Antenna Radiation Research Articles

Creation of optical chains with prescribed characteristics

We report a non-iterative method to create an arbitrarily spatially-orientated optical chain with prescribed characteristics through the use of antenna radiation theory and time reversal methodology. A pair of antennas consisting of an electric current line source (ELS) and a magnetic current line source (MLS) are employed to yield the required incident field pattern for focusing system. Numerical results demonstrate that the direction of the generated optical chain is consistent with the orientation of the combined antennas, and the length of the optical chain is approximately equal to the length of the combined antennas, and the amount, position and spacing of the dark hollow spots are determined by the length of the combined antenna and the amplitude periodic coefficient of the ELS. The generated optical chains may find potential applications in multi-points optical capture and particle delivery along prescribed directions.

A W‐band dual‐beam low side‐lobe level antenna with shared slotted waveguide arrays

AbstractA W‐band dual‐beam low side‐lobe level antenna with a shared slotted waveguide radiating layer was designed by the authors. The proposed antenna consists of a symmetrical dual ports feed network layer located on two sides of the antenna, a novel shared symmetrical 4 × 32 slotted waveguide array radiation layer, and a bottom layer. The compact slot distance was adjusted to achieve deflection of the radiation pattern and reduce the radiation grating lobes. Good antenna radiation efficiency and port isolation were obtained by optimising the position of the slots at the radiation layer. A low side‐lobe level (SLL) was obtained using Taylor distribution was used in the design of the offset of each slot. The optimised antenna was fabricated and measured. Based on measurement results, the designed antenna has a 24.8 dBi far‐field gain, −17/–25.5 dB E/H plane side lobe level, and 19.8° beam deflection at 94 GHz. The performances of the two ports were in good agreement with each other, and the measured isolation was above 14.5 dB at 94 GHz.

Design of ultra-wide band dual-polarized quad ridged horn antenna for obstacle penetrating radar imaging applications

In this study, a high-gain and dual-polarized Quad Ridged Horn Antenna (QRHA) is proposed and designed to be used in Obstacle Penetrating Imaging Radar (OPIR) applications. The quad ridged design is developed and then optimized by using the antenna design simulator software; CST Microwave Studio. The antenna parameters including the center frequency, frequency bandwidth and the antenna radiation pattern beam width are considered based on the requirements of OPIR applications. The final design is obtained for the center frequency of 2.785 GHz with a -10 dB bandwidth of at least 2.5 GHz. The final designed QRHA is able to provide a gain of 12.4 dB with a beam width of 36ᵒ at the center frequency of 2.785 GHz.

A Novel Compact Filtering Antenna for 5.0-GHz WLAN Communication System

The proposed antenna presents a microstrip filter antenna with both filter out-of-band rejection characteristics and antenna radiation characteristics for WLAN communication system. The antenna consists of four U-shaped microstrip resonators, one Γ-shaped antenna, and one parallel coupling line. The Γ-shaped antenna has the filtering function as the last order resonator, and the parallel coupling line integrates the filter and antenna as the conductance converter. After simulation and test, the results show that the center frequency of the filter antenna is 5.25 GHz, the fractional bandwidthis 8.0% (5.0 − 5.42 GHz), the in-band gain changes smoothly, the maximum in-band gain is 3.059 dBi, the gain at 150 MHz outside the passband rapidly decreases to 10.0 dBi, and the overall out-of-band gain drops to below −24 dBi. The filter antenna has a simple structure and thin substrate, which optimizes the overall size of the filter and antenna, reduces the transmission loss between them, and is applicable to the RF front-end of wireless communication systems.

A Miniaturized Dual-Band Short-Ended ZOR Antenna with Backed Ground Plane for Improved Bandwidth and Radiation Efficiency

This paper presents a miniaturized planar dual-band short-ended metamaterial antenna with the backed ground plane to improve antenna bandwidths and radiation characteristics. The proposed dual-band metamaterial (MTM) antenna has been made up of the composite right- or left-handed transmission line (CRLH-TL) concept. Here, the backed ground plane has been employed to generate an extra coupling capacitance (CC), which shifts the ZOR frequency in the lower band while also improving ZOR matching and increasing the impedance bandwidth of the higher-order mode. In this proposed MTM antenna, interdigital capacitance (IDC) has been used in place of a simple series gap, which shifts the higher-order impedance bandwidth into a lower frequency band for second-band Wi-MAX applications (3.3–3.7 GHz). The proposed antenna offers a short-ended MTM, and hence the ZOR frequency is controlled by a series of LC lumped parameters. The proposed antenna offers dual-band behavior with measured −10 dB impedance bandwidths of 5.55% and 41.57% at centered frequencies of 2.70 GHz and 4.33 GHz, respectively. The overall electrical size of the designed antenna is 0.225λ0 × 0.144λ0 × 0.0144λ0 at ZOR (f0 = 2.70 GHz), where λ0 is the free space wavelength; therefore, it is applicable for different Wi-MAX application bands (2.5–2.7 GHz/3.3–3.8 GHz). Furthermore, the proposed dual-band MTM antenna provides compactness, low loss, stable gain, and radiation efficiency, and also offers omnidirectional radiation patterns in the E-plane and dipolar type radiation patterns in the H-plane, respectively.

UAV-Based Wireless Data Collection from Underground Sensor Nodes for Precision Agriculture

In precision agriculture, information technology is used to improve farm management practices. Thereby, productivity can be increased and challenges with overfertilization and water consumption can be addressed. This requires low-power and wireless underground sensor nodes for monitoring the physical, chemical and biological soil parameters at the position of the plant roots. Three ESP32-based nodes with these capabilities have been designed to measure soil moisture and temperature. A system has been developed to collect the measurement data from the sensor nodes with a drone and forward the data to a ground station, using the LoRa transmission standard. In the investigations of the deployed system, an increase in the communication range between the sensor node and the ground station, from 300 m to 1000 m by using a drone, was demonstrated. Further, the decrease in the signal strength with the increasing sensor node depth and flight height of the drone was characterized. The maximum readout distance of 550 m between the sensor node and drone was determined. From this, it was estimated that the system enables the readout of the sensor nodes distributed over an area of 470 hectares. Additionally, analysis showed that the antenna orientation at the sensor node and the drone influenced the signal strength distribution around the node due to the antenna radiation pattern. The reproducibility of the LoRa signal strength measurements was demonstrated to support the validity of the results presented. It is concluded that the system design is suitable for collecting the data of distributed sensor nodes in agriculture.

Generation of a linear array of focal spots with prescribed characteristic using the radiation pattern from a tapered line source antenna

We report an approach for generating a linear array of focal spots with prescribed characteristics through the use of the antenna radiation theory and time reversal technology. A virtual line source antenna with a cosine-squared tapered distribution, placed at the vicinity of the common foci of a 4π-system, is employed to obtain the required illumination in the pupil plane. The polarization direction of the generated focal spots and the alignment direction of the linear array are determined by the spatial orientation of the line source antenna. The amount of focal spots depends on the period of the amplitude distribution. The position and spacing of the focal spots are related to the length and the period of the amplitude distribution. The generated linear arrays of focal spots have potential applications in laser micromachining, optical imaging and optical micromanipulation that require multiple focal points or synchronous optical operations.

Development of VHF-Band Conformal Antenna for UAV Mounting

In this paper, a VHF band conformal antenna for UAV mounting was developed. The proposed antenna was designed as an shape-adaptive structure by minimizing the antenna height to be advantageous in RCS reduction performance. As for the antenna radiator, the outer radiator was arranged around the inner radiator to apply the CRLH zeroth-order resonance structure. With this structure, the height of the antenna was minimized, and it was reduced by about 70 % compared to the existing blade antenna. In addition, for impedance matching, the intermediate frequency bandwidth of the VHF band was improved through the sleeve pin of the inner radiator, and the low frequency bandwidth of the VHF band was improved by applying an EMI shielding gasket to the shorting pin of the outer radiator. The proposed antenna was manufactured and measured to verify the performance of the device and the performance after UAV mounting. As a result, the standard was satisfied for the operating frequency.

A novel model-based technique to improve design processes for microstrip antennas

The present work aims to prove the concept of a novel approach to designing microstrip antennas with desired radiation patterns without time-consuming trials and simulations. While it is pretty straightforward to design a microstrip antenna operating at a specific frequency, it requires repetitive trials to design an antenna with a specific radiation pattern. For this purpose, a unique model-based design technique is applied using the cavity model expressions in the present work. The behaviors and mutual influences of various parameters in the intended design problem are described by two graph models. The “employer model” oversees the limitations and freedoms of the antenna's parameters, while the “employee model” uses graph theory and machine learning to define the relationships between graph nodes. These two models have a dynamic structure that changes every calculation step to minimize design error. After two models are constructed, these models suggest physical parameter values according to the cavity model for the desired antenna radiation pattern. Then, the results for examples are demonstrated, and the validity of the proposed technique is proven. Finally, the developability of the method and its further works are discussed.

A Compact Near-Field Resonant Parasitic Slot Helix Antenna With Wide Axial Ratio Bandwidth

A compact near-field resonant parasitic (NFRP) slot helix antenna with wide axial ratio bandwidth is developed in this Letter. The developed antenna consists of one hemispherical metallic surface (HMC) etched with dual curved helical slots and one driven helical monopole nested beneath. The working mechanism of wideband circular polarization radiation of a single-slot NFRP helix antenna is first investigated. Then, a dual-slot NFRP helix antenna with wider working bandwidth in a lower frequency range is evolved by organically collaborating two helical slots etched on the HMC. An optimized prototype of this dual-slot NFRP helix antenna was fabricated, assembled, and tested. The measured results, in good agreement with the simulated values, demonstrate that it possesses a compact size, and an effective fractional bandwidth of 19.15% along with the realized gain values of 3.52 ± 2.25 dBic. The above advantageous performance characteristics enable it to be a good candidate in applications into many wideband space-limited platforms, such as aerospace and mobile communication systems.

A wideband antenna based on self‐packaged suspended coplanar waveguide technology

AbstractIn this article, a wideband antenna is implemented by using a multilayer self‐packaged suspended coplanar waveguide (SCPW). The lower air cavity of the SCPW is not only used for antenna suspending but also as an antenna reflector, while the reflector structure can be expanded by copper coating on the periphery of the multidielectric substrates, which improves the antenna radiation and antenna gain effectively, while the antenna profile is not increased. An extra patch is introduced for generating more resonances, which extends the antenna bandwidth importantly. The proposed antenna is designed to work at 5.42 GHz with a fractional bandwidth of 26.2% (4.71–6.13 GHz), and a maximum gain of 8.4 dBi. The SCPW antenna has been fabricated and measured, and the design has been demonstrated with the advantages of self‐packaging, wideband, favorable gain, and even low profile as well as miniature circuit size.

Time-Gating method with automatic calibration for accurate measurements of electrically small antenna radiation patterns in Non-Anechoic environments

Non-anechoic sites represent a cheap alternative to measurements of antennas in dedicated facilities. However, due to a high noise—from the external EM signal sources and multipath interferences—the quality of radiation patterns obtained in non-anechoic conditions is poor. The characteristics can be corrected using a time-gating method (TGM), which involves filtering of the noise based on temporal analysis of the measured signals. Unfortunately, determination of appropriate TGM setup is prone to failure due to its manual, or semi-manual nature. In this work, an automatic TGM calibration algorithm for accurate measurements in non-anechoic environments has been proposed. The method involves calibration of the test site using the antenna with known accurate responses. The process is implemented as an optimization routine where TGM intervals are adjusted through a curve fitting of the on-site measurements to the reference radiation patterns. The proposed framework has been demonstrated using four compact radiators and validated against the state-of-the-art techniques. Applicability of the method for calibration of the measurements in distinct test sites, as well as the analysis of the aliasing and external noise on the quality of corrected measurements have also been investigated.

Split Ring Antennas and Their Application for Antenna Miniaturization

This paper investigates the miniaturization capability of split ring array antennas embedded in a low-permittivity dielectric substrate, in comparison with the same-sized high-permittivity dielectric resonator antennas (DRAs). In order to understand the miniaturization performance, a size-fixed dielectric substrate with different split ring arrays is studied. The simulation results show that the miniaturization capability increases with decreased unit cell resonant frequency and/or increased unit cell induced permeability. Miniaturizations as high as 25.54 times that of a high-permittivity DRA are obtained with split rings, etched on a dielectric substrate having a low permittivity of 2.2. Furthermore, this excessive miniaturization does not come at the expense of excessive deterioration of the antenna impedance bandwidth, gain, and radiation efficiency. Consequently, the miniaturized split ring arrays still provide high gains over wider bandwidths. This inference is further verified by comparing the miniaturization and other antenna performance parameters with three other modified split ring configurations. To experimentally verify this work, a split ring antenna was fabricated and tested, and good agreement between the simulated and measured results was observed. The results of this study indicate that adding resonant metallic inclusions into low- permittivity DRAs significantly increases their miniaturization capability, without overly deteriorating the performance.

Multiport Single Element Mimo Antenna Systems: A Review

In response to the increasing demand for voice, data, and multimedia applications, the next generation of wireless communication systems is projected to provide faster data rates and better service quality to customers. Techniques such as Multiple-Input-Multiple-Output (MIMO) and diversity are being studied and implemented to meet the needs of next-generation wireless communication systems. Embedding multiple antennas into the same antenna system is seen as a promising solution, which can improve both the system's channel capacity and the communication link's quality. However, for small handheld and portable devices, embedding many antennas into a single device in a small area and at the same time providing good isolation becomes a challenge. Hence, designing a shared antenna system with multiple feed ports with equivalent or better performance characteristics as compared to the approach of multiple antennas with multiple feed ports is a promising advantage which can reduce the size and cost of manufacturing. This paper intends to provide an in-depth review of different MIMO antenna designs with common radiators covering various antenna design aspects such as isolation techniques, gain, efficiency, envelope correlation coefficient, and size, etc. There is also a discussion of the mathematical concepts of MIMO and different isolation techniques, as well as a comparative analysis of different shared radiator antenna designs. The literature review shows that only very few antennas' design with common radiator have been suggested in the available literature at present. Therefore, in this review paper, we have endeavored to study different antennas' designs with common radiator. A comparison is provided of their performance improvement techniques in a holistic way so that it can lead to further develop the common radiator multiport antenna systems and realize the promising advantages they offer.

A Printed Reconfigurable Monopole Antenna Based on a Novel Metamaterial Structures for 5G Applications

A novel antenna structure is constructed from cascading multi-stage metamaterial (MTM) unit cells-based printed monopole antenna for 5G mobile communication networks. The proposed antenna is constructed from a printed conductive trace that fetches four MTM unit cells through four T-Resonators (TR) structures. Such a combination is introduced to enhance the antenna gain-bandwidth products at sub-6GHz bands after exiting the antenna with a coplanar waveguide (CPW) feed. The antenna circuitry is fabricated by etching a copper layer that is mounted on Taconic RF-43 substrate. Therefore, the proposed antenna occupies an effective area of 51 × 24 mm2. The proposed antenna provides an acceptable matching impedance with S11 ≤ -10 dB at 3.7 GHz, 4.6 GHz, 5.2 GHz, and 5.9 GHz. The antenna radiation patterns are evaluated at the frequency bands of interest with a gain average of 9.1-11.6 dBi. Later, to control the antenna performance, four optical switches based on LDR resistors are applied to control the antenna gain at 5.85 GHz, which is found to vary from 2 dBi to 11.6 dBi after varying the value of the LDR resistance from 700 Ω to 0 Ω, in descending manner. It is found that the proposed antenna provides an acceptable bit error rate (BER) with varying the antenna gain in a very acceptable manner in comparison to the ideal performance. Finally, the proposed antenna is fabricated to be tested experimentally in in free space and in close to the human body for portable applications.

Artificial Magnetic Conductor as Planar Antenna for 5G Evolution

A 5G wireless system requests a high-performance compact antenna device. This research work aims to report the characterization and verification of the artificial magnetic conductor (AMC) metamaterial for a high-gain planar antenna. The configuration is formed by a double-side structure on an intrinsic dielectric slab. The 2-D periodic pattern as an impedance surface is mounted on the top surface, whereas at the bottom surface the ground plane with an inductive narrow aperture source is embedded. The characteristic of the resonant transmission is illustrated based on the electromagnetic virtual object of the AMC resonant structure to reveal the unique property of a magnetic material response. The characteristics of the AMC metamaterial and the planar antenna synthesis are investigated and verified by experiment using a low-cost FR4 dielectric material. The directional antenna gain is obviously enhanced by guiding a primary field radiation. The loss effect in a dielectric slab is essentially studied having an influence on antenna radiation. The verification shows a peak of the antenna gain around 9.7 dB at broadside which is improved by 6.2 dB in comparison with the primary aperture antenna without the AMC structure. The thin antenna profile of λ/37.5 is achieved at 10 GHz for 5G evolution. The emission property in an AMC structure herein contributes to the development of a low-profile and high-gain planar antenna for a compact wireless component.

Efficiency-Driven Design for Planar Antennas With Lossy Materials

This article demonstrates a design strategy for improving the radiation efficiency of a planar antenna made of a layered conductor of MXene with modest conductivity on a lossy PDMS substrate. New methods to reduce the conductor loss and the dielectric loss are proposed. On the one hand, the conductor loss is minimized by identifying the location of high current density on the antenna radiator, and then accordingly altering its shape to redistribute the surface currents as uniformly as possible. On the other hand, the dielectric loss is reduced by employing a folded ground plane with elevated edges. This ground plane structure reduces the concentration of the electric field in the dielectric substrate and thus minimizes the power dissipation due to dielectric loss. The improvement techniques are implemented starting from a standard U-slot microstrip antenna. The method demonstrates to improve the radiation efficiency significantly by an average of 14% for a microstrip antenna fabricated using MXene conductor with a sheet resistance of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$2 {\Omega }$ </tex-math></inline-formula> /square and a lossy PDMS substrate. Importantly, the proposed method can preserve the overall antenna size and the operating frequency band. The optimized antenna exhibits a high radiation efficiency of 71% and offers a wide impedance bandwidth of 56% covering operation for the 5 GHz WLAN band.

An Additive 3D-Printed Hemispherical Lens With Flower-Shaped Stub Slot Ultra-Wideband Antenna for High-Gain Radiation

An Additive 3D-Printed Hemispherical Lens With Flower-Shaped Stub Slot Ultra-Wideband Antenna for High-Gain Radiation

DESIGN OF A COMPACT BROADBAND ANTENNA USING CHARACTERISTIC MODE ANALYSIS FOR MICROWAVE APPLICATIONS

A compact broadband antenna of dimensions 27 mm x 28 mm x 1.6 mm and with good impedance matching is designed for high-bandwidth radio systems with a short range. To improve the impedance matching, two rectangular slots are created on the radiating element, and the ground plane size is reduced to extend the ultra-wideband frequency band. The antenna bandwidth and radiation performance are analysed using characteristic mode theory (TCM). The performance is compared to the desired specifications, and the shape and size are modified to produce efficient radiation and dominant radiation patterns. The findings clearly demonstrate that the six modes are resonant with (λn = 0). This implies that the eigenvalues of the six modes contribute strongly to dominant electromagnetic radiation and have high modal significance values around 1 at their respective frequencies. Furthermore, the characteristic angle indicates that the antenna resonates at 180°, since the six modes intersect the axis line at 180° at their respective frequencies. Experimental results show a bandwidth of 109.7% between 5.64 and 19.34 GHz, a maximum gain of 6.3 dB, and a maximum efficiency of approximately 86.5%. These results make this antenna a versatile and effective choice for a wide variety of communications and electronics applications and easy to install in narrow spaces due to its easy design characteristics, small size, and light weight.

Wideband and Efficient 256-GHz Subharmonic- Based FMCW Radar Transceiver in 130-nm SiGe BiCMOS Technology

This article proposes a fully integrated single-channel bistatic frequency-modulated continuous-wave (FMCW) radar transceiver (TRX) that operates at a center frequency of 256 GHz. The main focus of this work is to realize a wideband and efficient radar TRX that offers high resolution of target detection in the short-range FMCW radar sensing application. The radar TRX chip is designed and manufactured using the 130 nm silicon–germanium (SiGe) bipolar complementary metal-oxide-semiconductor (BiCMOS) technology which offers heterojunction bipolar transistors (HBTs) with <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$f_{\mathbf {T}}/f_{\mathbf {MAX}}$ </tex-math></inline-formula> of 300/500 GHz. The transmitter (TX) of the radar TRX is based on a fundamentally operated multiplier-by-8 chain architecture that offers a 3-dB bandwidth of around 65 GHz with a saturated output power of −5.4 dBm. On the other hand, the receiver (RX) is based on a subharmonic architecture that provides a conversion gain (CG) of 10.4 dB with an average noise figure (NF) of 23.5 dB. This TRX is realized with two integrated on-chip folded dipole antennas. The antenna offers high antenna gain and radiation efficiency due to the use of the selective localized backside etching (LBE) technique. This chip consumes 305 mW of power from a 3.3-V supply and occupies a silicon area of 3.3 mm2. The radar range measurement is performed in an anechoic chamber, and it shows the maximum dynamic range (DR) of around 34 dB at 1-m range of the target.