In recent years, there has been more research on the use of photonic crystals PCs in the field of detection. The application of these materials as gas sensors seems very promising, because of their miniaturization and high spectral sensitivities. The aim of this work is to contribute to the design and study of a resonant microsystem based on one-dimensional photonic crystals for applications such as optical devices with high quality factor for detecting and measuring the concentration of gas in the air. Indeed, we have proposed a gas monitoring structure. This nanosystem is formed by an alternating stack of silicon Si layers and air with a resonant nanocavity in the middle. The numerical results show that the resonance peak that appears on the Photonic Band Gap (PBG) is caused by the creation of the nanocavity within the periodic 1D structure. This resonance peak can be used as a reference for real-time detection and environmental monitoring. In addition, we theoretically studied the relevance of these photonic systems and analyzed the effect of the intrinsic and extrinsic parameters of this device on the detection performance. We have also tried to improve the performance of such a device for the effect study of the inclination variation of the radiation incidence source on the selectivity of the detector.
A printed Yagi-Uda antenna with two closely-spaced driven dipole elements and truncated ground plane is presented for dual-band operation. It is designed on a low-cost FR4 substrate with a dielectric constant 4.6, loss tangent of 0.02, and thickness of 1.6 mm. The dipole, operating in the lower band (centered at 1.8 GHz), is elliptical-bow-tiein shape with rounded edges, whereas a J-shaped dipole enables its operation in the upper band (centered at 2.6 GHz). A trapezoid-shaped director is employed to achieve maximum gain over the required frequency bands. Measurements indicate that the antenna operates from 1.71 to 1.9 GHz and from 2.5 to 2.7 GHz with |S11| < -10 dB. The behavior of the proposed antenna has been investigated by studying different parameters to achieve the maximum gains of 6 and 7.7 dB in LTE band 3 and band 7, respectively, with optimal size. It is found that the experimental results of the final packaged antenna agree with the simulated ones in terms of reflection coefficients, gain, and radiation patterns.
This study proposes a broadband asymmetric Doherty power amplifier (A-DPA) with a broadband matching network and an improved power combination network (PCN). A broadband matching network in the form of a low-pass filter is analyzed and applied in this work. With the narrowband characteristic of a 1/4 wavelength transmission line, an improved PCN is also analyzed and applied to decrease the impedance transformation ratio of the 1/4 wavelength transmission line and then extend the working bandwidth of the DPA. In the design process, GaN HEMTs from Cree are selected to be the main and auxiliary power amplifier transistors, and the ADS software is used to complete the entire design process. In the working frequency band of 3.3-3.6 GHz, simulated results show that the gain is approximately 13 dB when the output power is lower than 40 dBm and that the power-added efficiency (PAE) is 39%-51% within the 9 dB power back-off (PBO) region. Measured results indicate that the proposed A-DPA exhibits a 36%-45% PAE within the 9 dB PBO region. The saturated PAE is between 58% and 62%, and the saturated output power is approximately 42 dBm.
A mixed phased array and retrodirective array providing auto tracking of the angular position of the unmanned aerial vehicle (UAV) is presented. The phase conjugation technique and complex vector multiplication are used together to find the geometric phase of each channel canceling the need to use direction finding algorithm (DOA). After generating the phase conjugated version of the received signal on each channel, its complex vector representation will be multiplied by the complex vector representation of the received signal on the reference channel. The UAV will stay on the beak of the array factor during its movement within the field of view (FOV), and a permanent high gain data link is obtained without the need of the tracking algorithm. The beamwidth of the resulted array is widened to be equal to the FOV. The computational cost of the tracking system will be reduced due to canceling the need of using the complex processing algorithms (DOA, and tracking) used in smart antenna. Direction finding algorithm, beamforming algorithm, and tracking algorithm are combined in one algorithm. The least square error pattern synthesis with nulls method is used to eliminate the predefined interference signals and add null steering ability to the resulted array. The effect of the phase errors is reduced to the case of single antenna due to including the phase errors of each channel in its complex weights. The beam pointing error is taken as a metric to evaluate the performance of the resulted array compared with the BPE of a phased array using the monopulse tracking method.
The design and calibration of high-precision analog phase shifters are crucial issues for phased arrays interferometric passive millimeter-wave imaging systems. In this paper, a high-precision analog phase shifter is presented for phased arrays interferometric passive millimeter-wave security sensing applications, which realizes analog phase shifting function by controlling high-precision DAC (digital to analog conversion) with FPGA. It is known that pre-measured phase delay of a phased array channel is a prerequisite for beam pointing control. However, since many active devices are included in phased array channel link, the phase delay would be affected by various factors such as device moving and ambient temperature. So, high-precision phase shifting of phased arrays could be achieved only by measuring and calibrating phases when all components of the system are under normal working conditions. The algorithm proposed in this paper makes it possible to measure and calibrate phases when all sub-modules are integrated into the system, and each component is under normal working state, thus effectively avoiding the errors caused by environmental changes when the laboratory-measured results are put into practical use. Meanwhile, the algorithm is tested on Ka-band phased arrays interferometric passive millimeter-wave imaging system. It turns out that the phase accuracy of phased array channel can reach 5°±1.5°, and it only takes 2 minutes to complete the phase calibrationof 256 arrays.
A miniaturized planar ultra-wideband (UWB) polygon-slot antenna with wideband-notched property is presented in this paper. With coplanar waveguide (CPW)-fed structure and miniaturized dimensions of 18.5×20.5 mm2, the antenna is easy to be integrated with microwave circuitry. By using one rectangular CSRR on rectangular patch, the WLAN band from 4.8 to 5.9 GHz is rejected. By cutting off two small rectangles in the lower corners of the rectangular patch, Antenna 2 is finally proposed, and UWB impedance matching from 3.1 to 12.6 GHz is achieved. The final proposed antenna is fabricated on a low-cost FR4 substrate and measured, and the measured and simulated results show an acceptable agreement. The antenna is validated to perform good radiation properties such as nearly stable radiation patterns, high gain, and high radiation efficiency.
A miniaturized rectangular monopole antenna (RMA) integrated with a T-shaped stub, inverted long and short L-shaped stub resonators based on application of the theory of characteristic modes (CMs) is investigated for multiband operation. CMs of embedded multistubs resonators on the RMA are examined and perceived that the entire structure is able to excite magnetic and electric CMs, in which three valuable CMs at 2.69/3.68/5.35 GHz are attained to cover WiMAX and WLAN bands. Based on CM analysis, the design formulation of multistubs resonators loaded antenna is presented. The proposed multiband antenna has been fabricated, tested, and experimentally characterized. The measured fractional bandwidths (FBWs) are 7.03% (180 MHz, 2.47-2.65 GHz), 10.43% (360 MHz, 3.27-3.63 GHz), and 11.42% (630 MHz, 5.20-5.83 GHz). The antenna exhibits isolated multiple frequency bands, stable monopole-like radiation patterns, and flat realized gains over the operating resonance bands while maintaining the small antenna size.
In this study, we propose a transceiver architecture for wireless chip-to-chip communication using on/off keying (OOK) modulation. The proposed transceiver is composed of an oscillator, coils, an envelope detector, and a Schmitt trigger. Given that the oscillator itself acts as an OOK modulator, the transmitter is simplified. Additionally, because the oscillating signal is coupled between the transmitter and receiver coils, the reliability of the chip-to-chip communication is improved compared to a pulse-type transceiver. To verify the feasibility of the proposed transceiver, we design a transceiver using a 180 nm CMOS process. For a design with a 1.5 GHz oscillation frequency and 1 MHz digital input signal, we verify that the proposed transceiver successfully recovers the original digital signal.
We present a highly accurate frequency-domain finite-difference algorithm for computing mode field solutions of microwave waveguides with regular and reentrant corners. Based on FBS (Fourier-Bessel series)-derived 3-by-3 compact coefficients, our method allows for a flexible layout of the 2-D uniform grids so that distance from the waveguide boundaries to the adjacent unknowns can be arbitrary. Fourth to sixth-order convergent rates of the proposed coefficients are verified by resonance-frequency error analysis for rectangular microwave waveguides for both TE/TM polarizations. We also study the first four Neumann/Dirichlet eigenvalues of the L-shaped MW-WGs calculated by the flexible scheme, and the Neumann results are reported for the first time. Although our results achieve sixth-order accuracy for analytic modes, the order of accuracy is about one and a third for both fundamental TE and TM modes due to singularity around the reentrant corner.
In this paper, we propose a convenient fixed-frequency beam steering method, using a single patch antenna controlled by only one electronically tunable component. The antenna is based on coupled-mode patch antenna (CMPA) [1] that is capable to scan the beam as the function of frequency. A ground-etched slot loaded with one varactor diode is tuned to be capacitive, resonant, or inductive. In order to test broader tuning range, two kinds of varactors with the ranges of 9.24 pF-1.77 pF and 2.67 pF-0.63 pF are implemented respectively. By analyzing how the loaded slot affects the cavity modes and fields, we demonstrate how the voltage bias tunes the frequency responses and steers beam of the antenna. Perturbed by the loaded slot, the frequency response of the antenna shifts from center frequency of 2.35 GHz with the bandwidth of 4.26% down to the band centered at 2.3 GHz with the bandwidth of 4.35%. The maximum scanning range is realized at around 2.29 GHz where the measured main beam continuously scans from -34° to +32° when the varactor with lower tuning range is used and biased. Meanwhile, the main beam of 2.35 GHz scans from +32° to +54° when the higher-range varactor is biased. The proposed single-element antenna is able to maintain high gain and efficiency that are comparable to a regular patch antenna with same size and substrate.
This paper studies the effect of incident wave angular power spectrum (APS) distribution and user hand effect on the envelope correlation coefficient (ECC) of two port MIMO antenna operating in frequency band of LTE-U sub 6 GHz. APS of uniform and Gaussian distributions are used with different Gaussian angular spread (AS) values i.e. 10˚, 30˚, 50˚ and 70˚. A prototype was fabricated, and three-dimensional radiation patterns of antenna elements were measured in anechoic chamber from 4 to 6 GHz in both cases of free space and when the user hand phantom grips the prototype in data mode. An algorithm to calculate ECC from the complex data of far field radiation pattern with different APS distributions is explained in details. Results show that user hand presence increases ECC between ports compare with free space, whose increase is more obvious under Gaussian APS. ECC values under uniform APS is practically zero over the entire frequency range expect at frequency values close to 6 GHz where the highest ECC values are 0.13 and 0.16 in free space and with user hand respectively. However, Gaussian APS with different AS's shows a significant impact of the ECC. With narrow AS of 10˚, ECC at some incident directions can be as high as 0.84 and 0.92 in free space and with user hand respectively and the mean ECC values under this AS are 0.25 and 0.37 respectively. ECC values keep decreasing as AS gets wider, at AS = 70˚, maximum ECC values are 0.23 and 0.34 in free space and with user hand respectively with mean values close to uniform APS. Statistical distribution of ECC show good agreement with exponential distribution, more agreement between measured ECC and exponential distribution is observed in free space with wider AS.
Differential signaling is used in digital circuitry and high speed communication links due to its lower level of radiation and lower susceptibility to interference. Signal skew, amplitude differences and unequal parasitic electric or magnetic coupling to nearby structures can lead to common-mode signals being present on differential communication links which can result in unwanted electromagnetic interference and crosstalk. Common-mode filtering is often employed to suppress common-mode signal propagation in order to mitigate against these negative effects. In this paper broadside coupled differential coplanar waveguides are used which provide effective differential transmission from dc through 40 GHz. Simulation and measurement show that dipole-like common-mode filtering elements placed between the broadside coupled traces offer common-mode suppression of more than 10 dB over bandwidths greater than 5 GHz. A design equation is developed which can be used to estimate filtering frequencies from filter dimensions through 30 GHz. Filters can be cascaded to broaden filtering around a single frequency to filter at multiple frequencies. Simulation based registration studies were conducted which show stable filtering performance in the presence of layer-to-layer misregistration up to 0.254 mm.
In this paper, we present a novel design for an end-fire antenna, which generalizes the concept of conventional Yagi-Uda antenna by introducing multiple driven elements. Through using the method of maximum power transmission efficiency, the optimal distribution of excitations for the multiple driven elements can be obtained, and the end-fire gain of the array can be significantly improved in comparison with the conventional Yagi-Uda antenna with a single driven element. In order to demonstrate the new idea, two different types of antenna arrays are designed and fabricated. The first design uses a split-ring resonator (SRR) as radiating element. Compared to similar planar Yagi-Uda SRR antenna arrays previously reported, the number of antenna elements can be reduced from fifteen to eight, and the longitudinal dimension is significantly reduced by 46% while the same performances are maintained with the gain reaching 11.7 dBi at 5.5 GHz. In the second design, printed half-wavelength dipoles are used as the antenna elements. It is shown that an eight-element dipole array with four driven elements has a peak gain of 13.4 dBi at 2.45 GHz, which is 1.8 dB higher than the conventional printed Yagi-Uda dipole antenna array with the same number of elements.
This document presents an evaluation of a near-field contactless inductive link, examined from a radiated disturbance standpoint, whose sources are low-power Analog Front End (AFE) circuits. Two basic types of AFE rectifiers based on Shottky diodes and Mosfet transistors were tested. Due to selective interference measurement, a map of distortions regarding the position of the coil was created. The obtained results referred to the analytical model, providing sufficient convergence to quickly assess the optimum position of the receiving coil.
In this paper, we use magnetic vector potential formulation, along with equivalence principle and image theory, to solve the electromagnetic scattering of a polarized incident plane wave by a subwavelength circular aperture in a conducting screen. The underlined analytical formulation yields a closed-form solution that is accurate for any angle of incidence or polarization and valid for the near-, intermediate- and far-field regions of observation. The formulation is based on Bouwkamp's diffraction model that uses dominant quasi-static magnetic current modes to represent the governing magnetic current distribution in the circular aperture for any incident wave. Taylor series expansion was implemented on the free-space Green's function, and the individual Taylor terms were integrated analytically to produce closed-form expressions for the scattered fields in all regions. In doing so, the Gegenbauer polynomial expansion was applied in order to allow evaluation of the resulting integrals for any observation point in the lower half space. The results obtained from the proposed analytical approach were compared with data generated through a direct application of a numerical integration technique. The comparison illustrates the validity and accuracy of the proposed analytical formulation.
Ultra-wideband antennas covering 1-18 GHz are required for Direction Finding (DF) and phased array applications in electronic warfare and communication systems. Several antennas such as Archimedean spirals, Log periodics, Ridged horns have been extensively used for ESM-DF applications. In this paper an all metal Vivaldi antenna covering 3-18 GHz is designed using HFSS software, and hardware has been realized. A measured VSWR of less than 2.5 over 3-18 GHz is obtained. Radiation patterns are satisfactory both in simulations and measurements. There is fairly good agreement between the two. Further parametric studies are carried out on the single antenna with side and back walls, and this design is optimized for VSWR of less than 2.5 over the band. This antenna is used in a linear array of 8 elements. For this array in simulations, scanned patterns devoid of grating lobes are obtained from 3.0 GHz to 9.0 GHz, and results are presented.
This work describes a theoretical study of filters using a defect in one-dimensional photonic comb-like structure. This photonic comb-like structure is constituted by finite or infinite segments which have negative permeability and grafted in each site by a finite number of lateral branches (play the role of the resonators), which consists of a negative permittivity. Numerical results exhibit the permissible bands which are separated by gaps (forbidden band). These gaps originate not only from the periodicity of the system but also from the resonance states of the grafted lateral branches. We study the effect of the presence of a resonator defect on the transmission behavior, phase, and phase time. The electromagnetic band structure shows that there is a defect mode in the gap. The transmission rate and the reduced frequency of this mode are related to the variation of defect length. Similarly, we calculate, for the first time, the quality factor evolution of this defect mode when the defect length varies. This structure can be used as a new optical filter in the microwave range with a high factor of quality and of transmission.
A compact Multiple Input Multiple Output (MIMO) antenna of size 41×30×0.8 mm3 is proposed in this paper for Ultra-Wideband (UWB) application with high isolation. The proposed UWB-MIMO antenna consists of two Semi-Circle Antennas (SCA) which acts as a radiating patch for achieving UWB operation. The frequency range of UWB is from 3.04 to 10.87 GHz. The high isolation is achieved by inserting an E-shaped slot in the radiating patch, and further enhancement is achieved by inserting a narrow slot in the ground plane. It can be seen that there is good agreement between the simulated and measured results which indicates that the proposed antenna is suitable for UWB applications.
This second paper presents the numerical evaluation of the statistical hybrid model for a number of indicative overhead medium-voltage (OV MV) and underground medium-voltage (UN MV) broadband over power lines (BPL) topologies. In essence, this paper assesses the effect of a number of key of factors already reported in [1], such as the distribution power grid type, BPL topology class, coupling scheme, channel attenuation statistical distribution, and injected power spectral density (IPSD) limits, on the computed capacity ranges of the statistical hybrid model. For the assessment of the different channel attenuation statistical distributions, the graphical analysis and the proposed metrics of capacity percentage change and average absolute capacity percentage change are demonstrated while two rules of thumb estimating the fidelity results are also proposed.
This pair of papers proposes a new approach towards the channel modeling of transmission and distribution broadband over power lines (BPL) networks either on the theoretical or on the practical basis. The proposed statistical hybrid model is the synthesis of the well-validated deterministic hybrid model and a set of well-known statistical distributions widely used in communications literature such as Gaussian, Lognormal, Wald, Weibull and Gumbel statistical distributions. In this paper, the theoretical framework of the statistical hybrid model, as well as the flowchart of the statistical hybrid model, is analytically presented.
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