The present invention relates to a transmission line transition, which is suited for a communication system using a microwave or millimeter wave band, and which is capable of making conversion from a microstrip transmission line to a coplanar strip transmission line or from a conductor for a coplanar strip transmission line to a microstrip transmission line.
Coplanar strip transmission lines have been generally utilized as transmission lines, which feed a signal to a planar antenna or transmit a signal received by a planar antenna when the planar antenna is utilized for communication using a microwave or millimeter-wave band.
A transmission line transition, which has been utilized to make conversion from a microstrip transmission line to a slot transmission line possible and conversion from the slot transmission line to a coplanar strip transmission line possible, is shown in
Additionally, the above-mentioned prior art reference is silent on specific dimensions of the electromagnetically coupling conductor 24 for a coplanar strip transmission line and the like.
It is an object of the present invention to solve the above-mentioned problems involved in the prior art and to provide a novel transmission line transition.
The present invention provides a transmission line transition comprising:
a first dielectric substrate;
a second dielectric substrate spaced from the first dielectric substrate;
a dielectric layer interposed between the first dielectric substrate and the second dielectric substrate;
the first dielectric substrate having a pair of conductors for a coplanar strip transmission line and an electromagnetically coupling conductor for the coplanar strip transmission line disposed on a surface close to the dielectric layer;
the electromagnetically coupling conductor for the coplanar strip transmission line being formed in a semi-loop shape with a discontinuity partly formed therein;
respective portions of the electromagnetically coupling conductor for the coplanar strip transmission line, which are located at both ends of the discontinuity or in the vicinity of both ends of the discontinuity, being connected to respective ends of the paired conductors for the coplanar strip transmission line or portions of the paired conductors in the vicinity of the respective ends of the paired conductors, the paired conductors extending toward a direction to be apart from the electromagnetically coupling conductor;
the semi-loop shape being a rectangular shape or a substantially rectangular shape;
the second dielectric substrate having a grounding conductor disposed on a surface close to the dielectric layer, the grounding conductor having a first slot and a second slot formed therein so as to be parallel or substantially parallel to each other;
the grounding conductor further having a connecting slot formed therein so as to connect between the first slot and the second slot so that the first slot, the second slot and the connecting slot form an electromagnetic coupling slot in an H-character shape or substantially H-character shape;
the electromagnetic coupling slot being disposed so that the connecting slot intersects a longitudinal direction of the rectangular shape or the substantially rectangular shape of the semi-loop shape as viewed in a plan view; and
the second dielectric substrate having an electromagnetically coupling conductor for a microstrip transmission line disposed on a surface remote from the dielectric layer so as to pass over or under the connecting slot.
The present invention also provides a transmission line transition comprising:
a first dielectric substrate;
a second dielectric substrate spaced from the first dielectric substrate;
a dielectric layer interposed between the first dielectric substrate and the second dielectric substrate;
the first dielectric substrate having a pair of conductors for a coplanar strip transmission line and an electromagnetically coupling conductor for the coplanar strip transmission line disposed on a surface close to the dielectric layer;
the electromagnetically coupling conductor for the coplanar strip transmission line being formed in a semi-loop shape with a discontinuity partly formed therein;
respective portions of the electromagnetically coupling conductor for the coplanar strip transmission line, which are located at both ends of the discontinuity or in the vicinity of both ends of the discontinuity, being connected to respective ends of the paired conductors for the coplanar strip transmission line or portions of the paired conductors in the vicinity of the respective ends of the paired conductors, the paired conductors extending toward a direction to be apart from the electromagnetically coupling conductor;
the semi-loop shape being a square shape or a substantially square shape;
the second dielectric substrate having a grounding conductor disposed on a surface close to the dielectric layer, the grounding conductor having a first slot and a second slot formed therein so as to be parallel or substantially parallel to each other;
the grounding conductor further having a connecting slot formed therein so as to connect between the first slot and the second slot so that the first slot, the second slot and the connecting slot form an electromagnetic coupling slot in an H-character shape or substantially H-character shape;
the electromagnetic coupling slot being disposed so that a portion of the connecting slot extending in a longitudinal direction passes over or under a side of the electromagnetically coupling conductor for the coplanar strip transmission line remote from the discontinuity; and
the second dielectric substrate having an electromagnetically coupling conductor for a microstrip transmission line disposed on a surface remote from the dielectric layer so as to pass over or under the connecting slot.
In accordance with the present invention, the electromagnetically coupling conductor for a coplanar strip transmission line is formed in a semi-loop shape with a discontinuity formed therein, and the respective portions of the electromagnetically coupling conductor for the coplanar strip transmission line, which are located at both ends of the discontinuity or in the vicinity of both ends of the discontinuity, are connected to the respective ends of the paired conductors for the coplanar strip transmission line or portions of the paired conductors for the coplanar strip transmission line in the vicinity of the respective ends of the paired conductors. When the semi-loop shape is a rectangular shape or a substantially rectangular shape, the transmission line transition can be made compact by 8.5 to 61% in comparison with the prior art.
When the semi-loop shape is a square shape or a substantially square shape, the transmission line transition can be made compact by 20 to 30% in comparison with the prior art.
The present invention can utilize the above-mentioned structure to realize transmission line conversion and impedance matching between the microstrip transmission line and the coplanar strip transmission line. Additionally, the present invention has an advantage of being capable of fabricating a transmission line transition at a low cost by a simple structure.
When a transmission line transition according to the present invention is utilized as a planar antenna transmission line, which is disposed at the front windshield or the rear windshield of an automobile, it is possible to effectively produce a high frequency antenna. In particular, it is possible to fabricate a high frequency antenna, which is suited for SDARS (Satellite Digital Audio Radio Service for about 2.6 GHz), GPS (Global Positioning System), VICS (Vehicle Information and Communication System), ETC (Electronic Toll Collection System), DSRC (Dedicated Short Range Communication) system and the like.
For a more complete understanding of the present invention and the advantages thereof, reference is now made to the following description taken in conjunction with the accompanying drawings, wherein like reference numbers represent like parts, and which may not be described in detail for all drawing figures:
Now, a transmission line transition according to the present invention will be described based on preferred embodiments shown in the accompanying drawings.
In FIGS. 1,2 and 3, reference numeral 1 (
In the embodiment shown in
The transmission line transition according to the present invention as best shown in
As best shown in
In the present invention, as best shown in
Conductor width W3≦0.6×conductor width W4, and
Conductor width W3′0.6×conductor width W4
In the embodiment shown in
The second dielectric substrate 2 has the grounding conductor 12 disposed on a surface thereof close to the dielectric layer 7, and the grounding conductor 12 has the first slot 5a and the second slot 5b formed therein so as to be parallel or substantially parallel to each other. The grounding conductor 12 additionally has the connecting slot 5c formed therein to connect the first slot 5a and the second slot 5b, and the first slot 5a, the second slot 5b and the connecting slot 5c form the electromagnetically coupling slot 5 in an H-character shape or a substantially H-character shape.
In the embodiments shown in
The second dielectric substrate 2 has the electromagnetically coupling conductor 10 for the microstrip line disposed on a surface remote from the dielectric layer 7 so as to pass over or under the connecting slot 5c. In the embodiment shown in
When it is assumed that an imaginary straight line extends in a direction perpendicular to the first dielectric substrate 1 and passes through the center of the connecting slot 5c, and when the center of the connecting slot 5c is viewed from the imaginary straight line, it is preferred from the viewpoint of improving transmission efficiency that the point where the connecting slot 5c and the electromagnetically coupling conductor 10 for the microstrip line intersect each other overlap or substantially overlap with the center of the connecting slot 5c.
When it is assumed that the imaginary straight line extends in the direction perpendicular to the first dielectric substrate 1 and passes through the center of the connecting slot 5c, and when the center of the connecting slot 5c is viewed from the imaginary straight line, it is preferred from the viewpoint of improving transmission efficiency that the center of the connecting slot 5c overlap or substantially overlap with the side 4d of the electromagnetically coupling conductor 4 for the coplanar strip transmission line.
When it is assumed that the imaginary straight line extends in the direction perpendicular to the first dielectric substrate 1 and passes through the center of the connecting slot 5c, and when the center of the connecting slot 5c is viewed from the imaginary straight line, it is preferred from the viewpoint of improving transmission efficiency that the center of the connecting slot 5c overlap or substantially overlap with the center of the side 4d of the electromagnetically coupling conductor 4 for the coplanar strip transmission line.
As stated above, it is preferred from the viewpoint of improving transmission efficiency that a portion of the electromagnetically coupling slot 5 overlap with the electromagnetically coupling conductor 4 for the coplanar strip transmission line as viewed in such a plan view. However, the present invention is not limited to have this arrangement. The present invention is operable even if all portions of the electromagnetically coupling slot 5 are disposed inside an inner peripheral edge of the electromagnetically coupling conductor 4 for the coplanar strip transmission line (
In the embodiment shown in
The electromagnetically coupling conductor 4 for the coplanar strip transmission line according another embodiment, which is different from the embodiment shown in
It is preferred that each of all four outer peripheral apexes have a cut-out portion formed therein as in the embodiment shown in
In the embodiment shown in
The outer peripheral edge of the first conductor 3a for the coplanar strip transmission line means a peripheral edge of the first conductor 3a for the coplanar strip transmission line, which is remote from the gap 3b for the coplanar strip transmission line. The inner peripheral edge of the first conductor 3a for the coplanar strip transmission line means a peripheral edge of the first conductor 3a for the coplanar strip transmission line, which is close to the gap 3b for the coplanar strip transmission line.
Additionally, in the embodiment shown in
It is preferred that the electromagnetically coupling conductor 4 for the coplanar strip transmission line have both the first inner cut-out portion and the second inner cut-out portion formed therein as shown in
When the electromagnetically coupling conductor 4 for the coplanar strip transmission line has a short side length of L4, and when the electromagnetically coupling conductor for the coplanar strip transmission line has a long side length L5, it is preferred from the viewpoint of improving transmission efficiency that the formula of 0.11≦(L4/L5)<1.0, in particular 0.11≦(L4/L5)<0.65, be satisfied.
It is preferred from the viewpoint of improving transmission efficiency that the length L3 of the first slot and the length of the second slot be the same or substantially the same as each other. However, the present invention is not limited to have this arrangement. The present invention is operable even if the length L3 of the first slot and the length of the second slot are different from each other. It is preferred from the viewpoint of improving transmission efficiency that the length L3 of the first slot of the length of the second slot be normally shorter than the length L5.
It is preferred from the viewpoint of improving transmission efficiency that the width W2 of the first slot 5a and the width W2′ of the second slot 5b be from 0.1 to 1.0 mm, in particular from 0.2 to 0.6 mm. It is preferred from the viewpoint of improving transmission efficiency that the conductor width W1 of the electromagnetically coupling conductor 10 of the microstrip line be from 1.0 to 2.0 mm, in particular from 1.3 to 1.6 mm. It is preferred from the viewpoint of improving transmission efficiency that the distance L1 be from 3.0 to 15.0 mm, in particular from 5.0 to 10.0 mm.
In the present invention, when the operating frequency is from 1.95 to 2.93 GHz, it is preferred that the length L5 of the side of the electromagnetically coupling conductor 4 for the coplanar strip transmission line, which is remote from the discontinuity 4a, be from 5.0 to 46.1 mm. The reason why the operating frequency is set at a value from 1.95 to 2.93 GHz is that the formula of (2.34/1.2)−(2.34/0.8) GHz≈1.95−2.93 GHz is established, providing a tolerance range of 20% from 2.34 GHz that is the frequency of SDARS in the United States. The permissible range is preferably from 2.13 to 2.6 GHz with a tolerance range of 10%, more preferably from 2.23 to 2.46 GHz with a tolerance range of 5%.
The length L5 preferably ranges from 8.0 to 40.8 mm, more preferably ranges from 12.0 to 37.2 mm.
Under the condition of the above-mentioned operating frequency range, it is preferred that the length L4 of two sides of the electromagnetically coupling conductor 4 for the coplanar strip transmission line, which are adjacent the side 4d opposite the discontinuity 4a, be from 5.0 to 46.1 mm. The length L4 more preferably ranges from 8.0 to 40.8 mm, most preferably ranges from 12.0 to 37.2 mm.
The inner edge of a side 4e of the electromagnetically coupling conductor 4 for the coplanar strip transmission line, which forms one of the two sides adjacent the side 4d opposite the discontinuity 4a and is close to the first conductor 3a for the coplanar strip transmission line, is called a first inner edge. The inner edge of a side 4f of the electromagnetically coupling conductor 4 for the coplanar strip transmission line, which forms the other one of the two sides adjacent the side 4d opposite the discontinuity 4a and is close to the second conductor 3c for the coplanar strip transmission line, is called a second inner edge.
When the leading edge of the first slot 5a, which is close to the first inner edge, is called a first leading edge 5a1 (
It is determined that the value of Loffx1 is positive when the first leading edge 5a1 of the first slot approaches toward the center of the electromagnetically coupling conductor 4 for the coplanar strip transmission line in a direction (indicated by an arrow 41 in
It is determined that the value of Loffx2 is positive when the second leading edge 5a2 of the first slot approaches toward the center of the electromagnetically coupling conductor 4 for the coplanar strip transmission line in a direction (indicated by an arrow 42 in
It is preferred that the values of Loffx1 and Loffx2 satisfy the formulas of Loffx1≧0 mm and Loffx2≧0 mm. It is particularly preferred that the values of Loffx1 and Loffx2 satisfy the formulas of Loffx1≧1 mm and Loffx2≧1 mm.
It is determined that the value of Loffy is positive when the edge 5a3 of the first slot close to the connecting slot 4c is disposed so as to be close to the side 4d of the electromagnetically coupling conductor 4 for the coplanar strip transmission line remote from the discontinuity 4a with the outer edge 40 of the side of the electromagnetically coupling conductor 4 for the coplanar strip transmission line close to the paired conductors (3a, 3c) for the coplanar strip transmission line used as the boundary (
The value of Loffy preferably satisfies the formula of −3.5 mm≦Loffy≦7.3 mm, particularly preferably satisfies the formula of 1.0 mm≦Loffy≦6.5 mm.
There is no particular limitation to the thickness of the first dielectric substrate 1 since the thickness of the first dielectric substrate is not directly related to electromagnetic coupling. For example, when the first dielectric substrate comprises an automobile windshield, it is preferred to use a glass sheet having a thickness of from 2.0 to 6.0 mm and a dielectric constant of (ε1) of from 5.0 to 9.0 as in a normal automobile windshield.
When the first dielectric substrate 1 comprises an automobile windshield, it is preferred that the grounding conductor 12 have a peripheral edge spaced from the opening edge of an automobile body by a length of 1 mm or more. However, the present invention is not limited to have this arrangement. The present invention is operable even if the peripheral edge of the grounding conductor 12 is connected to the opening edge of an automobile body. In this case, the opening edge means a peripheral edge of an opening of an automobile body, into which a windshield is fitted, which serves as ground connection through the automobile body, and which is made of a conductive material, such as metal.
It is preferred that the second dielectric substrate 2 have dimensions (an area) of from 2.6×26.0 mm (67.6 mm2) to 15.0×31.0 mm (465 mm2). It is preferred from the viewpoint of improving transmission efficiency that the second dielectric substrate have a dielectric constant (ε2) of from 1.0 to 8.0. The second dielectric substrate 2 may be normally a circuit board comprising a synthetic resin, ceramics or the like. It is preferred that the second dielectric substrate 2 have a thickness of from 0.1 to 6.0 mm. This is because it is easy to fabricate a substrate in such a thickness range in terms of production technique.
It is preferred that the dielectric layer 7 be interposed between the first dielectric substrate 1 and the second dielectric substrate 2 and have an insulating property. The dielectric layer 7 may normally comprise a dielectric composition containing, e.g., a synthetic resin, such as an adhesive or a filler, having an insulating property, or ceramics. The dielectric layer may comprise a gas layer. However, the present invention is not limited to have such arrangements. Any dielectric substance is applicable as the dielectric layer, and a dielectric substrate is also applicable as the dielectric layer.
An example of the adhesive having an insulating property is an adhesive containing an epoxy resin or the like. It is preferred to use an adhesive having a dielectric constant ranging from 1.0 to 4.0 since such an adhesive is easily available at a low cost. An example of the filler is a filler containing silicone having an insulating property.
When the dielectric layer 7 comprises a gas layer, an air layer is normally used because of being inexpensive. The present invention is not limited to use such an air layer. The gas layer may comprise an inert gas, such as nitrogen or argon. It is preferred that such a gas layer be sufficiently dried so as to prevent the moisture contained in the gas from being condensed according to temperatures.
It is preferred that the dimensions or area of the dielectric layer 7 be the same as the dimensions or area of the second dielectric substrate 2. It is preferred from the viewpoints of improving transmission efficiency that the dielectric layer 7 have a thickness of from 0.1 to 1.6 mm. It is preferred from the viewpoint of improving transmission efficiency that the dielectric layer 7 have a dielectric constant (ε3) of from 1.0 to 3.0. It is preferred that the present invention be applied to a frequency range of from 1 to 30 GHz, in particular a frequency range from 2 to 6 GHz.
Now, the present invention will be described referring to examples. The present invention is not limited to these examples. It should be noted that various improvement and modifications may be made without departing from the spirit and the scope of the present invention. Now, the examples will be described in detail, referring to the accompanying drawings.
On the assumption that a transmission line transition was fabricated just as shown in
On the assumption that a transmission line transition was fabricated so as to be the same as the one in Example 1 except that Loffx1 and Loffx2 were modified, transmission characteristics from a pair of conductors 3 for a coplanar strip transmission line to an electromagnetically coupling conductor 10 for a microstrip line were calculated according to the FDTD method. The operating frequency was set at 2.34 GHz. Characteristics of Loffx1 to insertion loss, which were obtained when the values of Loffx1 and Loffx2 were modified, are shown in
On the assumption that a transmission line transition was fabricated so as to be the same as the one in Example 1 except that Loffy was modified, transmission characteristics from a pair of conductors 3 for a coplanar strip transmission line to an electromagnetically coupling conductor 10 for a microstrip line were calculated according to the FDTD method. The operating frequency was set at 2.34 GHz. Characteristics of Loffy to insertion loss, which were obtained when the value of Loffy was modified, are shown in
On the assumption that a transmission line transition was fabricated so as to be the same as the one in Example 1 except that the long side width L5 of an electromagnetically coupling conductor 4 for a coplanar strip transmission line was modified, transmission characteristics from a pair of conductors 3 for the coplanar strip transmission line to an electromagnetically coupling conductor 10 for a microstrip line were calculated according to the FDTD method. The operating frequency was set at 2.34 GHz. Characteristics of length L5 to insertion loss, which were obtained when the value of the with L5 was modified, are shown in
The present invention is applicable to a transmission line transition for a high frequency antenna, which is suitable for use in SDARS, GPS, satellite digital broadcasting, VICS, ETC and DSRC system.
The entire disclosure of Japanese Patent Application No. 2005-73190 filed on Mar. 15, 2005 including specification, claims, drawings and summary is incorporated herein by reference in its entirety.
Number | Date | Country | Kind |
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2005-073190 | Mar 2005 | JP | national |
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10-163713 | Jun 1998 | JP |
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Number | Date | Country | |
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20060208825 A1 | Sep 2006 | US |