A Flexible Printed Radio Frequency Direction Finder Using Carbon Nanotube Field Effect Transistors

An inkjet printed radio frequency direction finder is presented in this paper for use in wearable electronics. The device is used to receive an alert signal from a high frequency source in its immediate proximity. The goal is to alert the person of a sudden accident or alert that could be dangerous and requires a quick response. Two loop antennas were used in a Watson-Watt configuration to receive the wave forms. The angle of arrival was estimated using a differential amplifier. This amplifier was used to compare the amplitude of two input channels. The differential amplifier was fabricated by printing two carbon nanotube field effect transistors (CNTFET) on a flexible substrate. Measurement of the circuit showed that a 90° change in the angle of arrival created a 10 mV amplitude change in output.