Communications: radio wave antennas – Antennas – Wave guide type
Reexamination Certificate
2002-09-20
2004-03-30
Wong, Don (Department: 2821)
Communications: radio wave antennas
Antennas
Wave guide type
C343S776000, C343S786000
Reexamination Certificate
active
06714166
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a converter for satellite broadcast reception for receiving radio waves that are transmitted from two satellites adjacent to each other. In particular, the invention relates to a converter for satellite broadcast reception that is suitable for the reception of circularly polarized radio waves that are transmitted from each satellite.
2. Description of the Related Art
In a converter for satellite broadcast reception for receiving radio waves that are transmitted from a plurality of satellites adjacent to each other, to receive, with one LNB (low noise block converter), left-handed polarized and right-handed polarized satellite broadcast signals that are transmitted from each of two satellites, for example, by causing those signals to enter separate waveguides, it is necessary to convert the left-handed polarized waves and right-handed polarized waves that have entered each waveguide into vertically polarized waves and horizontally polarized waves with a phase conversion portion and then receive the vertically polarized waves and the horizontally polarized waves by inputting those to a pair of probes.
As an example of such a converter for two-satellite broadcast reception, a converter is known in which dielectric feeders are held by the front end portions of two respective waveguides, a circuit board is disposed on the rear end side of the waveguides, and two sets of a probe for vertically polarized waves and a probe for horizontally polarized waves are patterned on the same surface of the circuit board in such a manner that the two sets correspond to the respective waveguides. A radiation portion and a phase conversion portion are integrated with each dielectric feeder at its respective ends in such a manner that the radiation portion projects forward from the open end of the waveguide and the phase conversion portion is inserted in and fixed to the waveguide. The probe for vertically polarized waves and the probe for horizontally polarized waves of each set are generally perpendicular to each other on the circuit board and the phase conversion portion of the dielectric feeder crosses each of the probe for vertically polarized waves and the probe for horizontally polarized waves so as to form an angle of about 45°. The circuit board is also provided with processing circuits, by which signals detected by the respective probes are frequency-converted into different intermediate frequency bands.
In the converter for two-satellite broadcast reception having the above-outlined configuration, when left-handed polarized waves and right-handed polarized waves that have been transmitted from each satellite enter one of the two dielectric feeders via the radiation portion, the left-handed polarized waves and the right-handed polarized waves are converted into vertically polarized waves and horizontally polarized waves in traveling through the dielectric feeder, which are input to the probe for vertically polarized waves and the probe for horizontally polarized waves that are provided on the circuit board. The use of the dielectric feeders having the phase conversion portions simplifies the shape of the waveguides thereby enables manufacturing cost reduction. And patterning the probes on the same surface shortens the overall length of the waveguides themselves and thereby makes it possible to reduce the size of the converter.
Incidentally, in the above conventional converter for satellite broadcast reception, since the two sets of a probe for vertically polarized waves and a probe for horizontally polarized waves are pattern on the same surface of the circuit board, there is a problem that isolation between vertically polarized waves and horizontally polarized waves is insufficient and hence a good cross-polarization characteristic cannot be obtained. To solve this problem, a technique has been proposed in which isolation between vertically polarized waves and horizontally polarized waves is secured by forming square or circular minute radiation patterns are formed on the circuit board at intersecting points of the extensions of the probes for vertically polarized waves and the probes for horizontally polarized waves.
However, each minute radiation pattern is symmetrical with respect to the axial lines of the probe for vertically polarized waves and the probe for horizontally polarized waves. Therefore, if the size (area) of each minute radiation pattern is made small, good isolation between vertically polarized waves and horizontally polarized waves cannot be obtained. Conversely, if each minute radiation pattern is made large, a problem arises that the reflection component increases to cause undue transmission loss. The use of such minute radiation patterns causes another problem. If the positional relationship between the dielectric feeder and the minute radiation pattern and other factors are not the same in the two waveguides, a phase deviation occurs between linearly polarized waves in either waveguide. Therefore, the layout of the probes and signal lines on the circuit board is determined automatically; that is, the degree of freedom in circuit designing is low.
SUMMARY OF THE INVENTION
The present invention has been made in view of the above circumstances in the art, and an object of the invention is therefore to provide a converter for satellite broadcast reception capable of increasing the degree of freedom in circuit designing while securing isolation between vertically polarized waves and horizontally polarized waves.
To attain the above object, the invention provides a converter for satellite broadcast reception having a pair of hollow waveguides, first and second dielectric feeders held by the respective waveguides, and a circuit board that is disposed perpendicularly to the axial lines of the respective waveguides in which left-handed and right-handed circularly polarized waves transmitted from each of two satellites adjacent to each other enter a radiation portion of one of the first and second dielectric feeders and are converted by a phase conversion portion of the one of the first and second dielectric feeders into vertically polarized waves and horizontally polarized waves, respectively, which are input to a probe for vertically polarized waves and a probe for horizontally polarized waves, respectively, that are provided on the circuit board, the converter comprising a first minute radiation pattern and a second minute radiation pattern each being provided on the circuit board so as to be inclined electrically by about 45° from the respective axial lines of the probe for vertically polarized waves and the probe for horizontally polarized waves, the first minute radiation pattern being approximately perpendicular to the phase conversion portion of the first dielectric feeder, the second minute radiation pattern being approximately parallel with the phase conversion portion of the second dielectric feeder, wherein the phase conversion portion of the first dielectric feeder is longer than that of the second dielectric feeder.
In the above-configured converter for satellite broadcast reception, each of the first minute radiation pattern and the second minute radiation pattern that are formed on the circuit board so as to correspond to the two respective dielectric feeders is inclined electrically by about 45° from the axial lines of the probe for vertically polarized waves and the probe for horizontally polarized waves. Therefore, the electric field disorder in each waveguide is suppressed by the relatively small, minute radiation pattern, and hence isolation between vertically polarized waves and horizontally polarized waves can be secured. Since the first minute radiation pattern is approximately perpendicular to the phase conversion portion of the first dielectric feeder and the second minute radiation pattern is approximately parallel with the phase conversion portion of the second dielectric feeder, the degree of freedom in the layout of the probes and signal lines on the circuit b
Dou Yuanzhu
Nakagawa Masashi
Sasaki Kazuhiro
Alps Electric Co. ,Ltd.
Brinks Hofer Gilson & Lione
Chen Shih-Chao
Wong Don
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