Standing wave antenna array of notch dipole shunt elements

Details Standing wave antenna array of notch dipole shunt elements Standing wave antenna array of notch dipole shunt elements

1999-03-24

2001-01-30

Ho, Tan (Department: 2821)

Communications: radio wave antennas

Antennas

Balanced doublet - centerfed

C343S770000, C343S771000

Reexamination Certificate

active

06181291

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of Invention
This invention relates to antennas. Specifically, the present invention relates to stripline fed dipole antennas and their associated transformers.
2. Description of the Related Art
Antennas are used in a variety of demanding applications ranging from cellular telecommunications systems to missile systems. Such applications often require very compact antennas that are easily tuned for certain signal environments.
Compact, tunable antenna designs are particularly important in military applications employing antennas for missile guidance. The antennas must often fit in very compact spaces such as radomes. The weight and space requirements of the antenna add design constraints to the missile thereby increasing system cost and may compromise performance.
Often, the antennas are tuned for different signal environments and/or to meet different system requirements such as phase error or antenna sidelobe specifications. To tune a typical dipole missile seeker antenna, the lengths of transformers and feed lines in the antenna are adjusted. The adjustments typically increase the space occupied by the antenna and result in undesirable antenna protrusion into the radome. The excess protrusion may result in less antenna aperture and a corresponding degradation in antenna performance. In addition, the line length adjustments are often ineffective at tuning out junction effects. As a result, in high frequency applications such as Ka band applications, where junction effects can be significant, transformer length adjustments are often ineffective. In addition, line length extension may result in undesirable electrical coupling between feed lines. The coupling may result in undesirable changes to sidelobe levels, null depths, and/or gain losses and a corresponding overall decrease in performance.
Hence, a need exists in the art for a compact tunable antenna for achieving maximum performance while occupying minimal space that is applicable to high frequency applications such as Ka band applications.
SUMMARY OF THE INVENTION
The need in the art is addressed by the compact high-performance antenna of the present invention. The inventive antenna includes a waveguide for providing or receiving electromagnetic energy. A feed circuit provides or receives the electromagnetic energy to or from the waveguide. A radiating circuit provides or receives the electromagnetic energy to or from the feed circuit. One or more notches in the feed circuit compensate for insertion phase errors in the electromagnetic energy. One or more tabs in the radiating circuit compensate for radiation phase errors in the electromagnetic energy.
In a specific embodiment, the antenna is a dipole antenna and includes an array of dipole cards. The radiating circuit includes first and second radiating circuits included in each of the dipole cards. The first and second radiating circuits include a plurality of quarter-wave stripline transformers. The transformers include one more rectangular tabs for tuning out radiation phase errors, capacitance effects, and/or junction effects. The feed circuit includes v-shaped notches near the bases of the transformers that compensate for insertion phase errors.
In the illustrative embodiment, the transformers are arranged so that an equivalent circuit of the radiating circuit appears shunt to an equivalent circuit of the feed circuit. Each transformer is connected to a slotline radiating element. The magnitude of the transmitted or received electromagnetic energy is a function of the sizes of the transformers. The feed waveguide includes indentations for inductive tuning.
The novel design of the present invention is facilitated by the use of a combination of notches and tabs that allow for effective adjustments of antenna radiating characteristics without the need for expanding the size of the antenna via the extension of transformer line lengths.


REFERENCES:
patent: 5023623 (1991-06-01), Krienheder et al.
patent: 5579019 (1996-11-01), Uematsu et al.
patent: 6043785 (2000-03-01), Marino

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