Low-Cost Magnetic Stripe Reader Using Independent Switching Thresholds

Abstract

A F/2F waveform generator has a comparator and an analog multiplexer. In a low-cost magnetic card reader application, a magnetic track signal is amplified, filtered, and compared with a threshold signal to create a digital signal output. The analog multiplexer detects changes in state of the digital signal. When a change of state is detected, the analog multiplexer switches among dynamically tunable threshold signals. The selected threshold signal is used for comparison with the magnetic track signal. Switching level detection enables accurate F/2F waveform generation from relatively noisy magnetic track signals, thus improving the robustness of magnetic card readers. The analog implementation eliminates the need for expensive A/D conversion and processing and the design can be readily implemented in a very compact and low-cost package.

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