Wideband transmission line balun

• US 5,296,823 A
• Filed: 09/04/1992
• Issued: 03/22/1994
• Est. Priority Date: 09/04/1992
• Status: Expired due to Fees

• Current Assignee: James Dietrich
• Original Assignee: James Dietrich
• Inventors: Dietrich, James
• Primary Examiner(s): GENSLER, PAUL L
• Application Number:
  US07/940,656
• Time in Patent Office: 564 Days
• Field of Search: 333/120, 333/25, 333/26, 333/161, 333/164
• US Class Current: 333/26
• CPC Class Codes: H01P 5/10 for coupling balanced lines or devices with unbalanced lines or devices

Abstract

A wideband transmission line balun divides an input signal equally between a single-conductor transmission line and a polarity reversing, two-conductor transmission line thereby providing balanced signals at the transmission line outputs. Simple printed circuit and shielded structures include a ferrite core interactive with the two-conductor transmission line for parasitic mode suppression.

Claims

1. A balun for converting between unbalanced and balanced signals and comprising:

(a) a first transmission line having an input and an output;

(b) a second transmission line having an input and an output;

(c) coupling means for dividing a power signal equally between said first transmission line input and said second transmission line input;

(d) said first transmission line and said second transmission line having substantially equal electrical lengths between said respective input and output;

(e) said first transmission line having a single electrical conductor;

(f) said second transmission line having a polarity reversing connection; and

(g) said balanced signals being taken at said first transmission line output and said second transmission line output.

2. A balun according to claim 1, further including ferrite means for suppressing parasitic transmission modes associated with said second transmission line.

3. A balun according to claim 1 wherein said second transmission line is wound in a coil configuration.

4. A balun according to claim 1 wherein said second transmission line is substantially one-quarter wavelength long.

5. A balun according to claim 1 wherein said coupling means comprises a parallel connection having said input of said first transmission line connected in parallel with said input of said second transmission line.

6. A balun according to claim 1 wherein said coupling means comprises a series connection having said input of said first transmission line connected in series with said input of said second transmission line.

7. A balun according to claim 1 wherein said first and said second transmission lines have characteristic impedance substantially 2Z₀ for matching an unbalanced impedance Z₀ to a balanced impedance 4Z₀.

8. A balun according to claim 1 wherein said first and said second transmission lines have characteristic impedance substantially Z₀ /2 for matching an unbalanced impedance Z₀ to a balanced impedance Z₀.

9. A balun according to claim 1 wherein said first and said second transmission lines provide impedance transformation between said respective input and output.

10. A balun according to claim 1, further including,

(a) a dielectric substrate having first and second opposed, substantially parallel surfaces;

(b) said second surface of said dielectric substrate having a planar signal ground conductor disposed thereon; and

(c) said first surface of said dielectric substrate having said first transmission line disposed thereon.

11. A balun according to claim 1, further including:

(a) a dielectric substrate having first and second opposed, substantially parallel surfaces;

(b) said second surface of said dielectric substrate having a planar signal ground conductor disposed thereon; and

(c) said first transmission line and said second transmission line being located next to opposite surfaces of said dielectric substrate.

12. A balun according to claim 1, further comprising conductive shielding means for preventing external electrical coupling to said balun.

13. A balun according to claim 12 wherein said first transmission line is placed next to an inner surface of said shielding means.