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About 5,042 papers for “Beamwidth”
Robert John McDonough · CSUN ScholarWorks (California State University, Northridge) · 1976
Characteristic of CBN Cutoff Section Insertion Phase Versus Normalized Frequency Differential Phase Versus Frequency For 180 Degree Phase Shifter . . . . .
Cited by 0Open access
Schmidt, R. F. · NASA STI Repository (National Aeronautics and Space Administration)
Two effective designs have been developed for Cassegrain and Gregorian antenna configurations. Each provides for both high-gain and low-gain operations. Cassegrain system sacrifices some efficiency due to small amount of increased spillover loss. Gregorian system provides for independent spillover control with two feeds.
Cited by 0Open access
R.P. Trefney · National Symposium on Electromagnetic Compatibility · 2003
An empirical investigation is described in which the author studied antenna beamwidth of radiation and how it contributes to errors in the measurement of radiated profiles due to the antenna's directivity. These errors result because measurements are often taken using highly directional antennas that tend to mask the full measurement amplitude of the equipment under test (EUT) due to the antenna's directivity. Errors from this oversight may cause units to appear within prescribed radiation limits when in fact they may be falling. The author suggests that either a variable test distance be used to accommodate the beamwidth of the given antenna or some fixed distance which would adequately include the narrowest beamwidth that would be used, thereby allowing the measurement antenna to illuminate the EUT fully. He further suggests that all measurements be conducted on bore sight with respect to the EUT as seen by the measurement antenna.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">></ETX>
Cited by 0
L. D. Luker, A. L. Van Buren, Michael D. Jevnager et al. · The Journal of the Acoustical Society of America · 1982
The theory of a broadband constant beamwidth transducer (CBT) which is based on Legendre function shading of a spherical cap was described in a previous report [P. H. Rogers and A. L. Van Buren, J. Acoust. Soc. Am. 64, 38–43 (1968)]. Theoretical calculations showed the CBT to have uniform acoustic loading, extremely low sidelobes, virtually no nearfield, an essentially constant beam pattern for all frequencies above a certain cutoff frequency, and a flat transmitting current response over a broad band for piezoelectric drive. In this paper we present experimental results obtained for a prototype CBT based on fifth-order Legendre function shading. The transducer is a spherical cap with a diameter of 30.5 cm and a total cap angle of 50 degrees. The spherical cap is an aluminum plate in which 849 lead zirconate-titanate disks, 0.635 cm in diameter and 0.318 cm thick, are arranged in 16 circular bands with each disk isolated from the plate by corprene. Measurements on the CBT showed it to possess very low sidelobes and a nearly constant beamwidth over the frequency range from 20 to 140 kHz and for ambient pressures up to 3.4 MPa.
Cited by 13
JA ROCHA · 2024
Cited by 0Open access
Tsutomu Suzuki · IEEE Aerospace and Electronic Systems Magazine · 1998
It is essential and desirable to get a high resolution echo in a radar image without using a large antenna. On scanning a radar antenna, the target's distribution is smoothed by the antenna beam and a smeared echo appears on the radar display. This paper describes three different types of beam compression radars: subsurface SAR; correlation array radar; and inversion processed radar. The experimental results show that the beamwidth on display was effectively compressed by the signal processing.
Cited by 12
Defense Technical Information Center (DTIC) · 1965
The report describes an antenna which can be used as a surveillance antenna over frequency bandwidths as large as 12:1, and, through mechanical motion of the feed portion, as an automatic tracking antenna over 10:1 bandwidths. The antenna produces a pattern whose half-power beamwidth is relatively constant over a large portion of the total frequency band of operation. Theoretical formulations are presented for an antenna of this type, together with some measured data taken from previous antennas built by EDL employing the constantbeamwidth principle. Finally, the results of a computer program are described which was aimed at determining the secondary radiation pattern of such an antenna according to several design variables. (Author)
Cited by 0
G. Kossoff · The Journal of the Acoustical Society of America · 1963
The design of focused transducers used to narrow the beamwidth over a finite distance in the nearfield region is outlined. A computer program was used to optimize the transducer's geometrical shape for beamwidth improvement, and off-axis computations for plane and focused transducers were programmed to check the improvement in beamwidth so obtained. The results of these computations show that a simple parameter can be used to describe and compare the degree of focusing of such transducers.
Cited by 34
P.J. Massey · 1988
This paper presents recent advances in the design of constant H-plane beamwidth horns. The theory of constant H-plane beamwidth horns is discussed and the relationship between aperture size and beamwidth is summarised. The expression for the beamwidth in terms of the H-plane flare angle is shown to be given by a simple formula. A new feed arrangement is described which possesses good vswr properties over at least a 3 to 1 bandwidth.
Cited by 3
Schmidt, R. F. · NASA STI Repository (National Aeronautics and Space Administration)
A switchable beamwidth antenna includes a concave parabolic main reflecting dish which has a central circular region and a surrounding coaxial annular region. A feed means selectively excites only the central region of the main dish via a truncated subreflector for wide beamwidth or substantially the entire main dish for narrow beamwidth. In one embodiment, the feed means comprises a truncated concave ellipsoid subreflector and separate feed terminations located at two foci of the ellipsoid. One feed termination directly views all of the main dish while the other feed termination, exciting the main dish via the subreflector, excites only the central region because of the subreflector truncation. In the another embodiment, the feed means comprises one feed termination and a convex hyperboloid subreflector via which the feed excites the main dish.
Cited by 0Open access
D. J. Allwright, J.B. Power · The Journal of the Acoustical Society of America · 1996
Many designs for constant beamwidth transducers have appeared over the years, but these usually involve complicated array shading techniques or ‘‘lenses’’ applied to ultrasonic devices. With locally reacting materials, such as PVDF for example, it is possible to manufacture a composite material which automatically produces the appropriate frequency-dependent shading of the response in a single, continuous transducer. The material makes use of the capacitive (dielectric) nature of the active element in conjunction with a specially designed, electrically resistive layer, to which a single point connection is made. The resulting CR circuit acts as an integrator, and since the resistance to the remote parts of the transducer is largest, the response of those parts progressively reduces as frequency is increased. In other words, the effective size of the transducer reduces (i.e., ‘‘shrinks’’) as frequency is increased. Correct design of the composite provides a constant directivity characteristic. Several applications of this ‘‘shrinker technology’’ are discussed, including microphones, loudspeakers, and hydrophones.
Cited by 1
Lei Ge, Kwai‐Man Luk · 2016
A novel beamwidth reconfigurable antenna is presented. The design methodology uses tunable strip gratings placed on the sides of a magneto-electric (ME) dipole along its H-plane. A fully functional prototype with an as wide as 40% impedance bandwidth (for SWR ≤ 1.5) is developed and tested, demonstrating the H-plane beamwidth with a tuning range from 81° to 153°. With the wide beamwidth variation and wide impedance bandwidth, the antenna is attractive for stationary terminals and base stations in mobile communications.
Cited by 0
Armin Doerry · OSTI OAI (U.S. Department of Energy Office of Scientific and Technical Information) · 2016
Abstract not provided.
Cited by 0Open access
Zhou Xia, Yicheng Lai · 2024
We design patch type SIW antennas for N257 application. SIW structure preserves most of the advantages associated with waveguides and microstrips, such as high Q-factor, low loss, high power-handling capability, easy integrated. With these advantages, the SIW is applied successfully to the conception of planar compact components for the microwave and millimeter wave applications. In this article. patch type SIW antenna is presented. The 2×2 patch elements are simulated and the simulated result shows that the S<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">11</inf> is from 27G–29G, the 3 dB beam width (deg) is larger than 30 degree, gain reach 12 dB. The test result meets well with the simulate result. It can used for N257 work band.
Cited by 0
Deerkoski, L. F., Schmidt, R. F. · NASA STI Repository (National Aeronautics and Space Administration)
A switchable beamwidth monopulse method and system are described. An antenna comprising a curved reflector and a first set of monopulse feeds positioned in the effective region of the airy disc of the antenna includes a second set of monopulse feeds. The second set of monopulse feeds is positioned outside the airy disc in the region of first bright airy ring. In narrow beamwidth monopulse operation, monopulse sum and difference channel patterns are obtained from the first set of feeds within the airy disc. In wide beamwidth monopulse operation, the difference channel pattern is obtained from the second set of feeds in the airy ring; the sum channel pattern is obtained by attenuation and phase shifting the sum channel signal obtained from the first set of feeds, and adding the resultant to the sum channel signal obtained from the second set of feeds. In a simplified form of the invention, the difference channel patterns for both narrow and wide beamwidth mode operation are obtained from the second set of feeds, while the sum channel patterns are obtained as described above.
Cited by 0Open access
Liu, Chun-Tai · Figshare · 2024
Satellite communication is proposed to fulfill the ubiquitous coverage for next-generation wireless networks. Considering the propagation delay and path loss, low-earth orbit (LEO) satellites are widely adopted. However, since the beam boresight directions become close in quasi-earth-fixed cells (QEFC) scenario at low elevation angles, the interference increases and causes low communication quality. This paper introduces the optimal beamwidth maximizing uplink coverage probability scheme for quasi-earth-fixed cells in LEO satellite communication systems. The proposed scheme dynamically adjusts the beamwidth to achieve max uplink coverage probability at different elevation angles. The simulation results show that the proposed scheme matches the exhaustive search method in different scenarios and target signal-to-interference-plus-noise ratios. Furthermore, the proposed scheme significantly mitigates interference and improves the uplink coverage probability. Compared with the 3GPP setting, the proposed scheme improves the uplink coverage probability by 0.93 at time 100 seconds, and compared with the three-color frequency reuse, the proposed scheme improves the uplink coverage probability by 0.195 at time 100 seconds. The dynamic beamwidth and boresight direction adjustments enable the satellite to maintain seamless and reliable communication services across a wide range of operating conditions, ultimately realizing the goal of ubiquitous communications in the QEFC LEO satellite system.
Cited by 0Open access
Liu, Chun-Tai · Figshare · 2024
Satellite communication is proposed to fulfill the ubiquitous coverage for next-generation wireless networks. Considering the propagation delay and path loss, low-earth orbit (LEO) satellites are widely adopted. However, since the beam boresight directions become close in quasi-earth-fixed cells (QEFC) scenario at low elevation angles, the interference increases and causes low communication quality. This paper introduces the optimal beamwidth maximizing uplink coverage probability scheme for quasi-earth-fixed cells in LEO satellite communication systems. The proposed scheme dynamically adjusts the beamwidth to achieve max uplink coverage probability at different elevation angles. The simulation results show that the proposed scheme matches the exhaustive search method in different scenarios and target signal-to-interference-plus-noise ratios. Furthermore, the proposed scheme significantly mitigates interference and improves the uplink coverage probability. Compared with the 3GPP setting, the proposed scheme improves the uplink coverage probability by 0.93 at time 100 seconds, and compared with the three-color frequency reuse, the proposed scheme improves the uplink coverage probability by 0.195 at time 100 seconds. The dynamic beamwidth and boresight direction adjustments enable the satellite to maintain seamless and reliable communication services across a wide range of operating conditions, ultimately realizing the goal of ubiquitous communications in the QEFC LEO satellite system.
Cited by 0Open access
M.A. Kott · IRE Transactions on Antennas and Propagation · 1964
A preliminary investigation of a millimeter wavelength antenna based upon the optical zoom lens system is presented. The antenna consists of an axial lens system of four elements and possesses a beamwidth that can be continuously varied over a range of 7.7 to 1 at 140 Gc and 5.3 to 1 to 70 Gc by the proper axial motion of its lens elements. An analysis based upon both visible and microwave optics is presented which provides approximate expressions for the beamwidth and gain variations in terms of the positions of the lenses of the system.
Cited by 3
Juan A. Vásquez-Peralvo, Juan Carlos Merlano Duncán, Geoffrey Eappen et al. · Open Repository and Bibliography (University of Luxembourg) · 2023
Satellite swarms have recently gained attention in the space industry due to their ability to provide extremely narrow beamwidths at a lower cost than single satellite systems. This paper proposes a concept for a satellite swarm using a distributed subarray configuration based on a 2D normal probability distribution. The swarm comprises multiple small satellites acting as subarrays of a big aperture array limited by a radius of 20000λ<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</inf> working at a central frequency of 19 GHz. The main advantage of this approach is that the distributed subarrays can provide extremely directive beams and beamforming capabilities that are not possible using a conventional antenna and satellite design. The proposed swarm concept is analyzed, and the simulation results show that the radiation pattern achieves a beamwidth as narrow as 0.0015° with a maximum side lobe level of 18.8 dB and a grating lobe level of 14.8 dB. This concept can be used for high data rates applications or emergency systems.
Cited by 0Open access
Schmidt, R. F., Deerkoski, L. F. · NASA STI Repository (National Aeronautics and Space Administration)
Basic configuration consists of large parabolic dish reflector, smaller hyperboloidal subreflector, and two sets of monopulse feeds located in conjugate focal region on boresight axis of dish.
Cited by 0Open access