A bidirectional, coplanar waveguide (CPW) fed dumbbell-shaped slot antenna with partially reflecting surface (PRS) with parasitic patches for gain, bandwidth, and radiation pattern improvement is investigated. A dumbbell-shaped CPW-fed slot antenna has a dimension of 0.71λg x 0.71λg x 0.0571λg. The proposed antenna is simple in design and has low profile structure. To achieve improvement in bandwidth, gain, and bidirectional radiation pattern, PRS with parasitic patches are placed on top and bottom of antenna at a distance of 0.25λg. The proposed design yields wide bandwidth of 4.11 GHz (4.48-8.59 GHz) with percentage bandwidth of 62.89%, S11 ≤ -10 dB, and peak gain of 5.61 dBi. The variation in the gain over desired bandwidth is less than 3 dB. The antenna is fabricated using an FR4 substrate with relative permittivity of 4.4. The measured results corroborate the design and stipulate the proposed structure to be suitable for applications in C Band.
Wave probing systems are used to obtain 2D or 3D images of objects. According to the nature of the waves used (acoustic-microwave and others), these waves can penetrate the fabrics or barriers that are in their way, so it is possible to photograph hidden objects. A system for ultrasonic wideband probing in air with multiple transmitters and multiple receivers with parallel digitization of signals from the receiving array using undersampling is proposed. Probing at frequencies from 38 kHz to 43 kHz is considered when receiving array signals are digitized at a frequency of 18 kHz. Transmitter and receiver placements have been optimized to minimize artifacts and noise. the transmitting and receiving arrays are located at the same plane. The presented results of the experimental study confirm that the processing of measured signals based on spatially matched filtering makes it possible to visualize scattering objects in the environment, including those hidden behind sound-permeable barriers.
A simple balanced bandpass filter is presented. It is constructed mainly by a loop-type resonator with loaded shorted/opened stubs. The resonator is fed by the balanced coupled-line structure. In the loop-type resonator, three approaches can be simultaneously utilized to achieve high common-mode suppression. One is that the loop-type resonator has different differential/common-mode resonant frequencies, which results in a good in-band common-mode suppression. The second is that the loaded short stubs with different lengths will make the input/output port couplings to have different coupling strengths, which will deteriorate the common-mode bandpass response. The third is that loading the grounded resistors can effectively dissipate the common-mode signal. Meanwhile, loading the grounded resistors in the balanced coupled-line structure can effectively dissipate the reflective common-mode signal. A detailed description about its structure, operational mechanism and design method is given. For demonstration, a prototype balanced bandpass filter working at 2.4 GHz is designed, fabricated and measured. A high in-band common-mode suppression of 49 dB is achieved. The measured and simulated results can verify the effectiveness of the proposed balanced bandpass filter and the design method.
In this paper, a new plasmonic absorbing metasurface sensor has been proposed to determine glucose concentrations. Surface Plasmon Resonance (SPR) shift has been used as the indicator of glucose concentration. The sensor employs metal-dielectric-metal configuration along with metal nano-cylinders to provide near unity absorption in the near infrared wavelength range (1800-2200 nm). The absorption frequency shifts when the sensor is surrounded by materials of different refractive indices. The structure has been investigated through Finite Difference Time Domain (FDTD) simulations. The results show reflectance and absorbance peaks with different analyte concentrations. The sensor displays a linear response along with sensitivity and Figure of Merit (FOM) equal to almost 500 nm/RIU and 11.82 RIU-1 respectively. The proposed sensor has potential applications in food and biomedical industries.
We show a new polarization- and angle-insensitive ultrathin metasurface design using four conjugated hexagonal split-ring resonators (CHSRRs). The CHSRRs are made of copper and arranged in a λ/4 cell-size polyimide film substrate with a dielectric constant of 3.5 and thickness of 0.2 mm (λ/400 at 3.75 GHz). Each CHSRR aperture faces one corner of the square unit cell, thus forming a conjugated loop to achieve TE and TM polarization-insensitive behavior in a wide range of incident angles. Results demonstrated a -10 dB impedance bandwidth of 530 MHz (3.44 to 3.97 GHz) under normal incidence, partially covering the n77 band used for 5G applications.
In this paper, a new method is introduced to design a simple-profile hybrid coupler in two arbitrary frequency bands. The structure is achieved by means of dual-band quarter-wavelength transformers as the arms of a traditional branch line coupler. A prototype of the coupler operating at 0.9 GHz and 2.45 GHz is designed and fabricated to validate the robustness of the method. Comparing simulated with measured results, a good agreement is observed. Moreover, the performance of the coupler in terms of impedance bandwidth and isolation level between the input ports is compared with existing works. Further, the suggested coupler has the simplest profile resulting from the most flexible design process.
How will the electrostatic interaction between two point charges change if they are shielded from the other by a dielectrical slab? While the physical setting of this electromagnetic problem is relatively simple, it is easy to be wronged, and the correct solution is surprisingly complicated. Here we will show a general answer using the method of images, in which the electrical field is not found by solving the Poisson's equation but by superposing an infinite number of image charges to recurrently satisfy all interfaces' boundary conditions. We also obtain analytical and algebraic results in some special cases.
In this paper, a planar passive array antenna is proposed with capability of reradiating the incoming incident wave to predetermined θ and φ reflection angles (2-D). This purpose is achieved by differentiating array elements' phases with the help of inter-connecting transmission lines. Incident and reradiated signal paths are isolated through two orthogonal polarizations used in the array structure. The idea is realized with a 2×2, microstrip, dual linearly polarized antenna arrays in 2 GHz operating frequency on the Ro5880 substrate with 1.2 mm height. Nonlinear nature of the theory behind this idea leads to some limitations in choosing the angles of incident and reflected signals which is thoroughly investigated.
In this letter, a broadband proximity coupled millimeter-wave microstrip array antenna is presented for automotive radar applications. The antenna array consists of a microstrip line and a series of trapezoidal radiating elements that are periodically arranged on both sides of the microstrip line, at intervals of about half the guided-wavelength. The introduction of the trapezoidal radiating patch enhances the excitation coupling while suppressing out-of-band frequencies, and it has a wider impedance bandwidth than the rectangular patch. In the design of proposed antenna, the normalized resistance of the trapezoidal radiating element is controlled by adjusting the gap with the microstrip line, so that a low-sidelobe level (SLL) can be achieved. Taking the 77-81 GHz frequency band allocated to automotive radar applications as an example, a 1×16 linear array is designed and fabricated. The measured SLL is better than -20 dB. The measured gain of 1×16 array is higher than 15 dBi over the operating frequency range of 77-81 GHz. The 1×16 linear array can achieve an impedance bandwidth of 7.6% (75.6-81.6 GHz).
In this paper, a novel ultra-wide band (UWB) antenna with a planar single-layer structure is proposed. The antenna consists of a main circular patch that is capacitively coupled to six circular patches of very small size relative to the main patch. The coupling is achieved through narrow gaps of semicircular shape which are uniformly distributed on the circumference of the main patch. A coplanar waveguide (CPW) is used for feeding the antenna to get the complete antenna structure with the feeding line printed on one face of a flexible dielectric substrate. The antenna is fabricated and subjected to experimental assessment of its performance regarding the bandwidth, gain, and radiation efficiency. The measurements show good agreement with the simulation results. It is shown that the proposed antenna operates efficiently over the frequency band of 3.1-10.6 GHz. The antenna has a radiation efficiency that ranges from 99% to 100% over the entire band. This high efficiency is attributed to the planar single-layer structure of the antenna and the use of a thin low-loss substrate. The antenna maximum gain ranges from 2 dBi to 5 dBi over the entire frequency band. The substrate material is Rogers RO3003TM which is flexible and can be conformal to planar and curved surfaces. The total substrate dimensions are 35 × 39.4 × 0.5 mm.
A hot-via chip-to-substrate interconnect with its operation frequency up to W-band for ultracompact radio frequency (RF) system in package (SIP) is reported in this paper. In order to improve the accuracy of the simulation model in millimeter wave bands, a trapezoidal platform model is established for modeling the RF performance of the hot-via which is formed by inductively coupled plasma (ICP) etching process. A three hot-vias structure in a gallium arsenide (GaAs) chip is employed to form a Ground-Signal-Ground (GSG) transition structure. Bumps on the Silicon substrate are designed as a half quasi-coaxial structure to make it compatible with the assembly process of SIP. A full-wave simulation model is established for a hot-via chip-to-substrate interconnect structure with HFSS, based on which structural parameters, such as the gap between the hot-vias and the radius of the quasi-coaxial structure, are optimized for the best performance over 92-96 GHz. A prototype of the hot-via chip-to-substrate interconnects in their back-to-back connected form has been fabricated. Measured results demonstrate that the overall insertion loss is less than 1.85 dB, and the return loss is better than 12 dB from 92 GHz to 96 GHz.
This paper presents a low profile and low-cost patch antenna with dual circularly polarized (CP) capability in X-band at a canter frequency of 8.3 GHz. The dual-CP antenna is divided into three layers, composed of a parasitic square patch, radiation square patch with four equal arms, and 90˚ patch coupler. Two arms of the radiation patch are connected to the 90˚ hybrid coupler using two metalized vias. right-handed circular polarization (RHCP) and Left-handed circular polarization (LHCP) is achieved by exciting two different ports. To validate the proposed design, the prototype of dual-CP antenna is fabricated and measured. Based on the measurement, the structure of proposed antenna has an excellent circular-polarization purity of less than 3-dB over the whole operational frequency bandwidth of the antenna (8 GHz-8.47 GHz) with a wide 3-dB axial ratio (AR) beamwidth of 133˚ across the angular range from -55° to +78° at 8.3 GHz.
This article presents a novel electrically small asymmetric coplanar strip (ACS) fed metamaterial inspired antenna for quad band operation. A metamaterial inspired open split ring resonator (OSRR) is the radiator which is fed using ACS to obtain four operating bands. The proposed antenna with a compact size of 18 mm × 15.5 mm × 1.6 mm is fabricated and tested. The experimental results are in good compliance with simulated ones. The proposed electrically small antenna has a radian sphere (ka) of 0.65 and achieves an average gain of 2.24 dBi with requisite radiation properties suitable for WiMAX and WLAN applications.
Limited endurance has become a bottleneck restricting the wide application of unmanned aerial vehicles (UAVs), and wireless power transfer (WPT) technology is expected to become an effective means to help UAVs break this bottleneck. UAV has strict restrictions on the weight of onboard system, so the lightweight design of the receiving side has become the core goal of UAV WPT systems design. In order to achieve this goal, this paper first proposes a novel magnetic coupler based on hollow copper-coated aluminum tubes, in which the receivers act as both landing gears and energy pick-up. The coupling mechanism of the magnetic coupler is analyzed. Secondly, based on the LCC-S resonant compensation network with a simple structure on the receiving-side, the system circuit is designed, and the system transmission model is established. Finally, a UAV WPT prototype is built and tested. The experimental results show that the transmission power of the designed system can reach 157 W, the overall efficiency 80%, and each receiver (also acting as landing gear) weight only 22 g. The weight power density ratio is 3.568 W/g.
The aim of this work is to provide a miniaturπized antenna pair, which has a smallest size of 5 mm × 25 mm (about 0.04λ × 0.20λ at 2.4 GHz) among the recent laptop antennas and yet is capable of 2.4/5/6 GHz Wi-Fi 6E operation with acceptable isolation. The antenna pair comprises two small and symmetrical antenna units. Each unit is identical in geometry and has a coupling strip and a parasitic strip with an in-series inductor. The back-to-back unit arrangement helps better isolation in the 2.4 GHz band. A decoupling coupled strip is introduced between the units with a 5 mm spacing. This floating strip of a half wavelength at about 5.36 GHz attracts the surface currents of one unit excited in the 5/6 GHz bands, which in turn helps much decreased currents entering the port of the other unit. As a result, enhanced isolation can also be achieved in the upper bands.
In this paper, we present a planar array for near-field shaped focusing. A near-field synthesis method for forming a special pattern on the focal plane is investigated. The phase and amplitude of the array are adjusted by digital phase shifters and attenuators. Prototypes are fabricated and measured to verify the effectiveness of this method. Near-field shaped focusing performances with square and triangular patterns are realized respectively. The experimental results show that the method can focus the electric field to a designated area clearly. Our work can provide a reference for applications such as microwave hyperthermia and wireless power transfer.
Power-absorbing layers on a microstrip line prepared by 3D printing are investigated in this study. Polylactic acid (PLA) with added carbon is used in the 3D printing process for the preparation of the power-absorbing layers. The S-parameters of the 3D-printed layers are measured using a vector network analyzer. The effect of the layer thicknesses on the power absorption, which enables high-frequency devices to function correctly, is discussed. As the layer thickness increases, the magnitude of S11 increases, while the magnitude of S21 decreases accordingly. The experimental results show that the power absorption is within 80-95% (sheet resistance: 75.1 Ω/□-823.76 Ω/□), in the frequency range of 2-6 GHz. In addition, simulated S-parameter analysis was performed using a high-frequency structure simulator. The simulation results are in good agreement with the experimental results.
The design procedure for UWB balun realized in the microstrip technology is proposed in the paper. The procedure applies Artificial Neural Network which corrects the dimensions of the approximate design found by appropriate scaling of the dimensions of the prototype. The scale coefficients for longitudinal and transverse dimensions of microstrip lines are determined from electromagnetic modeling based on transmission line equations. The scaling procedure of radial stubs is also proposed. The design procedure was verified experimentally for exemplary balun with radial stub.
In this paper, a novel flexible antenna for the new ISM band is proposed. A multi-objective optimization based on DDEA-SE is performed to optimize the antenna bandwidth and gain. The proposed optimized antenna has a 4 dB maximum realized gain and 50% maximum radiation efficiency on the ISM band. A fractal structure is used in this design to achieve a multi-band antenna. The bandwidth of this antenna covers several 5G bands. This multi-band antenna is fabricated on a cotton substrate. This antenna has a small dimension which makes it suitable for 5G applications. The bending tests are performed, and both simulation and measurement results show the good performance of the proposed antenna.
A compact bandpass filtering antenna operating at 5.1 GHz is introduced. The radiation layer makes up of a U-shaped patch and a trident resonator. The U-shaped patch is both the antenna and the last stage of the filter, which is excited by the insertion coupling part of the trident resonator. To improve the impedance matching and lower stopband suppression, a defective ground structure (DGS) is used. The dimension of the antenna is 0.36λ0×0.36λ0×0.01λ0 (λ0 is the wavelength at 5.1 GHz) without a complex external feed structure, which has enough bandwidth, a good frequency skirt selectivity, and a flat passband response. The measurement results manifest that the impedance bandwidth is 110 MHz, and the peak gain is 3.88 dBi. In addition, the filtering antenna also has a sharp roll-off rate and a satisfactory level of out-of-band suppression in the stopband.
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