Method for controlling the tuning to a communications frequency of an antenna connected to a component designed for contactless communication and corresponding system

Patent metadata

Field	Value
Publication number	US-9853677-B2
Application number	US-201514974146-A
Country	US
Kind code	B2
Filing date	Dec 18, 2015
Priority date	Jun 2, 2015
Publication date	Dec 26, 2017
Grant date	Dec 26, 2017

Abstract

A system includes an antenna, and a contactless component for receiving and/or transmitting information via the antenna according to a contactless communications protocol. An inductive-capacitive network is connected between the antenna and the contactless component and includes a configurable filter for filtering electromagnetic interference. A processor modifies an impedance of the configurable filter for filtering electromagnetic interference to control frequency tuning of the antenna.

First claim

The invention claimed is:

1. A system comprising:
an antenna;
a contactless component configured for exchanging information via the antenna according to a contactless communications protocol;
a configurable filter coupled between the antenna and the contactless component, the configurable filter configured to filter electromagnetic interference and is configurable to one of a plurality of filtering configurations that all have a cut-off frequency that is substantially the same and wherein the configurable filter comprises a reference inductance and a reference capacitive value associated with the reference cut-off frequency; and
a controller configured to modify an impedance of the configurable filter for filtering electromagnetic interference to control frequency tuning of the antenna by selecting one of the plurality of filtering configurations;
wherein the configurable filter comprises a configurable inductive-capacitive circuit coupled between the contactless component and terminals of said antenna and a configurable capacitive circuit coupled between said configurable inductive-capacitive circuit and a neutral point;
wherein the configurable inductive-capacitive circuit comprises a first set of switchable auxiliary capacitive circuits, and an inductive-capacitive module configurable by the first set of switchable auxiliary capacitive circuits;
wherein the configurable capacitive circuit comprises a second set of switchable auxiliary capacitive circuits, and a capacitive module configurable by the second set of switchable auxiliary capacitive circuits; and
wherein, in each filtering configuration, an impedance of the configurable inductive-capacitive circuit at the reference cut-off frequency is equal to the reference inductance, and an impedance of the configurable capacitive circuit at the reference cut-off frequency is equal to the reference capacitive value.

2. An apparatus comprising:
a contactless component having a first output terminal, a second output terminal, a first auxiliary terminal, and a second auxiliary terminal;
a configurable inductive-capacitive circuit coupled to the contactless component, the configurable inductive-capacitive circuit comprising:
a first main inductive element having a first input coupled to the first output terminal of the contactless component and a second input coupled to the first auxiliary terminal of the contactless component;
a second main inductive element having a first input coupled to the second output terminal of the contactless component and a second input coupled to the second auxiliary terminal of the contactless component;
a first main capacitor coupled in parallel to the first main inductive element;
a second main capacitor coupled in parallel to the second main inductive element;
a first plurality of switchable auxiliary capacitors, wherein each of the first plurality of switchable auxiliary capacitors is coupled between the first auxiliary terminal and the first output terminal of the contactless component; and
a second plurality of switchable auxiliary capacitors, wherein each of the second plurality of switchable auxiliary capacitors is coupled between the first auxiliary terminal and a neutral point;
a third plurality of switchable auxiliary capacitors, wherein each of the third plurality of switchable auxiliary capacitors is coupled between the second auxiliary terminal and the second output terminal of the contactless component; and
a fourth plurality of switchable auxiliary capacitors, wherein each of the fourth plurality of switchable auxiliary capacitors is coupled between the second auxiliary terminal and the neutral point.

3. The apparatus of claim 2 , wherein the configurable inductive-capacitive circuit further comprises:
a first additional capacitor coupled between the first auxiliary terminal of the contactless component and the neutral point; and
a second additional capacitor coupled between the second auxiliary terminal of the contactless component and the neutral point.

4. The apparatus of claim 2 , wherein the first main inductive element and the second main inductive element have identical inductance values.

5. The apparatus of claim 2 , further comprising:
an antenna coupled to the configurable inductive-capacitive circuit and having a first terminal and a second terminal; and
a controller coupled to the configurable inductive-capacitive circuit.

6. The apparatus of claim 5 , further comprising:
a third additional capacitor having a first input coupled to the first terminal of the antenna and having a second input coupled to the first auxiliary terminal of the contactless component; and
a fourth additional capacitor having a first input coupled to the second terminal of the antenna and having a second input coupled to the second auxiliary terminal of the contactless component.

7. The apparatus in claim 5 , wherein the contactless component further comprises a first input terminal coupled to the first terminal of the antenna and a second input terminal coupled to the second terminal of the antenna, and wherein the apparatus further comprises:
a first detector having a first detector input coupled to the first input terminal of the contactless component and a second detector input coupled to the first plurality of switchable auxiliary capacitors and the second plurality of switchable auxiliary capacitors; and
a second detector having a first detector input coupled to the second input terminal of the contactless component and a second detector input coupled to the third plurality of switchable auxiliary capacitors and the fourth plurality of switchable auxiliary capacitors.

8. The apparatus of claim 2 , wherein one or more of the first, the second, the third, and fourth plurality of switchable auxiliary capacitors are within the contactless component.

9. The apparatus of claim 2 , wherein the contactless component further comprising a switch coupled to the first output terminal and the second output terminal of the contactless component.

10. The apparatus of claim 2 , wherein the first main capacitor and the second main capacitor have identical capacitance values.

11. The apparatus of claim 2 , wherein each of the first, second, third, and fourth plurality of switchable auxiliary capacitors comprise a plurality of capacitors and a plurality of switches.

12. The apparatus of claim 11 , wherein each of the plurality of switches are MOSFET transistors.

13. The apparatus of claim 11 , wherein each of the plurality of capacitors in the first plurality of switchable auxiliary capacitors and each of the plurality of capacitors in the third plurality of switchable auxiliary capacitors have identical capacitance values, and wherein each of the plurality of capacitors in the second plurality of switchable auxiliary capacitors and each of the plurality of capacitors in the fourth plurality of switchable auxiliary capacitors have identical capacitance values.

14. The apparatus of claim 11 , wherein each of the plurality of capacitors in the first plurality of switchable auxiliary capacitors and each of the plurality of capacitors in the second plurality of switchable auxiliary capacitors have identical capacitance values, and wherein each of the plurality of capacitors in the third plurality of switchable auxiliary capacitors and each of the plurality of capacitors in the fourth plurality of switchable auxiliary capacitors have identical capacitance values.

15. An antenna frequency tuning system comprising:
a contactless component configured to exchange information in accordance with a contactless communications protocol;

Assignees

• Stmicroelectronics Rousset

Inventors

• Tramoni Alexandre

Classifications

• H04B1/0458

  Arrangements for matching and coupling between power amplifier and antenna or between amplifying stages (matching circuits in general H03H) · CPC title

• H04B1/40 Primary

  Circuits · CPC title

• H04B1/18 Primary

  Input circuits, e.g. for coupling to an antenna or a transmission line (coupling networks between antennas or lines and receivers independent of the nature of the receiver H03H) · CPC title

• H04B5/0025

  Electricity · mapped topic

• H04B5/70 Primary

  specially adapted for specific purposes · CPC title