has a −10 dB measured impedance bandwidth of 5800 MHz (7 to 12.8 GHz) with average radiation efficiency of 75.28%. The prototype antenna's size is 40 × 40 mm2 (1.32 × 1.32 at centre frequency 9.9 GHz) and a peak gain of 4.5 dB at 12.33 GHz. The fabricated antenna is suitable for biomedical applications in X‐band frequencies and can be implemented with a low‐cost manufacturing process. The radiating element is made by conductive copper tape. Muscle‐equivalent phantoms are used to analyze the body effect on antenna performance. The radiation effect emitted by the presented antenna on the human body is calculated by the specific absorption rate (SAR) value. The maximum SAR value of the proposed antenna is 1.84 W/kg at 12.33 GHz. This leads to promising results for wearable applications related to remote health care monitoring, such as biotelemetry and mobile health with a sensor‐driven approach.

Deep learning-based massive MIMO channel estimation with reduced feedback

The downlink channel state information (CSI) must be available on the base station (BS) side to take advantage of all the features of massive multiple-input multiple-output (MIMO) systems. The channel estimation in massive MIMO systems is a challenging task because of the huge pilot and feedback overhead due to the large size of antennas. In this paper, we have proposed a multi task deep network for the channel estimation with the aim of decreasing the pilot and feedback overhead. An encoder network is designed to compress the received signal and reduce the feedback overhead. Furthermore, a decoder network is developed to reconstruct the compressed feedback. The estimator network is suggested to provide the channel estimation from the reconstructed feedback. The performance of the presented scheme has been evaluated in various simulation scenarios. The results confirm that the proposed method is capable of estimating the channel more accurately than the contemporary works. Moreover, this method has reduced the feedback and pilot overhead to a great extent.

Performance Analysis of Different Shapes of Microstrip Patch Antenna Having Partial Ground for X and Ku Band Applications

The shape of the radiating patch exerts a great influence on the performance of the microstrip patch. The vital target of this research article is to constitute the microstrip antennas of rectangular, elliptical, triangular and square patches on FR4 substrate employing partial ground that notably lower the shape complexity and hence the antenna size reduction with profitable results on the basis of the center frequency of 8.5 GHz. The execution specification, such as S-parameter, gain, VSWR, and the directivity of the antenna, is investigated using ANSYS HFSS 13.0 software, which reveals beneficial outcomes of dual-band operation over the entire band frequency range of 5-15 GHz. The antenna gives poor results without any modification to the ground structure. But good bandwidth, dual band nature, better gain directivity, VSWR, and the best efficiency are achieved by the introduction of partial ground in the design of all the shapes. This is applicable for Marine Radar Communication (SART), Effective Satellite Communications, and Wireless Communication applications like weather monitoring, defense, and military purposes.

A Compact Size Antenna for Extended UWB with WLAN Notch Band Stub

An ultra-wideband (UWB), geometrically simple, compact, and high-gain antenna with a WLAN notch band is presented for future wireless devices. The antenna is printed on the top side of the Rogers RT/Duroid 5880 substrate and has a small dimension of 10 mm × 15 mm × 0.254 mm. The primary radiator of the proposed coplanar waveguide-fed monopole antenna is comprised of a rectangular-shaped structure initially modified using a slot, and its bandwidth is further enhanced by loading a Y-shaped radiator. As a result, the antenna offers a –10 dB impedance matching bandwidth of 11.55 GHz ranging from 3–14.55 GHz, covering globally allocated C-, S-, and X-band applications. Afterward, another rectangular stub is loaded in the structure to mitigate the WLAN band from the UWB spectrum, and the final antenna offers a notched band spanning from 4.59 to 5.82 GHz. Moreover, to validate the simulated results, a hardware prototype is built and measured, which exhibits good agreement with the simulated results. Furthermore, the proposed work is compared to state-of-the-art antennas for similar applications to demonstrate its design significance, as it has a compact size, wider bandwidth, and stable gain characteristics.

All-metal cavity antenna with light weight, high efficiency and circular polarization for satellite platform applications

In this paper, a lightweight high-efficiency circularly polarized (CP) all-metal antenna design method is presented for satellite industry applications. The proposed antenna is composed of a rectangular waveguide feeder, a high-order mode cavity and a metasurface circular polarizer (MCP). The cavity high-order mode TE440 is directly excited by four coupling slots in the waveguide. The MCP is placed on the cavity to generate the CP radiation. Due to the introduction of high-order mode technology and MCP, all metal walls inside the antenna can be removed, which are necessary in conventional waveguide structures, and weight is thereby significantly reduced. To reflect the weight advantage, a conventional metal wall-loaded waveguide antenna of the same size is designed. The measured results show that the proposed antenna has wider impedance and axial ratio bandwidths, and higher radiation efficiency. In particular, the proposed antenna is 40% lighter than the comparative one, indicating that it is more applicable to satellite platforms with limited loading capacities.

AWOA: An Advanced Whale Optimization Algorithm for Signal Detection in Underwater Magnetic Induction Multi-Input–Multi-Output Systems

With the increasing exploitation and use of marine resources, the limitations of acoustic, optical, and radio frequency technologies for underwater communications have become increasingly apparent. Magnetic induction (MI) is a new communication technology that enables wireless data transmission via magnetic field coupling between transmitting and receiving coils. MI offers advantages such as channel stability, small antenna size, and no multi-path loss. Multi-input–multi-output (MIMO) is a multi-antenna technology that significantly increases system capacity and spectrum utilization without increasing bandwidth. The whale optimization algorithm (WOA) is a well-known bio-inspired algorithm that mimics the hunting behavior of whales to optimize swarm intelligence. This paper proposes a model for an underwater MIMO communication system based on magnetic induction. We then construct a signal detection algorithm for MI-MIMO systems using the advanced whale optimization algorithm (AWOA) and conduct simulation experiments to compare the performance and complexity of three standard signal detection algorithms: zero-forcing (ZF), minimum mean square error (MMSE), and maximum likelihood (ML). The experimental results show that AWOA achieves suboptimal results, as its bit error rate (BER) is close to that of the ML algorithm. Furthermore, the complexity of AWOA is comparable to that of the MMSE strategy. This work supports the development of a high-performance MI-based underwater communication system.

Design of Miniaturised Circular Polarisation-Reconfigurable and Frequency Agile Slow-Wave SIW Based Microstrip Antenna for Wireless Applications

ABSTRACT Maintaining acceptable radiation performance over the entire operation bandwidth is a significant challenge in development of a miniaturized reconfigurable antenna To address this issue, a new Substrate Integrated Waveguide (SIW) based reconfigurable antenna using slow wave structure is presented in this study. The proposed SIW antenna is based on a layered construction with metallic blind vias connecting to ground plane of SIW. The multi-layer structure of SIW with blind vias helps to separate magnetic and electric fields in the SIW cavity. Thus, a slow wave effect is also utilized and it leads to 36% reduction in the antenna size as compared to conventional SIW cavity. To attain the polarization and frequency reconfiguration, a cross slot is introduced in the top metallic layer of the SIW cavity and four PIN diodes are connected into the cross-slot arms. Experimental results exhibit frequency reconfigurability in different operating regions with resonant frequencies 4.35, 5, 5.8, 6.4, and 9.6 GHz. The polarization reconfigurability of the proposed antenna is achieved at 5 GHz with LP/RHCP/LHCP. The proposed antenna exhibits 3-dB axial ratio bandwidth of 4.8 to 5.2 GHz with peak gain of 4.2 dBi.

Flexible and Small Textile Antenna for UWB Wireless Body Area Network

In this paper, a miniaturized textile microstrip antenna is proposed for wireless body area networks (WBAN). The ultra-wideband (UWB) antenna used a denim substrate to reduce the surface wave losses. The monopole antenna consists of a modified circular radiation patch and an asymmetric defected ground structure, which expands impedance bandwidth (BW) and improves the radiation patterns of the antenna with a small size of 20 × 30 × 1.4 mm3. An impedance BW of 110% (2.85–9.81 GHz) frequency boundaries was observed. Based on the measured results, a peak gain of 3.28 dBi was analyzed at 6 GHz. The SAR values were calculated to observe the radiation effects, and the SAR values obtained from the simulation at 4/6/8 GHz frequencies followed the FCC guideline. Compared to typical wearable miniaturized antennas, the antenna size is reduced by 62.5%. The proposed antenna has good performance and can be integrated on a peaked cap as a wearable antenna for indoor positioning systems.

High performance H-plane horn antenna using groove gap waveguide technology

In this study, a high-performance H-plane horn antenna using the concept of gap waveguide (GW) technology with high power handling in the Ka-band was investigated. It is composed of two parallel un connected metal plates with embedded metal pins in both of inner palates. These metal pins can be compensated the phase difference between the center and edges of the aperture. Therefore, the antenna proposed can provide higher gain. Furthermore, a triangular step in front of aperture lead to gain enhancement. The size of the horn antenna is about 4.9 λ × 3. 5 λ at center frequency. The antenna has low cross-polarization level across about −45 dB at the whole operating frequency band. The measured results shown that the antenna has a suitable bandwidth more than 34% for target |S11|<-10 dB in 19 to 27 GHz frequency operations. This antenna can provide peak gain about 13.5 to 15.9 dBi. The experimental results approved that the proposed antenna have a total efficiency better than 92% and a good agreement with simulation results.

Analysis of Flexible Silver-printed NFC Tag Antenna on Miniaturization and Bending Effect

Size and flexibility are the two main elements that must be considered in designing a near-field communication (NFC) tag antenna because they will determine the performance of the whole system. The previously designed NFC tag antenna, which is made of a rigid substrate such as FR-4, limited the application of the tag to only on a flat surface. The size of the tag antenna also needs to be optimised based on the application requirements since different sizes of the antenna will contribute to different electrical properties, including inductance and resistance. Therefore, this paper presents an analysis of a flexible printed tag antenna with different miniaturisation sizes and bending effects for NFC systems. The operating frequency of the proposed NFC tag antenna is 13.56 MHz, which is the same frequency as the NFC reader, allowing them to be coupled and to communicate with each other. Three sizes of silver printed tag antenna are presented, and the performance of the tag during bending is analyzed. Other tag antenna parameters and characteristics, including reflection coefficient, inductance, resistance, read range and output voltage, are also observed through simulation and accordingly measured. The results show that the Design 1 antenna has demonstrated the highest measured tag reading range of 3 cm, while the Design 2 antenna has shown good flexibility, withstanding bending at various angles and exhibiting a minimum reading range of 0.5 cm. Overall, the correlation between antenna size, flexibility and antenna performance has been determined and systematically validated.

Decreasing photosystem antenna size by inhibiting chlorophyll synthesis: A double-edged sword for photosynthetic efficiency

Improving photosynthetic efficiency has long been considered as an important strategy to increase crop yield. Optimization of antenna size of photosynthetic systems is one strategy to increase plant photosynthetic efficiency. However, applying this strategy to improve photosynthesis received conflicting results, and the reasons behind these conflicts are unclear. In this study, we constructed transgenic rice with amiRNA targeting to YGL1, which encodes a key enzyme of chlorophyll a/b synthesis in chlorophyll biosynthesis pathway, to generate different lines with different leaf chlorophyll contents and antenna sizes to test under what conditions reduction of antenna size can improve photosynthesis. We found that leaf photosynthesis, canopy photosynthesis (Ac), biomass and grain yield of the heterozygote were not significantly different from those of wild type (WT) while the Ac, biomass and yield of the homozygote were lower than those of WT. Further, when the maximal quantum yield of photosystem II (Fv/Fm) was larger than 0.8, decreasing antenna size by reducing chlorophyll biosynthesis didn't affect leaf photosynthesis. In view of this phenomenon, we proposed that the accumulation of protoporphyrin and the reduced photoprotection capacity might be the cause of the decrease in Fv/Fm and Ac. Therefore, this study shows that reduction of antenna size by inhibiting chlorophyll synthesis can lead to improved light distribution and photosystem efficiency, as long as photodamage and photobleaching can be avoided to maintain the photosystem II efficiency. The double-edged sword effect of inhibiting chlorophyll synthesis on photosynthetic efficiency should be considered when the antenna size is manipulated to gain higher photosynthesis.

Steerable composite right–left‐hand‐based printed antenna circuitry for 5G applications

AbstractIn this article, the proposed antenna structure is designed for modern wireless communication systems. The antenna structure is consistent with 11‐unit cells of composite right–left‐hand (CRLH) inclusions mounted on an FR4 substrate. Therefore, the antenna size is miniaturized effectively to 30 × 20 mm2 to cover the frequency bands around 2.45 GHz, for Wi‐Fi, and 4.2–6 GHz, for sub‐6 5G, networks. The design process is conducted on a circuit model and numerical simulations by evaluating the unit cell transmission phase spectra. For this, a comparison between the circuit model and the numerical simulations is invoked for validation. Such an antenna is found to provide a maximum gain of 6.2 dBi at 4.6 GHz. Next, 11 PIN diodes control the current motion between the antenna patch and the CRLH array. Therefore, PIN arrays are connected to the patch and the ground plane to maintain the surface current motion that realizes main lobe beam steering. The proposed antenna performance is simulated numerically using the CSTMWS software package. Then, it is fabricated and tested experimentally for validation. An excellent agreement is achieved between the simulated and measured results. Finally, it is found this antenna provides excellent beam steering −92° to 92° to suit many modern networks.

Bandwidth Improvement of a Cone-Inverted Cylindrical and Cross Hybrids Dielectric Resonator Antennas

This work employs the coaxial probe method to stack and excite two cone-inverted cylindrical and cross-hybrid dielectric resonator antennas at a standard operating resonant frequency of 5.438 GHz. A drawback of these standard Dielectric Resonator Antennas (DRAs) is their narrow bandwidth. For good antenna performance, a stacked DR geometry and a thick dielectric substrate with a low dielectric constant are desired since this provides large bandwidth, better radiation power, reduces conductor loss and reduces the nonappearance of surface waves. Many approaches, such as changing the shape of the dielectric resonator, have been used to enhance bandwidth. Using DRA, which has the lowest dielectric constant, increases the bandwidth and the electromagnetic energy. In the current work, bandwidth improvement was significantly achieved by the proposed geometry by varying the antenna size. A novel hybrid DRA configuration is used to increase the bandwidth of the antenna to 89.27% and 149.23% due to cone-inverted cylindrical and cross-hybrid dielectric resonator antennas, respectively. The DRA is designed numerically via the Finite Difference Time Domain (FDTD) method. Several parameters like return loss, input impedance (verified at ) and radiation pattern are calculated. Furthermore, the stacked-hybrid technique is used to enhance the antenna's performance, which is useful for broadband communication and the demand for wireless.

Low-Cost Broadband Circularly Polarized Array Antenna with Artificial Magnetic Conductor for Indoor Applications

In this paper, we report a sequential-phase fed broadband circularly polarized array antenna loaded with an artificial magnetic conductor-reflecting surface. Our proposed antenna is a two-part group. The upper structure is a sequential-phase fed circular wide-slot antenna. The lower part is an artificial magnetic conductor structured reflective surface. The overall antenna size is 106 × 106 × 14.9 mm3, both adopting 1.6 mm thick FR4 material. The thickness of the air layer sandwiched between the antenna and the artificial magnetic conductor reflective surface is 14 mm. The antenna consists of four circular wide-slot antenna units with a sequential rotation technique. To broaden the axial ratio bandwidth, three L-shaped branches and four metal plates are attached to the circular wide-slot antenna unit and around the artificial magnetic conductor-reflecting surface, respectively. To verify the accuracy of the simulation, we fabricated the sample and then tested it in an anechoic chamber. The measured results demonstrate that the proposed broadband circularly polarized array antenna realizes an impedance bandwidth of 77.67% (2.74–6.22 GHz) and an axial ratio bandwidth of 65.16% (3.00–5.90 GHz) with a peak gain of 11.1 dBi. The design can be used in space-constrained environments, such as indoor and dense building areas.

High-efficiency and CMOS compatible out-of-plane light emission based on a silicon coupler.

Photonic antennas are critical in applications such as spectroscopy, photovoltaics, optical communications, holography, and sensors. Metal antennas are widely used because of their small size, but they are difficult to be compatible with a CMOS. All-dielectric antennas are easier to integrate with Si waveguides, but are generally larger in size. In this paper, we propose the design of a small-sized, high-efficiency semicircular dielectric grating antenna. The antenna's key size is only 2.37µm×4.74µm, and the emission efficiency reaches over 64% in the wavelength range from 1.16 to 1.61µm. The antenna provides a new, to the best of our knowledge, approach for three-dimensional optical interconnections between different decks of integrated photonic circuits.

Design of Tight Coupling Antenna to Realize Ultra-Wideband Function

In this paper, according to the tightly coupled antenna theory, the dual-polarized tightly coupled antenna of 15–40 GHz is designed. The antenna size is 3.75 mm × 3.75 mm × 2.38 mm, and the spacing between the elements is 3.75 mm. The media used from bottom to top are Rogers5880, PP adhesive, RogersTMM10, and feed line using coaxial line directly, with a coaxial line inner core radius of 0.2 mm. Based on the simulations, we find that the antenna can easily cover ±45° and maintain good active standing wave performance. The antenna can support ±60° maximum Angle scanning and maintain good active standing wave performance.

The photosynthetic apparatus of the CAM plant Tillandsia flabellate and its response to water deficit

CAM plants are superior to C3 plants in drought resistance because of their peculiar photosynthesis pathway and morphological features. While those aspects have been studied for decades, little is known about the photosynthetic machinery of CAM plants. Here, we used a combination of biochemical and biophysical methods to study the photosynthetic apparatus of Tillandsia flabellate, an obligatory CAM plant. Most of the Photosystems super- and sub-complexes have properties very similar to those of Arabidopsis, with the main difference that in Tillandsia PSI-LHCI complexes bind extra LHCI. Functional measurements show that the PSI/PSII ratio is rather low compared to other plants and that the antenna size of both PSI and PSII is small. Upon 30-day water deficiency, the composition of the photosystems does not change significantly, PSII efficiency remains high and no Photosystem II photoinhibition was detected despite a reduction of non-photochemical quenching (NPQ).

Long-Term Alleviation of the Functional Phenotype in Chlorophyll-Deficient Wheat and Impact on Productivity: A Semi-Field Phenotyping Experiment.

Wheat mutants with a reduced chlorophyll synthesis are affected by a defective control of the photosynthetic electron flow, but tend to recover a wild-type phenotype. The sensitivity of some mutants to light fluctuations suggested that cultivation outdoors could significantly impact productivity. Six mutant lines of Triticum durum or Triticum aestivum with their respective wild-type cultivars were cultivated with a regular seasonal cycle (October-May) in a semi-field experiment. Leaf chlorophyll content and fluorescence parameters were analysed at the early (November) and late (May) developmental stages, and checked for correlation with morphometric and grain-production parameters. The alleviation of the phenotype severity concerned primarily the recovery of the photosynthetic-membrane functionality, but not the leaf chlorophyll content. Photosystem II (PSII) was less photoprotected in the mutants, but a moderate PSII photoinhibition could help control the electron flow into the chain. The accumulation of interchain electron carriers was a primary acclimative response towards the naturally fluctuating environment, maximally exploited by the mature durum-wheat mutants. The mutation itself and/or the energy-consuming compensatory mechanisms markedly influenced the plant morphogenesis, leading especially to reduced tillering, which in turn resulted in lower grain production per plant. Consistently with the interrelation between early photosynthetic phenotype and grain-yield per plant, chlorophyll-fluorescence indexes related to the level of photoprotective thermal dissipation (pNPQ), photosystem II antenna size (ABS/RC), and pool of electron carriers (Sm) are proposed as good candidates for the in-field phenotyping of chlorophyll-deficient wheat.