Apparatus and methods for dynamic impedance matching of a guided wave launcher

• US 9,973,940 B1
• Filed: 02/27/2017
• Issued: 05/15/2018
• Est. Priority Date: 02/27/2017
• Status: Active Grant

• Current Assignee: AT&T Intellectual Property I LP (AT&T, Inc.)
• Original Assignee: AT&T Intellectual Property I LP (AT&T, Inc.)
• Inventors: Rappaport, Harold Lee
• Primary Examiner(s): Tran, Khanh C
• Application Number:
  US15/443,941
• Time in Patent Office: 442 Days
• CPC Class Codes: H01P 5/04 with variable factor of coupling
• CPC Class Codes: H01P 7/08 Strip line resonators
• CPC Class Codes: H03H 7/40 Automatic matching of load impedance to source impedance
• CPC Class Codes: H04B 3/04 Control of transmission; Equalising
• CPC Class Codes: H04B 3/36 Repeater circuits H04B3/58 takes precedence
• CPC Class Codes: H04B 3/46 Monitoring; Testing
• CPC Class Codes: H04B 3/52 Systems for transmission between fixed stations via waveguides
• CPC Class Codes: H04B 3/54 Systems for transmission via power distribution lines
• CPC Class Codes: H04W 16/18 Network planning tools

Abstract

Aspects of the subject disclosure may include, for example, a guided wave launcher generates, in response to an output RF signal, a guided electromagnetic wave along a surface of a transmission medium, wherein the guided electromagnetic wave propagates along the surface of the transmission medium without requiring an electrical return path, and wherein the guided electromagnetic wave has a non-optical carrier frequency. A mismatch probe generates a mismatch signal based on the output RF signal, wherein the mismatch signal indicates an impedance mismatch of the guided wave launcher. A controller generates one or more control signals in response to the mismatch signal, wherein the one or more control signals adjust one or more adjustable circuit elements of an impedance matching circuit, wherein adjustment of the one or more adjustable circuit elements facilitates reducing the impedance mismatch of the guided wave launcher. Other embodiments are disclosed.

Claims

1. A launcher, comprising:

an impedance matching circuit that includes one or more adjustable circuit elements, wherein the impedance matching circuit receives an input radio frequency (RF) signal and generates an output RF signal in response to the input RF signal;

a guided wave launcher configured to generate, in response to the output RF signal, a guided electromagnetic wave along a surface of a transmission medium, wherein the guided electromagnetic wave propagates along the surface of the transmission medium without requiring an electrical return path, and wherein the guided electromagnetic wave has a non-optical carrier frequency;

a mismatch probe configured to generate a mismatch signal based on the output RF signal, wherein the mismatch signal indicates an impedance mismatch of the guided wave launcher; and

a controller configured to generate one or more control signals in response to the mismatch signal, wherein the one or more control signals adjust the one or more adjustable circuit elements of the impedance matching circuit, wherein adjustment of the one or more adjustable circuit elements facilitates reducing the impedance mismatch of the guided wave launcher.

2. The launcher of claim 1, wherein the impedance matching circuit is configured as a pi-network, an L-network or a T-network.

3. The launcher of claim 1, wherein the one or more adjustable circuit elements include one or more adjustable impedances.

4. The launcher of claim 3, wherein the one or more adjustable impedances include an adjustable capacitor or an adjustable inductor.

5. The launcher of claim 3, wherein the one or more adjustable impedances include a plurality of adjustable impedances, wherein the one or more control signals include a plurality of control signals and wherein each of the plurality of control signals controls a corresponding one of the plurality of adjustable impedances.

6. The launcher of claim 1, wherein the one or more adjustable circuit elements include a tunable transformer.

7. The launcher of claim 1, wherein the mismatch probe includes a voltage detector, a standing wave ratio meter, a directional coupler or a reflectometer.

8. The launcher of claim 1, wherein the controller includes a look-up table.

9. The launcher of claim 1, wherein the guided electromagnetic wave is modulated via a wideband modulating signal and the impedance matching circuit provides wideband impedance matching of a transmitter to the guided wave launcher.

10. The launcher of claim 1, wherein the guided wave launcher has an impedance that changes based on a weather condition in an area of the transmission medium and wherein the one or more control signals adjust the one or more adjustable circuit elements of the impedance matching circuit to compensate for the impedance that changes based on the weather condition in the area of the transmission medium.

11. The launcher of claim 1, wherein the guided wave launcher is a horn launcher, a stripline launcher, a non-coaxial launcher, a reflective launcher, a slot launcher or a spiral launcher.

12. The launcher of claim 1, wherein the guided electromagnetic wave has a range of frequencies below 10 GHz.

13. The launcher of claim 1, wherein the guided electromagnetic wave has a range of frequencies in a millimeter wave frequency band.

14. A method, comprising:

receiving an input radio frequency (RF) signal at an impedance matching circuit from a transmitter;

generating, via the impedance matching circuit, an output RF signal in response to the input RF signal;

generating, in response to the output RF signal and via a guided wave launcher, a guided electromagnetic wave along a surface of a transmission medium, wherein the guided electromagnetic wave propagates along the surface of the transmission medium without requiring an electrical return path, and wherein the transmission medium is opaque to optical signals;

generating a mismatch signal based on the output RF signal, wherein the mismatch signal indicates an impedance mismatch of the guided wave launcher;

generating one or more control signals in response to the mismatch signal; and

adjusting, in response to the one or more control signals, one or more adjustable circuit elements of the impedance matching circuit, wherein the adjusting facilitates reducing the impedance mismatch of the guided wave launcher to compensate for impedance changes of the guided wave launcher resulting from changing weather conditions in an area of the transmission medium.

15. The method of claim 14, wherein the impedance matching circuit is configured as a pi-network, an L-network or a T-network.

16. The method of claim 14, wherein the one or more adjustable circuit elements include an adjustable capacitor or an adjustable inductor.

17. The method of claim 14, wherein the one or more adjustable circuit elements include a tunable transformer.

18. The method of claim 14, wherein the one or more adjustable circuit elements include a plurality of adjustable circuit elements, wherein the one or more control signals include a plurality of control signals and wherein each of the plurality of control signals controls a corresponding one of the plurality of adjustable circuit elements.

19. A device, comprising:

circuit means for receiving an input radio frequency (RF) signal at an impedance matching circuit and generating an output RF signal in response to the input RF signal;

launcher means for generating, in response to the output RF signal, a guided electromagnetic wave along a surface of a transmission medium, wherein the guided electromagnetic wave propagates along the surface of the transmission medium without requiring an electrical return path, and wherein the guided electromagnetic wave has a non-optical carrier frequency;

probe means for generating a mismatch signal based on the output RF signal, wherein the mismatch signal indicates an impedance mismatch of the launcher means; and

controller means for generating one or more control signals in response to the mismatch signal, wherein the one or more control signals adjust an impedance of the circuit means, wherein the impedance reduces the impedance mismatch of the launcher means.

20. The device of claim 19, wherein an impedance of the launcher means changes based on a weather condition in an area of the transmission medium and wherein the one or more control signals adjust the impedance of the circuit means to compensate for changes of the impedance of the launcher means.