Special Seminar by Dr. DV Giri, Pro-Tech, Alamo

Special Seminar

TOPIC: : Generation and Radiation of Damped Sinusoidal Signals

Venue: MP1 Seminar Hall, ECE Dept, IISc

Date: May 15, 2019 (Wednesday)

Time: 4.00 PM

Speaker: Dr. DV Giri, Pro-Tech, Alamo, CA; Adjunct Professor, Dept. of ECE, University of New Mexico, Albuquerque, New Mexico, USA

Abstract

CW SOURCES OF SINUSOIDAL SIGNALS AND ANTENNAS ARE THE MAINSTAY IN MANY AREAS OF CIVILIZED LIFE SUCH AS COMMUNICATION, RADAR, RADIO AND  MICROWAVE COOKING. RECENTLY, DAMPED SINUSOIDAL SOURCES ARE ALSO FINDING THEIR PLACE IN VULNERABILITIES OF ELECTRONIC SYSTEMS. WHILE A CW SOURCE IS OF SINGLE FREQUENCY, A DAMPED SINUSOIDAL SOURCE HAS A MODERATE BANDWIDTH. WE DESCRIBE SEVERAL SUCH MODERATE-BAND SYSTEMS (SOURCES AND ANTENNAS) STARTING WITH A SYSTEM CALLED MATRIX WHICH WAS INTEGRATED INTO A HALF-PARABOLOIDAL REFLECTOR ANTENNA. BASED ON THE SWITCHED OSCILLATOR DESIGN IN MATRIX, WE OUTLINE THE PROBLEM OF DESIGNING, FABRICATING SWITCHED OSCILLATORS AT FOUR DIFFERENT FREQUENCIES, 200MHZ, 300MHZ, 400MHZ AND 500 MHZ. SUCH SOURCES CAN ALSO BE INTEGRATED INTO HELICAL ANTENNAS.

HELICAL ANTENNAS ARE VERY VERSATILE ANTENNAS CAPABLE OF PRODUCING MANY DIFFERENT TYPES OF RADIATION CHARACTERISTICS. THEY WERE INVENTED BY PROF. JOHN D. KRAUS OF OHIO STATE UNIVERSITY IN 1946 AND HE HAS AN INTERESTING ANECDOTE IN HIS BOOK ABOUT HOW AND WHY HE THOUGHT OF IT.  ITS PERFORMANCE IS BOUNDED BY A LOOP (LENGTH à 0) AND A DIPOLE (MAJOR DIAMETER à0). WITHIN THESE BOUNDS, THE HELICAL ANTENNA RADIATES A ~ CIRCULARLY POLARIZED ELECTROMAGNETIC WAVE WITH VARYING CHARACTERISTICS. THE CIRCULAR POLARIZATION IS VALUABLE IN SATELLITE COMMUNICATION INCLUDING GPS. A 500 MHZ DAMPED SINUSOIDAL OSCILLATOR HAS BEEN INTEGRATED INTO A MODIFIED COMMERCIAL HELICAL ANTENNA WITH A BANDWIDTH OF 400MHZ TO 600MHZ. SUCH DAMPED SINUSOIDAL SOURCES INTEGRATED INTO ANTENNAS HAVE FOUND THEIR APPLICATION IN SUSCEPTIBILITY STUDIES OF ELECTRONIC SYSTEMS.