Waveguide converter for transmitting input radio waves

Abstract: A bend portion (6) is provided on the inside of a waveguide main body (1) for bending a proceeding direction (A) of a radio wave from a waveguide (11) on the side of a primary feed horn and transmitting the radio wave with its proceeding direction changed such that an electric field of the radio wave is in parallel with a conversion unit (7). Further provided on the inside of the waveguide main body 1 is a conversion unit (7) comprised of a microstrip line (20) for converting the radio wave from the bend portion (6) to supply electric power.

Description: The present invention relates generally to waveguide converters, and more particularly, to a structure of a waveguide input unit for a satellite communication/satellite broadcasting receiving outdoor converter (also referred to as "LNB" hereinafter) mounted on an outdoor antenna for receiving satellite broadcasting. In general, a waveguide inlet of a LNB is provided between a waveguide on the side of a primary feed horn of a BS antenna and a main body of the waveguide of the LNB for receiving a radio wave of a predetermined band. The waveguide on the side of the primary feed horn constitutes an output side of the BS antenna (a parabola antenna etc.), while a probe connected to a microstrip line is provided in the waveguide main body of the LNB. Fig. 4 is a sectional view showing a structure of an inlet of a conventional LNB waveguide. In this conventional example, a probe 3 is provided so as to jut out of a hole 2 provided at an inner side surface of a hole 4 of a waveguide main body 1 into the hole 4. The probe 3 is coupled to a strip conductor (not shown) of a microstrip line 20 through a junction portion 5. Then, a radio wave in the waveguide main body 1 is transmitted through the probe 3. With the structure of the conventional example shown in Fig. 4, however, the portion 5 at which the strip conductor of the microstrip line 20 and the probe 3 are coupled to each other generates a signal loss. This is because the use of the probe 3, commonly in the form of a conductor of brass etc. surrounded by resin such as Teflon, causes variations of elements in size, variations in diameter of holes of the microstrip line 20 to which the probe 3 is attached and the amount of soldering for fixing the junction portion 5, resulting in generation of a signal loss. The signal loss adversely affects a noise figure (in general, a target noise figure is on the order of 1.0dB, which is reduced by 0.03-0.07dB due to said signal loss). Therefore, signal loss has needed to be compensated for and adjusted by the strip conductor on the microstrip line 20. This increases operation loss. In addition, the necessity of providing the hole 2 with a precise diameter size and fine-finished surface at the side of the hole 4 of the waveguide main body 1 along with the necessity of an expensive probe make the LNB waveguide inlet inapplicable to mass production and unprofitable. The present invention seeks to alleviate those disadvantages in the known converters. US Patent No. 4550296 discloses a form of waveguide-to-stripline converter in which an input waveguide section separates to accommodate a microstrip portion having a microstrip conductor which projects into the waveguide through a channel in a sidewall of the waveguide section. The microwaves impinge upon the microstrip conductor in a direction parallel both to the direction of propagation in the waveguide and to the plane of the microstrip portion. According to the present invention, as defined in claim 1, there is provided a waveguide-to-stripline converter comprising a waveguide section (1) for receiving a radio wave propagating in a predetermined direction (A) from a waveguide (11), and a microstrip line (20) for picking up said radio wave, wherein said microstrip line includes a plate-like dielectric (10), a ground conductor (9) on one side of said dielectric, and a strip conductor (8) on the other side of said dielectric, said microstrip line lying in a plane parallel to said predetermined direction (A), and wherein said strip conductor has a portion (7) on which the radio wave impinges with the orientation of the electric field of the radio wave parallel to said portion (7), characterised in that said waveguide section (1) includes waveguide bend means (6) for changing the propagation direction of the received radio wave so that it impinges on said portion (7) of the strip conductor (8) in a direction transverse to said predetermined direction (A), and to the plane of said microstrip line (20), and with said orientation of its electric field. Since the waveguide-to-stripline converter structured as defined above changes the propagation direction of an input radio wave and transmits the radio wave having its propagation direction changed to the microstrip line, signal loss is reduced without requiring an expensive probe. Preferred features of the embodiment are defined in sub-claims 2 to 4. An embodiment of the invention will now be described by way of example, with reference to the accompanying drawings, in which:- Fig. 1 is a schematic sectional view showing a structure of a main part of a waveguide-to-stripline converter according to an embodiment of the present invention; Fig. 2 is a view seen from II-II line of Fig. 1; Fig. 3 is a perspective view showing a specific structure of a microstrip line shown in Fig. 1; and Fig. 4 is a schematic sectional view showing a structure of a main part of a conventional waveguide-to-stripline converter. As shown in Figs. 1 and 2, the waveguide converter of the present embodiment is structured such that a waveguide main body 1 to be coupled to a waveguide 11 on the side of a primary feed horn includes a bend portion 6 for bending the proceeding direction of a radio wave from the waveguide on the primary feed horn and transmitting the radio wave having its direction of propagation changed, and a conversion unit 7 comprising part of a microstrip line 20 for converting the radio wave from the bend portion 6 to supply an electric power. As described above, in the present embodiment, the bend portion 6 for bending the radio wave so as to transmit an electric field in the waveguide is provided deep in the hole 4 of the waveguide main body 1. The bend portion 6 transmits the radio wave to the microstrip line 20 located in parallel with the radio wave proceeding direction A (arrows of Fig. 1). The radio wave proceeding direction A and the direction of the installation of the microstrip line 20 are in parallel with an axis direction X of the waveguide converter. That is, the present embodiment can improve a radio wave conversion efficiency because the waveguide of the present embodiment operates by bending a propagation direction of a radio wave from the waveguide 11 on the primary feed horn such that an electric field of the radio wave is in parallel with the conversion unit 7. Fig. 3 schematically shows the microstrip line 20 constituting the conversion unit 7, with a part of which omitted. As shown in the figure, the microstrip line 20 mainly includes a dielectric 10, a conductor 9 for grounding provided on one side of the dielectric and a strip conductor 8 provided on the other side thereof. A part of the strip conductor 8 serves as the conversion unit 7. The strip conductor part of the microstrip line 20 other than the part of the conversion unit 7, is provided with a conductor pattern and elements such as transistors as in the conventional example and the strip conductor part serves as a unit for transmitting a converted signal. Then, the strip conductor part other than the portion forming the conversion unit 7 is directly connected to that portion of the strip conductor 8 forming the conversion unit 7 on the microstrip line 20. The size of the strip conductor in the conversion unit 7 according to the present embodiment is 1.95mm for X and 6.45mm for Y. Such structure of the present embodiment does not require the probe 3 and involves no loss in conversion through probe or in coupling the microstrip line 20, so that it is possible to avoid deterioration of performance quality by using a low noise converter. In addition, there is no need for soldering of the probe 3 to the microstrip line 20, adjusting the microstrip line 20 and processing of a precise probe hole in the waveguide main body, whereby mass production of the waveguide converters is enhanced. Furthermore, avoiding the need for processing a hole in a waveguide main body leads to a reduction of material costs, and avoiding the need for a probe 3 and associated processes results in a large reduction of material costs and processing costs, thereby significantly improving profitability. Although the present invention has been described and illustrated in detail, it is clearly understood that the same is by way of illustration and example only and is not to be taken by way of limitation, the scope of the present invention being limited only by the terms of the appended claims.

Claims: A waveguide-to-stripline converter comprising a waveguide section (1) for receiving a radio wave propagating in a predetermined direction (A) from a waveguide (11), and a microstrip line (20) for picking up said radio wave, wherein said microstrip line includes a plate-like dielectric (10), a ground conductor (9) on one side of said dielectric, and a strip conductor (8) on the other side of said dielectric, said microstrip line lying in a plane parallel to said predetermined direction (A), and wherein said strip conductor has a portion (7) on which the radio wave impinges with the orientation of the electric field of the radio wave parallel to said portion (7), characterised in that said waveguide section (1) includes waveguide bend means (6) for changing the propagation direction of the received radio wave so that it impinges on said portion (7) of the strip conductor (8) in a direction transverse to said predetermined direction (A), and to the plane of said microstrip line (20), and with said orientation of its electric field. A waveguide-to-stripline converter according to claim 1, wherein said predetermined direction (A) and said microstrip line (20) are both parallel with an axis direction (X) of said waveguide-to-stripline converter. A waveguide-to-stripline converter according to claim 2, wherein said portion (7) of said strip conductor extends parallel to said axis direction (X) of said waveguide-to-stripline converter. A waveguide-to-stripline converter according to any preceding claim, wherein said waveguide section (1) includes an opening (4) for receiving said radio wave from the waveguide (11) and an inner portion (6) in waveguide communication with said opening (4) and bent toward the surface of said microstrip line (20) so as to constitute said bend means.

Inventors: HIROTA MAKOTO, HIROTA, MAKOTO
Applicants: SHARP KK, SHARP KABUSHIKI KAISHA
Application year: 1992
Main classification: H01P5
IPC codes: H01P1, H01P5