Optical: systems and elements – Extended spacing structure for optical elements – Extension of tubular element adjustable
Reexamination Certificate
1999-10-14
2001-01-16
Nguyen, Thong (Department: 2872)
Optical: systems and elements
Extended spacing structure for optical elements
Extension of tubular element adjustable
C359S486010, C359S506000, C343S7000MS, C343S843000, C343S909000, C343S910000
Reexamination Certificate
active
06175449
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates to device for changing the polarization of an incident electromagnetic wave.
The concept of changing the polarization of an incident electromagnetic wave can have various meanings. For example, it can be understood to be the conversion of linear polarization into circular polarization or vice versa, or also a rotation of the polarization direction of the incident electromagnetic wave.
The deliberate changing of the polarization of electromagnetic waves is used in many application fields for increasing signal quality. For example, in radar technology, circular polarization is used to suppress rain echoes and thus increases the range of radar in the event of bad weather. In a similar manner, in radio communication at frequencies in the microwave range, circular polarization permits the reduction of so-called inter-symbol interferences.
Interferences of this kind are produced when electromagnetic signals are reflected against objects on the way from the transmitter to the receiver. When an electromagnetic wave is reflected, its polarization changes. In the extreme instance of a circularly polarized wave perpendicularly striking a flat reflector, the reflected wave maintains the rotational direction in space, but the propagation direction in space is reversed so that, for example a right-handed circular polarized wave becomes a left-handed circular polarized wave. Therefore an antenna designed for right-handed circular polarization cannot receive the reflected, left-handed circular polarized signal so that the interfering signal does not appear in the receiver. Correspondingly, interfering signals whose polarization direction has not been completely reversed in a reflection are muted.
One conventional device for changing the polarization of an incident electromagnetic wave, for example, is the meander-line polarizer known from the literature [Derek McNamara “An Octave Bandwidth Meander-Line Polarizer Consisting of Five Identical Sheets”, IEEE—APS 1981, Vol. 1, pp. 237-240]. This has the following features:
five dielectric printed circuit boards, which are embodied as planar and are disposed one behind the other, flat side to flat side,
on the front side, the printed circuit boards have a number of electrically conductive lines that are disposed in a preferred direction,
an individual line is meander-shaped and extends over the cross section of a printed circuit board,
the meander-shaped lines on all of the printed circuit boards are aligned parallel, i.e. the two main axes of a meander-shaped line on a printed circuit board, which are disposed in the plane of the front side of the printed circuit board, and the two main axes of a meander-shaped line on another printed circuit board, which are disposed in the plane of the front side of the printed circuit board, do not differ from one another.
In particular, the multilayer structure of a meander-line polarizer made up of a number of layered printed circuit boards disposed one behind the other necessitates its comparatively large spatial breadth, which impedes the use of this polarizer in many application fields, if not actually preventing it.
With a suitable dimensioning of a meander-line polarizer, an incident electromagnetic wave with linear polarization in a direction A is converted into an electromagnetic wave with circular polarization in a rotation direction B. A second incident electromagnetic wave with a polarization perpendicular to this (cross-polarization), i.e. with linear polarization in a direction A′ perpendicular to the direction A, is converted into an electromagnetic wave with circular polarization in a rotation direction B′ opposite from the rotation direction B. This means that the decoupling of a signal, i.e. the relationship between useful polarization and cross-polarization, or the relationship between right-handed and left-handed circular polarization, cannot be improved by means of a meander-line polarizer.
SUMMARY OF THE INVENTION
The object of the current invention, therefore, is to disclose a device for changing the polarization of an incident electromagnetic wave, which improves the decoupling of a signal.
With regard to the device for changing the polarization of an incident electromagnetic wave, the object is attained according to the invention by virtue of the fact that the device
has at least one dielectric printed circuit board, which is embodied as planar,
the at least one printed circuit board has a multitude of homogeneously distributed strip conductor structures on both its front side and its back side,
the at least one printed circuit board is composed of elementary cells, which are each comprised of a strip conductor structure on the front side of the printed circuit board, a strip conductor structure disposed opposite it on the back side of the printed circuit board, and the substrate of the printed circuit board disposed between the two strip conductor structures,
in each elementary cell, the two strip conductor structures are disposed in such a way that the two main axes of a strip conductor structure on the front side of the printed circuit board, which are disposed in the plane of the front side, and the two main axes of a strip conductor structure on the back side of the printed circuit board, which are disposed in the plane of the back side, are respectively rotated in relation to one another by a predetermined angle.
A conspicuous optical difference between the known meander-line polarizer and a typical embodiment of the invention is comprised in that in the first, a single element—an elongated meander-line—extends over the entire cross section of a printed circuit board, while in the second, a multitude of elements—elementary cells or strip conductor structures—are disposed in rows that extend over the cross section of the printed circuit board.
A first advantage of the invention over the meander-line polarizer is comprised in that the desired changing of the polarization of an incident electromagnetic wave according to the invention can be achieved by means of a single printed circuit board and consequently, the spatial dimensions of a typical embodiment of the invention are significantly smaller than those of a meander-line polarizer, which distinctly increases the number of potential fields in which it can be used in comparison to the latter.
Primarily, though, the device according to the invention has functional differences in relation to a meander-line polarizer, by means of which the main advantage—a high degree of signal decoupling—can be achieved:
An incident electromagnetic wave with a particular polarization, for example an electromagnetic wave with linear polarization in a direction A, which strikes the device according to the invention undergoes a change in its polarization, for example into an electromagnetic wave with circular polarization in a rotation direction B. A second incident electromagnetic wave with a polarization that is perpendicular to that of the first wave (cross-polarization) is reflected to the greatest degree possible. This means that the decoupling of a signal, i.e. the relationship between useful polarization and cross-polarization, after the transmission of the signal through the device according to the invention, is decisively improved by means of the reflection of the cross-polarized portion.
Improvements in the decoupling of a signal after its transmission which go beyond this, can be achieved by means of embodiments of the invention described below, whose features contribute to the improvement both individually and in combination.
One advantageous embodiment of the invention is comprised in that
each individual strip conductor structure on the front side of the printed circuit board has different geometries in the direction of its two main axes, which are disposed in the plane of the front side, and/or
each individual strip conductor structure on the back side of the printed circuit board has different geometries in the direction of its two main axes, which are disposed in
Menzel Wolfgang
Pilz Dietmar
Curtis Craig
Daimler-Chrysler AG
Kinberg Robert
Nguyen Thong
Venable
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