Patent ID: 7855595
Filing Date: 2010-12-21
Classification: G06K,H03D,H03K,H04L

Abstract:
1. An Amplitude Shift Keying (ASK) demodulator for use in a Radio Frequency Identification (RFID) transponder, comprising a limiter circuit coupled to an antenna circuit and converting the ASK antenna field strength modulation into an ASK limiter current modulation by limiting the antenna voltage to a fixed value for generating a limiter current substantially proportional to the ASK antenna field strength, and a current discriminator circuit that discriminates the ASK limiter current modulation comprising: a first current mirror that mirrors the ASK limiter current or a copy of that current into a first pair of series-connected complementary MOS transistors; a second current mirror that mirrors the ASK limiter current or a copy of that current into a second pair of series-connected complementary MOS transistors; and a latch circuit with a set input coupled to the interconnection node of the first pair of complementary MOS transistors and a reset input coupled to the interconnection node of the second pair of complementary MOS transistors.