The present article shows the design, implementation, and measurement of a compact contactless electronic system for sensing small volumes of liquids. The system is based on two elements: an electronic reader and a passive sensor. The proposed sensor consists of a printed monopole antenna loaded with two Split-Ring Resonators. This results in a fully-passive and single-layer low-cost design. To allow the sensing of small volumes of liquids, a 1-mm-thick adhesive Kapton layer was attached on the top layer of the sensor, and two drop tanks were added to the structure. On the other hand, the reader was designed following a layered approach, which allows us to develop compact and low-cost electronic sensor readers for the Internet of Things. The resulting reader contains a Radio-Frequency interface for the generation of detection of signals, a minicomputer, and the radiating interface. This interface includes a patch antenna that allows us to interrogate the contactless sensor within a 1-cm range. The whole system was manufactured and tested. The total dimensions of the reader are 15 cm × 15 cm, and its weight is below 1 kg. These imply a dramatic form factor and weight reductions with respect to previous readers. Moreover, the manufactured system was used to measure the dielectric permittivity of different liquid drops. Results show that only 4 ml of liquid were needed to determine the dielectric permittivity with a 0.27% error. This volume means a 98.4% reduction compared to submersible sensors which can be found in the literature.

This paper investigates the effect of index finger position and distance on the radiated power of 4-element MIMO antenna, operating at 28 GHz. The antenna elements (AEs) are located at the top corner of the user terminal and separated at a distance of half a wavelength. Four different finger placements were investigated, one placement over each AE with six interaction distances between the AEs and the finger at each position starting from 0 up to 2.5 mm. When the finger is placed on an edge AE, the other edge AE maintained above 85 % of its free space radiated power irrespective of the interaction distance. However, the radiated power of each AE was severely affected when the finger was placed on it or on the AE adjacent to it. This effect ranged from total blockage at direct interaction with the element (with a distance of 0 mm) to maintaining more than around 60 % of free space radiated power after the interaction distance is increased to more than 2.0 mm. Besides the effects of the index finger on the amount of radiated power, this work also investigated the direction of radiated power resulting from the influence of this finger.

A problem of electromagnetic wave radiation by narrow slots cut in an end wall of a semi-infinite waveguide section into space above a perfectly conducting sphere is solved in a strict self-consistent formulation by the generalized method of induced magnetomotive forces (MMF). Inside the waveguide section, a reentrant cavity formed by the volume between a slotted diaphragm and the waveguide end wall is located. The waveguide is operating in the frequency range of a single-mode regime. The electrodynamic characteristics of this radiating system with the spherical screen of resonant dimensions are investigated numerically and ex-perimentally. The possibility to develop the spherical antennas with a narrow-band frequency, energy, and spatial characteristics is substantiated.

A wideband dual-mode band-pass filter (BPF) is proposed and implemented using a vertically stacked double-ring resonator (VSDR) and a pair of broadside-coupled input/output (I/O) feeding lines based on a 4-layer low temperature cofired ceramic (LTCC) substrate. The proposed BPF is required to cover the fifth generation (5G) N77/N78/N79 band (3.3-5 GHz), thus achieves a fractional bandwidth (FBW) of 40%. Furthermore, the proposed structure not only possesses a non-orthogonal I/O feeding style for convenient interconnection with neighboring devices, but also removes disturbing element for simpler layout. Comparison and discussion are implemented as well.

This paper presents Global Navigation Satellite System (GNSS) F-type and Bluetooth (BT) L-shaped antennas printed on flexible low loss substrate materials for smartwatch applications. The proposed printed antennas were designed along with the wristband of a smartwatch device with the main purpose of improving their electrical performance by using a new low loss polymer material and locating the antenna on the wrist strap. The antenna performances were simulated using CST Microwave Studio, and the prototypes were measured in a Satimo StarLab anechoic chamber. Silver printing and injection molding technologies were successfully utilized for fabricating new SEBS materials (styrene-ethylene-butylene-styrene) in wearable devices. The SEBS materials improved the radiation efficiency of the antennas by 1.6 dB for the GNSS and 2.2 dB for the BT over the previously used TPU (thermoplastic polyurethane) materials. The overmolded printed and hybrid integrated discrete antennas produced added-value for electronics fabrication thanks to its flexible and seamless integration technique. In addition, it is a low-cost mass manufacturing method. The research opens new perspectives for product definitions with a flexible, low loss material that enables better antenna performance.

In this paper, we design and fabricate a side lobe comb-line fed microstrip antenna array at the frequency of 77 GHz. This antenna can be used in car and also in peripheral protection radars. To design the antenna, a radiating microstrip element on a simple sublayer is first designed and optimized in order to have desirable specification at 77 GHz. Secondly, a one-dimensional array is formed using a row of microstrip antenna array with 32 serried elements. Finally, a two-dimensional antenna array with 16 rows is fabricated and subsequently fed with a waveguide to complete the antenna design.

Non-parallel microstrip lines are a layout often used in high-speed interconnections. This study initiates crosstalk reduction by interdigital capacitor for the non-parallel microstrip lines. This method reduces the far-end crosstalk by adding capacitive coupling to cancel inductive coupling after an interdigital capacitor is added at the near end of the non-parallel microstrip lines. Software simulation and actual measurement results show that the proposed method can effectively reduce the far-end crosstalk in non-parallel microstrip lines. The method is also easy to implement and in low cost.

In this paper we show a procedure to measure the impedance mismatch of antennas by exploiting the Time Domain (TD) option available in usual VNAs. The procedure can be applied even in the presence of reflecting obstacles in the measurement scenario surrounding the antenna under test (AUT). It is shown that effective application of the procedure requires to fulfill a reduced number of constraints basically involving the distance of the AUT from the nearest obstacle, the response resolution to be set through the TD option of the VNA, and the length of the gating aperture to be applied to the received signal. The proposed measurement procedure is in principle applicable to any antenna. However, it is very easy and advantageous for antennas having short responses in the time domain, such as horn antennas, where the method can likely be applied to frequencies less than 500 MHz. Comparison between the results obtained from measurements performed inside an anechoic chamber (that is, in the absence of reflecting obstacles around the AUT), outside the anechoic chamber, and even inside a reverberation chamber, demonstrate the effectiveness of the proposed measurement procedure.

This paper presents an efficient hybrid method consisting of nonuniform mesh finite-difference-time-domain (FDTD) method, thin wire model, and transmission line (TL) equations method, which is utilized to analyze transient responses of the microstrip patch antenna loaded on a vehicle platform illuminated by a high-power electromagnetic pulse (EMP). This hybrid method avoids over-fine mesh generation, thereby improving the computational efficiency and saving the computational memory. The accuracy and efficiency of this method are verified by comparing with the simulation results of traditional FDTD and computer simulation technology microwave studio (CST MWS). Then, considering the influence of the incident conditions of EMP and the support structure of antenna on the coupling effects of the antenna, the coupling responses of the 1.575 GHz microstrip antenna are discussed in terms of incident angles of EMP, heights of the support structure, top areas of the support structure, and different positions of the support structure on the platform. The obtained changing regularity of the transient responses is useful for further designing the installation structure of the antenna and electromagnetic protection against the external EMP.

This paper presents a novel compact multilayer meander strip line step-via electromagnetic band-gap (MLSV-EBG) structure with the application of mutual coupling reduction in a multilayer multiple input multiple output (MIMO) antenna. The proposed EBG-cell has been developed by using multilayer, novel meander strip line, and step-via concept. To analyse the proposed EBG a parallel LC model method is used. In the proposed MLSV-EBG structure, due to step-via concept, current path length increases, and compactness is achieved per unit cell. Parametric study is also presented. MLSV-EBG structure unit cell is simulated using ANSYS high frequency structure simulator (HFSS), and 5X5 cells are printed on an FR4 substrate for band-gap measurements. Simulated and measured results prove that compared with three-layer central located via EBG (CLV-EBG) and edge located via EBG (ELV-EBG), size reductions of 47.01% and 43.01% have been achieved, respectively, which shows that step via concept gives the significant size reduction per unit multilayer EBG cell. The application of proposed MLSV-EBG for the reduction of mutual coupling between two multilayer MIMO antennas is also demonstrated. The key contribution of the presented work is that the proposed compact multi-layer EBG structure is useful in a multi-layer environment at a lower frequency.

High data rates and good channel bandwidth are some of the requirements of today's wireless communication systems. The wireless communication systems are now rapidly adopting a Multiple Input Multiple Output i.e MIMO technique due to its advantages such as the data rates and bandwidth. The main focus of this paper is to design a highly isolated MIMO antenna with Wi-MAX bandwidth. This MIMO antenna design is prepared with four pentagonal slotted monopole antennas with a parasitic element structure operating in the band of 5.1 to 5.8 GHz which offers isolation more than 28 dB. Rectangular slots are used for each radiating patch for a band-notched frequency at 5.5 GHz frequency relative to the Wi-MAX frequency band. To improve the isolation of the antenna, on the surface of the dielectric substrate, a single plus-shaped parasitic structure is uniformly inserted between the antenna elements. The result obtained from the fabricated antenna is at an acceptable range with that of the simulated for the Wi-MAX band applications.

In this paper, a novel temperature dependent electromagnetic modeling for the design of airborne radome is presented. A smooth spatial temperature distribution on the radome surface is modeled using a piecewise cubic hermite interpolating polynomial as well as piecewise linear interpolation. The temperature gradient across the radome wall is modeled using the inhomogeneous planar layer. The performance of a radome is computed using the 3D ray tracing method in conjunction with aperture integration. A unique radome wall configuration is obtained for each ray for accurate representation of a hot radome. A streamlined radome designed using the proposed model shows a significant performance improvement over the radome designed at the average temperature. The designed radome has the minimum insertion loss of 0.015 dB and the maximum boresight error of 1.8 mrad. The proposed method can be easily used with the experimentally obtained temperature distribution to predict the changes in radome performance in changing hypersonic environment.

The sensitivities of an aluminum gallium arsenide Al_0.7Ga_0.3As based surface plasmon resonance (SPR) sensor with gold (Au) and silver (Ag) layers are numerically analyzed and compared at 633 nm wavelength for different thicknesses of the Al_0.7Ga_0.3As. As the thickness of Al_0.7Ga_0.3As increases, the sensitivity of aluminum gallium arsenide Al_0.7Ga_0.3As with a specific metal (Au or Ag) layer increases. Our calculations show that the sensitivities of the proposed sensors are 80.55% (Au film) and 34.74% (Ag film) higher than the conventional Au and Ag sensors successively. The aluminum gallium arsenide Al_0.7Ga_0.3As based SPR sensor has the advantages of high angular sensitivity, narrow resonance widths, and low minimum reflectance, making it a much better choice for biosensing applications.

Estimation of soil moisture using Synthetic Aperture Radar (SAR) backscatter values, over agricultural area, is still difficult. SAR backscatter is sensitive to the surface properties like roughness, crop cover, and soil type, along with its strong sensitivity to the soil moisture. Hence, to develop a methodology for agricultural area soil moisture estimation using SAR, it is necessary to incorporate the effects of crop cover and soil texture in the soil moisture retrieval model. A field experiment was conducted by the authors and used along with Sentinel 1A SAR data to estimate the soil moisture in the paddy agricultural fields. Generally, water used for irrigation in the study region was obtained from ground water. As in the hot climate conditions ground water level would be reduced, and the water for irrigation must be supplied optimally. Hence, available soil moisture in the field was estimated from SAR data on the day of satellite passing the crop fields and utilized for deciding the amount of water to be supplied. The soil moisture values of soil samples that are collected from the agricultural field are calculated with the laboratory experiments. A soil moisture retrieval model is derived and proposed in this paper after a comparative analysis of experimental soil moisture values and satellite values. The feasibility of above model for paddy agricultural fields is validated using the field measurements.

In this paper, the performance of a concentric hexagonal antenna array (CHAA) is investigated with the exploitation of a robust variable diagonal loading (VDL) technique in the presence of direction of arrival (DOA) mismatch. The performance of minimum variance distortionless response (MVDR) based CHAA is compared with the performance of existing MVDR based concentric circular antenna arrays (CCAAs), and it is found that the proposed MVDR based CHAA provides 25.54% narrow half-power beamwidth (HPBW) and lower side lobe level than the existing MVDR based CCAAs. When DOA mismatch occurs between main beam steering direction and actual signal-of-interest (SOI) direction, the performance of MVDR based CHAA is deteriorated. In the case of DOA mismatch, to ameliorate the performance of CHAA, this paper proposes VDL technique for the CHAA processor and compare the performance of proposed robust CHAA with existing robust CHAAs. The proposed VDL based robust CHAA delivers 88.37% and 78.56% higher output power for 2˚ DOA mismatch than existing fixed diagonal loading (FDL) and optimal diagonal loading (ODL) based CHAAs, respectively. Several tapering window functions are proposed to reduce the side lobe level of CHAA. Performance of the proposed beamformer is analyzed utilizing MATLAB environment in various scenarios.

This paper presents the design of flexible parasitic element patch (FPEP) antenna with defects on ground plane at ISM band for biomedical application. The antenna resonates at 2.46 GHz frequency with reflection coefficient of -16.8 GHz in free space and at 2.45 GHz frequency when being placed on cotton and the single layer skin tissue of human body. The proposed parasitic element patch antenna is used to measure the body temperature, and the specific absorption rate (SAR) of the proposed antennas is 1.0 W/kg. The measurement data with respect to reflection coefficient, and radiation pattern are presented.

This paper proposes an improved method for calculating static capacitance between two conductors with circular cross-sections in inductor windings. It considers the effects of electric field coupling and energy distribution on static capacitance. In this paper, the capacitance between two conductors in inductor windings is calculated by the improved calculation method and the finite-element method (FEM), respectively. The relative error of the improved calculation method is between 0.11% and 4.51% compared to the FEM. In order to verify the effectiveness of this method for inductor winding, the orthogonal stacking winding and staggered stacking winding are chosen as calculation examples to accurately predict the static capacitance of multi-layer circular-section induction coils. Finite element models for the two types of windings are built to determine the capacitances for our 3×3 array arrangement winding. The results show that the improved calculation method proposed in this paper highly conforms to FEM. Finally, we adopt an air-cored cylindrical inductor winding for experimental verification, and the improved calculation method is proved to be correct.

r exploring the possibility of dual frequency response, a higher order mode frequency response in the air suspended design of a wideband E-shape microstrip antenna is studied, by appropriately decreasing the air gap.The decrease in the air gap realizes the impedance matching at higher order TM12 mode which along with the fundamental TM10 mode,gives dual frequency response. On an air suspended FR4 substrate with total thickness of 0.043λg, optimized single patch configuration yields dual band response at 2427 and 5730 MHz giving frequency ratio of 1:2.36. It yields impedance bandwidths of 6.6 % and 4.8% at two frequencies with respective broadside gains of 6.8 and 2.1dBi. The proposed configuration satisfies the requirements of 2.4/5.8 GHz WLAN applications. Parametric formulations are proposed for various antenna dimensions. The MSAs redesigned using them at given fundamental mode frequency yield a similar dual band response.

With a constantly increasing number of cars equipped with 77 GHz automotive radar, the performance degrading effects of crosstalk are becoming a rising threat to radar-enabled automated driving functions. Since interference is sensitive to slight changes of temporal and spatial conditions of the scenario, meaningful measurements are hard to conduct which is why simulations are an important supplement. In this paper, a simulation model is introduced that estimates the distribution of the reduction of the detection range of automotive radars due to multiple interferers focusing on stochastic temporal conditions. The underlying system model calculates the direction- and timing-dependent influence of one single interferer on the detection range of the host radar. The model is kept simple, making it suitable for Monte Carlo methods, which allow the indispensable statistical evaluation of the broadly spread results. Finally, a method is presented that transfers multiple statistics regarding single interferers into a single environment. The computing time of the simulation grows linearly with the number of interfering radars, so the effects of vast numbers of interferers can be studied using this simulation model. Statistical evaluations of the detection performance degradation of a front-mounted radar in sample highway scenarios, containing up to ten interfering radar sensors, are performed in this paper.

A new wideband dual-polarized patch antenna using substrate-integrated waveguide (SIW) technology is proposed in this paper. The antenna is composed of a patch radiator and a square SIW cavity. The square patch is internally embedded in the square SIW cavity with a surrounded slot. A pair of L-shaped probes are used for the excitation of the orthogonal linearly-polarized signals. The dominant resonant mode of the square patch resonator (TM010) and the modes of the SIW cavity (TE110 and TE120/TE210) are employed to achieve a wide impedance bandwidth under these resonances. By introducing two shorting pins, the isolation between two feeding ports can be enhanced to more than 21 dB. The resonant properties of these modes are investigated based on the cavity model theory. Then, their resonant frequencies are discussed to provide information for designing and optimizing such an antenna. For demonstration, a prototype is fabricated and measured. The measured results show that the proposed antenna achieves a wide impedance bandwidth of about 66.7% (3.71-7.43 GHz) and 70.9% (3.58-7.52 GHz) for horizontal and vertical polarizations, respectively. A stable gain in the range of 7.15 to 8.03 dBi is obtained within the operating band. Due to the SIW cavity-backed structure, the antenna shows unidirectional radiation patterns and low back-lobe radiation at the resonant frequencies. Thus, the antenna is highly suitable for the base station antenna that is required to cover the bandwidth of 5.5 GHz WiMAX and 5.2/5.8 GHz WLAN systems.