Nfc Receiver And Design

Near Field Communication (NFC) is a wireless communication protocol of very short distance. Compatible with the smart card technology, NFC is safe, easy and fast which lead to the fast developing all over the world. The design of the receiver in Analog Front of NFC chip is present with detail in this paper.Active mode and passive mode are both defined in NFC protocol. So the data can be sent by transmitter or with load modulation. An envelop detector and a coherent detection circuit are therefore designed for different scenarios. In the circuit of coherent detection, a frequency synthesizer and VCO are necessary for the generation of 4 phase clocks.Interference in carrier frequency (13.56MHz) exists in the demodulated signal due to coupling. And the strong DC part of signal may saturate the following stages. Therefore RC active filters (include both high-pass and low-pass filters) are employed in the receiver chain.The signal is expected to be amplified to a fixed value just below the ADC scale to maximize the SNR of ADC. But the power varies dramatically in different modes and with different distances between NFC devices. So an Automatic Gain Control loop is necessary. However, the ADC was not integrated at this time, and more attention was paid to the design of PGA.A single ended receiver and a fully differential receiver are both taped out with SEVIC 0.18μm 1P6M Mix-Signal technology. The differential one performs better and the single ended one consume less power and is area efficient. They were tested for contrast.