Coplanar stripline with corrugated structure

Details Coplanar stripline with corrugated structure Coplanar stripline with corrugated structure

1999-06-10

2004-02-03

Lee, Benny (Department: 2817)

Wave transmission lines and networks

Plural channel systems

C333S238000

Reexamination Certificate

active

06686808

ABSTRACT:

CROSS-REFERENCE TO RELATED APPLICATIONS
The present invention claims priority and contains subject matter related to Japanese Patent Application No. 10-166939, filed with the Japanese Patent Office on Jun. 15, 1998, the entire contents of which are hereby incorporated by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a coplanar stripline for use in high-frequency transmission, particularly to the stripline provided with a corrugated structure, having an improved transmission capability.
2. Description of the Background
A coplanar stripline is known as a transmission line for high frequency electromagnetic waves such as those in microwave and millimeter wave regions, which has been incorporated in a monolithic microwave integrated circuit (MMIC) and microwave integrated circuit (MIC). The stripline is a coplanar type of the distributed constant circuit, which is constituted of a pair of strip conductor lines.
FIG. 4
illustrates electromagnetic field lines, or electric field and magnetic field component lines for the electromagnetic wave during the propagation. Referring to
FIG. 4
, a coplanar line
104
is composed of a pair of strip conductors
102
,
103
, each formed on a dielectric substrate
101
parallel to each other and separated by a predetermined distance. The construction of conductors in the coplanar striplines may thus be considered complimentary to that of the prior art coplanar waveguide.
The field lines includes the components of the electric field
401
and magnetic field
402
, of the electromagnetic wave, respectively. As shown in
FIG. 4
, it is known the components of the electric field
401
and magnetic field are located primarily in the area between, and surrounding, the strip conductors
102
,
103
, respectively.
The coplanar striplines have not been used often for several reasons such as a transmission loss larger than that of either micro striplines or coplanar waveguides and a difficulty caused by a complicated signal transfer to micro-strip lines.
Technological advances in the area of MMIC packaging are rapidly reducing the size of high frequency electronic assemblies. The distance of signal transmission is therefore reduced in the miniaturized circuits, and the transmission loss described above is becoming less significant.
In addition, along with the recent trend of the main stream of the high-frequency circuits toward uniplanar circuits from the previous circuits including microstrip lines, coplanar striplines and slot lines have been attracting much attention recently. Being able to be constructed with finite breadth of conductors, the coplanar striplines, in particular, are considered more advantageous, in principle, for miniaturization in contrast to the coplanar waveguides and slotlines, for which conductor strips of semi-infinite breadth have to be generally assumed.
Although the coplanar striplines are considered advantageous for the miniaturization because of finite breadth of conductors, as described above, the present inventors have realized shortcomings thereof, in that a plurality of the known coplanar striplines can not be disposed in close vicinity to each other or densely such as in an integrated circuit, because of the disturbance by crosstalk between the striplines. The present finding is based on the fact that the distribution of the electric field
401
and magnetic field
402
, of the electromagnetic wave of the present propagation mode, is somewhat different from the distribution shown previously in FIG.
4
.
As described earlier, the electric field components
401
have been considered to be located primarily in the area between the strip conductors
102
,
103
, as shown in FIG.
4
.
FIG. 5
is a perspective view of a coplanar stripline accompanied by an electric field
401
(represented by solid lines) and a magnetic field
402
(represented by dashed lines.
Referring now to
FIG. 5
, the difference mentioned above will be detailed hereinbelow, and is resolved by the present inventors. In addition to the electric field components
401
located primarily in the area between the strip conductors
102
,
103
(FIG.
4
), the present inventors have found an additional, concentrated distribution of the electric field component exists in the outside portion of the coplanar striplines
104
.
By the term “outside portion”, it is meant a side edge portion of each of the strip conductors
102
,
103
, which is positioned longitudinally and not facing to the other confronting strip conductor of the coplanar stripline. These side portions are shown in
FIG. 5
, as the left-hand side of the strip
102
and the right-hand side of the strip
103
both located on dielectric substrate
101
.
These side edge portions are hereinafter referred to as the outside portions, while the inside portions are those facing to the side edge of the other confronting strip conductor.
Referring now to
FIG. 5
, when an intense electric field
501
is applied to the outside portions of the strip conductors
102
,
103
, this gives rise to a large crosstalk between the neighboring stripline which is disposed in close vicinity to each other, to thereby cause a problem, in that a plurality of planar striplines can not be disposed close together. In such a circumstance, therefore, the aforementioned advantage for the coplanar stripline can not be fully utilized, for which a finite breadth for the strip conductor can be assumed, and therefore it cannot be any longer considered advantageous for achieving the miniaturization of the circuits.
The electric field distribution in
FIG. 5
is originated from the distribution of electric current flows illustrated in
FIG. 6
, in which a plurality of the arrows
601
,
602
designate the current flows including their direction. The current flows
601
are known previously to correspond to the electric field
401
of
FIG. 4
which is located in the in-between portions of the strip conductors
102
,
103
both located on dielectric substrate
101
, while other current flows
602
correspond to the electric field distribution applied to the outside portions of the strip conductors
102
,
103
.
As clearly seen from the arrows for illustrating the current flows shown in
FIG. 6
, there exist the current flows along the length of the strip conductor not only in the inside portions, but also in the outside portions, of the strip conductors
102
,
103
. The electric field
501
shown in
FIG. 5
is thus induced by the current flows
602
, thereby causing cross-talks between the neighboring striplines.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide a coplanar stripline, which overcomes the above-noted difficulties.
It is another object to provide coplanar striplines which is provided with a corrugated structure including a plurality of slits, having an improved transmission capability.
To achieve the foregoing and other objects, and to overcome the shortcomings discussed above, a coplanar stripline is provided for transmitting electrical data signals, including a dielectric substrate and a plurality of strip conductors formed on the dielectric substrate, substantially parallel to one another and separated by a predetermined distance. At least on one side of the strip conductors, a corrugated structure is provided, including a plurality of slits formed on the side of the strip conductor, so that the length direction thereof is substantially perpendicular to the direction of the electromagnetic wave transmitted through the coplanar stripline.
According to one aspect disclosed herein, a coplanar stripline is provided for transmitting electrical data signals, including a dielectric substrate, and first and second strip conductors formed on the dielectric substrate, substantially parallel to each other and separated by a predetermined distance. At least on one side of the strip conductors, a corrugated structure is provided, including a plurality of slits formed periodically on the side of the strip conductors, located in the outside portion of the

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