Wave transmission lines and networks – Coupling networks – Balanced to unbalanced circuits
Patent
1992-04-23
1994-01-18
Gensler, Paul
Wave transmission lines and networks
Coupling networks
Balanced to unbalanced circuits
333246, H01P 5107
Patent
active
052802531
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a microwave circuit used in a microwave communication apparatus, a satellite broadcast receiving converter or the like.
BACKGROUND ART
Recently, there have been remarkable developments in microwave devices used in microwave communication apparatuses, and it is easy to procure low-noise devices such as HEMT and MES-FET, so that the noise factor in reception-type low-noise converters, in particular, is decreasing year after year. However, even if the low-noise microwave device itself exhibits a satisfactory noise factor, the loss and impedance mismatching between the input section and the microwave device have a significant influence, making it impossible, in some cases, to obtain a desired noise factor for the low-noise converter as a whole.
Such a conventional microwave circuit will be described with reference to the drawings.
FIG. 5 shows a short-circuit section of a conventional cylindrical-waveguide (hereinafter referred to simply as "CWG") - microstrip line (hereinafter referred to simply as "MSL") conversion section; FIG. 6 is a sectional view of the same; FIG. 7 is an enlarged view of a dielectric substrate forming an MSL; and FIG. 8 is a reverse-side view of the same.
In FIGS. 5 to 8, numeral 1 indicates a conductor strip of the MSL; numeral 2 indicates a dielectric substrate; numeral 3 indicates a metal body having a CWG 4; numeral 5 indicates a post; numeral 6 indicates a Teflon supporter; numeral 9 indicates a through-hole for connecting the conductor strip 1 with the post 5; and numeral 11 indicates a ground plane of the dielectric substrate 2.
The operation of the microwave circuit, constructed as described above, will be explained. First, in FIGS. 5 and 6, a microwave propagated through the CWG 4 is converted to a coaxial-line mode in the section of the post 5, and propagated through the coaxial line using the Teflon supporter 6 as an internal dielectric. Next, in FIGS. 7 and 8, the microwave propagated through the coaxial line is mode-converted by a matching pattern 10 provided in the ground plane 11 of the dielectric substrate 2 to an MSL having the same characteristic impedance as the coaxial line without involving any deterioration in characteristics. Then, the post 5, which constitutes the central conductor of the coaxial line, is connected to the conductor strip 1 through the through-hole 9.
In the above-described construction, however, a sufficient contact may not be attained between the portion of the ground plane around the matching pattern 10 of the dielectric substrate 2 and the metal body 3 due to any warp of the dielectric substrate 2 or an inadequate flatness of the metal body 3. In such a case, the characteristic impedance of the coaxial line differs from that of the MSL, and mismatching is caused, resulting in a passing loss and deterioration in VSWR.
In view of the above problem, it is an object of the present invention to provide a microwave circuit in which the external conductor of the coaxial line is held in an adequate contact with the ground plane of the MSL, thereby preventing a passing loss and deterioration in VSWR in the coaxial-line/MSL conversion section.
DISCLOSURE OF THE INVENTION
To achieve the above object, the microwave circuit of the present invention comprises a concentric-circle-like prominence formed on a contact surface which is on the side of a metal body serving as an external conductor of a coaxial line and which connects a conductor strip of an MSL formed on a dielectric substrate to an internal conductor of the coaxial line through a through-hole extending from a ground plane of the MSL through the dielectric substrate.
Due to the above construction of the present invention, the coaxial-line-external-conductor section on the side of the metal body is positively held in contact with the ground plane of the MSL by virtue of the concentric-circle-like prominence, so that no mismatching is involved and it is possible to prevent any loss and deterioration in VSWR in the coaxial-line/MSL conversion se
REFERENCES:
patent: 4837529 (1989-06-01), Gawronski et al.
patent: 4868639 (1989-09-01), Mugiya et al.
Aono Shozo
Deki Akihito
Kashima Yukiro
Kinoshita Akira
Nishioka Kazuyoshi
Gensler Paul
Matsushita Electric - Industrial Co., Ltd.
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