| 摘要 |
<p>PURPOSE: To provide a low-level RF detection circuit which consumes very small power and is not affected by RF noises or fluctuation by providing a circuit for eliminating intermittent low-level RF interferences through detecting low level and varying strength RF signals. CONSTITUTION: An antenna 1 is used for receiving RF signals from a reader. An RF detector 2 converts RF energy provided from the antenna 1 into a DC signal. A transistor 3 is an N-type FET, chops the input DC signal and generates a rectangular wave proportional to that signal. Thus, an RF activating signal and a write data signal can be amplified by using the same amplifier. A signal generated by a rectangular wave generator 6 is passed through a voltage divider formed from resistors 4 and 5, and a low-level threshold reference voltage signal is generated. This reference voltage has a frequency equal to that of the DC signal chopped by the transistor 3 but with opposite polarity.</p> |
