Active transponder with means allowing the maximum communication distance to be varied

• US 20010028302A1
• Filed: 04/02/2001
• Published: 10/11/2001
• Est. Priority Date: 04/06/2000
• Status: Active Grant

• Current Assignee: EM Microelectronic - Marin SA (The Swatch Group AG)
• Original Assignee: EM Microelectronic - Marin SA (The Swatch Group AG)
• Inventors: Roz, Thierry, Rudin, Jurg, Degrauwe, Marc
• Granted Patent: US 7,015,794 B2
• Time in Patent Office: Days
• US Class Current: 340/10.5
• CPC Class Codes: G06K 19/0723 the record carrier comprising an arrangement for non-contact communication, e.g. wireless communication circuits on transponder cards, non-contact smart cards or RFIDs
• CPC Class Codes: G06K 19/07777 the antenna being of the inductive type

Abstract

The active transponder is intended for several applications or to operate in various modes requiring different levels of security. Security is controlled in particular by varying the maximum communication distance to a reader. The active transponder includes a battery (2) used for powering the various electronic circuits. It further includes amplifying means (8), a module (4) forming a demodulator for the incoming signals and means for validating the data comprised in said signals, and a data processing unit (10). The unit (10) includes a circuit (12) for controlling the maximum communication distance between the transponder and a reader transmitting signals at a determined power. This circuit (12) sends a security signal (S1, S2) respectively to the data validating means and/or to the signal amplifying means. This signal is used either to control the value of the reference value of the validating means, or to vary the gain of the amplifying means to vary the maximum communication distance.

Claims

1. An Active transponder including an electronic unit arranged so as to control several applications or operating modes, an antenna and an electric power supply in particular a battery, said electronic unit including a data processing unit, means for amplifying the incoming signals received by said antenna and means for validating these incoming signals as a function of their mean induced voltages in said antenna, these validating means supplying to said data processing unit a validating signal for the data contained in an incoming signal when its mean voltage on the input side of this unit is greater than or equal to a determined reference voltage, wherein it includes means for varying the maximum communication distance to a reader or transceiver as a function of the application selected from said applications and/the operating mode selected from said operating modes, these means being arranged to vary the amplification gain of said amplification means and/or said reference voltage of said validating means.

2. A transponder according to

claim 1

, wherein said validating means include a comparator a first input of which is connected to means supplying the mean induced voltage of the incoming signal, before or after said incoming signal amplifying means, and of which the second input is connected to means supplying said reference voltage.

3. A transponder according to

claim 2

, wherein said reference voltage is variable and defined by a security signal so that its value is relatively high when the selected application or operating mode is provided with a high level of security.

4. A transponder according to

claim 2

, wherein said reference voltage is fixed, said amplification gain being variable and defined by a security signal so that its value is relatively low when the selected application or operating mode is provided with a high level of security.

5. A transponder according to

claim 3

, wherein said means for varying the maximum communication distance include a memory in which a security code is stored for each of the applications and/or for each operating mode able to selected in the transponder, these security codes being used to generate said security signal.

6. A transponder according to

claim 4

, wherein said means for varying the maximum communication distance include a memory in which a security code is stored for each of the applications and/or for each operating mode able to selected in the transponder, these security codes being used to generate said security signal.