Narrow impedance conversion device
View Patent ↗An impedance conversion device has four conductors arranged so that the first and second conductors form a transmission line having a first characteristic impedance, the third and fourth conductors form a transmission line having the first characteristic impedance, the first and third conductors form a transmission line having a second characteristic impedance, and the second and fourth conductors form a third transmission line having the second characteristic impedance. The second and fourth conductors are interconnected at proximate ends through a resistance equal to the first characteristic impedance. The third and fourth conductors are interconnected at proximate ends through a resistance equal to the second characteristic impedance. The lateral dimensions of the impedance conversion device are small enough to permit insertion in a stacked pair line.
1. An impedance conversion device comprising:
a first conductor having a first end and a second end;
a second conductor having a first end and a second end, disposed relative to the first conductor so that the first conductor and the second conductor form a first transmission line having a first characteristic impedance;
a third conductor having a first end and a second end, disposed relative to the first conductor so that the first conductor and the third conductor form a second transmission line having a second characteristic impedance different from the first characteristic impedance;
a fourth conductor having a first end and a second end, disposed relative to the second conductor so that the second conductor and the fourth conductor form a third transmission line having the second characteristic impedance, and disposed relative to the third conductor so that the third conductor and the fourth conductor form a fourth transmission line having the first characteristic impedance;
a first resistor having a resistance equal to the first characteristic impedance, having a first end connected to the second end of the second conductor and a second end connected to the second end of the fourth conductor; and
a second resistor having a resistance equal to the second characteristic impedance, having a first end connected to the first end of the third conductor and a second end connected to the first end of the fourth conductor; wherein
the second ends of the second and fourth conductors are mutually proximate; and
the first ends of the third and fourth conductors are mutually proximate.
2. The impedance conversion device of claim 1 , wherein:
the first conductor has an input part, a central part, and an output part;
the second conductor forms said first transmission line with the input part and the central part of the first conductor;
the third conductor forms said second transmission line with the central part and the output part of the first conductor; and
the fourth conductor forms said third transmission line with a part of the second conductor facing the central part of the first conductor, and forms said fourth transmission line with a part of the third conductor facing the central part of the first conductor.
3. The impedance conversion device of claim 2 , wherein the first, second, third, and fourth conductors are mutually parallel.
4. The impedance conversion device of claim 2 , wherein the input part, the central part, and the output part of the first conductor are mutually contiguous.
5. The impedance conversion device of claim 1 , wherein:
the first conductor and the second conductor are mutually spaced apart in a first direction;
the third conductor and the second conductor are mutually spaced apart in the first direction;
the first conductor and the third conductor are mutually spaced apart in a second direction orthogonal to the first direction; and
the second conductor and the fourth conductor are mutually spaced apart in the second direction.
6. The impedance conversion device of claim 5 , wherein each one of the first, second, third, and fourth conductors has a rectangular cross section with a first side extending in the first direction and a second side extending in the second direction.
7. The impedance conversion device of claim 1 , wherein the first and second conductors are mutually separated by a first distance, the first and third conductors are mutually separated by a second distance, and the fourth conductor is at least ten times as long as the first distance and at least ten times as long as the second distance.
8. The impedance conversion device of claim 7 , wherein the first, second, third, and fourth conductors transmit a signal having a fundamental wavelength, and the fourth conductor has a length not exceeding one-fourth of said fundamental wavelength.
9. The impedance conversion device of claim 1 , wherein the first, second, third, and fourth conductors transmit a signal having a fundamental wavelength, and the fourth conductor has a length not exceeding one-fourth of said fundamental wavelength.
10. The impedance conversion device of claim 1 , further comprising a dielectric member having two major surfaces, the first and third conductors being disposed on one of said major surfaces, the second and fourth conductors being disposed on another one of said major surfaces.
11. The impedance conversion device of claim 1 , further comprising a dielectric member within which the first, second, third, and fourth conductors are embedded.