A Crystal-Less Temperature-Independent Reconfigurable Transmitter Targeted for High-Temperature Wireless Acoustic Telemetry Applications

Abstract

A reconfigurable acoustic telemetry transmitter that employs crystal-less temperature-independent frequency reference has been realized in a 1-mu m silicon-on-insulator complementary metal-oxide-semiconductor process. The transmitter can be configured to transmit either a three-channel chirp signal or a six-channel on-off keying (OOK) signal to provide flexibility based on channel characteristics. Different frequencies derived from the crystal-less temperature-independent frequency reference are directly modulated by input data before being combined and sent through a multiple-feedback low-pass filter. The resulting three-channel chirp signal achieves a total data rate of 60 b/s, whereas the six-channel OOK signal achieves a total data rate of 120 b/s. The frequency reference is realized through a frequency-locked loop that employs a resistor-capacitor phase shifter with a resistor temperature coefficient cancellation technique. It achieves a frequency inaccuracy of +/- 1.94% over the temperature range of 175 degrees C similar to 275 degrees C. Consuming 9 mW and occupying 25 mm(2), this brief is the first reported integrated solution targeted for high-temperature acoustic telemetry in oil-drilling applications with the highest reported data rate.