Radiation Patterns Of Elements Research Articles

A Dual-Band Dual-Polarized 2x2 Antenna Array with Beamforming for 5G AiP and mmWave Applications

In this study, we present a dual-band (28/39GHz) 2 by 2 antenna array design on a 10(4+2+4) multi-layer organic substrate with broad bandwidth and higher isolation onto a compact AiP module. In addition, the H-type slot antenna structure can improve interference and isolation between 28 and 39GHz bands. The measured result shows the isolation can larger than 15dB between low and high band. For antenna measurement, the spherical of probing chamber is utilized to validate 28/39GHz antenna pattern and performance with a package level passive testing. Our AiP measured result shows the return loss is better than 10 dB in 23.5-30.5 GHz range, with ~7 GHz bandwidth and provides a high-gain per element (above ~6 dBi) radiation pattern for 28GHz applications. For 39GHz band, the antenna has 7 GHz bandwidth and provides a 5 dBi gain between 38-45 GHz. Comparison of S-parameter between simulated and measured results, there is a good correlation to obtain the quality of manufacturing. Furthermore, a 28GHz beamforming array is designed and demonstrated. The beamfoming array consists of a four-channel transceiver with 2 x 2 antenna array. The beamformer IC is implemented by TSMC 90-nm CMOS technology and the flip-chip bonded on BT substrate. For beamforming test, an integrated socket and load board are designed for support the mmWave module and then connection between DUT and test system. The load board substrate includes the IF, LO, and DC distribution network for respectively. There are 4-channel transmit beamforming array front-end module for testing. Finally, the 3D beam steering of 2 by 2 antenna array is measured with multi-states at 28 GHz, with a maximum realized gain of 11.8 dBi achieved in the main beam (θ=0°). It shows that beamforming can be generated at a specific beam direction by controlling the phase of the signal in each antenna element.

A Novel Unit Classification Method for Fast and Accurate Calculation of Radiation Patterns

This paper proposes a novel unit classification technique to enhance the accuracy of the conventional pattern multiplication method by taking the mutual coupling effect and edge effect into consideration. The proposed technique classifies antenna elements into different groups based on their positions in arrays, specifically corner, edge, and inner groups. By simulating the radiation patterns of antenna elements with different boundary conditions, the pattern multiplication method is then used to calculate the radiation pattern of the antenna array based on the simulated results. Several numerical examples, including a square array, a hexagonal array, and a phased array, are provided to validate the effectiveness of the proposed method. The numerical results demonstrate that the proposed method not only reduces the computational time and memory usage but also significantly improves the accuracy. The proposed method provides a powerful tool for synthesizing and predicting the radiation pattern of array antennas and offers new avenues for optimizing array antennas and phased array antennas.

Impact of antenna directivity on compressed sensing-based DOA estimation employing UCA antenna

This letter investigates the impact of the antenna element directivity on compressed sensing (CS)-based direction of arrival (DOA) estimation employing the uniform circular array (UCA) antenna. In the CS-based approach, the reconstruction accuracy of sparse signals is determined by a sensing matrix, which depends on the array antenna configuration in the DOA estimation. In our study, we analyze the cross-correlation between column vectors of the sensing matrix and clarify the estimation accuracy for various antenna element radiation patterns.

A Graded Index All-Dielectric Lens for Field Decorrelation and Decoupling of a Wideband MIMO Antenna

In this paper a broadband graded index all-dielectric (GID) lens that enables field decorrelation and decoupling of closely spaced wideband multiple-input-multiple-output (MIMO) antenna elements, is presented. Reduction in correlation coefficient ρ for field decorrelation and port decoupling is realized by tilting the individual antenna element radiation patterns away from each other and by suppressing the surface wave propagation inside the antenna substrate through judicious control of the permittivity profile of the GID lens using the concept of transformation electromagnetics (TE). The permittivity profile of the GID lens is designed using air-hole technology and is fabricated by additive manufacturing. To validate the proposed concept, six different examples of lens loaded wideband patch-based MIMO antenna elements arranged in two different orientations are investigated. Simulated and measured results verify the effectiveness of the proposed technique, which constitutes the reduction in ρ for both isotropic and non-isotropic propagation environments along with port-isolation enhancement without reducing the fractional bandwidth (FBW) in all of the six tested cases. Further results indicate a wide FBW having a minimum of 8.5% and a maximum of 33%, while radiation patterns with no extra backward radiation are obtained.

Beam Shaping of Base Station Antenna Array by Using MMPTE

In this paper, a beam shaping scheme is presented for the optimal design of base station antenna array. The antenna array consists of four linearly arranged dual-band dual-polarized antenna elements, and it is designed to cover the LTE frequency band (2.3-2.69 GHz) and 5G frequency band (3.3-3.6 GHz). The shaped beams with possible maximum gain, suppressed sidelobe level smaller than -16 dB, front-to-back ratio larger than 18dB, and filled-up null point larger than -23 dB are accomplished through two steps by using the unconstrained methods of maximum power transmission efficiency (MMPET) and constrained MMPTE, respectively. In the proposed beam shaping scheme, all the realistic factors of the antenna array have been taken into account, such as the difference of element radiation patterns, complexity and tolerance of the element structure and spacing.

Decoupling of Dual-Polarized Antenna Arrays Using Non-Resonant Metasurface.

A non-resonant metasurface (NRMS) concept is reported in this paper to improve the isolation of dual-polarized and wideband large-scale antenna arrays. By properly designing the NRMS, it can perform stable negative permeability and positive permittivity along the tangential direction of the NRMS within a wide band, which can be fully employed to suppress the mutual couplings of large-scale antenna arrays. At the same time, the proposed NRMS can also result in positive permittivity and permeability along the normal direction of the NRMS, which guarantees the free propagation of electromagnetic waves from antenna arrays along the normal direction. For demonstration, a 4×4 dual-polarized antenna array loading with the proposed NRMS is designed to improve the isolations of the antenna array. The simulations demonstrate that the isolations among all ports are over 24 dB from 4.36 to 4.94 GHz, which are experimentally verified by the measured results. Moreover, the radiation patterns of antenna elements are still maintained after leveraging the proposed NRMS. Due to the simple structure of the proposed NRMS, it is very promising to be widely employed for massive MIMO antenna arrays.

Miniaturized Wide Scanning Angle Phased Array Using EBG Structure for 5G Applications

This article presents a miniaturized wide-angle scanning phased array for fifth-generation (5G) application. A subarray of two closely packed patch antennas on electromagnetic bandgap structure (EBG) ground with the operating bandwidth of 26–29 GHz is used as the basic module of the linear array, which contains four equally spaced subarrays. The existence of the EBG ground enables the array to be compact in size (3.2 × 0.6 × 0.12λL3), yet the mutual coupling between each element can reach to more than 22 dB within the whole band of interest. The EBG structures also contribute to the wide element radiation pattern of the aperiodic array and consequently the wide scanning angle performance of the array. The range of the main beam scan with EBG structure can reach from −70° to 70° with more than 6 dB side lobe levels (SLLs) at 26.5 GHz with 3 dBi scanning gain loss. This proposed method enabling the array to be compact and wide in scanning angle is very attractive for 5G mobile terminal applications.

Scanning Angle Extension of a Millimeter-Wave Antenna Array Using Electromagnetic Band Gap Ground

A compact phased array with extended beam steering characteristics for the millimeter-waveband of the fifth-generation (5G) applications is presented in this communication. An E-shaped patch antenna placed on an electromagnetic bandgap ground (EBGG) with operating bandwidth of 24.2–27.5 GHz is used as the basic building block of the eight-element linear array. The array utilizes both the in-phase reflection characteristic for broad element radiation pattern and the bandgap characteristic for mutual coupling reduction for limited inter-element spacing of the proposed array. The existence of the EBGG enables a compact array with the inter-element spacing of around 0.4 wavelengths at the center frequency, yet the isolation between each element is still above 17 dB within the whole band of interest, which also helps to increase the array directivity at large scanning angles. The scanning angle of the array with the electromagnetic bandgap (EBG) structure ranges from −75° to 75° at 26 GHz within 3 dB scanning loss. The proposed EBGG extends the antenna array’s spatial coverage and enables a compact size of the array, which is very attractive for 5G millimeter-wave (mm-wave) application.

Improved Beamforming in 3D Space Applied to Realistic Planar Antenna Arrays by Using the Embedded Element Patterns

Most of beamforming methods rely on the proper estimation of the steering vectors of the incoming signals in order to calculate appropriate array feeding weights. However, this estimation is often performed on a theoretical basis, since most methods assume that the array elements radiate like isotropic sources and consider only the phase differences between them due to their different spatial positions. This is a rough estimation as it ignores both the non-isotropic radiation pattern of the array elements and the mutual coupling between them. To overcome these limitations, we use a different approach for the construction of steering vectors based on the embedded patterns of the array elements, extracted through full-wave analysis. This approach is used in this paper to modify two well-known beamforming methods, namely the null steering beamforming and the minimum variance distortionless response method. Both modified methods are applied to a realistic model of a microstrip planar antenna array, and thus, both the azimuth and polar angles of the main lobe and nulls directions are controlled (beamforming in 3D space). Extensive statistical analyses are performed by implementing several scenarios of escalating difficulty, in order to examine the performance and temporal response of the modified beamforming methods in comparison to the respective conventional methods and also in comparison to beamforming methods based on evolutionary techniques.

An Efficient Adaptive and Steep-Convergent Sidelobes Simultaneous Reduction Algorithm for Massive Linear Arrays

Antenna arrays have become an essential part of most wireless communications systems. In this paper, the unwanted sidelobes in the symmetric linear array power pattern are reduced efficiently by utilizing a faster simultaneous sidelobes processing algorithm, which generates nulling sub-beams that are adapted to control and maintain steep convergence toward lower sidelobe levels. The proposed algorithm is performed using adaptive damping and heuristic factors which result in learning curve perturbations during the first few loops of the reduction process and is followed by a very steep convergence profile towards deep sidelobe levels. The numerical results show that, using the proposed adaptive sidelobes simultaneous reduction algorithm, a maximum sidelobe level of −50 dB can be achieved after only 10 iteration loops (especially for very large antenna arrays formed by 256 elements, wherein the processing time is reduced to approximately 25% of that required by the conventional fixed damping factor case). On the other hand, the generated array weights can be applied to practical linear antenna arrays under mutual coupling effects, which have shown very similar results to the radiation pattern of the isotropic antenna elements with very deep sidelobe levels and the same beamwidth.

A W‐band sparse phased array antenna with ultrahigh sparsity for radar applications

AbstractA sparse phased array with 4% sparsity is developed for advanced low‐cost W‐band radar applications. A high‐order radiation mode‐based substrate‐integrated waveguide antenna featuring waveguide feeding is employed as the antenna element to achieve feeding loss reduction and antenna gain enhancement. An improved optimization technique is adopted to optimize the antenna element distribution. The combination of the element distribution and the antenna element radiation pattern achieves grating lobe suppression. Both the simulation and measurement results show that a ±15° beam scanning range can be achieved, and the level of the measured normal and scanning sidelobes is lower than −18 dB and −13 dB, respectively.

High-Gain Circularly Polarized Array Antenna With Low Grating Lobe Property Based on TM30/TM03 Mode

In this letter, a high-gain circularly polarized (CP) array antenna with low profile and low grating lobe property is proposed. The array is composed of high-gain and low sidelobe CP patch elements based on odd high-order modes. By adding perturbation structure, a pair of orthogonal modes (TM <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">30</sub> /TM <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">03</sub> ) of the patch with 90° phase difference is diagonally excited. Meanwhile, by introducing five circular slots on the patch, four sidelobes of the element radiation pattern in <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">x</i> o <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">z</i> plane and <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">y</i> o <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">z</i> plane are effectively reduced. Consequently, the large grating lobes of array antenna can be avoided. Then, a 2 × 2 array prototype is designed and fabricated for verification. The thickness of array is only 0.5 mm (0.027 <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">λ</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> ). The peak gain and aperture efficiency reach up to 17.5 dBic and 55.5%, respectively. When the element spacing is more than 1 <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">λ</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> , the measured maximum grating lobe level at 16.25 GHz is only −15 dB.

Mutual Coupling Effect in Unequally - Spaced Linear Antenna Array Performance

Unequally-spaced arrays can offer some advantages over equally-spaced arrays as follows: reducing the side-lobed level for the broadband array with an identical excitation coefficient. However, array design techniques do not take into account the mutual coupling effect among elements. In this article, the effect of mutual coupling on the array radiation pattern is investigated and discussed through studying the input impedance of the elements. Next, a technique for reducingmutual coupling based on radiation patterns of elements is presented. In this technique, the log-periodic dipole antenna with a frequency ranging from 900 MHz to 2500 MHz is selected as an array element. The results based on the FEKO magnetic field calculation program have shown that at 900 MHz, the proposed antenna array reaches a side-lobed level of -17.4 dB. At frequencies of 1500 MHz, 2000 MHz, 2500 MHz, the grating lobe levels of this antenna array are lower than 6.7 dB, 9.5 dBand 8.3 dB compared to those of the equally - spaced antenna array.

A Necessary Model to Quantify the Scanning Loss Effect in Spaceborne iGNSS-R Ocean Altimetry

When the interferometric global navigation satellite system reflectometry (iGNSS-R) altimeter receives the direct and reflected signals through the digital multibeam phased array antenna, the roll-off of element radiation pattern will cause the scanning loss of directivity. If the scanning loss is neglected, the ocean altimetric precision will be biased with possible consequences for the instrument design. This article carries out the following research on this. First, based on the geometry of iGNSS-R altimetry and the principle of phased array antenna beamformer, the scanning loss model with the elevation angle at the specular point as a parameter is established. Second, this article uses the measured data of the phased array antenna to verify the model, and the result shows that the simulated value is in good agreement with the measured value, with an average deviation of 0.07 dB. Third, taking the GPS L1 signal (full composite) as an example, the model is used to analyze the influence of the scanning loss on the iGNSS-R altimetric precision estimation. The research results show that when the phased array antenna synthesizes four beams for iGNSS-R altimetry, the comprehensive effect of scanning loss on altimetric precision estimation is 0.16 m. The influence of scanning loss should be considered in the future high-precision iGNSS-R altimetry instrument design.

Element phase centre and orientation compensation in conformal arrays during continuous deformations based on spherical mode expansion

Radiation field of conformal arrays can be obtained by simulation computation. There must be a trade-off between computation accuracy and complexity. With respect to applications where both high efficiency or even real-time applications and accuracy are required, such as adaptive beamformers together with time-varying array structures due to deformations or vibrations, more effective methodologies have to be employed for precise mainlobe direction maintenance and rigorous suppression of existing interferences. A method combining spherical mode expansion, rotation and translation of spherical waves, spatial displacement phase compensation, and approximations of constant element radiation patterns in local coordinate systems is proposed here, featuring one-time numerical effort for isolated element radiation patterns, fast coupling matrix calculation based on updated array configuration, and analytical radiation field expressions with limited eigenmode expansion coefficients storage requirements. Adaptive beamformers are utilised to validate the effects of remaining approximations including constant element patterns in local coordinate systems and constant mutual coupling matrix, proving the proposed method has the potential for aircraft-borne conformal antenna array radiation field analysis where deformations and vibrations occur continuously.

An Effective Modification of Conventional Beamforming Methods Suitable for Realistic Linear Antenna Arrays

Antenna array beamforming (BF) refers to a real-time procedure that aims at calculating the proper feeding weights applied to the array elements in order to create a main lobe and a number of nulls toward respective preassigned directions. Most of the research performed on BF has been based on a simplified mathematical model, which ignores the nonisotropic radiation pattern of the array elements and the element mutual coupling. This article introduces an innovative way to incorporate the actual radiation pattern of the array elements and the element coupling into two popular deterministic BF methods, thus making these methods applicable to realistic antenna arrays. These two modified methods are applied in several scenarios, where a desired signal and several interference signals with various directions of arrival are received by a realistic microstrip linear antenna array. The statistical analysis performed in every scenario demonstrates the validity and effectiveness of the proposed modification.

Analytic approach to study a hybrid plasmonic waveguide-fed and numerically design a nano-antenna based on the new director.

In this paper, a wideband InP-based hybrid plasmonic nano-antenna (HPNA) operating at telecommunication wavelengths has been proposed. Monolithically integrating InP-based lasers with hybrid plasmonic waveguide (HPW) as a feed line of the proposed HPNA on the same InGaAsP/InP wafer can increase the antenna efficiency. A new vertical director has been employed to have a highly directive horizontal radiation pattern. This enhancement is attributed to the efficient coupling between the radiation patterns of arm elements as well as reduced side lobes and back-lobes levels due to the achieved impedance matching. As a result, the directivity has been increased considerably, 3.6 dBi at 193.5 THz (1550 nm) and 1.1 dBi at 229 THz (1310 nm). The HPNA shows the high directivity, total efficiency and quality factor of 11.8, 97.49% and 94.57, respectively. Further, to verify the validity of confining the fundamental TM mode to a thin layer with the lower refractive index, both theoretical and numerical methods have been employed. Therefore, we have derived an analytical formula to investigate the HPW dispersion relation based on the transfer matrix theory and genetic algorithm. Moreover, due to the HPNA ability to receive an optical signal from free space and transmit it to the waveguide based on the reciprocity theorem, the HPNA performance as an optical wireless on-chip nano-link has been investigated analytically and numerically. Additionally, to obtain a high optical power signal and steering the beam angle, the antenna gain and directivity have been calculated with two different types of array structure by controlling the relative phase shift between the array elements and elements number. To validate the array design performance, a three dimensional full-wave numerical simulation and array factor theory have been exploited. The HPNA fabrication is compatible with generic foundry technology.

Dual-Band Dual-Polarized Wearable Button Array With Miniaturized Radiator.

A dual-band dual-polarized wearable array is proposed, based on a miniaturized innovating button radiator topology. The diameter of the rigid button is only 19.5 mm (0.29 λ at 4.5GHz), which optimizes the users' comfort, and makes it the smallest up to date in literature. The operational bands are 4.50-4.61GHz and 5.04-5.50GHz. The antenna thus covers the 4.5-4.6 unlicensed future 5th generation (5G) communication band for the internet of things (IoT), and the 5.1-5.5GHz wireless local area network (WLAN) band, respectively. Two orthogonal linear polarizations are obtained in each band. A low mutual coupling between the button antenna elements (below -18dB) and between the two ports within each element (below -20dB) is achieved, guaranteeing a good diversity performance. The envelope correlation coefficient (ECC) and the specific absorption rate (SAR) performance are also analyzed. In order to demonstrate the robustness of the button antenna and to mimic realistic situations, a more complicated asymmetrical ground plane model of the button antenna is studied for the first time. A prototype of a two-element button array has been fabricated. The measurement results match well with the simulations. A 10-element button array is studied within the context of a 3-D channel model, taking into account the button element's radiation pattern. A high achievable spectral efficiency (SE) is obtained.

Impact of Element Pattern on the Performance of GNSS Power-Inversion Adaptive Arrays

Power-inversion (PI) adaptive arrays are widely used in Global Navigation Satellite System (GNSS) receivers for interference mitigation. The effects of element patterns on the performance of PI adaptive arrays are investigated in this paper. To this end, the performance of adaptive arrays is investigated by Monte Carlo simulations, using CST Microwave Studio (Dassault Systems, Vélizy-Villacoublay, France) to calculate the radiation patterns of circular microstrip elements which are used to compute the adaptive weight and the adaptive array gain. It is shown that the performance of PI adaptive arrays is mainly dependent on the gain pattern of the reference antenna element rather than the non-reference elements because the algorithm essentially pushes the elements into an unequal position. Furthermore, the results show that the impact of mutual coupling on the performance of the antenna array can be associated with the radiation patterns of the reference element, which is helpful in selecting the optimum reference element without increasing computational complexity, especially for small GNSS arrays.

Stochastic Geometric Coverage Analysis in mmWave Cellular Networks With Realistic Channel and Antenna Radiation Models

Millimeter-wave (mmWave) bands will play an important role in 5G wireless systems. The system performance can be assessed by using models from stochastic geometry that cater for the directivity in the desired signal transmissions as well as the interference, and by calculating the signal-to-interference-plus-noise ratio ( $\mathsf {SINR}$ ) coverage. Nonetheless, the accuracy of the existing coverage expressions derived through stochastic geometry may be questioned, as it is not clear whether they would capture the impact of the detailed mmWave channel and antenna features. In this paper, we propose an $\mathsf {SINR}$ coverage analysis framework that includes realistic channel model and antenna element radiation patterns. We introduce and estimate two parameters, aligned gain and misaligned gain , associated with the desired signal beam and the interfering signal beam, respectively. The distributions of these gains are used to determine the distribution of the $\mathsf {SINR}$ which is compared with the corresponding $\mathsf {SINR}$ coverage, calculated through the system-level simulations. The results show that both aligned and misaligned gains can be modeled as exponential-logarithmically distributed random variables with the highest accuracy, and can further be approximated as exponentially distributed random variables with reasonable accuracy. These approximations can be used as a tool to evaluate the system-level performance of various 5G connectivity scenarios in the mmWave band.