RF receiver and transmitter for insect mounted sensor platform

Low power consumption is a key design requirement for many systems, particularly small sensor platforms. Sub-threshold design allows for very low power operation of digital systems, especially when increased signal delay is not an issue. The objective of the work presented in this paper is to create a low power, small transmitter utilizing a sub-threshold IC, along with off-the-shelf components. This transmitter will be used for a low power sensor platform carried by a cockroach. We have earlier designed and fabricated a low power digital sub-threshold Binary Frequency Shift Keying (BFSK) modulator chip in a TSMC 0.25µm triple well CMOS process. This chip sends out two tones at 115KHz and 345KHz, corresponding to a binary data input. In this paper, we implement the RF transmitter circuit using this BFSK modulator chip with a carrier frequency of 80MHz. This RF transmitter circuit is designed and implemented using off-the-shelf components so that the overall transmitter board (BFSK modulator chip, RF circuit, antenna and batteries) is light, small and has a low power consumption. The signal was transmitted through a small coil antenna for the receiver base station, up to 100 feet away. We also implemented the RF front end and the demodulator circuit for the receiver base station. The receiver base station amplifies and filters the signal, then mixes the signal back down to the baseband. Our demodulator circuit is able to retrieve the original transmitted signal with an SNR of 10dB, at a distance of 100 feet.