摘要 |
A relaxation oscillator for a transponder (102, 200, 400) capable of measuring one or more parameters (e.g., temperature, pressure) in an object (e.g., a tire, 104) and transmitting a data stream (Figures 3C, 4B) to an external reader/interrogator (106). The transpond er typically operates in a passive mode, deriving its power (Vxx, Vcc, Vdd) from an RF interrogation signal received by an antenna system (210, 410), but can also operate in a battery-powered active mode. The transponder includes memory (238, 438) for storing measurements, calibration data, programmable trim settings (436b), transponder ID and the like. Measurement readings (N>T<, N>p<) comprise counting oscillations of a measurement signal (Fosc') during a fixed time window (t>W<, t>T<, t>p<). The measurement signal is generated by a relaxation oscillator (252, 312, 452, 512) diriven by the alternating charging and discharging of measurement capacitors (C>FX<, C>p<), wherein the capacitor charging rate is a function of current (a measurement current I(T)B which may be indicative of temperature), and of capacitance (which may be indicative of pressure).
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