Communications: radio wave antennas – Antennas – Slot type
Reexamination Certificate
1999-07-06
2001-03-06
Wong, Don (Department: 2821)
Communications: radio wave antennas
Antennas
Slot type
C343S767000
Reexamination Certificate
active
06198453
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention pertains generally to waveguide antenna devices and methods for propagation of RF energy. More particularly, the invention is a rectangular waveguide antenna apparatus having a continuous slot aperture, a variable height, variable width internal ridge, and a constant external cross section.
2. Description of the Background Art
Numerous types of waveguides are utilized for propagation of electromagnetic energy, typically in the frequency range of between 1 and 150 GHz. Different waveguide cross-sectional shapes and dimensions are selected for distinct electromagnetic field configurations or modes. Rectangular waveguides are widely used for propagation of the transverse electric or TE
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mode. In order to optimize the propagation and phase characteristics of waveguides for optimal energy transfer, designers often must use waveguide shapes and dimensions which are difficult and expensive to manufacture, which cause difficulty in mounting the waveguide, or which result in high losses.
U.S. Pat. No. 4,328,502 to Scharp discloses an antenna consisting of a single continues curved-slot in the broad face of a rectangular waveguide which is useful in reducing radiation pattern beamwidth and extending the range of overall slot length. U.S. Pat. No. 4,330,784 to Ryno et al discloses an antenna which is a continuous slot antenna having a rectangular waveguide whose broad dimension varies in proportion to the attenuation for providing an improved radiation pattern. While the antennas disclosed in these patents provide for an enhanced radiation pattern and, in particular, a means for amplitude control of the radiated energy, there is still a need for a waveguide apparatus which allows for independent control of the phase of the radiation pattern while maintaining the rectangular shape of the waveguide.
In addition, there is a need for an antenna having a shape and dimensions which facilitate manufacture and mounting, which allows for accurate control of the propagation constants, and which has low losses. The present invention satisfies these needs, as well as others, and generally overcomes the deficiencies found in the background art.
SUMMARY OF THE INVENTION
The present invention is a waveguide antenna apparatus which allows accurate and independent control of RF amplitude and phase characteristics while maintaining a constant external cross-sectional shape. In general terms, the invention comprises a waveguide section having first and second opposing broad faces, with the first broad face having a continuous slot therein, and the second broad face having a continuous ridge thereon.
By way of example, and not of limitation, the waveguide section generally includes first and second narrow faces. The slot in the first broad face is generally elongated, curvilinear or meandering in shape, and has a generally constant width, although the slot width may vary. Means for inputting RF energy are included adjacent a feed end of the waveguide section, and a resonant or non-resonant load is included at a load end of the waveguide section. The ridge is located on the internal side of the second broad face and extends longitudinally between the feed and load ends of the waveguide section. The ridge dimensions, including the width and the height of the ridge may vary.
In a first embodiment of the invention, the waveguide section is generally rectangular, with the first and second broad faces being generally parallel to each other and generally perpendicular to the narrow faces. In an alternate embodiment of the invention, the waveguide section is “conformarl” or curvilinear in cross sectional shape such that the first broad face, ridge and second broad face define sections of concentric circles, with the first broad face having a radius greater than the ridge, which in turn has a radius greater than the second broad face. The narrow faces are separated by a section of circle having a greater arc than the edges of the ridge. The conformal shape facilitates mounting to an underlying curved surfaces such as missile and aircraft surfaces.
The invention provides a fast wave antenna which is narrow and constant in cross section and which provides very accurate control of radiation along the slot. The waveguide antenna apparatus of the invention may be used for any wavelength for which rectangular waveguides are generally utilized. Amplitude and phase are controlled independently while maintaining a constant external cross section for the waveguide. The internal cross-section of the waveguide generally varies according to variations in the dimensions of the ridge on the internal surface of the second broad face. The internal ridge compresses the “a” dimension of the waveguide which, in equivalent circuit terms, serves to act like an artificial dielectric which provides additional capacitance to the transmission line. Adjusting the height and/or the width of the ridge within the waveguide allows optimization of antenna performance, provides for independent phase control, allows handling of a wider frequency bandwidth, and allows for accurate control of the waveguide phase and propagation constants. Adjustment of the length, position and shape of the slot allows control of main beam width, amplitude distribution, and side lobe level (SLL). Adjustment of the “a” dimension allows control of the antenna look angle. Very accurate amplitudes and phases can be achieved so that a high gain, high effective, very narrow beam width can be realized in production. SLL in excess of −30 dB can be achieved for short slot length of ten wavelength or less.
An object of the invention is to provide a waveguide antenna apparatus which allows accurate and independent control of RF amplitude and phase characteristics.
Another object of the invention is to provide a waveguide antenna apparatus which has a constant external cross-sectional shape.
Another object of the invention is to provide a waveguide antenna apparatus which is quick and easy to manufacture.
Another object of the invention is to provide a waveguide antenna apparatus that has an external shape which facilitates mounting of the antenna on surfaces.
Another object of the invention is to provide a waveguide antenna apparatus which allows accurate and independent control of amplitude and phase characteristics.
Another object of the invention is to provide a waveguide antenna apparatus which allows small and narrow waveguide structures.
Another object of the invention is to provide a waveguide antenna apparatus which can operate at very high temperatures.
Further objects and advantages of the invention will be brought out in the following portions of the specification, wherein the detailed description is for the purpose of fully disclosing the preferred embodiment of the invention without placing limitations thereon.
REFERENCES:
patent: 4328502 (1982-05-01), Scharp
patent: 4330784 (1982-05-01), Ryno et al.
patent: 5475703 (1995-12-01), Scalise et al.
Chen Shih-Chao
Kalmbaugh David
The United States of America as represented by the Secretary of
Wong Don
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