Near field communicator implementing switched circuit states for demodulation

摘要

A near field RF communicator has an inductive coupler to couple inductively to an H field of an RF signal from another near field RF communicator in near field range to provide a received signal, a demodulator coupled to extract any modulation from a source signal representing a received RF signal to provide an extracted modulation signal; and a controller coupled to receive an extracted modulation signal from the demodulator. The demodulator has a sampler to sample the source signal in sampling periods and to compare signal samples with at least one of other signal samples and a clock or reference signal to remove or reject the carrier of the received RF signal and to extract the modulation.

主权项

1. A near field communications (NFC) device, comprising:
a demodulator, including a first capacitor and a second capacitor, configured to:
sample a received signal over a first period to provide a first sample, store a first charge on the first capacitor, the stored first charge being related to the first sample and a first reference voltage; and store a second charge on the second capacitor, the stored second charge being related to the first reference voltage and to a second reference voltage in a first sampling configuration; andsample the received signal over a second period to provide a second sample in a second sampling configuration,wherein a change in the received signal between the first sample and the second sample causes charge to move from the first capacitor to the second capacitor to provide an output voltage representing the change in the received signal between the first sampling configuration and the second sampling configuration; and a controller configured to adjust a configuration of the demodulator between the first sampling configuration and the second sampling configuration, wherein the output voltage is a result of a capacitive charge transfer within the demodulator between the first capacitor and the second capacitor as the demodulator configuration is adjusted between the first sampling configuration and the second sampling configuration.