Cambridge Silicon Radio Limited

Steve Jones

James Digby Yarlet Collier

Simon Chang

Kwangseok Han

Marco Bruno

Stuart Aitken

A system for use in a near field communications (NFC) reader, for detecting the presence of an NFC tag, is disclosed. The NFC reader has an antenna tuned to a resonant frequency. The system comprises: a first signal generator for generating a carrier signal whose frequency varies about the resonant frequency; a second signal generator for generating a modulating signal for modulating the carrier signal; a modulator for modulating the carrier signal with the modulating signal; a driver for driving the antenna with the modulated signal; and a detection system for detecting harmonics of the modulating signal in a signal present in the antenna as a result of the modulated signal. The detector is configured to generate an output when a third or higher order harmonic is detected.

Near field communication apparatus

Systems and methods providing a transmitter for transmitting signals in a near-field communication (NFC) frequency band are disclosed. According to embodiments, a transmitter for transmitting signals in a near-field communication frequency band comprises an antenna, a first current source for generating a first current to excite the antenna, a first detector for detecting a first voltage at an output of the first current source, and means for reducing the current output by the first current source if the detected first voltage exceeds a first predefined threshold. An integrated circuit of embodiments may comprise the foregoing transmitter. A transmitter configuration of embodiments, including means for reducing the current, provides for limited distortion in the transmitted signal and reducing the risk of components in the transmitter being damaged.

Transmitter

Apparatus for controlling the generation of a DC signal at the output of a mixer, so that the DC signal is predictable, enabling a static offset compensation voltage to offset the DC signal. The apparatus comprises a mixer configured to receive a first and a second input signal, the mixer being such as to generate a first DC signal at the output of the mixer when the first and second input signals have the same frequency and a first relative phase, a phase detector for determining the relative phase of the first and second signals, and a phase modifier configured to modify the phase of the second signal relative to the first signal in dependence on the determination of the relative phase between the first and second signals such that the resulting DC signal at the output of the mixer is the first DC signal.

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Milton Keynes, United Kingdom

Steve Jones