TREA

Ultrawide-band linear-circular polarization converter

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Information

  • Patent Grant
  • 6624715
  • Patent Number
    6,624,715
  • Date Filed
    Tuesday, March 28, 2000
    24 years ago
  • Date Issued
    Tuesday, September 23, 2003
    21 years ago
Information
Abstract
In an ultrawide-band linear-circular polarization converter, in a noncircular waveguide which has negative-phase characteristics in which a phase gradually decreases in accordance with an increase in a frequency over an ultrawide-band frequency range, a dielectric structure which has positive-phase characteristics, in which a phase gradually increases in accordance with an increase in a frequency, having a complementary relationship with the negative-phase characteristics in the ultrawide-band frequency range is provided.
Description




BACKGROUND OF THE INVENTION




1. Field of the Invention




The present invention relates to ultrawide-band linear-circular polarization converters, and more particularly relates to an ultrawide-band linear-circular polarization converter which has a noncircular waveguide including a dielectric structure and which is set so that frequency-versus-phase characteristics of the noncircular waveguide and those of the dielectric structure complement each other in a range of the ultrawide-band.




2. Description of the Related Art




Hitherto, in a transmitter-receiver which transmits or receives a satellite broadcasting having a dual-band or an ultrawide-band circularly polarized signal, an ultrawide-band or wide-band linear-circular polarization converter has been used to convert a circularly polarized signal into a linearly polarized signal, and vice versa.




In this case, the dual-band has two frequency bands among satellite broadcasting frequency band at several giga-hertz, such as a frequency band of 12.2 GHz to 12.7 GHz and a frequency band of 19.7 GHz to 20.2 GHz. The wide-band is a frequency band of, for example, 10.7 GHz to 12.75 GHz among the satellite broadcasting frequency band of the above several giga-hertz.





FIGS. 5A and 5B

are cross-sectional views showing a first construction example of a known linear-circular polarization converter, in which

FIG. 5A

is a cross-sectional view perpendicular to the longitudinal direction and

FIG. 5B

is a cross-sectional view in the longitudinal direction.




As shown in

FIGS. 5A and 5B

, in the first construction example of a known linear-circular polarization converter, a circular waveguide


51


has a planar dielectric structure


52


provided so as to be along the direction of one diameter thereof. In this case, the planar dielectric structure


52


is provided so as to be along the direction of one diameter of the circular waveguide


51


which is sloped at approximately 45 degrees to the direction of the internal electric field E of the circular waveguide


51


. Both side faces extending in the longitudinal direction of the dielectric structure


52


are cut inwardly in a generally triangular shape.





FIGS. 6A and 6B

are cross-sectional views showing a second construction example of a known linear-circular polarization converter, in which

FIG. 6A

is a cross-sectional view perpendicular to the longitudinal direction and

FIG. 6B

is a cross-sectional view in the longitudinal direction.




As shown in

FIGS. 6A and 6B

, in the second construction example of a known linear-circular polarization converter, a ridged conductor structure


62


is provided at a part of the inner wall of a circular waveguide


61


. In this case, the ridged conductor structure


62


is provided at a position of the inner wall of the circular waveguide


61


which is sloped at approximately 45 degrees to the direction of the internal electric field E of the circular waveguide


61


. In the ridged conductor structure


62


, the height of an edge part in the longitudinal direction is lower than that of a central part.




In these linear-circular polarization converters, when a linearly polarized signal is input to an input terminal thereof, a circularly polarized signal can be output from an output terminal thereof, and vice versa.




Generally, linear-circular polarization converters can perform a predetermined linear-circular polarization conversion on a polarized signal propagating through the waveguide in a frequency band which causes the phase difference |φ| (=|φ


V


−φ


H


|) between the vertical-polarization phase φ


V


of the polarized signal and the horizontal-polarization phase φ


H


thereof to be maintained within a range of 90°±10°.




Since the frequency bands of known linear-circular polarization converters causing the phase difference |φ| to be maintained within the range of 90°±10° are relatively narrow frequency ranges, known linear-circular polarization converters cannot be used as wide-band linear-circular polarization converters or ultrawide-band linear-circular polarization converters which activate in a broader frequency range than that of the wide-band linear-circular polarization converters.




Since known linear-circular polarization converters only have a relative frequency band of several percent, favorable conversion characteristics cannot be obtained throughout a relative frequency band of the order of ten percent or a relative frequency band of several tens of percent.




SUMMARY OF THE INVENTION




Accordingly, the present invention is made considering such a technical background. It is an object of the present invention to provide an ultrawide-band linear-circular polarization converter for capable of offering favorable frequency-versus-phase characteristics as a linear-circular polarization converter in a frequency range of an ultrawide-band.




To this end, according to a first aspect of the present invention, there is provided an ultrawide-band linear-circular polarization converter in which, in a noncircular waveguide which has negative-phase characteristics in which a phase gradually decreases in accordance with an increase in a frequency over an ultrawide-band frequency range, a dielectric structure which has positive-phase characteristics, in which a phase gradually increases in accordance with an increase in a frequency, having a complementary relationship with the negative-phase characteristics in the ultrawide-band frequency range is provided.




In the ultrawide-band linear-circular polarization converter, the noncircular waveguide may be an elliptic waveguide.




In the ultrawide-band linear-circular polarization converter, the dielectric structure may be provided in the direction of the minor axis of the elliptic waveguide, and the dielectric structure may have edge parts which are thin in the thickness direction and a central part which is thick in the thickness direction.




As described above, according to the present invention, by combining the noncircular waveguide having negative-phase characteristics and the dielectric structure having positive-phase characteristics which complement the negative-phase characteristics, the following advantages are obtained: the ultrawide-band linear-circular polarization converter can be caused to have generally flat frequency-versus-phase characteristics which enable favorable linear-circular polarization conversion to be performed in the ultrawide-band frequency range; and the ultrawide-band linear-circular polarization converter can be obtained, having a simple construction, without causing an increase in manufacturing cost or the like.











BRIEF DESCRIPTION OF THE DRAWINGS





FIGS. 1A

,


1


B, and


1


C are diagrams showing the construction of an ultrawide-band linear-circular polarization converter according to one embodiment of the present invention;





FIGS. 2A

,


2


B, and


2


C are graphs showing frequency-versus-phase characteristics of the ultrawide-band linear-circular polarization converter, a noncircular waveguide, and a dielectric structure, shown in

FIGS. 1A

,


1


B, and


1


C;





FIGS. 3A

,


3


B,


3


C, and


3


D are cross-sectional views showing the constructions of other noncircular waveguides in which positive-phase characteristics can be obtained in an ultrawide-band frequency range;





FIGS. 4A

,


4


B,


4


C, and


4


D are cross-sectional views showing the constructions of other planar dielectric structures in which negative-phase characteristics can be obtained in the ultrawide-band frequency range;





FIGS. 5A and 5B

are cross-sectional views showing the construction of a first known linear-circular polarization converter; and





FIGS. 6A and 6B

are cross-sectional views showing the construction of a second known linear-circular polarization converter.











DESCRIPTION OF THE PREFERRED EMBODIMENTS




Embodiments of the present invention are described with reference to the accompanying drawings.





FIGS. 1A

,


1


B, and


1


C show the construction of an ultrawide-band linear-circular polarization converter according to one embodiment of the present invention;

FIG. 1A

is a cross-sectional view perpendicular to the longitudinal direction;

FIG. 1B

is a cross-sectional view in the longitudinal direction; and

FIG. 1C

is a lateral sectional view in the longitudinal direction.




As shown in

FIG. 1A

to

FIG. 1C

, the ultrawide-band linear-circular polarization converter according to the present embodiment has an elliptical waveguide


1


(noncircular) and a planar dielectric structure


2


provided along the minor-axis diameter of the elliptical waveguide


1


(noncircular). In this case, the planar dielectric structure


2


in which the plate thickness is thin at edges


2




1


and thick at a middle


2




2


is constructed. The planar dielectric structure


2


may have another configuration as long as the planar dielectric structure


2


has low reflection characteristics.





FIG. 2A

is a graph showing frequency-versus-phase characteristics of the ultrawide-band linear-circular polarization converter shown in

FIGS. 1A

to


1


C;

FIG. 2B

is a graph showing frequency-versus-phase characteristics of the noncircular waveguide


1


; and

FIG. 2C

is a graph showing frequency-versus-phase characteristics of the planar dielectric structure


2


.




In

FIGS. 2A

to


2


C, the axis of the abscissa represents working frequencies f and the axis of the ordinate represents phase differences |φ| (=|φ


V


−φ


H


|) in degrees.




As described above, φ


V


is the vertical-polarization phase of the polarized signal propagating through the waveguide, and the φ


V


is the horizontal-polarization phase of the polarized signal propagating through the waveguide.




Operations of the ultrawide-band dielectric linear-circular polarization converter shown in

FIGS. 1A

to


1


C are described with reference to

FIGS. 2A

to


2


C.




Frequency-versus-phase characteristics of the noncircular waveguide


1


alone are as shown in FIG.


2


B. In the frequency range of an ultrawide-band between a frequency f


C


and a frequency 2f


C


, as a frequency f increases from the frequency f


C


toward the frequency 2f


C


, the phase difference |φ| drops comparatively rapidly in the proximity of the frequency f


C


. In a subsequent frequency range, the phase difference |φ| drops slowly and becomes less than ninety degrees while dropping. Subsequently, the phase difference |φ| continues to drop at the same rate. In this case, a frequency range BW


1


in which the phase difference |φ| is maintained within a range of 90°±10° is limited to a very small part of the frequency range between the frequency f


C


and the frequency 2f


C


.




Frequency-versus-phase characteristics of the dielectric structure


2


alone are as shown in FIG.


2


C. In the frequency range of the ultrawide-band between the frequency f


C


and the frequency 2f


C


, as the frequency f increases from the frequency f


C


toward the frequency 2f


C


, the phase difference |φ| rapidly drops in the proximity of the frequency f


C


. After the phase difference |φ| drops below ninety degrees, the phase difference |φ| starts to gradually increase. When the phase difference |φ| exceeds ninety degrees and reaches a frequency range which is in the proximity of the frequency 2f


C


, the phase difference |φ| increases comparatively rapidly. In this case as well, a frequency range BW


2


in which the phase difference |φ| is maintained within the range of 90°±10° is limited to a very small part of the frequency range of the ultrawide-band between the frequency f


C


and the frequency 2f


C


.




As shown in

FIG. 2A

, frequency-versus-phase characteristics of an ultrawide band linear-circular polarization converter constructed by combining the noncircular waveguide


1


and the dielectric structure


2


have phase characteristics obtained by combining negative-phase characteristics in which, as shown in

FIG. 2B

, the phase difference gradually decreases in accordance with an increase in the frequency in the noncircular waveguide


1


, and positive-phase characteristics in which, as show in

FIG. 2C

, the phase difference gradually increases in accordance with an increase of the frequency in the dielectric structure


2


. By constructing the noncircular waveguide


1


and the dielectric structure


2


so that the above negative-phase characteristics and the above positive-phase characteristics are complementary in an ultrawide-band frequency range BW between the proximity of the frequency f


C


and that of the frequency 2f


C


, substantially flat phase characteristics can be obtained. To be concrete, the phase difference |φ| is maintained within the range of 90°±10°. As a result of this, this ultrawide-band linear-circular polarization converter enables favorable conversion characteristics to be achieved over the ultrawide-band frequency range BW.




When a linearly polarized signal is input to an input terminal of this ultrawide-band frequency linear-circular polarization converter, a circularly polarized signal is output from an output terminal of the ultrawide-band frequency linear-circular polarization converter where the linearly polarized signal is converted into the circular polarized signal, and vice versa. A predetermined linear-circular polarization conversion can be applied to a polarized signal over the ultrawide band frequency range BW.





FIGS. 3A

,


3


B,


3


C, and


3


D are cross-sectional views showing construction examples of other noncircular waveguides in which the above negative-phase characteristics can be obtained over the ultrawide band frequency range BW.




In this case, a noncircular waveguide


11


shown in

FIGS. 3A and 3B

is constructed by providing a ridged conductor structure


12


at the inner wall thereof.




A noncircular waveguide


13


shown in

FIGS. 3C and 3D

is constructed by providing ridged conductor structures


14


and


15


at parts of the inner wall thereof which face each other.




Instead of using the elliptic (noncircular) waveguide


1


as shown in

FIG. 1A

, by using the noncircular waveguide


11


or


13


having the construction shown in

FIG. 3A

or


3


C, the negative-phase characteristics shown in

FIG. 2B

may be also obtained over the ultrawide band frequency range BW.





FIGS. 4A

,


4


B,


4


C, and


4


D are cross-sectional views showing construction examples of other planar dielectric structures in which the above positive-phase characteristics can be obtained over the ultrawide band frequency range BW.




In this case, a planar dielectric structure


16


shown in

FIG. 4A

, which is identical to the planar dielectric structure


52


shown in

FIG. 5B

, has both side faces thereof extending in the longitudinal direction cut inwardly in a generally triangular shape.




A planar dielectric structure


17


shown in

FIG. 4B

has both side faces thereof extending in the longitudinal direction cut inwardly in a generally rectangular shape.




A planar dielectric structure


18


shown in

FIG. 4C

is provided at one side of the inner wall of a waveguide, and the height of the dielectric structure


18


in the longitudinal direction thereof is varied in a circular manner.




A planar dielectric structure


19


shown in

FIG. 4D

is provided at one side of the inner wall of a waveguide, and the height of the dielectric structure


18


in the longitudinal direction thereof is varied in a triangular manner.




Instead of using the planar dielectric structure


2


in

FIGS. 1B and 1C

, by using the planar dielectric structure


16


,


17


,


18


, or


19


having the construction shown in

FIGS. 4A

,


4


B,


4


C, or


4


D, the positive-phase characteristics shown in

FIG. 2C

may be also obtained in the ultrawide band frequency range BW.




In each embodiment described above, the examples in which the elliptic waveguides


1


,


11


, and


13


are employed as a waveguide for obtaining the negative-phase characteristics as shown in

FIG. 2B

over the ultrawide-band frequency range BW are described. However, in the present invention, waveguides enabling the above negative-phase characteristics to be obtained are not limited to those elliptic waveguides. Noncircular waveguides apart from elliptic waveguides, such as rectangular waveguides or their analog, may obtain such negative-phase characteristics.




As described above, according to the present invention, by combining the noncircular waveguide having negative-phase characteristics and the dielectric structure having positive-phase characteristics which complement the negative-phase characteristics, the following advantages are obtained: the ultrawide-band linear-circular polarization converter can be caused to have generally flat frequency-versus-phase characteristics which enable favorable linear-circular polarization conversion to be performed in the ultrawide-band frequency range; and the ultrawide-band linear-circular polarization converter can be obtained, having a simple construction, without causing an increase in manufacturing cost or the like.



Claims
  • 1. An ultrawide-band linear-circular polarization converter comprising:a waveguide having two orthogonal axes, which consist of a long axis and a short axis, in cross-section with different dimensions, the waveguide having negative-phase characteristics, wherein a phase of the long-axis and a phase of the short-axis have different phase delays as waves propagate through the waveguide in a direction of the long-axis and the short-axis, and a phase difference between the long-axis and the short-axis gradually decreases as a frequency increases within an ultrawide-band frequency range; and a dielectric member which extends along the short axis in the waveguide and which is arranged in a waveguide axis direction, the dielectric member having positive-phase characteristics, wherein the phase of the long-axis and the phase of the short-axis components have different phase delays as waves propagate through the dielectric member in the direction of the short-axis and the long axis, and the phase difference between the long-axis and the short-axis gradually increases as the frequency increases within the ultrawide-band frequency range, wherein complementary phase characteristics combining the negative-phase characteristics and the positive-phase characteristics are exhibited in accordance with an arrangement of the dielectric member.
  • 2. An ultrawide band linear-circular polarization converter according to claim 1, wherein said waveguide is an elliptic waveguide in cross section of a waveguide passage.
  • 3. An ultrawide-band linear-circular polarization converter according to claim 1, wherein:the cross section view of the dielectric member comprise edge parts extending in the waveguide passage of said waveguide that are thinner than the middle portion between the edge parts of the member.
  • 4. An ultrawide-band linear-circular polarization converter according to claim 1, wherein:a ridged conductor structure is positioned at the inner wall of a noncircular waveguide in cross section of a waveguide passage.
  • 5. An ultrawide-band linear-circular polarization converter according to claim 1, comprise:the dielectric member positioned at one side of an inner wall of the waveguide such that, when measured from a top surface of the waveguide, a height of the dielectric member stays constant from left edge part to half way to middle portion, then increases and stays constant until half way close to the right edge, then decreases and stay constant, when viewed from a cross sectional view of the member.
  • 6. An ultrawide-band linear-circular polarization converter according to claim 1, comprising:the dielectric member having both sides faces extending in a longitudinal direction cut inwardly in a generally triangular shape when viewed from a cross sectional view of the member.
  • 7. An ultrawide-band linear-circular polarization converter according to claim 1, comprising:the dielectric member having both side faces extending in a longitudinal direction cut inwardly in a generally rectangular shape when viewed from a cross sectional view of the member.
  • 8. An ultrawide-band circular polarization converter according to claim 1, when viewed from the cross sectional view of the waveguide comprising:a semi-circular shaped dielectric member positioned at one side of an inner wall of the waveguide such that a height of the dielectric member, when measured from a top surface of the waveguide, increases from edge parts to the middle portion of the member.
  • 9. An ultrawide-band linear-circular polarization according to claim 1, when viewed from the cross sectional view of the waveguide comprising:a triangular shaped dielectric member positioned at one side of an inner wall of the waveguide such that a height of the dielectric member, when measured from a top surface of the waveguide, increases from the edge parts to the middle portion of the member.
Priority Claims (1)
Number Date Country Kind
11-089960 Mar 1999 JP
US Referenced Citations (3)
Number Name Date Kind
4100514 DiTullio et al. Jul 1978 A
4344048 Mörz Aug 1982 A
4672334 Saad Jun 1987 A
Foreign Referenced Citations (3)
Number Date Country
00 30 2503 Jun 2000 EP
720153 Dec 1954 GB
7-142901 Jul 1995 JP
Non-Patent Literature Citations (5)
Entry
XP-002138855; International Journal of Electronics, Circularly Polarized Elliptical Beamshape Horn Antennas; (28 pages), Aug. 1982.
Alliance for Telecommunications Industry Solutions, Phase Delay, available at http://www.atis.org/home.htm and http://www.atis.org/tg2k/_phase_delay.html., pp. 1-4, printed on Feb. 5, 2003 and Feb. 13, 2003.
AML Wireless Systems, Glossary of Terms, available at http://www.amlwireless.com/list.htm, pp. 1-34, printed on Feb. 5, 2003.
Alliance for Telecommunications Industry Solutions, Phase Delay, available at http://www.atis.org/home.htm and http://www.atis.org/tg2k/_phase_delay.html., pp. 1-4, printed on Feb. 5, 2003 and Feb. 13, 2003.
AML Wireless Systems, Glossary of Terms, available at http://www.amlwireless.com/list.htm, pp. 1-34, printed on Feb. 5, 2003.