Beamwidth Control Research Articles

Controlling Beamwidth of Antenna Using Frequency Selective Surface Superstrate

A method of using frequency selective surface (FSS) to dynamically control beamwidth of antenna is proposed. The unit cell is composed of a two-layer periodic H-shape structure loaded with varactors. By tuning the bias voltage applied to the varactors, the unit cell has two different states that are transparent and absorptive to the incident wave at a certain frequency, respectively. We can control the transparent region of the whole FSS through reasonably setting the capacitance of the varactor loaded on each unit cell, and thus the beamwidth of the transmitted wave could be tuned. The above property has been validated by putting the FSS above the horn antenna array as superstrate. Simulation results show that E-plane beamwidth of the antenna can be enlarged from 13.2 ° to 31.1 ° at 5.5 GHz, and experimental results agree well with the simulated ones. In addition, it is found that the operation frequency for beamwidth control can be tuned as well.

Waveguide tapering for beam-width control in a waveguide transducer

In a waveguide transducer that transmits an ultrasonic wave through a waveguide unit to a test structure, it is most preferred to send a non-dispersive ultrasonic wave of a narrow beam width. However, there is an unresolved conflict between the generation of the non- or less-dispersive wave and the transmission of a narrow-beam wave into a test structure. Among others, the thickness of the waveguide unit in a waveguide transducer is the key variable determining these two conflicting criteria, but the use of a uniformly-thick waveguide of any thickness cannot fulfill the two conflicting criteria simultaneously. In this study, we propose a specially-engineered tapered waveguide unit for the simultaneous satisfaction. An excitation unit is installed at the end of the thin region of the tapered waveguide and generates only the lowest non-dispersive shear-horizontal wave. Then the generated wave propagates through the tapered region of the waveguide unit and reaches the thick region of the waveguide with insignificant mode conversion to higher modes. If the tapered waveguide is used, the surviving lowest mode in the thick region of the waveguide is shown to carry most of the transmitted power and is finally propagated into a test structure. Because the beam size of the propagated wave and the thickness of the contacting waveguide region are inversely related, the thick contacting region of the tapered waveguide ensures narrow beam width. Numerical and experimental investigations were performed to check the effectiveness of the proposed waveguide-tapering approach.

Static and dynamic control of emission beamwidth in horseshoe bats

Horseshoe bats (family Rhinolophidae) emit their ultrasonic biosonar pulses nasally with their nostrils surrounded by baffle structures known as “noseleaves.” The noseleaves are often characterized by intricate local shape details such as flaps, ridges, or furrows. Furthermore, some of these structures are capable of undergoing non-rigid shape changes over time. One part of the horseshoe bat noseleaf that has both static local shape features as well as a time dynamics is the lancet, a vertical projection on the top of the noseleaf. The most striking static shape features of the lancet are half-open cavities (furrows) and the most obvious in-vivo motion of the lancet is a rotation in the distal-proximal about the base of the lancet. In the present work, the acoustic effects of the furrows and the distal-proximal rotation of the lancet were studied in three individuals of the Greater Horseshoe bat (Rhinolophus ferrumequinum) using numerical methods. The lancet furrows were always found to act as beam-focusing devices irrespective of lancet rotation. The acoustic effect of forward lancet rotation within the range seen in bats (tested angles 0°, 5°, 10°) was always a significant widening of the beam.

Adaptive beam-width control of echolocation sounds by CF–FM bats,Rhinolophus ferrumequinum nippon, during prey-capture flight

The echolocation sounds of Japanese CF-FM bats (Rhinolophus ferrumequinum nippon) were measured while the bats pursued a moth (Goniocraspidum pryeri) in a flight chamber. Using a 31-channel microphone array system, we investigated how CF-FM bats adjust pulse direction and beam width according to prey position. During the search and approach phases, the horizontal and vertical beam widths were ±22±5 and ±13±5 deg, respectively. When bats entered the terminal phase approximately 1 m from a moth, distinctive evasive flight by G. pryeri was sometimes observed. Simultaneously, the bats broadened the beam widths of some emissions in both the horizontal (44% of emitted echolocation pulses) and vertical planes (71%). The expanded beam widths were ±36±7 deg (horizontal) and ±30±9 deg (vertical). When moths began evasive flight, the tracking accuracy decreased compared with that during the approach phase. However, in 97% of emissions during the terminal phase, the beam width was wider than the misalignment (the angular difference between the pulse and target directions). These findings indicate that bats actively adjust their beam width to retain the moving target within a spatial echolocation window during the final capture stages.

Beam-width control of echolocation pulses in Japanese CF-FM bats (Rhinolophus ferrumequinum nippon) during aerial prey hunting.

Beam-width control of echolocation pulses in Japanese CF-FM bats (Rhinolophus ferrumequinum nippon) during aerial prey hunting.

Wideband constant beamwidth coplanar waveguide-fed slot antennas using metallic strip loadings and a widened tuning stub with shaped reflectors

Sectored antennas with wideband operation for wireless communication systems are presented. The proposed configurations are based on a coplanar waveguide fed slot antenna using metallic strip loadings and a widened tuning stub above various reflector shapes. By shaping the reflector, noticeable enhancements in both unidirectional radiation pattern and beamwidth can be achieved while maintaining the simple fabrication and installation. Based on the results obtained, three sector antennas covering 72°, 90°, and 120° beamwidths suitable for five, four, and three sectors, respectively, have been proposed and designed. The simple structural configurations, low cost, and ease of half power beamwidth control of the proposed antennas make the design very attractive for practical implementation. © 2011 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2011.

Vespertilionid bats control the width of their biosonar sound beam dynamically during prey pursuit

Animals using sound for communication emit directional signals, focusing most acoustic energy in one direction. Echolocating bats are listening for soft echoes from insects. Therefore, a directional biosonar sound beam greatly increases detection probability in the forward direction and decreases off-axis echoes. However, high directionality has context-specific disadvantages: at close range the detection space will be vastly reduced, making a broad beam favorable. Hence, a flexible system would be very advantageous. We investigated whether bats can dynamically change directionality of their biosonar during aerial pursuit of insects. We trained five Myotis daubentonii and one Eptesicus serotinus to capture tethered mealworms and recorded their echolocation signals with a multimicrophone array. The results show that the bats broaden the echolocation beam drastically in the terminal phase of prey pursuit. M. daubentonii increased the half-amplitude angle from approximately 40 degrees to approximately 90 degrees horizontally and from approximately 45 degrees to more than 90 degrees vertically. The increase in beam width is achieved by lowering the frequency by roughly one octave from approximately 55 kHz to approximately 27.5 kHz. The E. serotinus showed beam broadening remarkably similar to that of M. daubentonii. Our results demonstrate dynamic control of beam width in both species. Hence, we propose directionality as an explanation for the frequency decrease observed in the buzz of aerial hawking vespertilionid bats. We predict that future studies will reveal dynamic control of beam width in a broad range of acoustically communicating animals.

Fabry-Pérot cavity antenna with lateral metallic walls for WiBro base station applications

A new Fabry-Perot cavity antenna simultaneously producing a high-gain and a wide beamwidth is proposed. To get increased antenna gain and reduced back radiation, all the openings of the antenna are enclosed with metallic walls, and to obtain a broader beamwidth, the antenna has been fabricated in a rectangular shape, with an aspect ratio of about 3.5:1. In addition we propose a new method to more accurately predict the frequency of the maximum gain by considering a resonance mode of the cavity enclosed by metallic walls. Good agreement between the prediction and measurement results ensures the validity of the new design approach to provide easy control of gain and beamwidth at the same time.

Two‐dimensional sonar beam characteristics of single harbour porpoise (Phocoena phocoena) echolocation clicks measured with a 16 hydrophone array

For the first time, the beam structure of single harbour porpoise echolocation clicks was simultaneously measured in both the vertical and horizontal plane. Echolocation clicks of a stationed animal and free‐swimming animals catching fish were recorded with a “plus‐shaped” array consisting of 16 hydrophones. The ‐3 dB beam width in the horizontal and vertical planes is in most cases similar to what has been previously measured by Au et al. (1999). However, individual clicks are sometimes broader or narrower than what has been previously reported. This may be caused by either voluntary control of the animal's beam width, or it may be a secondary effect of variations in intensity and air content within the sound production system.

Fourier Transform Optical Beamformer Employing Spatial Light Modulator

Optically controlled beam forming techniques are effective for phased-array antenna control. We have developed the Fourier transform optical beamformer (FT-OBF). The antenna radiation pattern inputted into an amplitude spatial light modulator (A-SLM) is optically Fourier transformed to a specific phase-front light beam equivalent to an antenna excitation in the FT-OBF. Optical signal processing, used the Fourier transform optics, is effective to large-scale, two-dimensional, and high-speed signal processing. To implement a flexible and finer antenna beam pattern control, we use an A-SLM as input image formation of the FT optics. And, to realize a small-size FT-OBF, we use symmetric triplet lenses with convex, concave and convex lens. The total optical system becomes below 1/5 length compared with the length using single lens. Finally, we evaluated the developed FT-OBF with the generated amplitude and phase distributions, which excitation signal of an array antenna. We measured an antenna radiation beam pattern, beam steering and beam width control, in the C-band. Measurement results agreed with theoretical calculated results. These results show the feasibility of the spatial light modulator based FT-OBF.

Design method for independent control of beam width and sidelobe level for wideband smart antennas

In this paper, a design method for wideband smart antennas with independently controllable beam width and sidelobe level in their patterns is demonstrated. Using a frequency domain frequency‐invariant beam former, the phases of the complex weights can be adjusted to obtain a beam pattern that is invariant over the frequency range of interest, and a modified Chebyshev approach is used to calculate the amplitudes of these complex beam‐forming weights, ensuring a relatively independent control of the beam width and the sidelobe level. The paper also briefly discusses different approaches for selecting the amplitudes leading to patterns with high directivities.

Beam-Width-Controllable Ultrasonic Transducer Array

In this paper, we present a new method for beam width control of transducer array using two-layered piezoelectric transducers of which electroacoustic efficiency can be controlled by a capacitor. The measured result for beam width control of the transducer array shows good agreement with the simulation result. It is confirmed that the beam width of the transducer array is easily controlled by varying the second harmonic generation efficiency of each element.

Retrodirective array augmentation for electronic RCS modification

In this paper, an active Pon type retrodirective array (RDA) is augmented with a passive array in order to provide electronic modification of the transmit function of the combination in response to the influence of an external interrogating signal. By the use of a single phase shifter and level setting control, it will be shown that different types of broadcast mode can be initiated. The first of these is the self-tracking capability normally associated with a Pon heterodyne RDA. Broadside radiation production associated with a conventional in-phase fed passive array operating in transmission mode is also demonstrated. Additionally, new modes of operation which include the use of the configuration are described: 1) as a radiation nulling device; 2) its use as a sidelobe suppressor; and 3) as a beamwidth control device.

Paraboloidally Shaped Antenna Possessing Pointing and Beam-Width Control

The surface shape of a paraboloidal ree ector was recone gured using electrostatic forces of repulsion. The experiment consisted of a recone gurable electrostatically shaped ree ector and a measurement system. A set of test cases demonstrated pointing and beam-width control of the radiating surface. The surface ree ector angles of rotation µx and µy were plotted vs eight test cases. The resulting sine functions show the near-linear relationship between voltage and pointing, indicating that expected rotations are in agreement with measurements and that a simple interpretation of Coulomb’ s law dominates the behavior of the system. Nomenclature a = vector of undetermined coefe cients C = coefe cient matrix Ex = error function for rotation about the x axis Ey = error function for rotation about the y axis i; j;k = counting indices p = number of sample points in one quadrant Rx;Ry = rotation matrices xn; yn;zn = coordinates in a new reference frame z = vertical position of ith point in the (j;k)th quadrant z = new vertical position of ith point in the (j;k)th quadrant z = vector of measured displacements z (x; y) = function to be curve e tted µx = angle of rotation about the x axis µy = angle of rotation about the y axis

The control of beam direction and beamwidth of loudspeaker arrays

By the control of time delay and the frequency function of each speaker in an array, the direction and coverage as a function of frequency can be controlled. Beamwidth can be held constant with frequency so that everyone in the coverage area will receive the same spectrum of sound. Examples of one-dimensional beam control will be presented using broadside and endfire line arrays. Then two-dimensional coverage control with crossed broadside and stacked endfire arrays will be demonstrated. Advantages of controlled loudspeaker arrays will be discussed.

Space-based electrostatic antenna design with pointing and beam width control

Covers advancements in spacecraft and tactical and strategic missile systems, including subsystem design and application, mission design and analysis, materials and structures, developments in space sciences, space processing and manufacturing, space operations, and applications of space technologies to other fields.

Optimization of discrete arrays of arbitrary geometry

The concept of Directivity Index with Beamwidth Control (DIBC) leads to a practical method for the optimization of element excitations to control the tradeoff between beamwidth and sidelobe level in a discrete array of arbitrary configuration. This optimization procedure depends on the design frequency, specified element positions, individual element field patterns, and ambient noise field. Each of these factors can be specified in a completely general manner. In addition, the optimization procedure can be adapted to computers of modest memory size by using subarrays of the full array. Examples are included to show the versatility of this approach to the optimization problem, as well as its limitations. One of these examples is a 105-element cylindrical array.

Study of control of beamwidth of radiation pattern of a waveguide using inclined slotted flanges

The effect of slotted flanges on the radiation pattern of a waveguide is investigated experimentally. The slotted flanges are mounted at the aperture of the waveguide. Both straight and inclined slotted flanges are used. It is seen that considerable changes can be effected in the beamwidth of the pattern by changing the flange inclination. Such a simple control on beamwidth thus makes it possible to use the slotted flange device as a feed to meet a variety of applications.

The use of cones and filters to reduce patient dosage in diagnostic radiology.

In a recent editorial reference was made to the need for a short review of the literature pertaining to the means of reducing patient dosage and for practical suggestions as to the steps that might be taken to reduce patient dosage in any X-ray department. The purpose of this paper is to present the facts relevant to the use of cones, diaphragms and other devices for beam definition and to the addition of filters external to the X-ray tube. The traditional type of cone and the more recent varieties of multi-leaf diaphragms provide essentially for (a) control of the X-ray beam width, (b) delineation of the X-ray beam as an aid to positioning. Consideration of beam direction is not relevant to this paper and will not be discussed. Control of beam width is of great importance since it has a direct bearing upon dosage to the operator and the production of scattered radiation within the patient. This latter point only will be discussed since our present concern is with patient dosage, but it should be noted th...

Electron Beams and Their Applications in Low Voltage Devices

A study has been made of the segregation into beams of the space current in devices of the over-all size of commercial receiver tubes and at potentials less than 300 volts. Electrode coatings of luminescent material were used to make the beam traces apparent on any or all electrodes. Qualitative relationships between beam formations and relative electrode potentials are stated. Space currents of a few milliamperes have been concentrated into beams less than 0.010 inch wide in simple structures. Special control grids associated with conventional cathodes have been found to combine good space current control with effective beam formation. These effects together with control of beam width and direction can be obtained in a single device. Simple structures are used to segregate the electron discharge from a single cathode into a few or many similar electron beams. Between such structures and the outermost electrodes are placed perforated positive electrodes with their openings disposed to receive and pass the electron beams. Such electrodes are found to receive as little as two per cent of the current computed from their projected area. Such perforated electrodes include conventional type grids. The relationships between beam widths and electrode potentials have been found to be such that mutual volt-ampere relations can be radically different from those hitherto utilized. Linear, saturation type, or special volt-ampere relations can be obtained.