Communications: radio wave antennas – Antennas – Microstrip
Reexamination Certificate
2000-08-23
2001-11-20
Wong, Don (Department: 2821)
Communications: radio wave antennas
Antennas
Microstrip
C333S262000, C361S781000
Reexamination Certificate
active
06320547
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates generally to antennas and, more particularly, to antennas formed using multilayer ceramic substrates.
BACKGROUND OF THE INVENTION
Antennas have become essential components of most modern communications and radar systems. One benefit of these antennas is the ability for their beams to be easily scanned or re-configured, as required by the system. Another benefit of these antennas is their ability to generate more than one beam simultaneously.
As operating frequencies rise, array antennas are desirably constructed as smaller devices. This is because the required spacing between radiating elements within the antenna is typically a function of wavelength. There is a strong technical incentive, therefore, to make these antennas compact.
In modern satellite services, each service generally covers a different frequency range, different polarization, and different space allocations. Consumers are interested in addressing these different services without having to use a different antenna to access each service.
Conventional solutions for designing a single antenna capable of communicating with various services entail the use of expensive phase shifters, typically using Monolithic Microwave Integrated Circuits (MIMIC) circuits. There is, therefore, also a strong commercial incentive, especially in the newly developing millimeter-wave LMDS and satellite services, to minimize size and cost.
As phased array antennas become smaller, however, it becomes more difficult to generate, distribute, and control the power needed to drive these devices.
In addition to the size constraints imposed on antennas by modern communications systems, higher frequency systems require the development of lower-loss power distribution techniques. Many RF systems operating in the millimeter-wave range, such as vehicular and military radars and various types of communications systems, require the distribution and collection of RF signals with minimal attenuation in order to maintain high efficiency and sensitivity. Conventional power distribution techniques, however, have associated problems which prevent this desired balance between efficiency, sensitivity and attenuation.
Planar antennas have been known to be very difficult to design, as they have historically used EM coupling from a buried feed network to radiating elements mounted on the surface of the antenna. In particular, EM waves are difficult to direct, and energy can leak in various directions, degrading the isolation between the feed network and the radiating elements. This problematic scenario is compounded if multiple signals having different polarizations are fed to the radiating elements, each polarization having its own feed network in a multi-level environment.
SUMMARY OF THE INVENTION
According to one aspect of the present invention, an array antenna includes a first ceramic layer and a second ceramic layer. A metal layer is disposed between the first and second ceramic layers. A plurality of radiating elements are mounted on the first ceramic layer, and a plurality of control circuits are mounted on the second ceramic layer. The control circuits are coupled to the radiating elements through a plurality of conductive vias which feed through the metal layer or other means.
The metal core layer serves several important functions. The metal core layer provides mechanical strength and structural support. In addition, the metal core layer may provide electrical shielding and grounding. The metal core layer also provides thermal management, as it is essentially a built-in heat sink, for efficient spreading of generated heat.
During firing, the metal core layer provides for minimal shrinkage in the plane of a structure in which the antenna is formed. The metal core layer also provides for confined and well-calculated shrinkage in directions normal to the plane of the structure in which the antenna is formed. The mechanical stability of the ceramic multilayers is maintained throughout processing and allows high density circuits to be screened over large areas of the ceramic with good registration between layers. Vias are precisely located, and conductor patterns with tight tolerances may be formed over a large area board.
According to other aspects of the present invention, the antenna may include a switch having a plurality of poles formed in the second ceramic layer and coupled to one of the radiating elements through one or more conductive vias. In addition, a plurality of phase delay elements may be coupled at a first end to a signal source and coupled at a second end to the respective plurality of poles of the switch. The plurality of phase delay elements may provide respective phase-delayed signals, in which case the switch would be activated to apply a selected one of the phase-delayed signals to the radiating element.
According to another aspect of the present invention, a waveguide is formed within a plurality of ceramic layers stacked on top of a metal layer. The waveguide may be shaped to branch into at least two portions in the plane of the ceramic layers.
According to another aspect of the present invention, an array antenna includes a first ceramic layer having a first feed element embedded therein, and a second ceramic layer having a second feed element embedded therein. A radiating element is disposed proximate the second ceramic layer opposite the first ceramic layer. A first ground plane is disposed between the first and second ceramic layers, and a second ground plane is disposed between the second ceramic layer and the radiating element. A first shielded coaxial transmission line feeds through the first and the second ground planes to couple the first feed element to the radiating element, and a second shielded coaxial transmission line feeds through the second ground plane to couple the second feed element to the radiating element.
According to another aspect of the present invention, a mechanical switch is formed in a plurality of ceramic layers stacked on top of a metal layer. A first electrode has a first portion disposed between a first pair of ceramic layers, and a second portion extends into a cavity formed in the ceramic layers. A second electrode has a fixed portion disposed between a second pair of the ceramic layers and a moveable portion extending into and moveable within the cavity to engage the first electrode.
According to another aspect of the present invention, an antenna includes a metal base layer, a first ceramic layer disposed on top of the metal base layer, and a first ground plane disposed on top of the first ceramic layer. A second ceramic layer is disposed on top of the ground plane, a second ground plane is disposed on top of the second ceramic layer, and a third ceramic layer is disposed on top of the second ground plane. A plurality of radiating elements are mounted on top of the third ceramic layer. A first distributed network is embedded in the first ceramic layer and coupled to the radiating elements through a plurality of vias which feed through the first and second ground planes to provide a first signal having a first polarization to the radiating elements. A second distributed network is embedded in the second ceramic layer and coupled to the radiating elements through a plurality of vias which feed through the second ground plane to provide a second signal having a second polarization to the radiating elements. A radiated signal provided by the radiating elements may be controlled in polarity and phase by controlling the first and second signals in magnitude.
The multi-layer capability of antennas constructed according to the present invention allows for design of compact structures, with short lengths between components, resulting in lower losses and better overall performance.
It is to be understood that both the foregoing general description and the following detailed description are exemplary, but are not restrictive, of the invention.
REFERENCES:
patent: 5387888 (1995-02-01), Eda et al.
patent: 5903421 (1999-05-01), Furutani et al.
patent:
Fathy Aly Eid
Geller Bernard Dov
Johnson Henry Charles
Perlow Stewart Mark
Rosen Arye
Burke William J.
Nguyen Hoang
Sarnoff Corporation
Wong Don
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