Method and apparatus for controlling circuitry with particular application to smartcards

A smartcard circuit for control of a near field RF communications chip for a smartcard, the circuit comprising:

• a splitter for connection to a near field antenna of a smart card for obtaining an RF electrical signal from the antenna and for splitting the RF electrical signal between an auxiliary circuit and the near field RF communications chip to enable the chip to perform near field RF communications for the smartcard;
• and
• switching circuitry coupled to the splitter and comprising a switchable element having a first state in which the RF electrical signal is provided from the splitter to the near field RF communications chip and a second state in which the RF electrical signal is diverted away from the near field RF communications chip to inhibit the chip from performing near field RF communications
• wherein the switchable element comprises an RF conduction path controlled by a transistor having a drain connected to one plate of at least one capacitor in the RF conduction path wherein a one-way conduction path is arranged so that transmission of RF signal along the RF conduction path causes accumulation of an electrical charge on the one plate of the at least one capacitor via the one-way conduction path.

A radio frequency, RF, switch for control of an electrical signal in a smartcard, the RF switch comprising:

• an RF conduction path for conducting RF electrical energy through the RF switch between a first main connection and a second main connection;
• a reference path connected to the RF conduction path wherein the reference path comprises:
• a switchable conduction path between the RF conduction path and a reference voltage connection;
• and
• a one way conduction path, in parallel with the switchable conduction path between the RF conduction path and the reference voltage connection;
• wherein the reference path is DC isolated from the first main connection and the second main connection so that, in operation, provision of an RF signal along the RF conduction path causes accumulation of an electrical charge on the RF conduction path via the one way conduction path.

A method of operating a smartcard, the method comprising:

• receiving, via an antenna of the smart card, an RF electrical signal for performing near field RF communications between a near field RF communications chip carried by the smartcard and a near field RF communications device in near field range;
• operating a splitter circuit of the smartcard to divide the RF electrical signal into (a) a first part provided to the near field RF communications chip and (b) a second part provided to an auxiliary circuit carried by the smartcard and separate from the chip;
• operating a switching circuit of the smart card to divert the first part of the RF electrical signal away from the near field RF communications chip to inhibit the near field RF communications chip from performing near field RF communications;
• and
• operating selectively, based on a signal provided from the auxiliary circuit, the switching circuit to provide the first part of RF electrical signal to the near field RF communications chip.