Yuk-Bun Cheng

Bio: Yuk-Bun Cheng is an academic researcher from Andrew Corporation. The author has contributed to research in topics: Space Shuttle & Conical surface. The author has an hindex of 2, co-authored 3 publications receiving 28 citations. Previous affiliations of Yuk-Bun Cheng include West Virginia University.

On the fields in a conical horn having an arbitrary wall impedance

Abstract: The electromagnetic fields propagating up a cone having an arbitrary wall impedance are found using an asymptotic solution. Three special cases are then considered: the smooth-metal wall, the corrugated wall, and the metal wall with a lossy-dielectric lining. The last case, in the form of an absorber-lining is then shown to behave like a corrugated horn since it too provides a highly tapered E -plane and H -plane aperture distribution. Furthermore, it does this over a much larger bandwidth, over 3:1, with negligible gain drop.

Antenna radiation modeling for microwave landing system

Abstract: Geometric optics and diffraction techniques are used to develop radiation models of antennas mounted on an aircraft structure. Measurements at 35 GHz on a 1/35 scale model space shuttle and 1/11 scale Boeing 737 are used for comparison with computed patterns and are in very good agreement. Radiation coverage in the elevation plane on full scale Boeing 737 and Boeing 747 at 5.1 GHz, as applied to the microwave landing system (MLS), is examined for vertically- and horizontally-polarized antennas mounted at different locations on the aircraft.

Horn-reflector microwave antennas with absorber lined conical feed

Abstract: A horn-reflector antenna comprising the combination of a paraboloidal reflector (11) forming a paraboloidal reflecting surface for transmitting and receiving microwave energy; a conical feed horn (10) for guiding microwave energy from the focus of the paraboloidal reflecting surface to the reflector (11); and a lower end portion (10a) of the inside surface of the conical horn (10) being formed by a smooth metal wall, the balance of the inside surface of the conical horn being formed by a layer of absorber material (30) on at least the opposed side walls of said conical horn (10) that effect the E-plane radiation pattern envelope (RPE) of a horizontally polarized signal, the surfaces of the metal wall (10a) and the absorber material (30) defining a single continuous conical surface, and the absorber material (30) increasing the Eigen value E and the spherical hybridicity factor (Rs) sufficiently to cause the E-plane and H-plane RPE's to approach each other. The exposed surface or the absorber material (30) inside said conical feed horn is preferably substantially flat.

Definition of artificially soft and hard surfaces for electromagnetic waves

Abstract: The widely used transversely corrugated surfaces and other alternative surfaces having the same anisotropic surface impedance deserve a common name. Here it is proposed to call them soft surfaces by analogy with the soft surfaces in acoustics. In the same way artificially hard surfaces are defined. Cylindrical hard waveguides of any cross-sectional shape can support TEM waves.

Dual-polarized shaped-reflector antenna

Abstract: A hog-horn antenna for producing two orthogonally polarized signals. The elevation plane pattern of each signal can be made to have virtually any shape, but is typically of a substantially cosecant-squared shape. In providing for the dual-polarization capability, the hog-horn antenna is designed to produce substantially equal gains for orthogonal polarizations, either simultaneously or separately. Two techniques to substantially equate the elevation plane radiation patterns of the two polarizations include corrugating or absorber-lining the surfaces of portions of the hog-horn antenna. Azimuthal pattern control may be achieved by corrugated/absorber lined flanges.

Soft and hard horn antennas

Abstract: Horn antennas with soft and hard boundaries are analyzed. A soft boundary which exists in classical hybrid-mode horns gives zero field intensity at the wall. A hard boundary corresponds to a uniform field distribution over the horn aperture. Soft and hard horn antennas are compared with respect to directivity, sidelobes, and beamwidth. The dependency between the edge taper directivity, and sidelobes is also calculated based on the solution to the spherical hybrid modes in a conical horn with arbitrary wall impedances. This makes it possible to study how to compromise between directivity and sidelobes. Also discussed is how the different wall impedances may be realized, and some preliminary experimental work on hard horns is presented. >

Analysis of soft and hard strip-loaded horns using a circular cylindrical model

Abstract: Strip-loaded horns with transverse (soft) and longitudinal (hard) strips are analyzed theoretically The method is based on a circular cylindrical and uniform waveguide model with a periodic strip structure The field is represented by an infinite series of space harmonics (Floquet modes) in the air-filled central region and in the dielectrically filled wall region The tangential field is forced to be continuous across the air-dielectric boundary The propagation constant and the total field (including the hybrid factor) can be determined by solving the resulting matrix equations The convergence of the solution has been accelerated by calculating the higher-order terms analytically It is shown that the soft-strip-loaded horn in principle exhibits the same electrical behavior as a corrugated horn The horn represents an interesting alternative to the corrugated horn in wide-band or dual-band applications, in particular for millimeter waves and for lightweight applications onboard satellites The hard-strip-loaded horn has potentially high gain and low cross polarization over a certain frequency range, dependent on the horn dimensions, thickness of the dielectric wall and on how strongly the stripline modes are being excited >

Radiation from a rectangular waveguide with a lossy flange

Abstract: The radiation from a rectangular waveguide with a lossy flange coating is studied both analytically and experimentally. An analytic method using Fourier analysis and an impedance boundary condition is proposed. The experiment was performed using a flange covered with a rubber ferrite sheet at an X-band frequency. The numerical and measured results agree well and show that the lossy flange improves the E-plane radiation pattern and the crosspolar radiation. A boresight gain drop of about 2 db is predicted theoretically and measured experimentally. >