In this work, a simple propagation channel model for microwave-based pinless subsea connectors in the 5 GHz band is presented. Both high electromagnetic attenuation in seawater due to absorption and the near-field working conditions typically present for underwater connectors are taken into consideration. Therefore, a simplified path loss model based on linear regression is identified. The study shows that high-speed pinless subsea connectors are a reality over several cm of seawater gap when appropriate microwave receiver technology is selected with sensitivities of about -100 dBm. Experimental results show that both half-duplex gigabits-per-second and full-duplex 100-Mbps technologies have a strong potential to be developed in the 5 GHz band.
This communication enlightens design, simulation, fabrication and testing of a novel compact CSRR etched ultra-wideband (UWB) patch Antenna with quadruple Band refusal characteristics. To design the antenna, the dimensions are chosen as 28x18x0.8 mm3. The design was done on FR4 substrate of 4.4 dielectric constant, 0.02 loss tangent. The planned antenna contains chamfered bevel slot rectangular radiating material with a complementary split ring resonator (CSRR) etched on one side and an incomplete ground plane on the other side of the substrate. To understand band rejection characteristics, four circular slots with different radii are etched on the radiating material as CSRR to reject bands at Worldwide Interoperability for Microwave Access (WiMAX) at 3.5 GHz, Indian national satellite (INSAT) at 4.6 GHz, wireless local area network (WLAN) services at 5.8 GHz, and Wideband Global SATCOM (WGS) at 8.2 GHz. The rejected bands center frequencies are perfectly coupled at particular slots with different radii. This compact antenna is effective and useful for short areas and can be easily incorporated in small devices. The results show that the antenna has a bandwidth from 2.77 GHz to 13 GHz. This antenna gains a worthy harmony between the simulated and measured results.
In this article, a new class of dual-/tri-band bandpass filters (BPFs) using a quintuple-mode resonator (QMR) is proposed. The classic odd-/even-mode analysis method is used to analyze the two filters due to their symmetrical structure. Owing to characteristics of the QMR, the dual-/tri-band BPFs based on the same topology are designed. The bandwidths (BWs) of the passbands are controllable. A dual-band BPF with center frequencies of 2.1 GHz/3.43 GHz and a tri-band BPF with center frequencies of 2.35 GHz/3.44 GHz/5.2 GHz are designed, fabricated, and measured. The fabricated filters are compact in size, and measured results are in good agreement with the simulated ones.
In this paper suppression of higher order modes of a microstrip antenna array is investigated. The array consists of two radiating elements which are fed by a corporate type microstrip feeding network. They array provides resonance at 5.2 GHz frequency for its fundamental mode (TM10 mode). Beside this fundamental mode, two harmonics at 10.4 GHz (1st harmonic) and 15.05 GHz (2nd harmonic) and few sub-harmonics at 7.8 GHz (TM12), 8.8 GHz (TM22), and 13.3 GHz (TM32) are excited. In order to suppress 1st harmonic, a pair of half wavelength open ended stubs (pair of stub-A) whereas for 2nd harmonic a pair of quarter wavelength open ended stubs (pair of stub-B) are employed. From the simulated results it is noticed that the 1st and 2nd harmonics are successfully suppressed, and the sub-harmonics are also suppressed. Prototypes of the antenna arrays are fabricated and measured. Measured results have good agreement with simulated ones.
In order to obtain a wideband sum-and-difference network, a novel ridged substrate integrated waveguide (RSIW) magic-T is designed. The proposed magic-T is composed of a five-layer RSIW structure. The signal input from the coaxial H-plane port is transmitted to RSIW through a stripline and split into two in-phase and equal signals at the output ports on the top and bottom layers because of the vertically symmetric structure. An E-plane SIW power divider is utilized to realize the E-plane input/output port of the magic-T. A remarkable bandwidth improvement is achieved due to the ridged structure and the wide bandwidth of a ladder-shape stripline optimized by genetic algorithm (GA). Measured results indicate that the magic-T has a fractional bandwidth (FBW) of 78.7% (6.4-14.7 GHz) with return loss better than 18.1 dB and great isolation characteristics.
A novel null steering method in a multi-mode circular microstrip patch antenna is presented in this letter. A stacked patch configuration, capable of exciting three different radiating modes, namely TM11, TM21, and TM31, is investigated. When two or three modes are excited simultaneously, up to three nulls can be formed in the upper hemisphere, and by tuning the amplitude ratio of these modes, a continuous null steering pattern is realized. It is shown that a full hemispherical null steering of ±90° range can be achieved using the proposed method. The null steering capability with different dielectric permittivities is also presented.
By etching a half-wavelength hook-shaped slot on the ground and adding quarter-wavelength rectangle-shaped strips in the patch, a novel triple band-notched ultra-wideband (UWB) antenna is proposed. The triple band-notches are used to prevent interferences from existing bands at 3.3-3.9 GHz, 5.15-5.35 GHz, and 5.725-5.825 GHz. Fed by coplanar waveguide, the antenna is printed on a 30*30 mm2 substrate. The parameters affecting antenna performance are simulated and analyzed. The simulated and measured results show that the proposed antenna achieves a wide bandwidth from 3 GHz to 11 GHz with triple band-notches. Radiation patterns and gain are also investigated and analyzed.
A novel beam scanning microstrip leaky wave antenna based on liquid crystal material is proposed in this paper. Based on the dielectric anisotropy of the liquid crystal, the main beam angle of the antenna pattern can be easily adjusted with the changing of external bias voltages. Good agreement between simulated and measured results is found for the presented leaky wave antenna. Both the simulation and test frequencies of the antenna are set at 12 GHz. Besides, the measured data show that when the dielectric constant of the liquid crystal changes from 2.4 to 2.52, about 10 degrees tuning range of the main beam angle is achieved.
In this letter, a methodology for the generation of received irradiance/power time series for a GEO downlink concentrated on small aperture receiver terminals is reported. The synthesizer takes into account the atmospheric phenomena that degrade the propagation of the optical signal and especially the turbulence effects. For modeling the scintillation effects, Kolmogorov spectrum is assumed, and the Rytov's approximation under weak turbulence is also used. The time series are generated using the theory of stochastic differential equations. Finally, the proposed synthesizer is compared in terms of first order statistics with experimental data from the ARTEMIS GEO optical satellite link campaign with very good agreement.
In this paper, we present our experimental study of the effect of the external DC magnetic bias field on the nonlinear properties of meta-atom loaded with ferrite elements of different shapes. It is demonstrated experimentally that the adjustment of the resonance frequency of the meta-atom loaded with the ferrite elements of different shapes is possible not only by the input microwave power but also by the external DC magnetic bias field. It is shown that as the external DC magnetic bias field is increased to a certain value, the resonance curve of the nonlinear meta-atom demonstrates bistability. In addition, we achieve significant enhancement of the meta-atom nonlinearity using the nonlinear properties of both ferrite and varactor diode.
This paper presents a quickly converging optimization technique for synthesis of filters with constant and frequency-variant couplings (FVC). Unlike the works so far appeared in the literature, the proposed technique is not based on the direct optimization of scattering parameters with assigned topology, but it consists of two procedures. Firstly, an FVC coupling matrix with assigned topology is suitably transformed by means of scaling and rotations for obtaining the new coupling matrix with constant couplings. Then, the cost function is constructed as a least squares problem involving both the eigenvalues of the new coupling matrix with constant couplings and that of the transversal coupling matrix. The solution is found via the solvopt optimization method. Two numerical examples with different topologies and specifications are synthesized to show the validation of the method presented in this paper.
A novel technique to design a wideband implantable antenna has been proposed by using magneto-dielectric material. The antenna is a half cutting of a coplanar waveguide fed antenna with symmetric geometry printed on a flexible substrate with 24 um thickness. A piece of magneto-dielectric sheet with 0.25 mm thickness is attached on the bottom layer of the antenna to tune the antenna bandwidth. The antenna is simulated in a one-layer body phantom. Simulation shows that the antenna has a wide bandwidth covering 902-928 MHz Industrial, Scientific, and Medical (ISM) band when the body phantom is filled with muscle. There are frequency bandwidth shifts when the body phantom is filled with different tissues of skin, small intestine, and stomach, respectively. The antenna has wide bandwidth covering ISM band in these tissues. Measurement has been done in meat mince. The measured bandwidth of proposed antenna is 810-1062 MHz. The proposed antenna has a compact size of 4 mm×12 mm×0.274 mm suitable to be applied in capsule endoscope, wireless pacemaker, etc.
In this letter, a microstrip dual-band band-pass crossover is proposed. By reducing the number of inner open stubs, miniaturization of a window-shaped crossover without reducing bandwidth can be achieved. An electromagnetic simulation and measurements are used to validate the compact (0.35λ × 0.35λ) crossover with a wide bandwidth.
A simple, small-sized, printed monopole antenna loaded with a chip inductor for achieving dual-band operation in notebook computers is introduced. The design consisted of a simple 5 GHz monopole, a chip inductor, and a tuning end portion. With the inductor inserted at the end of the 5 GHz monopole and connected to the tuning portion, the lower band resonance in the 2.4 GHz band can be attained, together with a reduced design footprint for 2.4 GHz operation. The frequency ratio of the upper and lower bands were also controllable by inductance values. The results showed that the antenna was capable of operating in 2.4 GHz (2400-2484 MHz) and 5 GHz (5150-5825 MHz) wireless local area network (WLAN) bands and yet occupied a small size of 5 mm × 12 mm (about 0.04l × 0.09l at 2.4 GHz) only.
Since passive millimeter wave synthetic aperture interferometric radiometer (SAIR) has the advantages of high spatial-resolution and large field of view, it is an attractive tool for wide area surveillance. Among the SAIRs, the Rotating Scanning SAIR (RS-SAIR) with linear sparse array is a popular system with low redundancy and high reliability. According to the detection mechanism of RS-SAIR, we extend RS-SAIR to deal with higher-order moving target detection (HMTD) for the first time in this paper. In the proposed HMTD method, the 2D time-projection image is constituted by the 1D projection images measured by RS-SAIR firstly. Then, the projection trajectory of moving target can be extracted from the time-projection image. Finally, the positions and motion parameters are estimated by fitting the moving target's trajectory. Simulation results indicate that the position and motion parameters of higher-order moving target can be well estimated with high real time and accuracy by the proposed HMTD method.
In this letter, a wideband dual-polarized dipole antenna is proposed for base station applications. By bending the arms of the dipole, the radiator size is reduced. Meanwhile, a new resonant mode occurs at high frequency. Besides, four shorting stubs are employed to improve the impedance matching. Finally, a wide operating bandwidth is realized by combining all resonant modes. A prototype of the proposed antenna is fabricated and tested. Experimental results show that the antenna has a wide impedance bandwidth of 53% (1.65-2.84 GHz) for VSWR<1.5 at two ports and a high port isolation of 26 dB. Also, a stable antenna gain around 7.9±0.5 dBi and a stable radiation pattern with 3-dB beamwidth of 67.5°±3.5° are obtained within the entire band of operation.
A novel design to enhance the bandwidth of a low-profile substrate integrated waveguide (SIW) cavity antenna is presented. Distinct from traditional antennas with unilateral slots, bilateral slots are utilized as radiating elements in the proposed design. By etching an additional slot at the bottom plane, a new resonant mode is introduced, and quality factors of two original modes are significantly reduced. Antenna's bandwidth can be dramatically enhanced by merging these three modes within a single operating band. A prototype is fabricated and measured. With the height of 0.018λ0, the measured 10-dB bandwidth is 410 MHz (3.24-3.65 GHz), corresponding to 11.9% fractional bandwidth. The measured gain is higher than 4.3 dBi, and the measured efficiency is around 75% within the operation band. Those attractive features, e.g. low profile, enhanced bandwidth and moderate radiation performance, make the proposed antenna suitable for future 5G systems.
An X-band pyramidal horn antenna with a fourth order Chebyshev filtering function is presented in this paper. Four resonators are implemented in linear rectangular waveguide in the filter design. The last stage resonator provides not only resonance pole but also radiation function. To achieve high directivity, a pyramidal horn is attached to the filter output port, with negligible effect on the filter performance. Theoretical results are calculated based on the coupling matrix between the resonators. Finally, a pyramidal horn antenna operating at 10 GHz is designed and fabricated for demonstration. The measured results have found to be in good agreement with the simulated ones.
A wideband filter with a notched band is presented. The proposed filter is formed by cascading three coupling units, and each coupling unit is composed of two curved T-shaped microstrip patches at the top and bottom layers and a circular coupling slot at the mid layer. Overlapping three coupling units could result in a wideband filter with a tunable notched band. To analyse the resonance characteristics, the equivalent circuit model is presented. The notched frequency is 5.8 GHz, and within the passband, the insertion and return losses are better than -2 dB and -15 dB, respectively. The group delays are 0.08 ns and 0.12 ns correspondingly, and the upper stopband reaches 15 GHz. The multi-layer structure leads to a compact size and tight coupling characteristics, and the feasibility and excellent performance of the design is verified.
The current wireless technology demands wide frequency operation, like WLAN 5GHz band, which requires 12.75% frequency bandwidth. In this paper, a unit cell metamaterial structure is proposed, which consists of 4 compact bend triangular resonators (CBTRs) that offer wideband frequency rejection. The single negative metamaterial based resonators give band rejection response, but it is generally bandwidth limited. With the proposed unit cell, rejection bandwidth of 16.78% for rejection level of -12 dB is achieved. It can be further increased by increasing the order of unit cells. The proposed unit cell structure is analyzed for the resonant frequency of 5.5 GHz, and the design is suitable for the application where 15% or more rejection band is required.
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