Radiation Pattern Control Research Articles

Personal audio system for neckband headset with low computational complexity.

Personal audio systems have been developed based on various approaches with the goal of synthesizing an isolated sound zone that avoids disturbing others in different locations. In this work, a near-field solution for a neckband headset using three loudspeakers positioned close to each ear is proposed. In particular, it is an attempt to derive a simple multichannel filter for reducing the computational cost in mobile devices. Unlike super-directive beamforming techniques, the controlled radiation pattern is not highly directional but can boost the near-field sound, thereby providing an extra sound level difference between the listener's ear locations and far-field surrounding areas. For this purpose, a multichannel filter is designed using a conventional pressure matching technique for reproducing a target signal at the ear location while suppressing sound radiation to a far-field. It is shown that the optimal filter weights can be successfully approximated in the form of a simple broadside differential array pattern. The simplified filter structure can be realized using only two second-order infinite impulse response filters for driving the middle and two side loudspeakers. Through various simulations and experiments, it is demonstrated that the proposed solution can effectively realize a personal audio system with a minimal loss of sound isolation performance.

Radiation beam scanning for leaky wave antenna by using slots

This paper provides an insight of a new, microstrip leaky wave antenna. It holds the ability to continue steer its beam at a swapping frequency. This is done with acceptable impedance matching while scanning and very little gain variation. Investigation is carried out on LWAs’ control radiation pattern in steps at a band frequency via vertical and horizontal slots. The enhancement is realized by etching horizontal and vertical slots on the radiation element. This study also presents a novel half-width microstrip leaky wave antenna (LWA). The antenna is made up of the following basic structures group’s vertical and horizontal slots. The reactance profile at the microstrip’s free edge and thus the main beam direction is changed once the control-cell states are changed. The radiation pattern direction changes by sweeping the operating frequency between 4 GHz to 6 GHz.The main beam may be directed by the antenna between 15 o and 55 o . C band achieved the measured peak gain of the antenna of 10 dBi at 4.3 GHz beam scanning range.

Reconfigurable Transmitarray With Near-Field Coupling to Gap Waveguide Array Antenna for Efficient 2-D Beam Steering

A novel array antenna architecture is proposed that can enable 2-D (full-space) radiation pattern control and efficient beam steering. This solution is based on a gap waveguide array antenna and a reconfigurable transmitarray (TA) that are coupled in the radiative near field. An equivalent two-port network model of the coupling mechanism is presented and validated numerically. The desired TA reconfiguration capability is realized by an $8 \times 8$ array of cavity-backed patch resonator elements, where two AlGaAs p-i-n diodes are integrated inside each element providing a 1-bit phase shift. The TA is implemented in an eight-layer printed circuit board (PCB), which includes radiating elements, fixed phase-shifting inner-stripline sections, impedance matching, and biasing circuitry. The combined antenna design is low profile (~1.7 wavelength) owing to the small separation between two arrays (~0.5 wavelength), as opposed to conventional TAs illuminated by a focal source. The design procedure of the proposed architecture is outlined, and the measured and simulated results are shown to be in good agreement. These results demonstrate 23.5–25.2 GHz −10-dB impedance bandwidth and 23.3–25.3 GHz 3-dB gain bandwidth, a beam-steering range of ±30° and ± 40° in the E- and the H-planes with the gain peak of 17.5 dBi, scan loss $\le3.5$ dB, and TA unit cell insertion loss $\le1.8$ dB, respectively.

Application of the Electrostatic Micro-Speakers for Producing Audible Directional Sound

In recent years, the demand for control of sound power and radiation patterns in personal messaging, calls, automotive entertainment, and gaming has brought a new interest in the audio world. The aim of this paper is to investigate the feasibility of producing the sound waves in the audible range and directing them in the desired listening zone by electrostatic micro-speakers. Therefore, a capacitive circular micro-plate has been modeled as an electrostatic micro-speaker. Then a Bessel panel array has been developed using a number of these plates arranged in a square array. The equations governing the vibrations of the micro-speaker’s diaphragm, as well as radiation pattern of the sound waves, have been introduced and solved. The results have shown that the Micro-Electro Mechanical Systems (MEMS) electrostatic diaphragms have the capability of producing the directional sound in the human hearing range. Moreover, we have investigated the effect of different excitation frequencies, radii size and the number of the diaphragms as well as the inter-element spacing on the sound radiation pattern of the Bessel panel array.

Microwave Modulated Scatter Active Array Distortion Sidelobes

A signal processing antenna consisting of an array of modulated scatter elements is described. Time-modulation of array elements for radiation pattern and sidelobe control was initially described more than a half-century ago. Recent decades have produced many advances and extensive documentation for both transmit and receive arrays with time modulated elements. The new article presented here includes both receive and transmit functions in an array of modulated scattering elements. This new approach to time-modulated array experiments greatly simplifies both the physical array elements and the measurement apparatus. An incoming continuous wave (CW) signal in space arrives at the array, is time-modulated by the elements, and then re-radiated in space. The only electrical connections to the individual array elements are low-frequency time-modulation signals. The measurement apparatus consists of a spectrally pure and frequency stable CW source, an audio sine wave modulator with different phases for each element, a microwave receives down-converter to a baseband IF from dc to 24 kHz, and an audio frequency power spectrum analyzer running on a laptop computer. Models that incorporate both the CW signal arrival angle and radiation angles for each modulation and distortion product are presented, along with measurements of 16 element arrays in the anechoic chamber at 2.3 GHz using time-modulation frequencies near 1 kHz. The individual array element time-modulators are nearly ideal RF switches, and the agreement between the new time-modulated scatter array models and measurements is remarkable.

A Comprehensive Survey on “Various Decoupling Mechanisms With Focus on Metamaterial and Metasurface Principles Applicable to SAR and MIMO Antenna Systems”

Nowadays synthetic aperture radar (SAR) and multiple-input-multiple-output (MIMO) antenna systems with the capability to radiate waves in more than one pattern and polarization are playing a key role in modern telecommunication and radar systems. This is possible with the use of antenna arrays as they offer advantages of high gain and beamforming capability, which can be utilized for controlling radiation pattern for electromagnetic (EM) interference immunity in wireless systems. However, with the growing demand for compact array antennas, the physical footprint of the arrays needs to be smaller and the consequent of this is severe degradation in the performance of the array resulting from strong mutual-coupling and crosstalk effects between adjacent radiating elements. This review presents a detailed systematic and theoretical study of various mutual-coupling suppression (decoupling) techniques with a strong focus on metamaterial (MTM) and metasurface (MTS) approaches. While the performance of systems employing antenna arrays can be enhanced by calibrating out the interferences digitally, however it is more efficient to apply decoupling techniques at the antenna itself. Previously various simple and cost-effective approaches have been demonstrated to effectively suppress unwanted mutual-coupling in arrays. Such techniques include the use of defected ground structure (DGS), parasitic or slot element, dielectric resonator antenna (DRA), complementary split-ring resonators (CSRR), decoupling networks, P.I.N or varactor diodes, electromagnetic bandgap (EBG) structures, etc. In this review, it is shown that the mutual-coupling reduction methods inspired By MTM and MTS concepts can provide a higher level of isolation between neighbouring radiating elements using easily realizable and cost-effective decoupling configurations that have negligible consequence on the array's characteristics such as bandwidth, gain and radiation efficiency, and physical footprint.

Phase Only Control Radiation Patterns for Uniform Spaced Array

Phase Only Control Radiation Patterns for Uniform Spaced Array

Metal-dielectric nanoantenna for radiation control of a single-photon emitter

The control of fluorescent properties of single-photon sources in solid-state host systems via optically resonant nanostructures is a key issue in quantum nanophotonics. Here we propose a design of a resonant metal-dielectric nanoantenna for the Purcell factor and radiation pattern control of a quantum emitter placed in the gap between metal and dielectric components of the nanostructure. We demonstrate that large Purcell factor, considerable field enhancement in the gap as well as high directivity can be achieved. The developed nanosystem can be utilized for different solid-state host systems from nanocrystals to 2D materials.

Review on fixed-frequency beam steering for leaky wave antenna

This paper aims to survey the efforts of researchers in response to the novel and effective technology of control radiation pattern at a fixed frequency for leaky wave antenna (LWA), map the research landscape from the literature onto coherent taxonomy and determine the basic properties of this potential field. In addition, this paper investigates the motivation behind using beam steering in LWA and the open challenges that impede the utility of this antenna design. This paper offers valuable recommendations to improve beam steering in LWA. The review revealed the development and improvement of several techniques of beam scanning LWA. However, several areas or aspects require further attention. All the articles, regardless of their research focus, attempt to address the challenges that impede the full utility of beam scanning and offer recommendations to mitigate their drawbacks. This paper contributes to this area of research by providing a detailed review of the available options and problems to allow other researchers and participants to further develop beam scanning. The new directions for this research are also described.

Directed Illumination by Side-Emitting Fibers With Trilobal Cross Section

We present a fiber-based illumination scheme with directed and controllable radiation patterns using a novel fiber type with a trilobal, non-circular cross section. The particular shape forms a distinct asymmetrical radiation pattern, which can be used to concentrate light on particular locations in order to cure resins or polymers, but can also find its applications for lighting purposes.

Novel and active technique for controlling the radiation pattern of the half-width microstrip leaky wave antenna array

A novel, half width–microstrip leaky wave antenna (HW–MLWA) array is presented in this paper. It can electronically control its beam at fixed frequency using a double gap capacitor with diodes and has good impedance matching and very small variation gain while scanning. The control radiation pattern of leaky wave antennas (LWAs) is examined in steps at a certain frequency using binary switches, and a novel HW–MLWA array is proposed. This antenna is mainly composed of two elements of HW–MLWA and seven control unit cells (CUCs). In addition, a reconfigurable CUC is created by combining two triangle patches as double–gap capacitors with two diodes as a switch to connect the patches with a ground plane. The proposed antenna is fabricated and validated. To achieve certain–frequency beam steering, a patch in each CUCs is independently disconnected or connected with the ground plane by using PIN diode switches. When the state of the patch cell is changed, the reactance profile is altered at the free edge of the microstrip that caused the direction of the main beam to change. This proposed antenna prototype can scan the main beam between +22° to +63° at 4.2 GHz, and the antenna has a measured peak gain of 12.72 dBi at 4.2 GHz.

Electronically controlled radiation pattern leaky wave antenna array for (C band) application

This paper provides an insight of a new, leaky-wave antenna (LWA) array. It holds the ability to digitally steer its beam at a fixed frequency by utilizing only two state of bias voltage. This is done with acceptable impedance matching while scanning and very little gain variation. Investigation is carried out on LWAs’ control radiation pattern in steps at a fixed frequency via PIN diodes switches. This study also presents a novel half-width microstrip LWA (HWMLWA) array. The antenna is made up of the following basic structures: two elements and reconfigurable control cell with each being comprised of two diodes and two triangle patches. A double gap capacitor in each unit cell is independently disconnected or connected via PIN diode switch to achieve fixed-frequency control radiation pattern. The reactance profile at the microstrip’s free edge and thus the main beam direction is changed once the control-cell states are changed. The main beam may be directed by the antenna between 61o and 19o at 4.2 GHz. C band achieved the measured peak gain of the antenna of 15 dBi at 4.2 GHz beam scanning range.

Effective Epsilon-Near-Zero (ENZ) Antenna Based on Transverse Cutoff Mode

In this paper, inspired by the homogeneous field configuration and the exotic flexibility of the epsilon-near-zero (ENZ) metamaterial, an effective ENZ antenna is proposed with length-irrelevant operating frequency and controllable radiation pattern. In our approach, the ENZ response is achieved by using the substrate-integrated waveguide at its cutoff frequency, with two open ends for radiation. Interestingly, this transverse cutoff mode decouples the operating frequency and the spacing distance between the radiating apertures, such that the radiation pattern can readily be adjusted by stretching or even bending the structure without changing the operating frequency. The prototypes with straight and planar-curved styles are designed and experimentally tested, both working on transverse cutoff mode at 3.5 GHz while offering the difference pattern and the broadside fan-shape pattern, respectively. The measured radiation patterns are in a good agreement with the simulation, with the peak total efficiencies higher than 63%. In addition, the high quality factor with narrow bandwidth (~0.5%) is observed and discussed. With devisable radiation pattern and extremely low profile ( $\sim 0.02\lambda _{0}$ ), the proposed ENZ antenna exhibits promising potentials for sensing, conformal, and reconfigurable applications.

Radiation pattern control of microstrip antenna in elevation and azimuth planes using EBG and pin diode.

An important issue in wireless communication systems, which is related to the antenna gain degradation in case of changing the main direction of the antenna radiation pattern, this variation is not approval in many communications systems. In order to improve antenna radiation performances, Electromagnetic band gap (EBG) - antenna with radiation pattern control capability is presented. Mushroom-like EBG structure for suppressing surface waves has been combined, with the switching diode to produce the radiation pattern control with improving antenna characteristics of gain, directivity and efficiency. EBG of several cells are surrounded the patch antenna and placed symmetrically for the two opposite sides, generating different radiation patterns control ability in both the elevation (E) (-20° < φ < 20°) and azimuth (Z) planes (−18° < θ < 18°). At the ground plane of antenna the diodes have been switched ON and OFF states, the EBG sector properties in stop band (connecting vias) and pass band (disconnecting vias) are altered. Using CST Microwave Studio (CST MWS) the results show the flexibility in radiation pattern control for the Z and E planes using only four diodes. Antenna directivity of 10 dBi, gain 9.86 dB and efficiency 96.5% at the operating frequency of 6 GHz, more results for all direction has been stated in Table1. Significantly, unlike a conventional beam steering, this method does not suffering from gain degradation and the main lobe gain is approximately constant for all steerig angles.

Smart Terahertz Graphene Antenna: Operation as an Omnidirectional Dipole and as a Reconfigurable Directive Antenna

A graphene antenna with dynamical control of radiation pattern is proposed in this article. The device consists of a dipole with two coplanar graphene parasites. Working in the frequency range of 1.94-2.13 THz, the antenna has four radiation operation states that can be selected by setting specific chemical potentials by external electric field on the graphene elements. In state 1, a dipole-like radiation diagram is produced. States 2 and 3 are characterized by specific directional radiation patterns. By selecting the operation state 4, the antenna is switched off. When an SiO2 substrate with thickness of 1 mm is considered, chemical potentials are adjusted so that the device operates in the 1.94-2.15-THz range, with negligible changes of its four radiation patterns with respect to the case without substrate.

Radiation pattern control of core shell nanoantenna by manipulation of nonlinear properties

In this article, a new structure of core–shell spherical nanoparticle as nanoantenna has been evaluated in which the main lobe direction of its radiation pattern is controllable. In other words, the main lobe direction of core–shell nanoantennas are rotated by using of nonlinearity and pumping secondary wave. As a matter of fact, a unique method is presented in order to turn and tune the radiation pattern of nanoantenna in a considered direction. The control of core shell nanoantenna’s main lobe direction is done by manipulation of the nonlinear properties and an excitation wave as secondary pump. Specifically, Increase in pumping leads to motivate the nonlinear properties of the proposed nanoantenna, therefore the main lobe of radiation pattern is turned slowly and its direction is changed. Based on this method, the designers can implement the structures which have been the controllable scatterings in specific directions. Basically, we indicated that it is possible to control the main lobe direction by means of nonlinear perturbation in core–shell nanoantenna and incidence of secondary wave. For more study, the effect of existence of substrate under spherical nanoantenna is investigated and variation of its pattern is also illustrated. The constituent materials of structures have nonlinear properties. The obtained results in final section show that the substrate also plays effective role in directing of nanoantenna’s beam. Turning lobe direction of presented nanoantenna is evaluated on 600 THz as well.

Selective bright and dark mode excitation in coupled nanoantennas.

Coupled nanoantennas as metamaterial unit elements possess peculiar spectral and radiational behaviors. We show that nanoantennas made of two identical plasmonic slot resonators can greatly enhance the quality factors of resonance spectra and control radiation patterns through the selective excitation of bright and dark coupled modes. We confirm experimentally the enhanced quality factor of a bright mode in coupled nanoantennas. Adding phase modulators to the coupled microwave antennas, we demonstrate the "dark mode only" excitation of coupled microwave antennas with an incident plane wave. We also show that the bright-to-dark mode conversion and the related changes in radiation patterns can be controlled by the polarization of incident waves. In particular, we achieve leftward or rightward uni-directional radiation upon the injection of left or right circularly polarized waves.

Improved Vivaldi Antenna with Radiation Pattern Control Features

Vivaldi antenna has been considered as a mitigation to the scattering effect of an antenna. However, the current performance of Vivaldi antenna suffers from multipath effect, interfering signals and radiation pattern control. This paper proposed an improved Vivaldi antenna which combined triple radiating slot to enable control of radiation pattern features. This is accomplished by controlling the position of the radiating element through the asymmetric arrangement of ideal switches to steer the beam in three desired-directions. The Using operating frequency lied between 900 MHz and 2.5GHz, the proposed design was fabricated and tested. Depending on the radiating element, the proposed antenna covered about ±90o with an almost equal gain at the three different focal in contrast to ±45o coverage of traditional rectangular microstrip antenna beam. The results satisfied pattern reconfigurability and the proposed design can be very useful for wireless communications where multipath fading problems are frequently encountered.

OLED Panel Radiation Pattern and Its Impact on VLC Channel Characteristics

Organic light-emitting diodes (OLEDs) show several attractive features superior to traditional semiconductor LEDs for visible light communication (VLC). This paper experimentally tests and models the radiation pattern of a bent OLED panel for the first time. Different from a Lambertian radiation pattern, we propose an improved analytic mixed Gaussian model to describe the rotational radiation asymmetry, whose parameter values are found by applying an expectation-maximization algorithm for curve fitting with measurements. The OLED radiation pattern is observed to show strong directionality along the bent axes. Its impact on VLC channel characteristics is further studied. Compared with the Lambertian source, the OLED source is more flexible in radiation pattern control and shows advantages in smaller root mean square delay spread and optical path loss.

Efficient Excitation of Characteristic Modes for Radiation Pattern Control by Using a Novel Balanced Inductive Coupling Element

A design strategy exploiting the characteristic mode (CM) analysis (CMA) is described for improving the radiation efficiency of a mounted-on-platform radiator. To this aim, a novel balanced inductive exciter (BIE) is introduced to improve the modal excitation purity of some CMs. In fact, even if the optimal position of the exciters on the hosting platform is determined by using the CM theory, the excitation purity of each mode plays a fundamental role in the radiation efficiency of the radiating system. In particular, achieving a good level of excitation purity strongly reduces the reactive power ( $P_{{{reac}}}$ ) stored in the near-field zone and hence maximizes the amount of the radiated power ( $P_{r}$ ). To better highlight the benefits offered by the presented approach, a set of BIEs is applied on a platform to obtain a fully reconfigurable radiation pattern. The evaluation of the $P_{{{reac}}}$ , $P_{r}$ , and equivalent isotropically radiated power provided by the BIE reveals the importance of a pure modal excitation. To assess the reliability of the proposed BIEs, some prototypes have been manufactured and tested.