Steering Approach Research Articles

A Millimeter-Wave Beam-Steering Lens Antenna With Reconfigurable Aperture Using Liquid Crystal

For the first time, a liquid crystal (LC) filled lens antenna is investigated for beam steering in this paper. The LC’s anisotropy is applied inside a semicircular shaped parallel-plate waveguide to achieve a deflection of the propagating electromagnetic wave at the interface of lower and higher permittivities. Using an electrode network, the direction of the sector of higher permittivity can be adjusted and, therefore, so can the beam direction. The main advantage of this antenna concept is that neither phase shifters nor switching networks are needed, resulting in a very simple approach for beam steering. Operating at $V$ -band, from 50 to 75 GHz, the first demonstrator proves the antenna concept by reconfiguring the beam in predefined directions of −30°, 0°, and +30° to simplify the electrode biasing network. Furthermore, it is feasible and being demonstrated to adjust the beamwidth and to generate multiple beams. In the measurements, the antenna exhibits a measured input reflection below −10 dB over the complete frequency range. For the unsteered radiation pattern, the sidelobe level is between −8 and −12 dB, whereas these values degrade to −4.5 to −6 dB for the steered radiation pattern at ±30°. The measured gain is between 13 and 15 dBi.

A Broadband CMOS RF Front End for Direct Sampling Satellite Receivers

This paper presents a comparative analysis between two new architectures for RF programmable-gain amplifiers (RFPGAs): voltage-mode RFPGA-V and current-mode RFPGA-I. RFPGA-V utilizes multiple-switch-multiple-amplifier configuration and gain interpolation method to achieve a fine gain step of 0.25-dB over 42-dB gain range for the band of 250 MHz to 2.3 GHz. Meanwhile, RFPGA-I uses a current steering approach to achieve a fine gain step of 0.25-dB over 42-dB gain range for an even wider band of 250 MHz to 3.4 GHz. Since the active feedback topology is used, no off-chip inductor is needed in either RFPGA, especially for the low-frequency band. In addition, both RFPGA-V and RFPGA-I are able to handle maximum 4.4 V peak-to-peak input signal without compromising their high operating bandwidth. Two broadband RF front ends for direct sampling receivers, which include either RFPGA-V or RFPGA-I followed by the same gain buffer and RF filter, have been demonstrated. For the RF front end with RFPGA-V, the measured gain, noise figure, third-order input-referred intercept point (IIP3), and second-order input-referred intercept point (IIP2) in the differential mode are 29.5 dB, 5.2 dB, −10.9 dBm, and 31.4 dBm, respectively. With RFPGA-I, they are 30.5 dB, 3 dB, −10.5 dBm, and 21.1 dBm, respectively. Both RF front ends consume approximated 50 mW and occupy the similar area of 0.32 mm2 in 28-nm CMOS technology.

Steering the ‘C-Day’: Insights from the rapid, planned transition of the UK's natural gas conversion programme

The article studies the steering strategies pursued during a major sociotechnical transition in the then state-owned British gas industry. We focus on the ten-year (1967–1977) national project to convert 35 million appliances to run on natural gas instead of manufactured gas. The article : a. addresses the issue of steering in the multi-faceted, complex process of conversion and identifies the context of and challenges faced by the natural gas conversion programme in the 1960s and how actors responded and coordinated action; b. Identifies modes of steering followed by key actors and institutions of the period; c. Identifies essential precursors for this successful steering, including: the recognition of the challenges the industry faced in the pre-transition years; an openness to experimentation, R&D and organizational and technical change; and harmonious relations with government. We argue that the steering approach needs to combine an emphasis on planning and institutional and regulatory innovation with aspects of the mundane governance approach. Our analysis shows, with reference to the UK’s low-carbon gas transition, that while rapid, planned transitions are achievable, they may require complex, demanding forms of steering and governance that may prove hard to achieve in today’s socioeconomic and political conditions.

A New Grid-Connected DC/AC Inverter With Soft Switching and Low Current Ripple

This paper presents a new dc/ac inverter for low-power applications (i.e., high-voltage, low-current applications), which offers soft switching of the power semiconductors and low output current ripple. In the proposed power circuitry, a novel ripple steering approach is used that can provide soft switching for the power semiconductors and significantly attenuate the high-frequency current ripple of the inverter. The proposed ripple steering technique utilizes the switching frequency and the duty cycle in order to perform the aforementioned tasks. Basically, the ripple steering technique steers the energy of the ripple to the output capacitances of the power semiconductors in order to provide the soft-switching condition. Theoretical analysis, simulation results, and experimental results verify the feasibility of the proposed technique and demonstrate the superior performance of the proposed inverter.

Pseudo-monopulse tracking method for low profile mobile satellite antenna system

A novel pseudo-monopulse tracking (PMT) method is presented for Ku-band Satcom-on-the-move (SOTM). An antenna architecture consisting of multiple distributed panels capable of moving back and forth mechanically is introduced firstly, which can effectively reduce the overall height. Two independent beams with hybrid beam steering approach are introduced to keep the excellent performance in terms of tracking accuracy and antenna gain over wide scan coverage. Then, a hybrid compensation method using switched delay lines and phase shifters is applied to solve the frequency scan effect. Finally, the tracking beam is sequentially scanned at a prescribed offset angle in different directions, and the pointing error is calculated by comparing the corresponding received beacon signal strengths. Simulation results confirm the veracity of the proposed tracking method.

Studying the Chinese Policy Process in the Era of ‘Top-Level Design’: the Contribution of ‘Political Steering’ Theory

Making sense of the Chinese policy process has been one of the most challenging endeavors for China scholars since the beginning of ‘reform and opening up’. Although a great deal of empirical knowledge has been gathered over the years on policy-making and implementation in many different fields, theorizing on the Chinese policy process has mostly been concerned with individual policy instruments or various modes of policy-making so far instead of looking at how these are interconnected. In this article, we propose ‘political steering theory’ as an integrative theoretical framework to fill in this gap. Originating from policy research conducted by German social scientists starting in the 1970s, we consider ‘political steering theory’ to be the most appropriate approach to the Chinese case, particularly in the current era of ‘top-level design’ led by Xi Jinping. We demonstrate how China recently recalibrated its political steering approach and propose new directions for research into the Chinese policy process under the current administration.

An investigation of active safety control strategies for improving the lateral stability of car-trailer systems

This paper presents an evaluation of control strategies for improving the lateral stability of car-trailer systems. A linear stability analysis method is proposed for the evaluation. The strategies include active trailer differential braking, active trailer steering and variable geometry approach. A linear 3 degrees of freedom (DOF) yaw-plane car-trailer model is generated for the controllers' design and a nonlinear 21-DOF yaw-roll car-trailer model is developed in CarSim to validate the stability control strategies by means of numerical simulations. To determine the stable motion boundary, eigenvalue analysis is conducted for identifying the vehicle critical speed. The linear quadratic regulator technique is applied to the design of controllers for active trailer braking, active trailer steering and variable geometry strategies. It is revealed that the active trailer braking strategy is feasible and effective for improving the lateral stability of car-trailer systems. Simulation results demonstrate the effectiveness of the linear stability analysis method.

Steering the Sales Force for New Product Selling: Why Is it Different, and How Can Firms Motivate Different Sales Reps?

This study investigates how to direct and assemble the sales force for new product selling. In a first step, the authors draw on self‐determination theory to explore and empirically test a threefold conceptualization of motivation. Results provide insights into why sales force steering works differently in the new product selling context. Specifically, results show that for new products’ financial performance, internalized new product selling motivation is more important than intrinsic and controlled motivation. In a second step, the authors show how firms can motivate different sales reps to achieve higher financial performance of new products. In doing so, they examine the interaction effects of sales reps’ predispositions and widespread firm‐steering instruments on new products’ financial performance. Results reveal that the new product sales orientation of the bonus strengthens the positive relationship between sales reps’ performance predisposition and new product financial performance but weakens the relationship between sales reps’ learning predisposition and financial new product performance. Moreover, results reveal that the new product sales orientation of the periodic review strengthens the positive relationship between sales reps’ learning predisposition and financial new product performance. A post hoc analysis shows that a differentiated steering approach that matches appropriate steering instruments with sales reps’ varying predispositions substantially enhances reps’ financial new product performance.

Beam Steering for the Misalignment in UCA-Based OAM Communication Systems

Radio frequency-orbital angular momentum (RF-OAM) is a technique that provides extra degrees of freedom to improve spectrum efficiency of wireless communications. However, OAM requires perfect alignment of the transmit and the receive antennas and this harsh precondition greatly challenges practical applications of RF-OAM. In this letter, we first investigate the effect of non-parallel misalignment on the channel capacity of the RF-OAM communication system equipped with uniform circular array. Then, we propose a transmit/receive beam steering approach to circumvent the large performance degradation in not only non-parallel case, but also off-axis and other general misalignment cases. The effectiveness of the beam steering approach is validated through both mathematical analysis and numerical simulations.

Investigation of reconfigurable antennas by foldable, e-textile tessellations: Modeling and experimentation

Physical deformation mechanisms are emerging as compelling and simple ways to adapt wave propagation properties of antenna arrays in contrast to digital steering approaches acting on topologically fixed antennas. Concepts of physical reconfigurability also enable exceptional capabilities such as deployable and morphing antenna arrays that serve multiple functions and permit compact transport with ease. Yet, the emergent concepts lack broad understanding of effective approaches to integrate conformal, electrically conductive architectures with high-compliance foldable frameworks. To explore this essential interface where electrical demands and mechanical requirements may conflict, this research studies e-textile-based reconfigurable antenna arrays that conform to adaptable topologies by origami-inspired tessellations. The e-textiles leverage embroidered conductive threads along frameworks established on origami tessellations to permit large compliance at folding edges as needed while retaining the desired electromagnetic wave propagation characteristics. Computational modeling is used to guide experimental fabrications and validations. It is found that e-textile origami antenna arrays permit significant adaptation of wave radiation while maintaining the required mechanical robustness under folding sequences. These findings may motivate future concepts for reconfigurable antennas established upon physical deformation processes.

Value Creation Mechanics: An Analytical Reduction of Cash Flows and Net Present Value to Accounting

We propose a mathematical theory of accounting that helps to reformulate, generalize, and study core financial value models (Discounted Cash Flows and Net Present Values), by providing a general accounting formulation of the core underlying cash flows. Using this approach, we reveal new facets of these financial value models’ behaviors, specifically, certain accounting-based symmetries and dynamic-financial limits rooted in the underlying economic activities. We show how this knowledge, which is used to identify the roles and effects of different value creation factors, can be actioned by companies using a value creation steering approach. Finally, we show the relevance of these factors, from the perspective of investors acting on financial markets, regarding the inner potential of companies to create value through cash flows, and regarding the sensitivity of their investments to different market factors, namely growth, financing, and inflation rates.

Unambiguous and Reliable Positioning in the vehicle in terms of Functional Safety and Cyber Security

Functional security and agile software development are two modern areas in product development, which initially have very opposite approaches. For example, formal tests are required by the relevant standards for the former, which must be documented very extensively. The agile software development, on the other hand, tries to come to its conclusion with as few documentation and flexible tests as possible. Also, the proof that testing and development are independent of each other for safety-critical projects is difficult in the context of the use of agile methods. However, taking the constraints of functional safety as given and taking advantage of the enormous flexibility of agile software development, e.g. With the use of Scrum, the Daily Team Meetings create new opportunities in product development. In contrast to previous positioning methods for linearly movable axles, a new developed approach for rear axle steering has not been used as an absolute value encoder, but a novel positioning concept has been researched and developed. Functional Safety first! A new safety concept must therefore be developed. The absolute value encoder, usually realized as an optical or magnetic bar-coded sensor, is used reliably but cost-effectively in a large number of systems. In order to save costs as well as space, the development of the new approach to the sensor will be dispensed with and the positioning will be realized via a new concept. The conventional concepts for position determination of axes is an absolute value encoder. However, this is not highly reliable and has no redundancy. With the new safety concept, the exact position of an axis can be determined and output with high accuracy by means of the various safety devices directly after switching on the system. As a result, the sensor system is hardly susceptible to errors. Here, a detailed error analysis has been carried out. Even after system crashes, there are enough detection points, which are constantly detected during normal operation and thus the plausibility check can be restored. The new explored approach allows the steering to work normally even in safe modes. However, the algorithms for protection have to take effect immediately if, for example, an expected index signal does not occur.

Efficient Continuous Beam Steering for Planar Arrays of Differential Microphones

Performing continuous beam steering, from planar arrays of high-order differential microphones, is not trivial. The main problem is that shape-preserving beams can be steered only in a finite set of privileged directions, which depend on the position and the number of physical microphones. In this letter, we propose a simple and computationally inexpensive method for alleviating this problem using planar microphone arrays. Given two identical reference beams pointing in two different directions, we show how to build a beam of nearly constant shape, which can be continuously steered between such two directions. The proposed method, unlike the diffused steering approaches based on linear combinations of eigenbeams (spherical harmonics), is applicable to planar arrays also if we deal with beams characterized by high-order polar patterns. Using the coefficients of the Fourier series of the polar patterns, we also show how to find a tradeoff between shape invariance of the steered beam, and maximum angular displacement between the two reference beams. We show the effectiveness of the proposed method through the analysis of models based on first-, second-, and third-order differential microphones.

A Fresnel-inspired approach for steering and focusing of pulsed transmit beams by matrix array transducers

Matrix ultrasound transducers for medical diagnostic purposes are commercially available for a decade. A typical matrix transducer contains 1000 + elements, with a trend towards more and smaller elements. This number renders direct connection of each individual element to an ultrasound machine impractical. Consequently, it is cumbersome to employ traditional focusing and beamforming approaches that are based on transmit and receive signals having an individual time delay for each element. To reduce cable count during receive, one approach is to apply sub-arrays that locally combine the element signals using programmable delay-and-sum hardware, resulting in reduction by a factor 10. In transmit, achieving cable count reduction while keeping focusing and steering capabilities turns problematic once it becomes impossible to locally equip each element with its own high voltage pulser. To overcome this bottleneck for decreasing element size, here we present a Fresnel-inspired hardware and beam forming approach that is based on transmit pulses consisting of several periods of an oscillating waveform. These will be derived from one oscillating high voltage signal by using local switching and timing hardware. To demonstrate the feasibilities of our approach, we will show beam profiles and images for a miniature matrix transducer that we are currently developing.

Wide Field-of-view and Broadband Terahertz Beam Steering Based on Gap Plasmon Geodesic Antennas

Despite a plethora of applications ranging from wireless communications to sensing and spectroscopy, the current terahertz beam steering technologies suffer from tremendous insert loss, stringent control of electric bias, limited scanning angle, relatively complicated configuration and narrow operation bandwidth, preventing further practical application. We propose and demonstrate a conceptually new approach for terahertz beam steering by virtue of gap plasmon geodesic antennas. By adjusting the geometric dimension of the gap plasmon geodesic antennas, all gap plasmon modes add coherently along a peculiar direction that depends on the geodesic mean surface. Consequently, high directive beams are generated through the antenna, whose direction could be changed within a wide-angle range spanning ±45° by lateral motion of the feed. Furthermore, an assembled antenna structure consisting of four-element geodesic antennas array is proposed for full 360° beam steering, which can operate in a broadband range from 0.8 THz to 1.2 THz.

Two-dimensional refractive index modulation by phased array transducers in acousto-optic deflectors

Acousto-optic deflectors are photonic devices that are used for scanning high-power laser beams in advanced microprocessing applications such as marking and direct writing. The operation of conventional deflectors mostly relies on one-dimensional sinusoidal variation of the refractive index in an acousto-optic medium. Sometimes static phased array transducers, such as step configuration or planar configuration transducer architecture, are used to tilt the index modulation planes for achieving higher performance and higher resolution than a single transducer AO device. However, the index can be modulated in two dimensions, and the modulation plane can be tilted arbitrarily by creating dynamic phase gratings in the medium using phased array transducers. This type of dynamic two-dimensional acousto-optic deflector can provide better performance using, for example, a large deflection angle and high diffraction efficiency. This paper utilizes an ultrasonic beam steering approach to study the two-dimensional strain-induced index modulation due to the photoelastic effect. The modulation is numerically simulated, and the effects of various parameters, such as the operating radiofrequency of the transducers, the ultrasonic beam steering angle, and different combinations of pressure on each element of the transducer array, are demonstrated.

A hybrid finite element and surrogate modelling approach for simulation and monitoring supported TBM steering

The paper proposes a novel computational method for real-time simulation and monitoring-based predictions during the construction of machine-driven tunnels to support decisions concerning the steering of tunnel boring machines (TBMs). The proposed technique combines the capacity of a process-oriented 3D simulation model for mechanized tunnelling to accurately describe the complex geological and mechanical interactions of the tunnelling process with the computational efficiency of surrogate (or meta) models based on artificial neural networks. The process-oriented 3D simulation model with updated model parameters based on acquired monitoring data during the advancement process is used in combination with surrogate models to determine optimal tunnel machine-related parameters such that tunnelling-induced settlements are kept below a tolerated level within the forthcoming process steps. The performance of the proposed strategy is applied to the Wehrhahn-line metro project in Düsseldorf, Germany and compared with a recently developed approach for real-time steering of TBMs, in which only surrogate models are used.

Beyond Coexistence: Traffic Steering in LTE Networks with Unlicensed Bands

In this article, we study how to efficiently utilize heterogeneous network resources for various service provisioning in LTE networks with unlicensed bands. Our focus is on traffic steering, which is to intelligently distribute traffic among heterogenous cells, radio access technologies, and spectrum bands based on the desires of the network or users. We first highlight the significance of traffic steering, and then present the typical applications and approaches for traffic steering. After that, discussions on how to leverage unlicensed bands for traffic steering are provided, followed by case studies to demonstrate the benefits of traffic steering. Finally, some research issues essential for traffic steering in LTE networks with unlicensed bands are identified.

A new steering approach for VSCMGs with high precision

A new variable speed control moment gyro (VSCMG) steering law is proposed in order to achieve higher torque precision. The dynamics of VSCMGs is established, and two work modes are then designed according to command torque: control momentum gyro (CMG)/reaction wheel (RW) hybrid mode for the large torque case and RW single mode for the small. When working in the CMG/RW hybrid mode, the steering law deals with the gimbal dead-zone nonlinearity through compensation by RW sub-mode. This is in contrast to the conventional CMG singularity avoidance and wheel speed equalization, as well as the proof of definitely hyperbolic singular property of the CMG sub-mode. When working in the RW single mode, the motion of gimbals will be locked. Both the transition from CMG/RW hybrid mode to RW single mode and the reverse are studied. During the transition, wheel speed equalization and singularity avoidance of both the CMG and RW sub-modes are considered. A steering law for the RWs with locked gimbals is presented. It is shown by simulations that the VSCMGs with this new steering law could reach a better torque precision than the normal CMGs in the case of both large and small torques.

Ultra-thin anisotropic metasurface for polarized beam splitting and reflected beam steering applications

In this paper, we propose a polarization beam splitter utilizing an ultra-thin anisotropic metasurface. The proposed anisotropic element is composed of triple-layered rectangular patches spaced with double-layered dielectric isolators. By tailoring the metallic patches, the cell is capable of transmitting x-polarized waves efficiently and reflecting y-polarized beams with almost 100% efficiency at 15 GHz. In addition to this, the reflected phases can be modulated by adjusting the size of the element, which contributes to beam steering in reflection mode. By assigning gradient phases on the metasurface, the constructed sample has the ability to refract x-polarized waves normally and reflect y-polarized beams anomalously. For verification, a sample with a size of 240 240 mm2 is fabricated and measured. Consistent numerical and experimental results have both validated the efficiently anomalous reflection for y-polarized waves and normal refraction for x-polarized beams operating from 14.6–15.4 GHz. Furthermore, the proposed sample has a thickness of 0.1λ at 15 GHz, which provides a promising approach for steering and splitting beams in a compact size.