Wideband impedance transformer

Patent metadata

Field	Value
Publication number	US-9537198-B2
Application number	US-201414305808-A
Country	US
Kind code	B2
Filing date	Jun 16, 2014
Priority date	Oct 1, 2013
Publication date	Jan 3, 2017
Grant date	Jan 3, 2017

Abstract

Embodiments of a low-complexity and potentially physically small wideband impedance transformer that can be used in a combining network of a wideband Doherty amplifier are disclosed. In one embodiment, a wideband Doherty amplifier includes Doherty amplifier circuitry and a wideband combining network. The wideband combining network includes a wideband quarter-wave impedance transformer that includes a quarter-wave impedance transformer and compensation circuitry connected in parallel with the quarter-wave impedance transformer at a low-impedance end of the quarter-wave impedance transformer. The compensation circuitry is configured to reduce a total quality factor of the wideband quarter-wave impedance transformer as compared to a quality factor of the quarter-wave impedance transformer, which in turn increases a bandwidth of the wideband quarter-wave impedance transformer, and thus a bandwidth of the wideband Doherty amplifier.

First claim

What is claimed is:

1. A wideband quarter-wave impedance transformer, comprising:
a quarter-wave impedance transformer; and
compensation circuitry connected in parallel with the quarter-wave impedance transformer at a low-impedance end of the quarter-wave impedance transformer, the compensation circuitry configured to reduce a total quality factor of the wideband quarter-wave impedance transformer as compared to a quality factor of the quarter-wave impedance transformer.

2. The wideband quarter-wave impedance transformer of claim 1 wherein:
the compensation circuitry has a quality factor that is at least approximately equal to the quality factor of the quarter-wave impedance transformer such that the total quality factor of the wideband quarter-wave impedance transformer is less than the quality factor of the quarter-wave impedance transformer.

3. The wideband quarter-wave impedance transformer of claim 1 wherein the compensation circuitry comprises two open stubs connected in parallel to the quarter-wave impedance transformer at the low-impedance end of the quarter-wave impedance transformer.

4. The wideband quarter-wave impedance transformer of claim 3 wherein a total quality factor of the two open stubs is at least approximately equal to the quality factor of the quarter-wave impedance transformer such that the total quality factor of the wideband quarter-wave impedance transformer is less than the quality factor of the quarter-wave impedance transformer.

5. The wideband quarter-wave impedance transformer of claim 3 wherein the two open stubs are implemented by multi-layer transmission lines.

6. The wideband quarter-wave impedance transformer of claim 5 wherein a total quality factor of the two open stubs is at least approximately equal to the quality factor of the quarter-wave impedance transformer such that the total quality factor of the wideband quarter-wave impedance transformer is less than the quality factor of the quarter-wave impedance transformer.

7. The wideband quarter-wave impedance transformer of claim 3 wherein at least the two open stubs are implemented on a printed circuit board, and the two open stubs comprise:
a first open stub comprising a first portion in a first metal layer of the printed circuit board and a second portion in a second metal layer of the printed circuit board, wherein the first and second portions are connected by one or more vias; and
a second open stub comprising a third portion in the first metal layer of the printed circuit board and a fourth portion in the second metal layer of the printed circuit board, wherein the third and fourth portions of the second open stub are connected by one or more vias.

8. The wideband quarter-wave impedance transformer of claim 1 wherein the compensation circuitry comprises a half-wave transmission line connected in parallel to the quarter-wave impedance transformer at the low-impedance end of the quarter-wave impedance transformer such that:
a first portion of the half-wave transmission line that extends from the quarter-wave impedance transformer to a first end of the half-wave transmission line forms a first open stub having a first length; and
a second portion of the half-wave transmission line that extends from the quarter-wave impedance transformer to a second end of the half-wave transmission line forms a second open stub having a second length.

9. The wideband quarter-wave impedance transformer of claim 8 wherein the first and second lengths are configured such that a quality factor of the first and second open stubs is at least approximately equal to the quality factor of the quarter-wave impedance transformer such that the total quality factor of the wideband quarter-wave impedance transformer is less than the quality factor of the quarter-wave impedance transformer.

10. The wideband quarter-wave impedance transformer of claim 8 wherein the half-wave transmission line is a micro strip.

11. The wideband quarter-wave impedance transformer of claim 8 wherein the half-wave transmission line is coaxial line.

12. The wideband quarter-wave impedance transformer of claim 8 wherein the half-wave transmission line is bent or meandered.

13. The wideband quarter-wave impedance transformer of claim 8 wherein the first and second lengths are optimized to maximize a bandwidth of the wideband quarter-wave impedance transformer.

14. The wideband quarter-wave impedance transformer of claim 1 wherein the wideband quarter-wave impedance transformer has a relative radio frequency bandwidth that is greater than 40%.

Assignees

• Ericsson Telefon Ab L M

Inventors

• Seneviratne Sashieka
• Spokoinyi Igor

Classifications

• H03F1/42

  Modifications of amplifiers to extend the bandwidth · CPC title

• H03F1/565

  using inductive elements · CPC title

• H03F2200/451

  the amplifier being a radio frequency amplifier · CPC title

• H01P1/20345 Primary

  Multilayer filters · CPC title

• H01P1/2039

  Galvanic coupling between Input/Output · CPC title