In this article, a low-profile microstrip patch antenna using an FR-4 substrate with relative permittivity of 4.4 and thickness of 1.6 mm is designed. On the top of a substrate, it consists of one metallic hexagonal patch and a metallic-fed hexagonal ringtone, and the ground part of the structure is covered with orthogonal rectangular slots. The designed structure operates in the ISM band of 434 MHz, and the overall size of the antenna is 124x124x1.6 mm3. The antenna provides a valid SAR input profile.
As wireless devices become increasingly compact, portable, and accessible anywhere, there is a need to increase isolation between them and reduce frequency interference. The purpose of this paper is to suppress interference by using pixelated patterns on a single layer in a miniaturized unit cell. To miniaturize of unitcell, the surface was pixelated into 50 × 50 pixels with a resolution of 0.2 mm × 0.2 mm. The proposed unitcell occupies a small area of 0.06λ0 × 0.06λ0 at GSM frequency (f = 1.8 GHz). The pixelation of the surface allows the surface current to follow a long path. Therefore, unlike the previous works, the miniaturized structure is obtained using a 1D layer without any vias and lumped elements. A significant advantage of this structure is that it is significantly more miniaturized than the current state-of-the-art unitcells and allows for a wider range of applications. Full-wave simulation and measurement results are in good agreement with each other and show stopband at operation frequency. As a result, both simulation and measurement results show that the proposed structure has a dual-polarized characteristic with good angular stability under a variety of incidence angles.
A narrowband, high selectivity Substrate Integrated Waveguide (SIW) bandpass filter with perturbing vias and CSRR is proposed for Sub-6 GHz applications. Firstly, the perturbing vias are positioned at the symmetrical axis of the SIW cavity which produces distinct electric field distribution for the first two modes. Next, the ground plane is engraved with the CSRR placed at an offset distance on either side of the perturbing vias, forming the coupling arrangement that combines mixed and magnetic, electric coupling. The presence of CSRRs resulted in a narrowband filter. The filter's center frequency is 4.947 GHz with a fractional bandwidth of 1.16%. By comparing the fabricated filter to an existing SIW conventional multi-cavity or cascaded resonator, a size reduction of 117% is achieved. The simulated and measured results agree with each other.
A W-band dual-circular-polarization (dual-CP) monopulse Cassegrain antenna for polarization detection of radar target is presented in this letter. The proposed antenna consists of a main reflector, a sub reflector, a dual-CP feed source based on the septum polarizer, and a comparator. Two orthogonal circular-polarized signals [left-hand circular polarization (LHCP) and right-hand circular polarization (RHCP)] electromagnetic wave can be transmitted and received simultaneously by this antenna. The principle of the antenna is introduced and analyzed, and then a prototype of the antenna is simulated, fabricated, and measured. Measured results are in good agreement with the simulated ones. At 94 GHz, the gains of the LHCP and the RHCP sum beam (SUM beam) are 38.6 dBi and 38.8 dBi counting the insertion loss of the comparator, which indicates that the radiation efficiency is better than 44.2%. The 3-dB beamwidth is about 1.5° with a sidelobe level (SLL) of -16.6 dB, and the axial ratio is lower than 1.43. A null depth of -26 dB for the difference beam (DIFF beam) is observed, and the gain ratio between the LHCP monopulse beams is 5.9 dB. Measured results demonstrate that the proposed antenna is very applicable in the polarization detection of radar target at W-band.
In this paper, a high front-to-back ratio (FTBR), broad bandwidth planar printing structure, and electromagnetic dipole complementary antenna that generates end-fire radiation pattern is investigated. The antenna consists of a segmented loop, planar electric dipole, and microstrip coupling feed structure, which are printed on the top and bottom surfaces of a dielectric substrate. The segmented loop is equivalent to a magnetic dipole. A high front-to-back ratio is achieved by combining the electric dipole and equivalent magnetic dipole with the same radiation intensity and antiphase. The proposed antenna is fabricated and measured. The measured results show that the proposed antenna achieves an impedance bandwidth of 48.05% (1.66 GHz-2.71 GHz). The largest gain can get to 3.89 dBi, and the maximum front-to-back ratio is 25.4 dB in the frequency band. The measured results are well consistent with simulated ones.
This paper presents a new design of a compact microstrip ultra-wideband (UWB) single notch-band bandpass filter (BPF) along with its equivalent circuit model. The basic structure of the proposed filter consists of dual symmetrical multiple-mode resonator (MMR), four stub-loaded stepped impedance resonators (SLSIRs), two defected ground structure (DGS) units and a coupled folded arm resonator (CFAR) with feeding line. The presented filter is tested using R&S® ZNB20 vector network analyzer (VNA) to validate the simulated results. A good agreement between the measured and simulated (EM and circuit model) results is achieved.
In the paper, a compact single-fed wide-beamwidth circularly polarized (CP) antenna is proposed. The main radiator of the antenna is a bent dielectric resonator (DR), which is conformal to a rectangle substrate with the same curvature and is excited through a crossed-two-ring slotted ground fed by a T-shaped feeding line. By bending the DR to different curvatures, the half-power bandwidth (HPBW) of the dielectric resonator antenna (DRA) can be adjusted. Besides, to improve the 3-dB axial ratio (AR) beamwidth, as well as further enhance the HPBW, a copper reflector is inserted below the DRA. A prototype operating in BeiDou Navigation Satellite System (BDS) B1 band (1.561 GHz) was designed, and measurement was done to verify the simulations. Measurement results show that from 1.55 GHz to 1.58 GHz, the return loss is more than 10 dB and the AR is less than 3 dB. At 1.561 GHz, the measured 3-dB AR beamwidths are 165° and 210° at xoz and yoz planes, respectively, while the HPBWs are 143° and 154° at the two planes.
In this letter, a novel ultra-wideband (UWB) bandpass filter (BPF) configuration with a quad-mode resonator (QMR) structure is proposed, which hasa highly selective and compact performance. The QMR is composed of a funnel-shaped resonator loaded in the middle and a low-impedance folded microstrip line. Initially, the resonant frequencies are uniformly distributed in the UWB passband by varying the length of QMR physical stubs, and later the three-line parallel coupled lines are employed to enhance coupling to obtain a flat passband. The feedlines are then loaded with a pair of λ/2 stepped impedance radial stubs (SIRSs) to provide excellent band-stop characteristics. Finally, a filter prototype is created, and its performance is evaluated using the generated data. The proposed UWB filter has sharp roll-off ratio of 99 and 63 dB/GHz, respectively, at the lower and upper edges of the passband.
A wide-band dual-circularly polarized transceiver antenna with high port isolation is proposed in this paper. The antenna element uses M-shaped and U-shaped microstrip lines to excite the quasi-cross-shaped aperture to achieve wide-band and lower cross-polarization level. Dual-circular polarization is accomplished via the sequential rotation technique. To obtain high port isolation of the antenna, phase cancellation technique and decoupling structure are utilized. The measurements show that the impedance bandwidth with reflection coefficient less than -10 dB is larger than 34.5% (4.6-6.5 GHz) for left-hand circular polarization (LHCP) port and 29.8% (4.86-6.5 GHz) for right-hand circular polarization (RHCP) port, while the 3 dB axial ratio bandwidth for LHCP and RHCP is greater than 29.1% (4.8-6.4 GHz) and 32.7% (4.7-6.5 GHz), respectively. The port isolation of the antenna is higher than 30 dB in 4.5-6.5 GHz band. The peak gain is about 12 dBic.
An end fire antenna architecture based on transmission line (TML) theory is suggested. N element end fire antenna array could be constructed with N-1 elements of full wave dipole antennas and one half wave dipole antenna without additional impedance matching network. The N dipole antennas are placed with each other with a distance of quarter wave length, while the one half wave dipole antenna is at the outer most of the array, the farthest from the feeding point of the antenna array. And three 24 GHz dipole end-fire antenna arrays with gains of 7.1, 8.4 and 9.4 dB respectively are presented to explain and verify this end fire antenna architecture based on transmission line theory. Simulation and measurement results of the three end-fire antennas are given and compared. This 24 GHz end-fire antenna architecture could be utilized in 24 GHz planar end-fire antenna arrays to increase the effective isotropic radiated power (EIRP) of the transmitter.
This article proposes an approximate analytical formulation to calculate the low-frequency magnetic shielding of a rectangular metallic box, with all walls perforated periodical holes. The solution is obtained by the combination of two submodels: the finite conductivity box with the holes covered and the perfect conductor box with the holes present. The first submodel represents the diffusion effect of magnetic field penetration through the conducting shell, and the second one denotes the aperture effect of magnetic field leakage through the holes. The total shielded magnetic field is the superposition of these from the two submodels. For the diffusion effect, an existing empirical formula based on the shape factor is used. To solve the second submodel, we employ two approximate methods: the method of images and the surface-impedance method. The method of images models each hole in the walls as an equivalent magnetic dipole and its images based on Bethe's small aperture coupling theory. A PEC box is first considered. Comparisons with finite element simulations show that the method of images has better accuracy than the surface-impedance method. Then, a cubic aluminum box of 0.2 m in length is treated, which verifies that combining the two submodels can produce results in good agreement with finite element simulations for frequencies up to 10 MHz. In addition, the dependence of the shielding effectiveness on frequency is also analyzed.
This paper presents a new compact dual-band bandpass filter (BPF) with a stub-loaded resonator structure that can independently change its operating band to support GSM and WiFi applications for modern wireless communications. A short-circuit stub with a metal through hole is placed into the symmetrical resonator together with a pair of step impedance stubs and a pair of uniform open-circuit stubs. Inside the resonator, the open stubs fold in on themselves, minimizing the circuit for integration with other parts and enhancing the selectivity of the filter. Even-odd mode theory can be employed to investigate the circuit because of the resonator geometric symmetry. The first and second operational frequency bands can then be built using the calculated odd and even mode frequencies to match our requirements. The manufactured experimental dual-band filter is compared to the simulation results, and the statistics revealed good agreement. The calculated structural measures 0.13λg × 0.1λg.
In underwater wireless sensor networks (UWSNs), the limited availability and non-rechargeability of sensor node batteries necessitated the advancement of energy optimization techniques. Optimal clustering is one such technique that reduces the energy consumption of the networks. In this letter, we propose optimal cluster compression technique jointly with energy harvesting. In optimal clustering compression, we perform optimal clustering of networks with singular value decomposition (SVD) as compression technique to reduce the redundant data generated at the cluster heads (CHs). Besides, adopting energy harvesting technique, node batteries are periodically recharged. The performance of the proposed model is evaluated in terms of network lifetime and throughput.
A new defected ground structure (DGS) with two transmission zeros is presented for the first time by loading the conventional dumb-bell-shaped (DBS) DGS with the comb-shaped structure. Equivalent circuits are developed and electric parameter extraction is derived. The low-pass filter (LPF) design method based on the proposed new DGS is given. The fabricated filter demonstrates a sharp, wide and high stopband rejection with an ultra-wide 20 dB rejection bandwidth of 21.9fc and the sharp attenuation rate is more than 129.4 dB/GHz.
This paper proposes an improved design of a W-band slot array antenna, based on a ridge waveguide and a rectangular micro-coaxial line. To achieve a high gain and wideband antenna with element spacing smaller than half a wavelength, a broadband transition of rectangular coaxial line to ridge waveguide was designed. The improved design has bandwidth around 15.4 GHz (94.8 GHz-110.2 GHz), and the simulated realized gain is about 14.6 dB. Measured results of the fabricated antenna demonstrate that the gain at theta = 0°, and VSWR is better than 13 dB and 2.7, respectively. The antenna's size is about 12 mm × 5.5 mm × 0.46 mm.