ACTIVE TRANSPONDER WITH VERY LOW ELECTRIC POWER CONSUMPTION IN STANDBY MODE

• US 20100245153A1
• Filed: 03/24/2010
• Published: 09/30/2010
• Est. Priority Date: 03/26/2009
• Status: Active Grant

• Current Assignee: EM Microelectronic - Marin SA (The Swatch Group AG)
• Original Assignee: EM Microelectronic - Marin SA (The Swatch Group AG)
• Inventors: Kuratli, Christoph
• Granted Patent: US 8,482,386 B2
• Time in Patent Office: Days
• US Class Current: 342/42
• CPC Class Codes: G06K 19/0701 at least one of the integrated circuit chips comprising an arrangement for power management
• CPC Class Codes: G06K 19/0705 the battery being connected to a power saving arrangement
• 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

Abstract

The active transponder includes an input amplifier (26) arranged between an envelope detector (8) and a demodulation circuit (28). It further includes an activation unit (30) for the input amplifier and also for the demodulation circuit, which is formed by a frequency changer or mixer circuit (32), which decreases a significant modulation frequency of the modulated signal received by the antenna to a low frequency, the resulting low frequency signal then being amplified and filtered by low frequency elements. The activation unit thus consumes little electric power and sends a wake up signal to the elements operating at a high frequency when it detects said significant modulation frequency, in a very selective manner.

Claims

1. An active transponder including a logic circuit and an RF input-output circuit, wherein said input-output circuit is formed by an input amplifier arranged between an envelope detector for the signal received by an antenna of the transponder and a demodulation circuit for said signal that also forms said input-output circuit, wherein said transponder includes an activation unit for said input amplifier, which is formed of a frequency changer or mixer circuit, which receives as input an envelope signal of the antenna signal and a clock signal generated by an internal clock at a clock frequency that is different from, but close to a modulation frequency of an interrogation signal of an RF system for which the transponder is intended, and which supplies as output, when it receives said interrogation signal as input, a low frequency signal, whose value is approximately equal to the difference between said modulation frequency and said clock frequency, said activation unit also including a low pass filter and low frequency amplifying means for amplifying said low frequency signal, and said activation unit supplying a wake up signal to said input amplifier when it receives an envelope signal having said modulation frequency and a sufficiently large amplitude.

2. The active transponder according to claim 1, wherein said low pass filter and said low frequency amplifying means are provided with a narrow bandwidth such that only signals modulated approximately at said modulation frequency are amplified and generate a wake up signal.

3. The active transponder according to claim 1, wherein, downstream of said low pass filter and said low frequency amplifying means, it includes a comparator that supplies a logic detection signal as output.

4. The active transponder according to claim 1, wherein the input part of said activation unit includes AC coupling means for removing any DC component from said envelope signal.

5. The active transponder according to claim 1, wherein the output part of said activation unit includes a flip-flop, which receives said logic detection signal as input.

6. The active transponder according to claim 1, wherein said frequency changer or mixer circuit is a passive circuit formed of switches controlled by a pulse generator connected to said internal clock.

7. The Active transponder according to claim 1, wherein said wake up signal is also supplied to said demodulation circuit so as to activate said circuit simultaneously with said input amplifier.