High Gain Directivity Research Articles

Focal Region Ray Tracing for Slanted Incident Rays on Spherical Reflector Antenna

Abstract Multi beam antenna system is required at base station for fifth-generation (5G) mobile communication and also to cover large portions of field of view for the satellite antenna. A spherical reflector antenna is promising to give high gain directivity of each independent beams for its multiple beam capabilities. The study of the feed elements system is carried out by analysing the focus of slanted incident rays in receiving mode from 0° to 30° at step angle 10°. Simple analytical equations are derived to find the incident and reflected rays. This focal region of spherical reflector is studied in MATLAB program. Accuracy of the MATLAB results are validated by examining the focal region using an electromagnetic simulator, FEKO. The locus of feed of spherical reflector antenna for certain angles of the incident rays are presented in this study.

Compressed Beam Alignment with Out-of-Band Assistance in Millimeter Wave Cellular Networks

Network transmission over millimeter-wave (mmW) bands has a big potential to provide orders of higher bandwidth. However, beamforming is generally needed to compensate for the high path loss. As mmW antennas have a potentially large number of candidate beamforming directions, to achieve high network throughput, the finding of a high gain direction between a base station and each mobile in the mmW network may involve a large overhead if training signals are directly sent along all possible directions or according to a large volume of codebook. Taking advantage of the block sparse characteristics of the mmW channel and coexistence of legacy antennas, we propose a comprehensive design for more efficient beam direction finding. Different from existing compressive-sensing-based schemes which just take a random subset of directions to measure, taking advantage of the path clustering feature of the mmW channel, we develop a self-adaptive block sparse algorithm which can benefit from preliminary channel estimation during each iteration of the problem solving to significantly improve the overall channel estimation accuracy thus the beam alignment gain. We also explore two methods to exploit co-located legacy antennas to provide further guidance for transmission direction finding. Simulation results indicate that our proposed beam alignment scheme outperforms the baseline and peer schemes in terms of the beamforming gain and training cost. By taking advantage of the block sparse properties of mmW channel, our proposed design is able to achieve the transmission throughput comparable with the exhaustive direction search at much lower overhead.

CSRR Loaded Tunable L-Strip Fed Circular Microstrip Antenna

A tunable L-strip fed circular microstrip antenna on thick substrate with CSRR in the ground plane has been analysed and investigated. The antenna is analysed using cavity model and circuit theoretic approach for initial design and then simulated on IE3D simulation software. The antenna is made tunable with PIN diode which makes it to work in different configurations. Two diodes were used to implement a double annular slot, one annular slot and one split slot and CSRR in the ground plane. While other configurations of diodes provide bandwidth and radiation pattern diversity, CSRR provides size reduction of upto 13.31 % along with high gain directivity and radiation efficiency. A maximum gain of 8 dBi, directivity 8.3 dBi has been achieved in the respective band of operations. The antenna exhibits wideband along with multiband characteristic.

Optical gain and gain saturation of blue‐green InGaN quantum wells

AbstractUsing varied stripe length method we systematically studied optical gain properties of blue‐green 3 nm InGaN QWs grown on c‐plane and (11−22) semipolar substrates. We determined that for such structures when the product of modal net gain at peak and stripe length exceeds factor 5 the gain saturation occurs due to depletion of pumped carriers. We then focused our attention on the gain in unsaturated conditions. We observed strong gain peak position blue shift with increase of pumping power for both substrate orientations due to quantum well state filling and for c‐plane due to piezoelectric field screening. Thus in order to increase lasing wavelength, minimizing optical losses, and maximizing modal gain are essential. We then found that for the semipolar QWs the gain at ∼500 nm was 2× higher with the stripe along [−1−123] direction despite the fact that at low pumping level the polarization switching of spontaneous emission resulted predominant E||[−1−123]. Finally we compared the semipolar and c‐plane QWs and found that the gain increase with pumping power of c‐plane QW is slower than that for semipolar QW in high gain direction while the transparency pumping power is lower for c‐plane.

Identification of an Ill-Conditioned Distillation Column Process using Rotated Signals as Input

The standard uncorrelated test signals estimate the low-gain direction of ill-conditioned multivariable systems poorly. Therefore, the low-gain information needs to be excited more. In this paper, identification of an ill-conditioned distillation column process using rotated signals is proposed. Rotated input signals allow more excitation to be applied in the weak gain direction of the process and less excitation in the strong gain direction. In this approach, the singular value decomposition (SVD) of the steady state gain matrix is used to rotate the input signals along the directions of the right singular vectors. Simulation results show good accuracy of the proposed method in identifying low and high gain directions.

Constrained minimum crest factor multisine signals for "Plant-Friendly" identification of highly interactive systems

Highly interactive systems are ill-conditioned and highly sensitive to model uncertainty, which imposes limitations to achievable closed-loop performance. In this paper, the goal is to develop an identification testing framework meaningful to highly interactive systems based on the application of constrained minimum crest factor multisine signals. "Plant-friendliness" in the design procedure is accomplished by imposing constraints on the overall span, move size, and variability of both input and output signals. A modified 'zippered" power spectral density is proposed which contains both correlated and uncorrected harmonics to simultaneously excite low- and high-gain directions in the data. This signal design procedure is applied to a simple 2-by-2 multivariate system that exhibits challenging interaction and gain directionality issues. Validation of these signals in a closed-loop setting is accomplished by evaluating the performance of decentralized PI with sleady-state decoupler controller designs based on models estimated from noisy open-loop experiments. The modified "zippered" spectrum signals present a clear advantage over standard zippered designs for short data sets under noisy conditions.

Wiener model identification and predictive control for dual composition control of a distillation column

The benefits of using the Wiener model based identification and control methodology presented in this paper, compared to linear techniques, are demonstrated for dual composition control of a moderate–high purity distillation column simulation model. An identification experiment design is presented which enables one to identify both the low and high gain directions of the distillation column, properties which are important for control and hard to identify in a conventional identification experiment setup as is demonstrated in the paper. Data from the proposed experiment design is used for indirect closed-loop identification of both a linear and a Wiener model, which shows the ability of the Wiener model to approximate the nonlinearity of the distillation column much closer than the linear model can. The identified Wiener model is used in a MPC algorithm in which the nonlinearity of the Wiener model is transformed into a polytopic description. In this way a convex optimisation problem is retained while the effect of the nonlinearity on the input–output behaviour of the plant is still taken into account. The performance of the proposed Wiener MPC is compared with linear MPC based on the identified linear models, and with a Wiener MPC in which the nonlinearity of the Wiener model is removed from the control problem via an inversion, a popular way to handle Wiener models in a MPC framework. The simulations demonstrate that the proposed Wiener MPC outperforms the other MPC algorithms.

Dynamics of ideal heat integrated distillation columns.

An ideal heat integrated distillation column (HIDiC), which has neither a reboiler nor a condenser, was studied based on its non-linear and linearized dynamic models. It was found that heat integration between rectifying and stripping sections does not lead to an unstable plant. Moreover, the thermal interaction appears to be relatively stronger at low pressure difference than that at high pressure difference.Strong gain directionality has been found in the ideal HIDiC, where the pressure difference and feed thermal condition correspond to low and high gain direction respectively. With proper design of the process, thermal interaction, affects the system time constant only to a limited extent, and intensifies the interaction within a dual point composition control scheme. In fact, the degree of coupling between top and bottom control loops is governed by feed thermal condition since it is in line with high gain direction and can simultaneously introduce changes of both internal and external flows.

Identification for robust multivariable control: The design of experiments

An approach to the design of experiments for the identification of linear MIMO models that will provide robust model-based control is presented. The design criteria, based on conditions for robust stability and performance, are developed from singluar value decompositions (SVD) characterization of structured model mismatch. The resulting designs minimize uncertainties in certain structural parameters in the SVD of the multivariable model rather than simply the magnitude of the model mismatch. An important feature of these designs is that input perturbations applied in the low-gain directions of the multivariable process have much larger magnitudes than those applied in the high-gain directions. This leads to input sequences which are neither binary nor independent. The results are used to provide an intuitive justification for performing identification under closed-loop multivariable control. Examples are presented which illustrate both the physical interpretations of the designs, and the effectiveness of using a sequential design approach.