Active impedance matching in communications systems

• US 6,768,472 B2
• Filed: 05/23/2003
• Issued: 07/27/2004
• Est. Priority Date: 08/24/2001
• Status: Expired due to Fees

• Current Assignee: Avago Technologies General IP PTE Limited (Broadcom, Inc.)
• Original Assignee: Broadcom Corporation (Broadcom, Inc.)
• Inventors: De Flaviis, Franco, Alexopoulos, Nicolaos G.
• Primary Examiner(s): Vannucci, James
• Application Number:
  US10/443,739
• Publication Number:
  US 20030206141A1
• Time in Patent Office: 431 Days
• Field of Search: 343/860, 330/144, 330/284, 330/129, 330/145, 330/279, 363/15, 363/40, 363/95, 333/17
• US Class Current: 343/860
• CPC Class Codes: H03H 7/40 Automatic matching of load impedance to source impedance

Abstract

A signal sensing module senses an RF signal and produces one or more secondary signals representative of the RF signal. An impedance matching control module generates a control signal, based on the one or more secondary signals, which is indicative of an impedance mismatch between a load and a communications device. The control signal is then applied to at least one variable impedance device to adjust the impedance of an impedance matching network and thereby reduce the impedance mismatch between the load and the communications device. In an embodiment, the at least one variable impedance device is a barium strontium titanate, thin film, parallel plate capacitor. In other embodiments, other variable impedance devices such as other types of thin film capacitors or varactor diodes are used to adjust the impedance of the impedance matching network.

Claims

1. A system for coupling a load to a communications device, comprising:

a signal sensing module having at least a first, second, and third port;

an impedance matching module that is automatically reconfigured to match a load whose impedance changes over time, said impedance matching module having at least a first, second, and third port; and

an impedance matching control module having at least a first and second port, said impedance matching control module comprising

means for receiving at least one input signal from said signal sensing module indicative of an impedance mismatch between said load and said communications device,

a memory and a table that enable generation of at least one control signal proportional to said at least one input signal,

means for generating said at least one control signal,

an amplifier, wherein said amplifier receives said at least one control signal and generates at least one amplified control signal, and

means for communicating said at least one control signal to said impedance matching module,

wherein said first port of said signal sensing module is coupled to said communications device, said second port of said signal sensing module is coupled to said first port of said impedance matching module, said third port of said signal sensing module is coupled to said first port of said impedance matching control module, said second port of said impedance matching control module is coupled to said third port of said impedance matching module, and said second port of said impedance matching module is coupled to said load.

2. The system of claim 1 wherein said at least one control signal is a DC bias control signal.

3. The system of claim 1 wherein said at least one input signal from said signal sensing module is a voltage signal proportional to an impedance mismatch between said load and said communications device.

4. The system of claim 1 wherein said at least one input signal from said signal sensing module is a current signal proportional to an impedance mismatch between said load and said communications device.

5. The system of claim 1 wherein said at least one amplified control signal adjusts a variable impedance device.

6. The system of claim 5 wherein said variable impedance device is a capacitor.

7. The system of claim 5 wherein said variable impedance device is a varactor diode.

8. A method for automatically matching an impedance of a load to an impedance of a communications device in a system including a signal sensing module, an impedance matching module, and an impedance matching control module, wherein said impedance matching module includes a first variable impedance device and a second variable impedance device, said method comprising the steps of:

sensing a radio frequency signal in said signal sensing module;

generating in said impedance matching control module at least one control signal proportional to said at least one signal received from said signal sensing module based on data stored in a memory and a table;

amplifying said at least one control signal to generate at least one amplified control signal;

applying a first amplified control signal to said first variable impedance device; and

applying a second amplified control signal to said second variable impedance device.

9. The method of claim 8 wherein said first variable impedance device is a first thin film capacitor and said second variable impedance device is a second thin film capacitor.

10. The method of claim 9 wherein said first thin film capacitor and said second thin film capacitor are parallel plate capacitors each having a ferroelectric thin film dielectric.

11. The method of claim 10 wherein said ferroelectric thin film dielectric is barium strontium titanate.

12. The method of claim 9 wherein said first thin film capacitor is a capacitor having a permittivity that is a function of a first applied bias voltage and said second thin film capacitor is a capacitor having a permittivity that is a function of a second applied bias voltage.

13. A method for automatically matching an impedance of a load to an impedance of a communications device in a system including a signal sensing module, an impedance matching module, and an impedance matching control module, wherein said impedance matching module includes a variable impedance device, said method comprising the steps of:

sensing a radio frequency signal in said signal sensing module;

generating in said impedance matching control module at least one control signal proportional to said at least one signal received from said signal sensing module based on data stored in a memory and a table;

amplifying said at least one control signal to generate at least one amplified control signal; and

applying said at least one amplified control signal to said variable impedance device in said impedance matching module.

14. The method of claim 13 wherein said variable impedance device is a thin film capacitor.

15. The method of claim 14 wherein said thin film capacitor is a parallel plate capacitor having a ferroelectric thin film dielectric.

16. The method of claim 14 wherein said thin film capacitor is a capacitor having a permittivity that is a function of an applied control signal.

17. The method of claim 13 wherein said variable impedance device is a varactor diode.