Design of Low Voltage Low Power LPF for WSN Node

A fourth-order low-pass continuous-time filter for a WSN transmitter is presented. The active RC filter was chosen for the high linearity, designed by using the leapfrog topology imitates the passive filter. The operation amplifier (op-amp) adopted by the filter is feed-forward operation amplifier, which could get the GBW as large as possible under the low power consumption. The cut-off frequency deviation due to the process corner, aging and temperature deviation is adjusted by an automatic frequency tuning circuit. The filter in a 0.18μm RF CMOS technology consumes 1mW from a 1V power supply. The measured results of the chip show that the bandwidth is about 1.5MHz. The voltage gain of filter is about-4.5dB with the buffer, the ripple in the pass-band is lower than 0.5 dB, and the channel rejection ratio is larger than 30dB at 4MHz.

Round-Guard System Based on the Vibration Cable Transducer

Adopting a new kind of transducer technology vibration cable technology, can round-guard in large region without bodyguard whole day, and using display and warning on the end equipments may judge abnormal conditions occurred in what time and in what place. The system makes use of quadratic and own source filter, suppress the disorder waves induced in transducer, install two-rank amplifier which kernel being operation amplifier, especially for micro-vibration originating undercut can judge illegal invader, and can judge the invaders are human or heavy equipment according to vibration intensities.