An Effective Antenna Array Diagnosis Method via Multivalued Neural Network Inverse Modeling Approach

Failure of element (s) in antenna arrays impair (s) symmetry and lead to unwanted distorted radiation pattern. The replacement of defective elements in aircraft antennas is a solution to the problem, but it remains a critical problem in space stations. In this paper, an antenna array diagnosis technique based on multivalued neural network (mNN) inverse modeling is proposed. Since inverse analytical input-to-output formulation is generally a challenging and important task in solving the inverse problem of array diagnosis, ANN is a compelling alternative, because it is trainable and learns from data in inverse modelling. The mNN technique proposed is an inverse modelling technique, which accommodates measurements for output model. This network takes radiation pattern samples with faults and matches it to the corresponding position or location of the faulty elements in that antenna array. In addition, we develop a new training error function, which focuses on the matching of each training sample by a value of our proposed inverse model, while the remaining values are free, and trained to match distorted radiation patterns. Thereby, mNN learns all training data by redirecting the faulty elements patterns into various values of the inverse model. Therefore, mNN is able to perform accurate array diagnosis in an automated and simpler manner.

MIMO CPW-Fed Bent Antenna Based USB Dongle for ECMA-368 WPANs

A multiple-input-multiple-output (MIMO) ultra-wideband (UWB ) printed bent antenna, suitable for MB-OFDM ECMA-368 system integration with the wireless universal serial-bus (WUSB) dongle is proposed. The antenna consists of two antenna elements with an overall area of 18 X 53 mm2. Each antenna element is a simple modified folded-monopole fed by a coplanar waveguide (CPW). The design process of proposed MIMO UWB CPW-fed bent antenna configuration is presented in four simple steps. Experimental results show that the proposed design has a good impedance bandwidth in the range of 2.95–18.55 GHz with 147.2% fractional bandwidth (FBW). Moreover, the proposed antenna enjoys, low envelope correlation coefficient (ECC), good diversity gain (DG), low total active reflection coefficient (TARC) and omnidirectional radiation patterns. The bit error rate (BER) of the overall MB-OFDM ECMA-368 system with the existence of the proposed MIMO UWB CPW-fed bent antenna is evaluated in more realistic transmission channel scenario by using the extracted transmitting and receiving UWB antennas transfer functions.

Multi-Band Polarization Insensitive Ultra-Thin THz Metamaterial Absorber for Imaging and EMI Shielding Applications

this article, a multi-band polarization-insensitive metamaterial absorber is designed for THz imaging and EMI shielding. A unique oval-shaped structure with three circular ring-shaped resonators is proposed with a unit cell dimension of36×36×19.6μm3. The absorbance of the proposed multiband MMA is 98.57%, 90%and 99.85% at 5.58, 7.98-8.84, 11.45THz frequency respectively. Return loss is nearly the same for the changing incident and polarization angle. Therefore, this metamaterial absorber with a wide range of polarization insensitivity is found and it is also suitable for quantum RADAR Imaging, energy harvesting, and optoelectronic devices.

CSRR-DGS Bandpass Filter Based on Half Mode Substrate Integrated Waveguide for X-Band Applications

In this paper, a half mode substrate integrated waveguide (HMSIW) bandpass filter using defected ground structure cells (DGS) is proposed. By using the periodic square CSRR resonant properties of DGS according to design requirement, an X-band band-pass filter is designed and analyzed to meet compact size, low insertion loss, and high rejection. The simulation results obtained by CST in X-band show that the proposed filter is characterized by a large transmitted bandwidth of about 1.38 GHz from 13.03 to 14.41 GHz. The higher simulated insertion loss is about −2.6 dB and the lower return loss is about −34 dB. The proposed filter size is 9.50 × 38.00 mm2 which make it a compact component. The structure is optimized using CST simulator. For the proposal validation, the simulation results is compared by HFSS. The simulation results are in good agreement for the two simulator.

Square Waveguide Polarizer with Diagonally Located Irises for Ka-Band Antenna Systems

This article presents the results of development and optimization of a new square waveguide polarizer with diagonally located square irises. The application of suggested geometrical modification of irises form and location instead of a standard wall-to-wall irises configuration allows to exclude 45-degree twists between wideband waveguide polarizer and orthomode transducer of a dual-polarized antenna feed system. In addition, a waveguide polarizer and polarization duplexer can be manufactured by milling technology as two single details, which makes the proposed engineering solution reliable, simple for simulation, development and application. Suggested new polarizer design was developed for the satellite operating Ka-band. It contains 12 irises, which are symmetrically located in the diagonal corners of a square waveguide. Obtained optimal polarization converter provides excellent matching and polarization performance. The maximum level of VSWR is less than 1.04 for both orthogonal polarizations. Values of cross-polarization discrimination are higher than 32 dB in the operating Ka-band. Developed square waveguide polarizer with diagonally located irises can be applied in modern wideband satellite antennas.

Electromagnetic Simulation of New Tunable Guide Polarizers with Diaphragms and Pins

In this article we present the results of mathematical simulation, development and optimization of a waveguide polarizer with a diaphragm and pins. A mathematical model was developed using the proposed approach on the example of a waveguide polarizer with one diaphragm and two pins. The diaphragm and pins were modeled as inductive or capacitive elements for two types of linear polarization of the fundamental modes. The applied model uses a wave scattering matrix. The total matrix of a polarizer was obtained using wave matrices of transmission of individual elements of the device structure. Using the elements of the common S-parameters the electromagnetic characteristics of the device, which is considered, were obtained. To check the performance of the developed mathematical model, it was simulated in a software using the finite element technique in the frequency domain. The designed structure of the polarizer is adjustable due to mechanical change in the length of the pins. The developed waveguide polarizer with one diaphragm and two pins provides a reflection coefficient of less than 0.36 and a transmission coefficient of more than 0.93 for two types of polarizations. Therefore, a new theoretical method was developed in the article for analysis of scattering matrix elements of a waveguide polarizer with diaphragms and pins. It can also be used for the development of new tunable waveguide polarizers, filters and other components with diaphragms and pins.

Compact Broadband Microstrip Triangular Antennas Fed By Folded Triangular Patch for Wireless Applications

This study presents two new designs of reduced size broadband microstrip patch antennas for ultra-wideband (UWB) operation. A folded triangular patch’s feeding technique, V-shaped slot, half V-shaped slot and shorting pins are employed to design the suggested antennas. The shorting pins are applied at the edge of structures to miniaturize the size of the patches. The suggested design with the V-shaped slot provides the measured impedance bandwidth (S11˂-10 dB) of 3.91-12 GHz (101.7%) for broadband application. In the suggested design with the V-shaped slot, the wide bandwidth with an acceptable size reduction is achieved. By introducing a suggested half design with the half V-shaped slot, the impedance bandwidth of the proposed half structure is improved from 4 to 17.22 GHz. The half design includes a measured impedance bandwidth of 124.6% with reduced size of more than 93% compared to the corresponding full design and an enhanced measured bandwidth of 23%. The obtained radiation and impedance results show that the suggested designs are applicable for wideband operation. Besides, the effects of some basic concepts and surface currents on the suggested structures are investigated to explain their broadband performance.

Exploring microwave absorption by non-periodic metasurfaces

In recent years there has been a large body of work investigating periodic metasurface microwave absorbers. However, surprisingly few investigations have focused on the absorption performance of similar non-periodic designs. In this work, the electromagnetic response of a large area (310 mm x 310 mm) microwave absorber that lacks a global periodicity is experimentally studied. The top metallic layer of the ultra-thin (0.3 mm) absorber is structured with rectangular patches given by a procedurally generated non-periodic pattern, known as the toothpick sequence. The specular reflectivity of both p-polarised and s-polarised incident radiation shows coupling to an additional low frequency mode when compared to a standard square patch periodic absorber. To further explore the coupling efficiency of such non-periodic absorbers, finite element models were used to investigate the influence of increasing sample size.

Frequency Reconfigurable Multiband MIMO Antenna Base on Gradient Arcs for IoT Devices

A frequency reconfigurable multi-band MIMO antenna is presented in this study. The single antenna consists of only one PIN diode that can change antenna operating frequencies from different quad-band to another one. Their bands not only cover the popular NB-IoT bands such as 900MHz, 1.8GHz, 2.4GHz for Z-Wave, ZigBee, RFID, GSM communication but also contain 5G IoT bands which are 2.4GHz, 2.6 GHz and 5GHz for LTE-A, 802.11n, ac, and 5G below 10GHz. Basing on the complex structure of ring and new moon shape, the single antenna achieves a compact size of 30 mm x 30 mm x 1.6 mm which is about 76% reduction compared to a conventional ring antenna at 900MHz. Besides, a structure of gradient arcs is proposed to decrease mutual coupling among closed-spaced elements of MIMO antenna for the distance of 0.033l at the lower band from edge to edge. The proposed antennas are analyzed by CST software, VNA measurement, and IEEE 802.11 USB Adapter that the simulated, measured as well as experimental results are agreed well.

Summation of Powers in Open Resonator with Slotted Coupling Elements

The paper analyzes the summation of the powers of two sources in a hemispherical open resonator (OR) during its tuning. The first higher axially asymmetric TEM10q oscillation mode is excited in the resonator. A circuit with an E- tee waveguide is proposed, which makes it possible to research the summation of the powers using a Gunn diode. Studies of the conducting part of the millimeter range have been undertaken. It is shown that the coefficient of powers summation of two sources in the OR using slot coupling elements does not exceed 72%. The use of one H- polarized diffraction grating, which is in the resonator, does not lead to a significant increase in the summation coefficient when moving it. This is due to the excitation of the first type of TEM10q oscillations in the resonator.