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Summary This study presents the design, fabrication, and measurement of a novel MIMO antenna for 28 GHz 5G applications. The design includes two compact antennas with dimensions of 12.8 × 12.8 × 1.6 mm3, placed side by side in a symmetrical arrangement. The antenna being considered operates within the 28 GHz frequency range and has excellent characteristics in terms of reflection coefficient, isolation, and impedance matching. The measurements conducted encompassed both single and MIMO setups and focused on important parameters such the reflection coefficient, transmission coefficient, gain, and efficiency. The MIMO antenna exhibited a reflection coefficient of −62.52 dB at a frequency of 27.93 GHz, while the transmission coefficient was found to be −37.23 dB. The antenna attained a gain of 6.02 dB relative to an isotropic radiator (dBi) and exhibited a maximum efficiency of 90.73%, encompassing a bandwidth of 4.45 MHz (MHz). The simulated envelope correlation coefficient (ECC) was found to be less than 0.003, indicating a very low error rate. Additionally, the antenna attained a diversity gain of 9.998 dB. The suggested MIMO antenna is very suitable for 5G applications operating at 28 GHz. [ABSTRACT FROM AUTHOR]

This paper presents analytical solutions for full-field radiation in magnetoelectric (ME) antennas, considering a fully magneto-elastic coupled constitutive relation. A nonlinear converse ME coupling model is established, incorporating mechanical, electric, and magnetic variables with generalized Maxwell equations. This model emphasizes the essence of ME antennas, where radiation is achieved through strain/stress-mediated coupling between different phases. The magnetic flux density and electric displacement obtained from the model are used as sources to solve the full-field radiations of ME antennas. The proposed model is validated through existing experiments and simulations, demonstrating that the radiation performance of ME antennas is strongly influenced by nonlinear magneto-elastic coupling. The material parameters and magnetic bias significantly impact the magnetic flux density and far-field radiation due to the nonlinear magnetization process. The study reveals the mechanisms behind enhanced working bandwidth and frequency tuning by examining the frequency response of the radiation impedance with material parameters. By adjusting the initial magnetization rate, saturation magnetostriction, and saturation magnetization, the radiation efficiency/gain can be increased by 340%, 108%, and 112% respectively. This model enhances our understanding of the full-field radiation of ME antennas and provides a foundation for designing tunable ME antennas. [ABSTRACT FROM AUTHOR]

• APAA performance is analyzed through a stochastic multi-physics model. • The random multi-physics responses can be accurately calculated. • Huge amount of computational cost is saved compared with the MCS method. A random field based thermal-structural-electromagnetic (RF-TSE) coupling model is proposed to deal with the stochastic analysis of the Active Phased Array Antenna (APAA) performance considering material spatial uncertainty. Firstly, the spatial uncertainty of APAA material parameters is characterized by the random field model. Then, the material spatial uncertainty is embedded into the thermal-structural coupling analysis of APAA and the random displacement information of APAA units is calculated. To avoid supplemental analytical error of the APAA performance, the obtained deformation results are directly introduced into the antenna radiation pattern function without any additional assumptions. Finally, the stochastic spatial phase error caused by deformation is further calculated and utilized to obtain the statistical information of the APAA performance based on the power pattern function. The validity of the proposed RF-TSE model is fully investigated and the analytical results show that it can obtain very accurate statistical information of APAA electromagnetic (EM) performance and the computational efficiency can also be greatly improved compared with the Monte-Carlo simulation (MCS) approach. [ABSTRACT FROM AUTHOR]

Antennas with complex radiation characteristics can enhance the adaptability of radiofrequency systems in complex electromagnetic environments. However, The realization of complex targets is extremely challenging for conventional antenna design methods. It is difficult to find a suitable initial topology of the antenna with complex radiation characteristics. Therefore, in this paper, topology optimization is used to explore the initial structure with complex radiation properties. A two‐dimensional lossy thin layer model based on the transitional boundary condition is constructed, and target field functions for complex radiation are proposed. To verify the effectiveness of the algorithm, a high gain antenna with 10.2 dBi is realized, which has the highest aperture efficiency compared with the literature in similar directions. Then, for more complex targets, the radiation patterns of arbitrary direction null, arbitrary direction beam, and equal‐amplitude dual beam are realized, respectively. The topology optimization algorithm provides a new approach for the design of complex multitarget antennas. [ABSTRACT FROM AUTHOR]

The paper proposes a new method for finding the optimal design of complementary split ring resonator cells for a microstrip antenna, which makes it possible to purposefully optimize the parameters of resonator cells, which significantly improve the electrical characteristics of the antenna. This antenna is designed for cellular communication 5G. The proposed method combines a regression model using a deep network based on fully connected neural layers with a search based on the conditional optimization algorithm COBYLA to find the optimal design parameters of resonator cells. This approach fully automates the process of creating microstrip antennas with resonator cells based on metamaterials and makes it possible to find the parameters of complementary split ring resonator cells that provide the optimal operating mode as a whole and gives the maximum level of antenna radiation while maintaining the bandwidth. The small size of complementary split ring resonator cells opens up the possibility of using this peculiar configuration to create compact and efficient microstrip antennas.

In this paper, a CPW-fed monopole radiating patch with a two-port MIMO network is presented. The triple band response of the antenna is obtained by embedding CSRR slots. The proposed MIMO antenna operates across 2.02 GHz, 3.4 GHz, and 5.69 GHz with a reflection co-efficient value of − 38 dB, − 11 dB, and − 31 dB, respectively. The proposed antenna covers wireless applications as well as Wi-MAX applications. The overall size of the proposed antenna is 30 × 30 × 1.6 mm3. The proposed design of the MIMO antenna is simulated and measured. The measurements are validated with simulated results. Diversity parameters are evaluated for the proposed two-element MIMO antenna. The obtained results are satisfactory for MIMO applications. The gain obtained varies from 2.56 to 7.26 dBi. The radiation efficiency is greater than 75% corresponding to the triple resonating bands. [ABSTRACT FROM AUTHOR]

In this study, it is aimed to obtain two different asymmetric radiation patterns obtained from antennas in the shape of the cross-section of a parabolic reflector (fan blade type antennas) and antennas with cosecant-square radiation characteristics at two different frequencies from a single antenna. For this purpose, firstly, a fan blade type antenna design will be made, and then the reflective surface of this antenna will be completed to the shape of the reflective surface of the antenna with the cosecant-square radiation characteristic with the frequency selective surface designed to provide the characteristics suitable for the purpose. The frequency selective surface designed and it provides the perfect transmission as possible at 4 GHz operating frequency, while it will act as a band-quenching filter for electromagnetic waves at 5 GHz operating frequency and will be a reflective surface. Thanks to this frequency selective surface to be used as a reflective surface in the antenna, a fan blade type radiation characteristic at 4 GHz operating frequency will be obtained, while a cosecant-square radiation characteristic at 5 GHz operating frequency will be obtained. [ABSTRACT FROM AUTHOR]

Nearly 10 years ago, the 79 GHz band was utilized in automotive radar applications. In difficult conditions, this frequency band improves the ability and accuracy of target detection. This work presents a good design for a key component of the radar sensor. It maintains the performance parameters needed for mm-wave radar and Internet-of-Things applications (IoT). We present a single patch antenna, 1x4 and 1x8 series feed patch antenna array that operates at the 79 GHz band by using an inset-feed line feeding technique that is one of the most popular techniques for perfect matching. The simulated results were obtained by two different software programs CST microwave studio 2020 and Ansys HFSS 2021. These software packages are basically different and used for confirming the results. these results include the return loss, voltage standing wave ratio, Band Width, Gain, Directivity, and Efficiency. A new technique has been used to optimize the bandwidth and overcome one of the most popular weaknesses of the series array microstrip antenna. The proposed design's good results make it appropriate for medium-range and short-range radar in the 77-81 GHz frequency band. The antenna is fabricated, and the simulated results are validated by the experimental measurements. [ABSTRACT FROM AUTHOR]

In this work a compact size capacitive load dual band planar inverted-F implant antenna is presented. The suggested antenna is modeled on RO3010 substrate that has a thickness of 2 mm, dielectric constant of 10.2, and tangent loss of 0.0023 to operate at both the Medical Implant Communications Services (MICS) and Industrial, Scientific, and Medical (ISM) bands. A capacitive load is inserted between the patch and the ground plane to get a dual band and compact size implant antenna. The idea behind the capacitive load is to support a simple structure with a dual band and compact size in addition to get a gain enhancement. The antenna size is 20 × 12 × 2 mm3. The antenna designed in this work operates at 402 MHz with a return loss of − 23.23 dB over a frequency band [397.15–409.4 MHz] for MICS band and operates at 2.42 GHz with a return loss of − 20 dB over a frequency band [2.37–3 GHz] for ISM band. The simulated gain is − 27.52dBi at 402 MHz for MICS band and − 1.85dBi at 2.42 GHz for ISM band. The proposed antenna has a good performance inside three-layered tissue model. The Computer Simulation Technologies (CST) Microwave studio is used to model and simulate the proposed antenna. [ABSTRACT FROM AUTHOR]

The three-dimensional printed wideband prototype (WBP) was proposed, which is able to enhance the horn feed source by generating a more uniform phase distribution that is obtained after correcting aperture phase values. The noted phase variation obtained without the WBP was 163.65 ∘ for the horn source only, which was decreased to 19.68 ∘ , obtained after the placement of the WBP at a λ /2 distance above the feed horn aperture. The corrected phase value was observed at 6.25 mm (0.25 λ) above the top face of the WBP. The use of a five-layer cubic structure is able to generate the proposed WBP with dimensions of 105 mm × 105 mm × 37.5 mm (4.2 λ × 4.2 λ × 1.5 λ), which can improve directivity and gain by 2.5 dB throughout the operating frequency range with a lower side lobe level. The overall dimension of the 3D printed horn was 98.5 mm × 75.6 mm × 192.6 mm (3.94 λ × 3.02 λ × 7.71 λ), where the 100 % infill value was maintained. The horn was painted with a double layer of copper throughout its surface. In a design frequency of 12 GHz, the computed directivity, gain, side lobe level in H- and E- planes were 20.5 dB, 20.5 dB, −26.5 dB, and −12.4 dB with only a 3D printed horn case and, with the proposed prototype placed above this feed source, these values improved to 22.1 dB, 21.9 dB, −15.5 dB, and −17.5 dB, respectively. The realized WBP was 294 g and the overall system was 448 g in weight, which signifies a light weight condition. The measured return loss values were less than 2, which supports that the WBP has matching behavior over the operating frequency range. [ABSTRACT FROM AUTHOR]

Antenna design with the traditional numerical methods is a highly computationally expensive task. In this letter, a complex-valued graph neural network (GNN) with residual connections is proposed to efficiently predict radiation pattern for antenna arrays with different geometric structures. The model uses GNN as a backbone, and the topological structure and excitation of the antenna array are encoded into a graph representation. Complex weights and residual connections are designed to improve the accuracy of the model. Experiments are conducted on five kinds of arrays under amplitude–phase control. The experimental results show that the average mean absolute percentage error and the average root-mean-square error of the model on five types of the antenna array are 1.86% and 0.032, respectively, while the time efficiency of the model is six orders of magnitude faster than that of the traditional full-wave simulation. [ABSTRACT FROM AUTHOR]

The three dimensional printing method is currently on stage of rapid development to realize complex nature of structure in simpler and feasible ways. In this paper, we proposed a 3D printed wideband antenna structure with high performance to improve the characteristics properties of feed source by eliminating the use of expensive superstates. A 60 mm $\times60$ mm $\times22.5$ mm wideband structure was first fabricated from VERO CMYK material through Multijet 3D printing method where the bottom layer are copper painted so as to realize the higher permittivity layer. The proposed structure is maintained at 16 mm ( $0.64\lambda $ ) above the ground plate of 60 mm $\times60$ mm $\times $ 1 mm, which is feed by WR-75 waveguide. The proposed antenna is designed to have a wide operating bandwidth from 10 to 15 GHz, which cover Ku-band frequency range. Directivity enhancement is obtained over a large bandwidth by using high permittivity material for Layer 1 and lower permittivity material for Layer 2 and Layer 3. The resulting antenna prototype demonstrates a directivity bandwidth product (DBP) of 3012.79 and DBP per unit area (DBP/A) of 523.06, where directivity and gain are found to be higher than 15 dBi over the entire operating frequency band. The total area of the new antenna prototype is $2.4\lambda \times 2.4\lambda \times 0.9\lambda $ ( $4.16\lambda _{g} \times 4.16\lambda _{g} \times 1.56\lambda _{g}$ ), and overall electrical height is $1.54\lambda $ at the design frequency of 12 GHz. The proposed prototype weight 36 g and overall system have weight of 118 g, which is light in weight. The measured VSWR is less than 2, which signifies wideband characteristics of overall system.

Summary: This paper proposes a novel planar rectangular slot antenna designed and fabricated for a sub‐6 GHz 5G wireless application. The proposed design can work in sub‐6 GHz 5G, WiMAX, and LTE Band 42. The antenna has an inverted stub and E‐shaped and rectangular radiating slot with a circular parasitic element on its upper side concurrently activated by a microstrip feed line with a two‐folded T‐shaped design. The proposed antenna covers the 5G N77 band at 3.5 GHz. It has a dimension of 32.4 × 27.9 × 1.6 mm3 with good reflection coefficient characteristics and excellent impedance matching. The reflection coefficient (S11) is found at −26.5 dB, and the resonant frequency is 3.5 GHz, with a peak gain of almost 4.2 dB. The proposed antenna has ≈82% efficiency for the whole frequency band and provides 19 MHz of total bandwidth. Finally, the proposed antenna is an attractive solution for sub‐6 GHz 5G wireless applications. [ABSTRACT FROM AUTHOR]

In a previous work, we derived optimum conditions for the design of finite-size 1-D unidirectional leaky-wave antennas (LWAs) in the general case. The bandwidth and the gain–bandwidth figure of merit are, however, structure-specific and have not been discussed yet. A practical case that is widely investigated in the literature is that of 1-D unidirectional LWAs based on partially reflecting surfaces (PRSs). In this work, we not only evaluate these features for this specific class of antennas, but we also derive design rules for optimizing the PRS impedance and cavity height to get maximum gain. Numerical results and full-wave simulations are finally proposed for a realistic example based on a metal strip-grating structure, to validate the theoretical findings. [ABSTRACT FROM AUTHOR]

In this paper, a compact frequency and polarization agile patch antenna is presented. The antenna comprises a square patch with truncated corners along with a triangular slot etched at the center of the patch. Pin diodes are used to bridge the gap between the truncated corners and center triangular region with a radiating square patch. By appropriately biasing the pin diodes the antenna achieves frequency and polarization diversity. The antenna achieves five distinct states with three linear polarization (LP) states operating at three different frequencies and two circular polarization (LHCP/RHCP) states operating at the same frequency. The antenna gives a −10 dB impedance bandwidth of 95 MHz (1.825–1.92 GHz) in the GSM band for LP state 1, 115 MHz (2.365–2.48 GHz) in the ISM band for LP state 2, 145 MHz (2.08–2.225 GHz) in UMTS band for LP state 3, 100 MHz (2.1–2.2 GHz) UMTS band for CP state 4 and 5. The antenna attains a measured peak gain of ∼4.8 dBi at LP states and ∼4.54 dBi at CP states in its operating band. [ABSTRACT FROM AUTHOR]

An ultra-wideband (UWB) antennas used with the applications of wireless communication systems (WCS), the following five antenna parameters; radiation patterns, directivity, bandwidth, efficiency, and antenna gain should be well optimized. A new design approach based on the coupling matrix theory of synthesis antenna has been presented. The most important parameters of this matrix are; external normalized quality factor, normalized un-loaded quality factor, radiation quality factor, and coupling coefficients between the resonators. Accuracy in calculating these parameters will greatly facilitate control of the antenna bandwidth to be designed. The design approach included a BPF which was also expanded to become an antenna arrays-filter in the hope of increasing the gain and bandwidth of the antenna. Further, a matching unit is placed between the designed BPF and the antenna, to overcome the mismatching situation, and to achieve a high transmission power. The paper presented a new design approach for an active BPF at a frequency “2.45 GHz” and then its integration with a 3rd-order dipole antenna [1]. This design is followed by the creation of another efficient couple-resonant filter (CRF), in which each resonant grid is represented by a radiator. Moreover, a lossless two-port dipole antenna was introduced. Here, each of the poles is integrated with an inductor, to sure that the bipolar antennas can exploit as a resonator. The scores of the simulation sketches and the computed results were convincing. Finally, the performance efficiency of the designed filter at the resonant frequency 2.45 GHz and for both “H-plane” and “E-plan” were summarized in Table 1.

The work carried out the calculation and synthesis of antenna arrays used in radio-electronic complexes on unmanned aerial vehicles. The analytical model is designed to find asymptotic estimates of the polarization components of the electric field of the grating in the far zone of the carrier surface; the results obtained with its use are the initial data for constructing a technique for the numerical solution of a boundary value problem for a grating on a carrier surface in the CST MWS electrodynamic simulation environment. The synthesis of gratings with the maximum achievable coefficient of directional action is carried out with the control of radiation patterns at a given set of angles. A two-mirror antenna system has been calculated. It is shown that with an increase in the number of re-reflections taken into account, the convergence of the result for the calculated characteristics of the antenna is observed. To test the proposed method, the same antenna was calculated using the integral equation method. The comparison showed a high degree of agreement between the results obtained by two different methods. The results of the simulation based on a software algorithm designed to quantify the input matching at the input of a multichannel frequency-scanning antenna array power divider are presented. It was found that when performing wide-angle scanning in a relative frequency band of more than a few percent, the disadvantage of the known method for eliminating the normal effect is a sharp deterioration in matching in the lower and upper frequencies of the operating range. A new method is proposed based on an automated iterative process of optimizing the divider geometry, which makes it possible to obtain an acceptable match over the entire operating frequency band. The feasibility of switching from a serial power divider construction scheme to a series-parallel scheme is analyzed for wide-angle scanning in a relative frequency band of about 5%.

The three-dimensional printed wideband prototype (WBP) was proposed, which is able to enhance the horn feed source by generating a more uniform phase distribution that is obtained after correcting aperture phase values. The noted phase variation obtained without the WBP was 163.65∘ for the horn source only, which was decreased to 19.68∘, obtained after the placement of the WBP at a λ/2 distance above the feed horn aperture. The corrected phase value was observed at 6.25 mm (0.25λ) above the top face of the WBP. The use of a five-layer cubic structure is able to generate the proposed WBP with dimensions of 105 mm × 105 mm × 37.5 mm (4.2λ× 4.2λ× 1.5λ), which can improve directivity and gain by 2.5 dB throughout the operating frequency range with a lower side lobe level. The overall dimension of the 3D printed horn was 98.5 mm × 75.6 mm × 192.6 mm (3.94λ× 3.02λ× 7.71λ), where the 100 % infill value was maintained. The horn was painted with a double layer of copper throughout its surface. In a design frequency of 12 GHz, the computed directivity, gain, side lobe level in H- and E- planes were 20.5 dB, 20.5 dB, −26.5 dB, and −12.4 dB with only a 3D printed horn case and, with the proposed prototype placed above this feed source, these values improved to 22.1 dB, 21.9 dB, −15.5 dB, and −17.5 dB, respectively. The realized WBP was 294 g and the overall system was 448 g in weight, which signifies a light weight condition. The measured return loss values were less than 2, which supports that the WBP has matching behavior over the operating frequency range.

A new broadside and conical beam reconfigurable dielectric resonator antenna (DRA) with three orthogonal linear polarizations (LPs) and two orthogonal circular polarizations (CPs) agility is presented. It consists of a quad-strip-fed DRA element and a reconfigurable feeding network. First, the DRA element is designed to make unidirectional ${\mathrm{HEM}}_{11 \delta }$ mode and omnidirectional ${\mathrm{TM}}_{01 \delta }$ mode operate in the same wide band by tactfully removing a concentric annular column from its interior. Furthermore, a center-loaded metal post helps to improve the impedance matching of the ${\mathrm{TM}}_{01 \delta }$ resonance significantly. Afterward, the switchable feed network is designed to implement diverse phase distributions of four output ports, i.e., providing the quad-port in-phase excitation, dual-port differential excitations, and quad-port sequentially rotated phase excitation strategies for a vertical LP, ±45° slant horizontal LPs, and two CPs, respectively. Finally, a fully functional prototype is designed, fabricated, and measured to validate the design. The measured results show that the overlapping impedance bandwidth of 36.8% for all the states and the axial-ratio bandwidth of 33.8% for the CPs are obtained. [ABSTRACT FROM AUTHOR]

In this letter, a neural network-based interelement phase estimation method using radiation power pattern of the linear phased array is proposed. To validate the proposed method, a radiation pattern measured in an anechoic chamber is input to the neural network to estimate the initial phase errors, and to confirm practical estimation accuracy. The proposed method requires only single radiation pattern measurement and no additional measurements only for estimation. This indicates the proposed method is significantly more time-saving, compared to other conventional techniques. Furthermore, we propose a method to suppress the failure rate of estimation by recursively reinputting patterns into the neural network, and discuss its effectiveness. These results show that the proposed methods useful for phase estimation of the linear array in experiments. [ABSTRACT FROM AUTHOR]

This paper presents analyses of the 3D acoustic fields generated by motorcycles at very low frequencies (< 1 5 0 Hz) at the idle speed and during sudden acceleration. Diagnosis and analyses of sound sources at low frequencies have always been a significant challenge because the directivity of low-frequency sound is very poor. To date, there are no research papers and/or reports that have demonstrated low-frequency sources localization and radiation patterns of any kind at high spatial resolution in 3D space. This study shows that by using sound viewer technologies, which include the passive sonic detection and ranging (SODAR), the Helmholtz equation least squares (HELS) method, advanced signal processing, denoising, etc., the locations of sound sources and visualization of the sound fields can be determined with high spatial resolution, even at frequencies below 150 Hz. In particular, the HELS method allows for reconstructing all the acoustic quantities, including the acoustic pressure, time-averaged acoustic intensity, time-averaged acoustic power on the source surfaces and in 3D space. The hardware needed consists of a 3D array with six free-field precision microphones with pre-amplifiers, a miniature wide-angle camera, an eight-channel digital signal processor and a laptop computer. [ABSTRACT FROM AUTHOR]

• Locating and quantifying transformer noise from 20–20,000 Hz using SODAR and HELS. • Conducting portable and easy-to-operate tests with a six-microphone array. • Diagnosing 3D sound fields and pinpointing low-frequency noise (<400 Hz). • Visualizing TSFVA (time-space-frequency-visual-audio) correlations in 3D space. This paper presents diagnosis and analyses of the sound fields radiated from power transformers in 3D space under normal operational conditions. Transformers are crucial components in the power system. Good condition of a transformer is an important factor to ensure safe and reliable operations of the entire power system. Diagnosis and analyses of transformer noise are challenging because of the complexity of the acoustic environment surrounding the power grid. Previous studies have revealed that transformer noise is predominantly concentrated in the low frequency range. This low-frequency nature of transformer noise has made it extremely difficult to pinpoint the precise source locations. The present study shows that by using the Sound Viewer system, which is built on the principles of passive SODAR (Sonic Detection And Ranging) and HELS (Helmholtz Equation Least Squares) methods, we can not only pinpoint the precise locations of noise sources of a transformer, but quantify individual source strengths. Specifically, SODAR enables one to locate multiple sound sources simultaneously in 3D space over the frequency range of 20–20,000 Hz, and the HELS method enables one to reconstruct the acoustic field and acquire the optimal approximation of the acoustic pressure distribution in 3D space, time-averaged acoustic intensities, and time-averaged acoustic powers of the individual acoustic sources. The accuracy in reconstruction depends on the SNR (Signal to Noise Ratio) of the input data. The higher the SNR is, the more accurate the reconstruction becomes. Moreover, by using a spatial filter, we can eliminate the interferences of unwanted sound sources and extract the time-averaged acoustic power of a specific target. This salient feature enables us to perform a source ranking, which can be critical in designing the most cost-effective noise mitigation strategy. Results of the present study demonstrate that this technology can play a significant role in diagnosing and analyzing complex acoustic field in a non-ideal test environment, especially for transformer health monitoring and predictive maintenance in power systems. [ABSTRACT FROM AUTHOR]

Cube Satellites, aka CubeSats, are a class of nano satellites that have gained popularity recently, especially for those that consider CubeSats as an emerging alternative to conventional satellites for space programs. This is because they are cost-effective, and they can be built using commercial off-the-shelf components. Moreover, CubeSats can communicate with each other in space and ground stations to carry out many functions such as remote sensing (e.g., land imaging, education), space research, wide area measurements and deep space communications. Consequently, communications between CubeSats and ground stations is critical. Any antenna design for a CubeSat needs to meet size and weight restrictions while yielding good antenna radiation performance. To date, a limited number of works have surveyed, compared and categorised the proposed antenna designs for CubeSats based on their operating frequency bands. To this end, this paper contributes to the literature by focusing on different antenna types with different operating frequency bands that are proposed for CubeSat applications. This paper reviews 48 antenna designs, which include 18 patch antennas, 5 slot antennas, 4 dipole and monopole antennas, 3 reflector antennas, 3 reflectarray antennas, 5 helical antennas, 2 metasurface antennas and 3 millimeter and sub-millimeter wave antennas. The current CubeSat antenna design challenges and design techniques to address these challenges are discussed. In addition, we classify these antennas according to their operating frequency bands, e.g., VHF, UHF, L, S, C, X, Ku, K/Ka, W and mm/sub-mm wave bands and provide an extensive qualitative comparison in terms of their size, −10 dB bandwidths, gains, reflection coefficients, and deployability. The suitability of different antenna types for different applications as well as the future trends for CubeSat antennas are also presented.

The optimization of antenna parameters such as gain is an important aspect of all antenna design. In the context of leaky-wave antennas (LWAs), it is important to have accurate design rules for optimizing the gain of the antenna for practical finite-length structures. In this work, taking advantage of the recent formulas derived for the accurate evaluation of the beamwidth in finite-size 1-D unidirectional LWAs, we obtain optimum conditions for this general class of antennas. In particular, design rules for minimizing the beamwidth or maximizing the gain are obtained. The latter is evaluated with a fully analytical procedure through the definition of a correction function that improves the accuracy of the common gain–beamwidth relation. The effects of material losses are also discussed to show how they can affect the optimization procedure. These results apply to any 1-D unidirectional LWA, because no assumptions are made on the wavenumber dispersion, which is instead structure-specific. However, the optimization of two practical examples, namely a holey and a slitted LWA, is discussed to show practical application of the proposed design rules. [ABSTRACT FROM AUTHOR]

Wideband slot-coupled microstrip antenna (SCMSA) is a distinctive electromagnetic wave radiator in recent years with wide bandwidth and low profile. In such a wide frequency range, the electrical distance, i.e., normalized to operating wavelength, between dual equivalent magnetic currents increases obviously with upward frequency. Therefore, the realized gain is usually with a large variation, which limits the wideband performance of SCMSA. In this communication, a feasible method is proposed to stabilize the realized gain of an SCMSA over its entire impedance bandwidth by utilizing a properly designed reflector-plus-sidewall structure (RPSS), which includes a reflector with an optimized height and two vertical sidewalls. Each part has its own function in realized gain compensation and enhancement, performing a flatter and higher realized gain in a wide frequency range. To validate this method, an antenna prototype is fabricated and tested. Compared with the referenced SCMSA, the measured results indicate that the proposed one adding RPSS maintains a wide impedance bandwidth of 24.8% (3.75–4.81 GHz), but reduces gain variation from 4.1 to 0.5 dB (10.5–11 dBi) with an average realized gain increment of 2.1 dB. [ABSTRACT FROM AUTHOR]

Geometry-induced resonant modes with intrinsic broad beam coverage are synthesized within step-shaped dielectric resonator antennas (DRAs). Following the idea of mode fusion, a synthesized mode inherits and combines the modal features from several conventional ones of regular DRAs. Superior flexibility and design freedom in beam shaping are thus obtained, leading to a 3 dB beamwidth exceeding 200° in both main planes. To form such a broad-beam mode, three regular higher-order modes from rectangular DRAs are chosen and merged. Their modal radiation patterns have fine complementation, meanwhile, they are readily excited by a shared feed. To further demonstrate the mechanism of mode fusion, the modal field distribution of the presented DRAs is analyzed. A design guide is presented as well. [ABSTRACT FROM AUTHOR]

A pattern- and polarization-reconfigurable dielectric resonator antenna (DRA) is presented. It deploys a conventional cylindrical dielectric resonator (DR) with a new switchable feeding network. The feeding network has four slots that are etched in the ground. By tuning the phase distributions in these slots, three DR modes (the TM01δ and two degenerated HEM113 modes) are excited. The former has an omnidirectional radiation pattern, whereas the latter two have boresight patterns with orthogonal polarizations (x- and y-polarization). By tuning the height-to-radius ratio, these modes can be designed to operate at the same frequency, thus enabling both the pattern and polarization reconfigurability. A prototype of the reconfigurable DRA working in 2.4 GHz is fabricated and measured to verify ideas. Reasonable agreement between measurements and simulations is obtained. Our design provides both pattern and polarization reconfigurability, with good efficiency in the band of interest. [ABSTRACT FROM AUTHOR]

In this paper, the concept and recent development of exploiting frequency diverse array (FDA) and its variants for the physical-layer wireless security have been revisited and carefully examined. Following rigorous analytical derivation and illustrative simulations, the authors realize that the investigations performed in some recent works overlooked one critical issue facing the real-world applications, and system models established and used before were based on a limited assumption, i.e. that the legitimate and eavesdropping users at different ranges sample the signal waveforms at the same time instant. The limitation of this assumption results in their studies inconclusive. The authors aim to take the first step to divert research efforts and rectify the previous incomplete analyses. The authors argue that in the current technology base the FDA cannot secure a free-space wireless transmission in range domain, because the previously claimed `secure reception region' propagates in range domain as time elapses.

This article presents a novel concept for a highly accurate and simple two-port vector signal analyzer. A current phase ratio measurement method is defined for one independent external signal with a restriction of the measuring range ±90 or ±180°. The article presents a new way of phase ratio evaluation of two independent external signals with precise phase determination in a wide range from 0° to 360°. The new functional blocks of the analyzer circuit element act as a four-position radio frequency (RF) switcher and an algorithm for phase determination is presented. Practical application and verification of the results achieved are demonstrated by measuring the phase directional radiation pattern of a complex object such as an aircraft fuselage.

In this article, we propose a deep neural network (DNN)for the radiation pattern synthesis of an antenna. The DNN utilizes the radiation patterns as inputs and the amplitude and phase of the antenna elements as outputs. Consequently, the radiation patterns of the array antenna can be easily obtained from the outputs of the trained DNN, which are amplitude and phase of the antenna elements. However, it is difficult to determine the amplitude and phase of each antenna element from the desired pattern in an environment where inter-element coupling exists. For this purpose, 6,859 radiation pattern samples for a 4×1 array patch antenna were generated by changing the phases of the antenna elements, and those patterns were leveraged to train the proposed DNN with low complexity. The radiation patterns of the ideal square and triangular array shapes, which are practically infeasible to implement, were used as inputs to the DNN. It was confirmed that the radiation pattern generated from the output signals of the DNN was very similar to the input radiation pattern.

We investigate the use of spherical cross-correlation as a similarity measure of sound radiation patterns, with potential applications for their study, organization, and manipulation. This work is motivated by the application of corpus-based synthesis techniques to spatial projection based on the radiation patterns of orchestral instruments. To this end, we wish to derive spatial descriptors to complement other audio features available for the organization of the sample corpus. Considering two directivity functions on the sphere, their spherical correlation can be computed from their spherical harmonic coefficients. In addition, one can search for the 3-D rotation matrix which maximizes the cross-correlation, i.e. which offers the optimal spherical shape matching. The mathematical foundations of these tools are well established in the literature; however, their practical use in the field of acoustics remains relatively limited and challenging. As a proof of concept, we apply these techniques both to simulated radiation data and to measurements derived from an existing database of 3-D directivity patterns of orchestral instruments. Using these examples we present several test cases to compare the results of spherical correlation to mathematical and acoustical expectations. A range of visualization methods are applied to analyze the test cases, including multi-dimensional scaling, employed as an efficient technique for data reduction and navigation. This article is an extended version of a study previously published in [Carpentier and Einbond. 16th Congrès Français d’Acoustique (CFA), Marseille, France, April 2022, pp. 1–6. https://openaccess.city.ac.uk/id/eprint/28202/].

A wideband printed monopole antenna with two rejection bands is proposed in this article. The antenna provides a wideband from 5.4 GHz to 17.2 GHz with two rejection bands covering 6.9 to 7.4 GHz and 8.3 to 9.2 GHz with two peak notch frequencies of 7.2 GHz and 8.6 GHz respectively. Tested peak gain at two peak notch frequencies of 7.2 GHz and 8.6 GHz are 2.5 dBi and −1.5 dBi respectively. These two rejection bands are effectively used to avoid undesired intrusion from the C band and the X band. The lower rejection band has been realized by cutting an open ring circular slot on the metal patch whereas U like slot has been inserted on the ground plane just beneath the feed line to achieve the upper rejection band. Simulated and tested S11 parameter, gain, radiation efficiency, E-H radiation patterns, and surface currents of the antenna are presented here. The antenna uses small dimensions and it is very simple to design. The proposed antenna confirms that it is useful for short-range and fast data communication systems. [ABSTRACT FROM AUTHOR]

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A rectangular patch antenna design with fundamental TM100 mode for on‐metal applications is presented. The patch is excited by an inset‐fed microstrip feedline and optimized for better performance by varying the inset‐fed parameters. The patch is then loaded with a circular slot of radius Ry at its center to create additional resonance at TM11 mode. The radius Ry is varied to elongate the circular slot into biconcave shape, to increase its electrical length. Thus, manipulating TM11 mode with respect to TM100 mode to achieve wideband by combining the two resonances using overlap technique. Equations of the resonance of the circular slot is stated and so is the surface area of the biconcave. The resulting antenna is etched on a 130 μm‐thick RO3003 microwave laminate and stamped on a metallic pipe cladding using the pipe as the metallic ground. The realized bandwidth is enhanced by 13% with reasonable achieved directivity. The simulated and measured results agreed reasonably with marginal discrepancy. [ABSTRACT FROM AUTHOR]

This paper discusses the synthesis of a steerable frequency-invariant radiation pattern for broadband scalable antenna arrays (SAAs). The proposed method allows to achieve constant beamwidth and beam direction over a 3 : 1 bandwidth and is based on an appropriate radiating elements' placement in the SAA and a proper amplitude and phase excitation of the array. Both amplitudes and phases of signals exciting the radiating elements are varied with frequency to ensure the radiation pattern invariance. Additionally, the paper proposes solutions to problems occurring in SAAs i.e., the problem of overlapping radiating elements and the problems of sidelobe and grating lobe reduction. To verify the proposed synthesis method, a set of radiating elements, which operate over a 3 − 9 GHz frequency range, has been manufactured and measured. The overall radiation pattern of the antenna array has been obtained by a summation of the radiation patterns produced by each of the radiating elements. • Synthesis of a steerable frequency-invariant radiation pattern. • Methods for grating lobe and side lobes reduction. • Solution to the overlapping radiating elements problem. [ABSTRACT FROM AUTHOR]

Compact arc-shaped conformal dielectric resonator antennas (DRAs) loaded by metal plates and high-dielectric-constant (HiK) patches are investigated. Their miniaturizing principles are analyzed from different aspects. Closed-form expressions are derived to characterize the function of the conformal ground in size reduction. Difference between the conventional flat ground and conformal one is discussed. As to lateral metal loading, its influence on radiation patterns are utilized to acquire additional function. Next, to replace the metallic structure, HiK patches are used as perfect electric conductor (PEC) walls. Their working mechanisms are analyzed through the electromagnetic theory in layered media, and waveguide-based simulation methods. As validation, a dielectric-loaded arc DRA is proposed. By working like a PEC, the thin dielectric patch reduces the DRA size to one half. Similar characteristics are observed between the dielectric- and metal-loaded antennas. Finally, a bare DRA and a miniaturized one are fabricated and measured. This research expands the miniaturizing theory of conformal arc DRAs.

Ground effects on arc-shaped conformal dielectric resonator antennas (DRAs) working in the TE11δz mode are investigated and utilized to attain various radiation performances. Manipulation of directivity patterns are achieved with the help of the three-dimensional curved metal ground. The backlobe, beamwidth, broadside gain, backscattering, and cross-polarization level of the antenna are all readily controllable. The geometric theory of diffraction is applied to provide an intuitional explanation for the radiation changes. Detailed analysis is then conducted from the perspective of ground current. It is found that the current distribution is affected by configurations of both the arc DRA and ground plane. Based on this, analytical methods are developed to calculate the ground effects exclusively for conformal arc-shaped DRAs. Next, the design theory of arc DRAs with curved ground is proposed. To demonstrate it, two conformal DRAs owning directional and wide beams, respectively, are designed as paradigms. At last, a prototype is fabricated and measured for validation.

This work provides design and analysis of a beam steering reflectarray antenna, designed at 26 GHz, based on the mechanical rotation of the array. Unit cells based on circular ring elements are designed, and scattering parameter measurements have been carried out for obtaining progressive phase distribution. The unit cell measurements demonstrated a maximum reflection loss of 4 dB with a total phase range of almost 360°. Symmetricity of the array and the resonant elements has been exposed to steer the main beam by tilting the reflectarray at different angles. A beam steering range of more than ±60° has been demonstrated by varying the tilt angle from +30°to -30°. The designed 20 × 20 element array provided a maximum gain of 26.47 dB at 0° which reduced to 19.8 dB at 61.9° in the elevation plane. On the other hand, the reflectarray antenna demonstrated a maximum bandwidth of 13.1% with a minimum side lobe level of -25.9 dB.

A full-wave leaky-wave analysis of 1-D periodically corrugated metallic surfaces with wide gaps is presented. Such wide gaps, in the order of half-wavelength, are employed in the most cited designs for corrugated metallic antenna implementation due to the high attainable gain performance. A full-wave periodic unit cell method is described and implemented on a corrugated metal surface design for the first time. The results are compared with the known matrix pencil method. The complex dispersion characteristics verify that these structures operate as leaky-wave antennas. The calculated wavenumber of the leaky mode is then used for the analytical calculation of the radiation patterns of a finite-size antenna, based on a simple array factor approach and a near-field inspection of the electric fields of the simulated unit cell. The calculated patterns are compared to those obtained from a commercial simulation software (CST Microwave Studio), exhibiting a very good agreement. [ABSTRACT FROM AUTHOR]

Compact coplanar waveguide Ultra-wideband (UWB) monopole antenna with band notched characteristics is presented in this paper. The band rejection is achieved by etching a circular slot on the radiating patch. The antenna is printed on the FR4-Epoxy substrate with overall dimensions of 23.5 x 31 x 1.5 mm³. The measured results indicate that the antenna operates in the frequency range from 1.76 to 11.07 GHz and rejects the band 2.42 to 5.37 GHz with an acceptable measured input impedance over the whole operating frequency bandwidth. Furthermore, the simulated results indicate that the antenna exhibits stable radiation patterns with appreciable gain and efficiency over the whole operating band except at the notched-band. Accordingly, this antenna provides a good solution for wireless communication systems with good characteristics. [ABSTRACT FROM AUTHOR]