A 3-dB compact hybrid coupler is presented in this paper in an ultra-wideband frequency range from 1.5 GHz to 3.2 GHz with 90˚ phase deference between the two output ports. The proposed coupler is formed by two notched elliptically shaped microstrip lines and four phase shifters, which are broadside coupled through an elliptically shaped slot. A combination of impedance matching technique and structural modification then has been employed to increase coupler efficiency. The design is demonstrated assuming a 0.51-mm-thick Rogers RO4350B substrate. Results of simulation and measurements show that the designed device exhibits a coupling of 3±1 dB across the aimed bandwidth. This ultra-wideband coupling is accompanied by smooth isolation in the order of better than 25 dB and return loss in the order of better than 17 dB. The manufactured device including microstrip ports and phase shifters occupy an area of 35 mm × 30 mm × 1.1 mm (0.27λ × 0.23λ × 0.009λ) which makes it a compact suitable device for UHF applications and measurements, specifically measuring and determining isolation in in-band full duplex transceivers, because of its smooth isolation versus frequency and ultra-wideband bandwidth.
In this work, we propose a liquid crystal (LC)-based double-dipole phase shifter. By manipulating the electric field, we change the resonant frequency and phase of the electromagnetic wave by deflecting the orientation of LC molecules. We made the LC-based device with a 30 × 30 array of two parallel unequal dipoles on a Quartz substrate. The substrate has an area and thickness of 4×4 cm2 and 480 μm, respectively. The experimental results show that the phase shift of 0°-385.4° is achieved at 94 GHz by changing the applied bias voltage on the LC layer from 0 V to 8.4 V. The phase shift is greater than 360° in the range 91.75-94.85 GHz. When the LC molecules are most significantly affected by the electric field, the maximum precision of phase shift is 4.08° with a bias voltage of 2 mV.
This letter proposes a differentially-fed broadband dipole and its 1×8 array. The antenna achieves cost-effectiveness by using a low-cost FR4 substrate. The antenna obtains surface mount capability due to the ball grid array (BGA) package. The measured results show that the proposed antenna array achieves a wide impedance bandwidth of 37.8% (24-35.2 GHz). The gain of the 1×8 array is greater than 10.1 dBi, and the cross-polarization level in the main beam direction is less than -20 dB. the radiation pattern of the 1×8 array is stable and unidirectional. The proposed antenna array covers the 5G N257 (26.5-29.5 GHz), N258 (24.25-27.5 GHz), and N261 (27.5-28.35 GHz) bands.
A low-profile, compact size and light weight wide band BPF prototype is presented for satellite communication applications (Ku-band). The proposed wideband BPF satisfies the International Telecommunication Union's (ITU) region 3 spectrum requirement. Direct broadcast service (DBS) and fixed satellite service (FSS) in transmitting mode, respectively, employ the frequency band 11.41-12.92 GHz. The proposed filter offers an impedance bandwidth of 1.5 GHz and group delay of 0.2 ns. The proposed wideband BPF is fabricated, and various parameters such as return loss, insertion loss, group delay and quality factor are measured. Miniaturization of filter size reveals the filter's suitability to use on smaller platforms with smaller surfaces.
This letter proposes a two element multiple-input multiple-output (MIMO) antenna with compact decoupling structure for 5G wireless communication applications. A compact decoupling structure was developed based on the elliptic curve, achieving isolation between the two antenna elements with a wideband response. The proposed concept is discussed and verified numerically and experimentally. The MIMO antenna system has demonstrated a wideband impedance matching with high isolation capability, while maintaining a good far-field and MIMO performance.
This paper presents a novel design structure of a series fed array antenna for desired shaped beam pattern synthesis. The desired beam shape is obtained by varying the width of patch elements. A uniform array is designed for the desired frequency, and then the proportionate values of the widths are calculated using amplitude coefficients obtained from the Woodward Lawson array synthesis method, while keeping excitation phase and inter element spacing constant. The proposed antenna is designed and simulated in HFSS. A prototype is fabricated on FR-4 epoxy dielectric material and tested at 12.5 GHz. The overall antenna has a compact size of 112 mm x 34 mm x 0.8 mm. The array structure exhibits impedance bandwidth of 1.8 GHz from 11 GHz to 12.8 GHz frequency range with return loss of -27.1 dB and high gain 14.2 dBi. The series fed configuration results in a VSWR of 1.38 and considerably low side lobe level of -24 dB in H-plane. There is a fine similarity between simulation and fabrication measurement parameter values such as return loss, VSWR, gain, and bandwidth.
A dual-band wideband circularly polarized (CP) microstrip antenna is proposed for sub-6G application. The antenna consists of an upper L-shaped radiator and two circular strips on the ground. This produces the right-handed circular polarization (RHCP) in the Wi-Fi (2.4-2.48 GHz) and n77 (3.3-4.2 GHz) band with the help of two circular strips at the left and right corners on the lower ground. The antenna occupies a small radiating area of 45×45×1.0 mm3. The measured results show wide -10 dB reflection coefficient bandwidths of 46.4%（1.82-2.92 GHz）and 40.5% (3.15-4.75 GHz). The 3-dB axial ratio bandwidths of the antenna are 25.1% (1.88-2.42 GHz) and 40.6% (3.20-4.83 GHz). The measured peak gains are 4.8 and 7.5 dBi at the lower and higher bands, respectively. Therefore, the proposed antenna in this study is suitable for the dual-band wideband CP antenna as a reference.
In order to satisfy the requirements of terahertz time-domain spectrum system under specific circumstances, an off-axis focus reflective polarization converter in terahertz band is proposed. By combining the principle of phase compensation and phase gradient metasurface, a reflective array containing units is designed. The phase distribution along the metasurface is calculated through the principle of optical path reversibility. Geometric rotation and resonant frequency modulation constitute the phase variation of the unit, which can be superimposed on each other without interference. Compared with the conventional reflective polarization converter in terahertz band, the proposed one could deflect the normally incident terahertz wave while providing larger energy at the focus. The simulation results show that the proposed polarization converter has good performance in both polarization conversion and electromagnetic focus, which has significant practical application in numerous situations.
A simple and novel polarization-dependent phase gradient metasurface (PGMS) is proposed to synthesize a flat-top radiation pattern by dividing the metasurface (MTS) into multiple regions. Each sub-region generates a beam in a particular direction and multiple beams with different directions form a flat-top pattern in the far-field. A flat-top pattern in a single and 3D plane are realized by dividing the MTS into two and four regions, respectively. The proposed MTS consists of a multi-layered elliptical geometry encircled by a square loop. The elliptical shape of the unitcell offers polarization dependent behavior and produces dual-band characteristics for different incident wave polarizations at 10 and 12 GHz. Two microstrip patch antennas operating at 10 GHz and 12 GHz are placed at the focal point of the MTS. The simulated flat-top beamwidths in a single plane with a 1 dB ripple are 36˚ and 34˚ at 10 and 11.8 GHz respectively. Similarly, in 3D space, the beamwidths are 33˚ and 31˚ at 10 and 11.8 GHz, respectively. Both simulated and measured results are presented for 3D flat-top patterns.
For the first time, an extended hemispherical integrated lens antenna on a low-cost substrate, FR408HR, is presented. The antenna is designed for industrial and automotive radar sensor applications operating in the 24 GHz ISM band. The proposed antenna has a gain of 15.2 dBi, low sidelobes, and half-power beamwidth of 16 degrees. To reduce the cost, we used low loss materials; Teflon for the lens and low-cost FR408HR as a patch antenna substrate. The size of the reported 24 GHz antenna is small. The diameter of the base of the lens is 38 mm (3 times of free space wavelength), and its height is 43.5 mm (with an extended height of 24.5 mm). Simulated results match well with measurements.
In this paper, a numerical electromagnetic model of a low-cost detection modality for red palm weevil pests in palm trees using resonant-based microwave sensors is presented. The developed sensor is based on the complementary split-ring resonator concept. The complementary resonator is easily modeled using printed circuit board technology, where the transmission response from two ports at ends of 50 Ω-matched transmission line is recorded. The microwave sensor has been designed to work at the 2.45 GHz ISM-band and is placed underneath a finite size 3D model of a palm tree trunk infested with the red palm weevil pest. For comparison purposes, the numerical simulation results are compared against a reference case of a healthy palm trunk. The results show the capability of the proposed numerical electromagnetic model in detecting presence of the red palm weevil in palm trees.
Shale oil and gas are unconventional oil and gas resources that can be used as alternative energy sources in the future. Shale reservoirs are the new growth point for the exploitation of oil and gas and development of China's oil and gas industry. The heterogeneity of the shale stratum determines the complexity of its mining. Accurate identification and detection of its oil-bearing characteristics are principal tasks in the oil shale deposit evaluation and economically exploitable interval division. Dielectric logging cannot rely on traditional resistivity logging curves, and it is not affected by the formation water salinity, which can provide the formation water porosity. Combined with other types of logging, it can effectively evaluate the formation oil saturation. In this study, we applied a new type of high-frequency dielectric logging tool in the production of shale oil, developed by the 22nd Institute of China Electronics Technology Group Corporation, based on different dielectric constants of oil, rock matrix, and water. We first introduced the principle of dielectric logging and the major advantages of the dielectric logging tool, and further proposed a new complex refractive index model with clay correction and explained the processing methods, which improved the accuracy of calculating the formation water saturation. Furthermore, the developed technology was applied and evaluated in the Songliao Basin.
As the explicit finite-difference time-domain (FDTD) method is restricted by the well-known Courant-Friedruchs-Lewy (CFL) stability condition and is inefficient for solving numerical tasks with fine structures, various implicit methods have been proposed to tackle the problem, while many of them adopt time-splitting schemes that generally need at least two sub-steps to finish update at a full time step, and the strategies used seem to be an unnatural habit of computation compared with the most widely-used one-step methods. The procedure of splitting time step also reduces computational efficiency and makes implementation of these algorithms complex. In the present paper, two novel one-step absolutely stable FDTD methods including one-step alternating-direction-implicit (ADI) and one-step locally-one-dimensional (LOD) methods are proposed. The two proposed methods are derived from the original ADI-FDTD method and LOD-FDTD method through some linear operations applied to the original methods and are algebraically equivalent to the original methods respectively, but they both avoid the appearance of intermediate fields and are one-step method just like the conventional FDTD method. Numerical experiments are carried out for validation of the two proposed methods, and from the numerical results it can be concluded that the proposed methods can solve equation correctly and are simpler than the original methods, and their computation efficiency is close to that of the existing one-step leapfrog ADI-FDTD method.
This paper discusses the design of a 6-m Cassegrain optics based multiband reflector antenna integrated with beam waveguide (BWG) optics, which consists of an ellipsoidal mirror and three plane mirrors. The presented antenna has been simulated, and 75.8% and 76.8% aperture efficiencies have been achieved at 0.225 THz and 0.338 THz, respectively. The initial design parameters of elements of BWG network are computed using fundamental Gaussian beam parameters. The simulated results of the antenna including aperture efficiency have been presented and discussed in detail. The antenna has been designed for the ground based THz telescope for radio astronomy.
This letter proposes a 2×2 surface-mount dipole antenna array based on via fence for 5G millimeter-wave applications. The dipole antenna element was first proposed, which has a compact size and low cost. Then the via fences are introduced to reduce coupling between adjacent elements and enhance isolation. In this way, compared with a 1×2 antenna array without the via fence, the isolation of a 1×2 antenna array with a via fence is improved by 12 dB at 26 GHz. The elements are extended into 2×2 arrays with and without the via fence, and their performance is evaluated by the evaluation board. The measurement results show that the -10-dB impedance bandwidth of the antenna array is 19% (24.7-29.9 GHz), and the peak gain is 9.5 dBi at 25 GHz. The proposed 2×2 array can be used in the N257 (26.5-29.5 GHz), N258 (24.25-27.5 GHz), and N261 (27.5-28.35 GHz) frequency bands. Low cost, small size, and high isolation characteristics make it one of the candidates for 5G millimeter-wave applications.
Substrate integrated E-plane waveguide (SIEW) was invented recently to design E-plane waveguide devices on printed circuit board, which cannot be achieved by using the conventional substrate integrated waveguide (SIW). This paper is the first time to present an E-plane displaced SIEW junctions bandpass filter. The proposed design is shorter than the recently published SIEW septa filter and has a smaller footprint than several other SIW filters. It is designed by mapping an equivalent E-plane waveguide filter to its SIEW implementation. A filter prototype is built and measured for validation.
A new design of broadband cavity-backed slot antenna (CBSA) based on substrate integrated waveguide (SIW) technology is presented in this paper. An entire proposed antenna is printed on a Rogers RT/Duroid 5870 substrate, which consists of the SIW cavity, bow-tie slot, microstrip line feed. The proper position and size of the bow-tie slot on top of the SIW cavity will generate the cavity modes, which can be merged to obtain the broadband response. Moreover, to understand the effects of the geometric dimensions of the broadband antenna on S11 are examined using parametric study. The final antenna configuration operates on a frequency band ranging from 9.25 GHz to 10.5 GHz with a fractional bandwidth of about 12.65% for the simulation part. The measured bandwidth for S11 is about 12.1% (9.3 GHz to 10.5 GHz). The proposed antenna has a good measured gain of 6 dBi and 6.6 dBi, at 9.55 GHz and 10.35 GHz, respectively. The gain, the reflection coefficient, and the radiation patterns of the fabricated antenna are measured and indicated a very good agreement with simulations.
This paper proposes a design method of vertically polarized VHF high-gain antenna, a four-element array form. Our design improves the overall gain of the antenna and reduces its loss. In our design, the conventional impedance conversion methods are abandoned. Instead, we directly use transmission lines for impedance match which greatly reduces the loss of the antenna in the frequency range of 150 MHz-300 MHz, ensuring that the antenna provides a higher gain, and its signal transmission efficiency is also improved.