The growing interest in collision avoidance automotive radar systems in K-band necessitates the development of dedicated antenna systems with 45˚ inclined linear polarization (LP). In this letter, a 45˚ inclined LP array antenna with Taylor distribution is proposed, designed, and fabricated.
A flexible antenna with high robustness is presented for wireless body area networks (WBANs) in-body communications. The coplanar waveguide (CPW) fed hexagon slot structure is employed to obtain a wide bandwidth of 34.4%. A parasitic patch is used to enhance in-body gain to -3.36 dBi. With these advantages, the proposed antenna is insensitive to frequency shift and gain reduction caused by environmental changes. Besides, the proposed low-profile antenna on a flexible substrate is well fit for wearable applications.
Contactless identifying different life states can result in improved rescue strategies in post-disaster rescues (such as earthquake and mine accident). If the buried targets are identified extremely endangered with very poor life states, the rescuing principles should be time first. Conversely, if the life states of the buried targets are relatively good, more reliable and safer methods should be given priority although they may cost a little more time. Unfortunately, there are few corresponding reports in life states identification, and current researches mainly focus on detecting or locating under penetration condition. This paper conducts a research on the change laws of physiological parameters of six New Zealand white rabbits, 3 females and 3 males. Experimental condition is under water and food deprivation to simulate one of the typical trapped situations of buried targets in post-disaster rescuing missions. Respiration is synchronously detected by an ultra-wideband (UWB) system in non-contact and an RM6240E system in contact. Heart rate, weight, and anal temperature are measured in contact measurement meanwhile. Over the time under water and food deprivation condition, there are typical and regular varieties in the respiration waveforms and heart rate values, which provide the possibility to identify different life states. Particularly, the respiration waveform changes in UWB radar signals are envisioned to be applied in practical post-disaster rescue where only UWB radar can penetrate ruins through penetrating measurement method.
In this paper, a design method for near-field focusing cylindrical holographic impedance metasurfaces is proposed. Firstly, based on the design theory of planar holographic impedance metasurface, we deduce the design formula for cylindrical holographic impedance metasurface by using the method of major axis matching. Then the feasibility of theoretical analysis is verified by simulation and measurement. The results show that the design method can effectively realize the near-field focusing, which can provide a reference for the application of conformal devices for microwave hyperthermia and energy harvesting.
A simple electromagnetic system composed by a Schottky barrier diode (SBD) and linear lossless microstrip line is introduced in this paper. The period doubling phenomenon in this circuit system is studied following the train of thought, which is adopted in the field of the driven Resistor-Inductor-Diode (RLD) series circuit. The related phenomenon and its origins have been studied extensively in RLD circuit. However, it will not be able to exhibit period doubling and chaos if SBD is applied in RLD circuit. We show period doubling phenomena in a microwave circuit containing SBD for the first time. This paper reveals that the given circuit can produce cycle period doubling at microwave frequency by means of simulations and experiments. Physical verification and theoretical explanation have been given in this paper.
In this paper, a modified magnitude-selective affine function-based behavioral model is proposed for the linearization of power amplifiers in multiple-input multiple-output (MIMO) systems. In this model, high-order polynomials in the crossover memory polynomial (COMPM) are replaced by magnitude-selective affine functions to compensate for the crosstalk and nonlinear distortion, leading to a highly efficient hardware implementation. The performance of the model is validated using two 3-carrier long-term evolution (LTE) signals of 20 MHz bandwidth. Experimental results show that the proposed model can achieve nearly the same adjacent channel power ratio (ACPR) and normalized mean square error (NMSE) as COMPM with about 70% reduction of hardware complexity.
The properties of the angular glint of radar reflections from the propeller hub are considered. Analytical expressions were obtained based on a known multipoint geometric model of the propeller hub to calculate the probability density function parameters of angular glint for the planes, azimuth, and elevation angle for a single-blade rotor at an arbitrary rotation angle of the head. The relations obtained for a propeller hub with a single blade are generalized to the case of a propeller hub with an arbitrary number of blades. It is shown that the angular glint of the propeller hub is a random process with periodically changing parameters. The theoretical results are confirmed by mathematical modeling.
In this paper, we propose a phase compensation method for cylindrical reconfigurable reflectarray antennas and design a cylindrical reconfigurable reflectarray antenna (CRRA) for generating steering beams. Using a PIN diode loaded reflectarray element, 1-bit reflection phase-shift with phase difference of 180°, can be realized. The cylindrical reflectarray consists of 16×18 unit cells whose reflection phase shifts are controlled by bias network independently. Using phase quantization, the reflectarray can generate the desired phase distributions for steering beams. Both simulated and measured results show that the proposed CRRA can achieve beam scanning in ±40˚ angle range. In addition, the measured gain reaches 20.5 dBi, and 1 dB gain bandwidth is 6.9%. The proposed cylindrical conformal reconfigurable reflectarray antenna can provide a reference for the application of the conformal scenario of a reconfigurable reflectarray antenna in the future.
The design of a Complementary Split Ring Resonator (CSRR) embedded compact Asymmetric Coplanar Strip (ACS) fed monopole antenna is presented in this paper. By incorporating the ACS feed, a substantial reduction of 27% in antenna dimensions is achieved. Further miniaturization of 68.6% is obtained by embedding CSRR on the designed patch and a trapezoidal ground. The overall size of the antenna is 13.2 × 27 × 1.6 mm3, and it is printed on an FR4-epoxy substrate. The antenna operates with a resonant frequency of 3.6 GHz and a bandwidth of 3.3 GHz (3.2-6.5 GHz). Thus it is appropriate for sub-6 GHz 5G applications. It exhibits a return loss of -28 dB and a gain of 2.8 dBi at the resonant frequency. The antenna is fabricated, and the measured results match well with the simulated ones. Being a simple, cheap, and uniplanar structure, the proposed antenna can meet the requirements of a modern wireless communication system.
Radio Frequency Identification (RFID) technology is one of the simplest forms of wireless communication systems. It is a unique concept that aims to connect and identify tagged assets or objects to RFID readers to collect information. This paper presents the design and implementation of a compact dual-band RFID applications. The proposed design is a microstrip anetnna composed of two coupled armed meander-lines having 90° between them to achieve circular polarization. The proposed design is mounted on a 1.6 mm thick FR4-epoxy substrate backed by a partial ground plane with the total area of (58 x 80 mm2) to ensure compact size of the tag. The designed antenna is fed through a 50-ohm transmission line of length 28.5 mm. The antenna is considered dual bands that resonate at 850 MHz and 1.5 GHz and radiates circularly polarized waves with axial ratio about 1.4. The simulation results using HFSS software showed promising performance with a bandwidth of 141 MHz at center frequency 850 MHz and 287 MHz at centre frequency 1.5 GHz, respectively after optimizing the proposed design of the tag antenna. The S11 parameter shows return loss at -21 dB at 850 MHz band while at the higher frequency the return loss is much better which was -39 dB. The design provides a perfectly omnidirectional radiation pattern and high radiation efficiency of 93%. Fabrication of the proposed design is done with practical results having a similar trend to the simulated ones to convey good performance of the designed antenna.
A miniaturized lumped-element quadrature hybrid with a high density stacked structure is proposed in a 24-layer low temperature co-fired ceramic (LTCC) substrate. Stacking vertical-interdigital-capacitors (VICs) and vertically-spiral-inductors are for an entire size reduction. The transition between inductors realized in the inner space of the inductor further improves the utilization of three-dimensional space. The overall size of the quadrature hybrid is only 10.1×3.8×2.4 mm, or equivalently 0.0040×0.0015×0.0009λg3, which achieves a size reduction of 30.2%. Meanwhile, the proposed hybrid operates at 60 MHz with a fractional bandwidth (FBW) of 33.3%. The measured S11, S21, S31 and S41 are -14.5, -3.8, -3.7, and -14.2 dB within the operating frequency band, respectively, and both of the low phase imbalance and amplitude imbalance are achieved.
In this paper, a novel all-metallic probe-fed antenna is proposed for L5, L1, and S bands for Navigation with Indian Constellation (NavIC) applications, and it can be used for tracking applications. The proposed antenna dimensions are 30 mm x 80 mm x 8 mm (0.11λ x 0.31λ x 0.03λ) electrical size calculated at 1176.45 MHz (L5). The radiating plane has a comb like structure where there are 8 slots which are of identical size 24 mm x 1 mm and a short slot with 6 mm x 1 mm. The ground plane is 30 mm offset with respect to the radiating plane (top plane). Usually, a high dielectric substrate antenna can resonate at lower frequencies keeping the size of the antenna electrically small, but without substrate the proposed antenna resonates at lower frequencies keeping the antenna size electrically small. The proposed design is electrically compact and economical, and the dielectric loss in the antenna is zero as the antenna is designed with copper alone, which gives a strong impression that a substrate free antenna can resonate at lower frequencies. So, from this method it can also make the antenna light weight.
In this paper, we present a dual-polarized, pattern reconfigurable, liquid metal dipole antenna. The proposed design consists of a pair of ±45° polarized reconfigurable dipole antennas, two vertically placed feeding structures with filtering branches, and a resin frame for injecting liquid metal to adjust pattern. By introducing the U-shaped structure, a better impedance matching performance is achieved in two bands. The polarization can be switched by injecting liquid metal into different dipole microfluidic channels. By controlling the liquid metal reflector around the magnetic dipole, the reconfigurable pattern of +45° polarized antenna can be realized at 0°, 180° and 90° on the plane of phi=90°, and the reconfigurable pattern of -45° magnetic dipole antenna can be achieved at 0°, 90° and 270° on the plane of phi= 0°. The basic antenna operates with linear polarization around 4.8 GHz. The VSWR is less than 1.5. In the radiation pattern of the antenna, the port isolations of the two crossing ports are S12 and S21. S21 port isolation is more than 35 dB. The antenna has good pattern reconfigurable characteristics, and the simulation results of the antenna indicate good radiation directivity. Moreover, the height of the proposed antenna is 0.625λ at 4.8 GHz. The good performance of the antenna makes it a candidate for base station systems below 5G sub-6 GHz.
A quasi-isotropic dielectric resonator antenna (DRA) is proposed under the 5.8 GHz industrial, scientific, and medical (ISM) standard. The antenna consists of a hollow cylinder and and a coaxial probe which feeds electricity. By digging a large hole in the cylindrical dielectric resonator, the HEM11δ mode and the TM10 mode of the floor are excited, the two modes are orthogonal, and the radiation characteristics are equivalent to orthogonal magnetic dipoles and electric dipoles, so as to achieve quasi-isotropic radiation characteristics. The large hole can also reserve space for other electronic components for Bluetooth devices with small space, such as capsule endoscope, mobile phone and Bluetooth headset. The characteristics of the antenna are simulated and analyzed by HFSS, and the optimized antenna structure parameters are obtained. The antenna is made for experimental testing. The measured results demonstrate that the antenna exhibits a good -10 dB-impedance bandwidth at 5.38-5.68 GHz and has the characteristics of miniaturization, quasi-isotropy, and high gain.
A circularly polarized (CP) patch antenna with a fractal structure that can be applied to the BeiDou navigation satellite system (BDS) is proposed. Etching two incomplete rings of different sizes with the antenna center as the center on the radiation patch generates CP. By adding a periodic structure based on the Sierpinski Carpet fractal around it, the size can be reduced while the gain is further improved. The dimension of the antenna is 0.35λo × 0.35λo × 0.03λo. Measured results manifest that the impedance bandwidth (S11 < -10 dB) is wider than 40 MHz at 1.561 GHz; the gain in 3-dB axial ratio (AR) bandwidth can reach 3.33 dBi; the beamwidth exceeds 140° in the 3-dB AR bandwidth.
This paper aims to test the concentration of dissolved particles such as salt and sugar in a water sample and also test the quality of water. Ultra-Wide Band (UWB) antenna has been designed and used to test the water sample. The proposed UWB antenna has been resonated from 3.2 GHz to 10.6 GHz. The fractional bandwidth of the UWB antenna is 1.15. The measured antenna's characteristics were in good agreement with the simulated results. Then, the designed UWB antenna was used as a sensor on the water samples such as distilled water, rainwater, pond water, seawater, and Reverse Osmosis (RO) water. Hence, this paper explains the concentration of dissolved particles and testing of the quality of the water sample by using the return loss characteristics of the antenna when it is immersed in the water sample. This technique can be further extended for testing the quality of any other liquids.
A compact and broadband stub-loaded dual-mode dipole antenna is proposed. In this paper, the first- and third-order modes are combined to achieve broadband frequency response. To do so, the third-order mode is compressed close to the first-order mode by loading two pairs of identical stubs at an optimal distance from the dipole-centre. Stubs are symmetrically loaded to both the arms of the dipole. Stub parameters such as length, width, and location play a critical role in decreasing the third-order mode frequency. Therefore, a parametric analysis is also carried out to see the effects of variation in the stub parameters. The proposed antenna is fabricated, and measurements are performed to verify the simulation results. A good agreement between the simulated and measured results is obtained.
A Metamaterial Terahertz perfect absorber is proposed in this letter. The structure comprises Vanadium oxide (VO2) resonator hexagonal rings placed on top of a silicon dioxide (SiO2) substrate in a concentric pattern on a metal ground layer, with 1 THz and 6 THz operating frequency. Numerical studies are done by an electromagnetic solver. The results show almost perfect absorption, with 112% average absorption at different incident polarization angles, in the range of 1.64 to 6.1 THz. The optimization is carried out on physical dimensions for maximum absorption results. The proposed design can be used as a highly efficient absorber in applications like solar energy harvesting, cloaking, sensing, imaging technology, and EMC projects.
In this paper, two G-band sub-harmonic mixers based on planar antiparallel Schottky diodes are presented. The proposed type-I mixer is designed using the conversional THz Schottky diode mixer circuit architecture. In order to broaden the bandwidth further, a novel type-II sub-harmonic mixer based on new circuit topology is proposed. In type-II mixer, an antiparallel Schottky diodes chip is directly connected with metal ground using silver epoxy. The simulated results show that single-sideband (SSB) conversion loss of type-II mixer is less than 10 dB in the frequency range of 160-194.8 GHz. For validation, the type-I mixer is fabricated and tested. Measurement results show that single-sideband conversion loss of type-I mixer is basically less than 10.7 dB in the frequency range of 166-190 GHz.
A multi-probe sensor for water content analysis, in liquid biofuels, by using reflection and transmission measurements in microwave frequencies range, is proposed in this letter. As preliminary step and for a better understanding, the measurements were carried out with ethanol/water mixtures, which mimic bioethanol applications, at room temperature. In order to study water/alcohol mixtures, each of them was characterized using classical techniques like open ended coaxial probe or reflection/transmission coaxial line, before being tested in multi-probe sensors. At the end, the multi-probe sensor aims to be implemented in-line production in order to perform diagnosis of water in liquid biofuels.
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