High-frequency signal transmission line
A flexible high-frequency signal transmission line includes a dielectric body including laminated flexible dielectric layers. A signal line is provided in the dielectric body. A grounding conductor is arranged in the dielectric body to be opposed to the signal line via one of the dielectric layers. The grounding conductor is of a ladder structure including a plurality of openings and a plurality of bridges arranged alternately along the signal line. A characteristic impedance of the signal line changes between two adjacent ones of the plurality of bridges such that the characteristic impedance of the signal line rises from a minimum value to an intermediate value and to a maximum value and falls from the maximum value to the intermediate value and to the minimum value in this order.
1. A high-frequency signal transmission line comprising:
a dielectric body including laminated dielectric layers;
a linear signal line provided in the dielectric body;
a first grounding conductor that is opposed to the signal line via one of the dielectric layers, the first grounding conductor having a ladder structure including a plurality of openings and a plurality of bridges alternately arranged in a longitudinal direction in which the signal line extends; and
a floating conductor that is opposed to the signal line via the plurality of openings of the first grounding conductor, the floating conductor is not connected to the first grounding conductor, wherein
the floating conductor has a rectangular shape having a longitudinal dimension extending in the longitudinal direction in which the signal line extends; and
the floating conductor at least partially covers the plurality of openings.
2. The high-frequency signal transmission line according to claim 1 , wherein the width of the opening decreases towards the plurality of bridges in a step-by-step manner or a continuous manner.
3. The high-frequency signal transmission line according to claim 1 , wherein the dielectric layers are flexible.
4. The high-frequency signal transmission line according to claim 1 , wherein each of the plurality of openings has a shape that is symmetrical with respect to the signal line.
5. The high-frequency signal transmission line according to claim 1 , wherein the first grounding conductor includes no other openings between two adjacent ones of the plurality of openings.
6. The high-frequency signal transmission line according to claim 1 , wherein each of the plurality of openings has a continuously decreasing width from a center of the opening to both ends in the longitudinal direction in which the signal line extends.
7. The high-frequency signal transmission line according to claim 1 , wherein a width of the floating conductor is smaller than a width of the plurality of openings.
8. The high-frequency signal transmission line according to claim 7 , wherein the width of the floating conductor is larger than a width of the signal line.
9. The high-frequency signal transmission line according to claim 1 , wherein each of the plurality of openings includes a first width in an area where an impedance of the signal line exhibits a maximum value, and includes a second width smaller than the first width in an area where the impedance of the signal line exhibits a first intermediate value, the first and second widths being dimensions in a direction perpendicular to the longitudinal direction in which the signal line extends.
10. The high-frequency signal transmission line according to claim 9 , wherein each of the plurality of openings has a length greater than the first width, the length being a dimension in the longitudinal direction in which the signal line extends.
11. The high-frequency signal transmission line according to claim 1 , further comprising a second grounding conductor that is opposed to the first grounding conductor such that the signal line is sandwiched between the first grounding conductor and the second grounding conductor.
12. The high-frequency signal transmission line according to claim 11 , further comprising a via-hole conductor that pierces through the dielectric layers and that connects the first grounding conductor and the second grounding conductor to each other.
13. The high-frequency signal transmission line according to claim 11 , wherein the signal line is located closer to the first grounding conductor than to the second grounding conductor with respect to a thickness direction of the dielectric body.
14. A high-frequency signal transmission line comprising:
a dielectric body including laminated dielectric layers;
a linear signal line provided in the dielectric body;
a first grounding conductor that is opposed to the signal line via one of the dielectric layers, the first grounding conductor having a ladder structure including a plurality of openings and a plurality of bridges alternately arranged in an extending direction of the signal line;
a second grounding conductor that is opposed to the first grounding conductor such that the signal line is sandwiched between the first grounding conductor and the second grounding conductor;
a via-hole conductor that pierces through the dielectric layers and that connects the first grounding conductor and the second grounding conductor to each other; and
a floating conductor that is opposed to the signal line via the plurality of openings of the first grounding conductor, the floating conductor is not connected to the first grounding conductor.