Surrogate-model based isolation analysis of slotted waveguide antennas

Slotted waveguide antennas are widely used in radio engineering systems for various purposes due to their advantages: high directivity, the possibility of constructing linear and lattice radiators, compactness and manufacturability. Despite the advantages, designing slotted waveguide antennas is a difficult task. The problem is that the antenna characteristics are determined not only by the electrodynamic processes occurring inside the waveguide, but also by the parameters of the slots, their location and orientation. In this case, it is necessary to take into account the mutual influence of the slots on each other, as well as the matching of the antenna with the supply path. In particular, resonant and non-resonant slotted waveguide antennas are distinguished. In resonant designs, the slots are excited by a standing wave, which ensures high efficiency, but imposes strict matching requirements. Traveling wave is used in non-resonant antennas, which makes it possible to expand the band and simplify matching, however, the task arises of distributing the characteristics along the structure. An important task in the design is the formation of a directional pattern with inclination of the main lobe and sidelobe level. These parameters are determined by the amplitude-phase distribution and depend on the location and characteristics of the slots. The correct choice of their size and position allows you to control the orientation and achieve the required characteristics. The article presents a scientific justification of the mathematical apparatus for calculating gaps for optimization and obtaining the characteristics. The algorithm takes into account the processes in the waveguide, the mutual influence and the alignment with the supply path. The technique involves numerical modeling, followed by analysis of the results and optimization of parameters to achieve the tilt of the main lobe, reduce the level of the side lobes and provide the electrical characteristics. Purpose – development and optimization of a slotted waveguide antenna with a given inclination of the main lobe of the radiation pattern and the required sidelobe level based on the slot calculation algorithm. A slotted waveguide antenna designed to operate at a frequency of 10 GHz is calculated based on an algorithm for determining slot conductivities at equal-amplitude current distribution. A non-resonant slotted waveguide antenna with variable-phase slots in a waveguide with an absorbing load is considered. Numerical modeling in the FEKO has been performed, confirming the correctness of the calculations. Optimization of the design parameters in DT Seven has been carried out to form a directional pattern with a given inclination of the main lobe and the required sidelobe level. Radiation characteristics meeting the set requirements have been obtained. A universal algorithm has been developed for calculating a non-resonant slotted waveguide antenna with variable-phase slots, which allows forming a radiation pattern with specified parameters. The possibility of optimization makes the method adaptable to different requirements and ensures wide applicability in practice. The implemented approach allows us to expand it to calculate antennas with nonuniform amplitude current distribution, as well as other types of slotted waveguide antennas.

Introduction. A resonant slotted waveguide antenna allows providing broadside radiation, which coincides with the normal line to the longitudinal axis of the array. Such an antenna can be well-matched in a very narrow frequency band. Even a slight deviation from the operating frequency leads to a significant distortion of the radiation pattern. In this regard, the distortion of the radiation pattern is becoming an urgent task. Aim. The main objective of this work is to preserve the radiation pattern of the resonant slotted waveguide antenna with longitudinal slots in the broad face in operating bandwidth. Materials and methods. Subarraying was performed to preserve the undistorted radiation pattern of the slotted waveguide antenna array in the operating bandwidth. The antenna model and its directional properties were analyzed in CAD Ansys HFSS using Visual Basic Scripting Edition macros. Results. Three slotted waveguide antennas’ models, consisting of two, four, and eight subarrays were developed in Ansys HFSS CAD. The effect of subarraying on the radiation pattern at the center frequency and the upper and the lower operating frequencies is studied. It is shown that the growing number of subarrays leads to a more stable radiation pattern in the operating bandwidth. Conclusions. Full-wave electromagnetic simulations have shown that subarraying of a resonant slotted waveguide antenna is a useful measure that preserves undistorted radiation pattern in the operating frequency band. Usage of Visual Basic Scripting Edition macros allows to minimizing the time spent creating a model in CAD Ansys HFSS.

Antennas are becoming crucial in an increasingly growing number of vital applications, particularly with the emergence of the 3G and 4G generations of communications. Point-to-multipoint configuration is a major interest nowadays; therefore antennas are designed for this purpose where efficiency, size, and cost play a decisive role. The common practice is to refer to the already existing antennas in the market for this sole purpose. Nonetheless, a major drawback of such solutions is that the aforementioned criteria are extremely hard to simultaneously optimize. The purpose of this project is to present a new configuration relying on the use of Slotted Circular Waveguide Antennas, which are initially used in Radar applications, as an ultimate alternative that allows drastically enhancing the ratio of performance versus cost. Moreover, the antenna will be remodeled and designed to function as an enhanced Circular Slotted Waveguide Antenna with optimized directional characteristics with gain above 10 dBi (to be considered as high gain). Simulation results were carried out at 2.4 GHz frequency and indubitably demonstrated high effectiveness in terms of directivity and high gain given a reduced cost, shape and size. A prototype was fabricated to measure its parameters and compare them with simulation results. It is still noteworthy to mention that these results matched with an elevated accuracy since the pattern simulated is meshed and modeled to a far extent taking into account all non-ideal characteristics.

We present a complete linear scaling method for hybrid Kohn-Sham density functional theory electronic structure calculations and demonstrate its performance. Particular attention is given to the linear scaling computation of the Kohn-Sham exchange-correlation matrix directly in sparse form within the generalized gradient approximation. The described method makes efficient use of sparse data structures at all times and scales linearly with respect to both computational time and memory usage. Benchmark calculations at the BHandHLYP/3-21G level of theory are presented for polypeptide helix molecules with up to 53 250 atoms. Threshold values for computational approximations were chosen on the basis of their impact on the occupied subspace so that the different parts of the calculations were carried out at balanced levels of accuracy. The largest calculation used 307 204 Gaussian basis functions on a single computer with 72 GB of memory. Benchmarks for three-dimensional water clusters are also included, as well as results using the 6-31G** basis set.

This paper describes the design of a novel Ku-band slotted waveguide antenna (SWA), taking into consideration the advantages and drawbacks of using a 3D direct metal laser sintering (DMLS) process. Indeed, the DMLS process makes it possible to produce a SWA with 64 radiating slots and its feeding network in a single and monolithic process. However, considering the lack of accuracy of the process, the whole design must be completely thought out and planned to avoid sensitive dimensions. Coupling irises inside such structures are elements of major sensitivity in this regard, so the radiating waveguides in the present work were designed to be TE20 ones, avoiding this kind of iris. Thus, a TE10 to TE20 converter was designed to be implemented in the overall power supply structure of an antenna array made up of four linear SWAs with 16 slots each. Both the elementary 16-slot SWA and the complete SWA with the feeding network were manufactured using DMLS. At a resonant frequency of 15 GHz, the measured realized gain is 22.26 dB with sidelobe levels below 10.1 dB. The measured reflection coefficient is lower than −12.6 dB at the center frequency. These measured performances confirm the proof of concept.

Although deep compositional features have achieved an amazing performance in many application scenarios, it is not easy for them to directly tackle big data case due to their high computing time and memory usage. This paper presents a comparative evaluation for the simplification of deep compositional features by exploring the existing vector quantization and binarization techniques. Different techniques display different capabilities in similarity-preserving or memory-saving when projecting the original deep compositional features into more compact visual words or binary codes. We propose a dedicated image searching framework to evaluate all the techniques in terms of computational cost, memory usage and discrimination preserving. Extensive experiments demonstrate that it is feasible to greatly reduce computational cost and memory usage of the deep compositional features while preserving enough discriminative power. In addition, some useful conclusions are derived to guide the design of better simplifying schemes.

For the synthetic aperture radar (SAR) systems, there is an increasing demand for achieving resolutions of 0.2 m times 0.2 m. As the range resolution and system bandwidth are inversely proportional, the system bandwidth are expected to be larger than 1 GHz. Thus an antenna with wider band must be developed. Waveguide slot antenna has been implemented on several SAR satellites due to its inherent advantages such as high efficiency and power handling capacity, but its bandwidth is limited. To avoid the manufacture difficulties of the ridge waveguide, which can be used to broaden the bandwidth of the slot antenna, a novel antenna element with conventional waveguide is designed, fabricated and tested. The bandwidth of VSWR les1.5 is greater than 1 GHz at X- band, which can meet the specifications of the system. The radiation pattern and gain agree well with the simulated results.

This paper introduces a waveform generation algorithm from three speech parameters (fundamental frequency fo, spectral envelope, and band aperiodicity). The conventional speech analysis/synthesis system based on a vocoder mainly has a waveform generator based on pitch synchronous overlap and add (PSOLA). Since it uses the fast Fourier transform (FFT) to generate the vocal cord vibration, the processing speed is proportional to the f <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">o</sub> . The algorithm also uses the spectral representation of the aperiodicity, whereas the band aperiodicity is mainly used in speech synthesis applications such as statistical parametric speech synthesis. We propose a waveform generation algorithm that reduces the computational cost and memory usage without degrading the synthesized speech. The algorithm utilizes excitation signal generation by directly using the band aperiodicity. The computational cost in a certain period is fixed because the excitation signal is filtered and processed by the overlap-add (OLA) algorithm. We used the re-synthesized speech to perform two evaluations for the processing speed and sound quality. The results showed that the sound quality of speech synthesized was almost the same by our proposed algorithm as by the conventional algorithm. The proposed algorithm can also reduce computational cost and memory usage.

In this paper, Discrete Dipole Approximation (DDA) is presented as a simulation tool for predicting the electromagnetic properties of one dimensional metasurface antennas and slotted waveguide antennas. The proposed method is verified by demonstrating excellent agreement between DDA predictions and that of a full-wave electromagnetic solver. This technique is especially attractive since it allows us to simulate and design metasurface antennas with unusual tapering and irises with unconventional geometries (e.g. metamaterial elements), in order to achieve the desired radiation characteristics, such as beamwidth and sidelobe level, while maintaining steering capabilities.

This paper presents a novel passive tuning technique to mechanically tune the resonant frequency of a substrate integrated waveguide (SIW) slot antenna, by using cylindrical rods of different dielectric materials in the air holes. A full‐wave 3‐dimensional Electromagnetic simulator software is used to estimate tunability in the resonant frequency of the SIW slot antenna, which is then analysed using its equivalent circuit, and then verified experimentally. Tunability is obtained by changing relative permittivity of dielectric rods. Measurements show good frequency tunability even with a limited number of dielectric rods and gains over 5 dBi. The similarity in the radiation patterns with tuning, demonstrates a good characteristic for tunable antennas. The technique is simple but effective and does not require external direct current bias circuitry, which removes parasitic effects and less power consumption. The low field perturbation of dielectric rods provides better loss performance and a higher Q‐factor over a wider bandwidth. The initial design demonstrates a cost‐effective tuning technique achieving return loss (&gt;10 dB) in the X‐band. This technique is also suitable for practically overcoming the performance deviation due to fabrication inaccuracies and temperature variation.

We apply a source‐receiver compression approach to reduce the computational time and memory usage of three‐dimensional acoustic full‐waveform inversion. By detecting and quantifying the extent of redundancy in the data, we assemble a reduced set of simultaneous sources and receivers that are weighted sums of the physical sources and receivers used in the survey. Because the number of these simultaneous sources and receivers can be significantly less than those of the physical sources and receivers, the computational time and memory usage of any inversion method can be tremendously reduced. The scheme is based on decomposing the data into their principal components using a singular value decomposition scheme and the data reduction is done through the elimination of the small eigenvalues. For the inversion method, we employ the multiplicative‐regularized Gauss‐Newton approach, in which the regularization parameter is automatically and adaptively determined by the inversion process. For the forward solver, we employ a frequency‐domain iterative solver using the perfectly matched layer absorbing boundary condition and a multigrid preconditioner. We demonstrate the advantage of our approach by using the 3D SEG/EAGE salt model.

This paper presents the design of a 5-element array consisting of four complementary split ring (CSR) slots on the narrow-wall of a rectangular waveguide and an H-plane-bend (HPB) radiator. Subwavelength CSR slots are recently proposed as elements of slotted waveguide antenna (SWA) arrays. Combining CSR slots on the narrow-wall of a rectangular waveguide with an HPB radiator provides significant size reduction while maintaining high-power handling ability. A periodic air-filled corrugation is applied to the post narrow-wall of the rectangular waveguide to achieve better return loss.

In this paper, a novel broadband slotted waveguide antenna is presented. A double-slot structure and a ridged waveguide are used. The structure of the double-slot is analyzed by means of the transmission line model. The analysis shows that the theoretical design is in good agreement with experimental results.

This paper proposes the design of weather radar antenna on X-Band frequency with two polarizations. The antenna is built based on slotted waveguide antenna array (SWAA) with its antenna structure consists of 2 layers, first layer is a radiating waveguide and second layer is a feeder waveguide. The first layer is composed of 5 waveguides in which each of waveguide consist of 64 slots, while the second layer is a single waveguide. The simulation result shows that the key antenna parameters performace reaches the specification such as: operating frequency = 9380 MHz, S 11 = −22.567, bandwidth = 51.4 MHz, 3 dB-beamwidth for H-pol = 1.2 degree, 3 dB-beamwidth for V-pol = 1.0 degree, sidelobe level for H-pol = −17.3 dB, sidelobe level for V-pol = −15.2 dB, co-pol for H-pol = 20.6 dB, co-pol for V-pol = 16.2 dB, cross-pol for H-pol = −20 dB, and cross-pol for V-pol = −20.3 dB. Therefore, the proposed antenna is suitable for use as a weather radar antenna.

In this paper, by using structure superposition approach and smart design method, a multifunction antenna was composed by a waveguide slot antenna and a microstrip array antenna. Microstrip array antenna is dual polarization and works at microwave band. Waveguide slot antenna works at Ka band. Simulation results are presented to show the performance of the antenna.