Texas A&M University s1

TEXAS A&M UNIVERSITY Department of Electrical and Computer Engineering College Station, Texas 77843-3128 TEL (979) 845-9583 FAX (979) 845-7161 [email protected] http://amsc.tamu.edu S E M I N A R

Room 203 ZEC Wednesday, February 22, 2012 3:00-3:50 P.M.

A Self-Sustained Fully-Integrated Microwave Chemical Sensor Using a Frequency Synthesizer

by Ahmed A. Helmy Texas A&M University Abstract: Sensing the dielectric properties of chemicals and biochemicals is quite relevant to a variety of applications. such as gas and smoke detection, alarm sensing and oil exploration and processing. Also, in medical diagnosis, some studies have shown that the dielectric properties of biological samples such as blood, semen, and cerebra spinal fluid show appreciable change in patients with specific diseases compared to healthy people at microwave frequencies. Fully integrated sensors on silicon capable of direct detection of dielectric properties of chemicals/biochemicals are promising to achieve size and cost reduction, lower power consumption, enormous signal processing capabilities and high throughput for portable lab-on-chip applications. The proposed sensor is a fully-integrated CMOS sensor to the detect dielectric constant of organic chemicals. The dielectric constant of these liquids is measured using the oscillation frequency shift of an LC voltage controlled oscillator (VCO) upon the change of the tank capacitance when exposed to the liquid. To make the system self-sustained, the VCO is embedded inside a frequency synthesizer to convert the frequency shift into voltage that can be digitized using an on-chip analog-to-digital converter (ADC). The dielectric constant is then estimated using a detection procedure including the calibration of the sensor. The dielectric constants of different organic liquids have been detected in the frequency range of 7 to 9 GHz with an accuracy of 3% compared to theoretical values for sample volumes of 10 - 20 µL. The sensor is also applicable for binary mixture detection and estimation of the fractional volume of the constituting materials with an accuracy of 1 - 3%. Ahmed A. Helmy (S’09) was born in Cairo, Egypt, in 1983. He received the B.Sc. degree (with honors) and M.Sc. degree in electronics engineering from Cairo University, Giza, Egypt, in 2005 and 2008, respectively, and is currently working toward the Ph.D. degree in electrical and computer engineering at Texas A&M University, College Station. From 2005 to 2008, he was a Research Assistant with the Yousef Jameel Science and Technology Research Center, The American University, Cairo, Egypt. From 2005 to 2008, he was a Teaching Assistant with the Electronics and Communications Engineering Department, Cairo University. In Summer 2011, he was an RF Design Intern with Samsung Telecommunications America, Dallas, TX, where he was involved with millimeter- wave wireless transceivers. His research interests include RF integrated circuit (RFIC) design, CMOS sensors, UWB systems and microelectromechanical systems (MEMS).