Nxp B.v.

Lukas Zoescher

Ulrich Andreas Muehlmann

Erich Merlin

Slawomir Rafal Malinowski

Davide Maschera

Jorge Vicente De La Cruz Marin

An antenna tuning circuit is provided. The antenna tuning circuit includes an envelope detector, an operational amplifier, and a switch. The envelope detector is configured to track an envelope of a signal received at an antenna terminal. The operational amplifier includes a first input coupled to an output of the envelope detector to receive a first signal and a second input coupled to receive a second signal and is configured to generate an output signal at an output based on the first signal and the second signal. The switch includes a first terminal coupled to the output of the operational amplifier, a second terminal coupled to the second input of the operational amplifier, and a control terminal coupled to receive a first control signal. The operational amplifier is configured in a follower configuration when the first control signal is at a first voltage value.

Antenna tuning circuit for an RFID transponder

A radio frequency (RF) voltage limiter for a radio frequency identification (RFID) transponder is provided. The RF voltage limiter includes an envelope detector configured to track an envelope of a signal received at the antenna. The envelope detector has an output for providing an envelope signal. A peak detector is included and has an input coupled to the output of the envelope detector. The peak detector includes a current mirror having an input coupled to the output of the envelope detector, and an output configured to provide a control signal. A shunt circuit is coupled to provide an impedance to the antenna in response to the control signal. The impedance decreases with an increasing voltage of the control signal to limit a maximum voltage at the antenna. In another embodiment, a method is provided for limiting a RF voltage at the antenna.

Radio frequency voltage limiter for an RFID transponder

In accordance with a first aspect of the present disclosure, an active load modulation (ALM) transceiver is provided, comprising a transmitter configured to send a transmit signal to an external device, wherein the transceiver is configured to adjust one or more parameters of the transmit signal at the end of at least one burst of said transmit signal. In accordance with a second aspect of the present disclosure, a method of operating an active load modulation (ALM) transceiver is conceived, comprising sending, by a transmitter of the transceiver, a transmit signal to an external device, and adjusting, by the transceiver, one or more parameters of the transmit signal at the end of at least one burst of said transmit signal.

Active load modulation transceiver

A radio frequency transponder circuit, comprising: an AC-DC converter () connected to an RF input terminal () and a DC output terminal () and operable to convert an RF signal (RF) at the RF input terminal () to a DC output signal (V) at the DC output terminal (); and a voltage limiting circuit () connected to the RF input terminal () and operable to limit the amplitude of the RF signal (RF); wherein the voltage limiting circuit () comprises a NMOS limiting transistor () in parallel with a complimentary PMOS limiting transistor ().

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Graz, Austria

Lukas Zoescher