Guest Lecturer: Prof. Ramakrishna Janaswamy, University of Massachusetts, Amherst
TITLE: Operating Electrically Small Antennas for High Information Bandwidths
Date: Tuesday, May 20, 2014 Time: 3:00 PM
Location: MITRE (Building C Lobby) Refreshments served at 2:30pm
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Abstract: It is well known that electrically small (size to be much smaller than the wavelength at the operating carrier frequency), passive antennas suffer from fundamental limitations on achievable bandwidths. The bandwidth of electrically small antennas could, however, be substantially improved by incorporating lossy matching networks. But this will be at the cost of significantly higher power dissipation in the matching networks, which will tend to decrease the overall radiation efficiency. If, on the other hand, the antenna currents could somehow be made to change rapidly at a rate directly dictated by the message signal, then there is no difficulty in radiating such a rapidly varying waveform from the induced antenna currents, despite its narrow input impedance bandwidth.
In this talk we discuss the theory of operation of a linear, electrically small, time-varying antenna by considering a thin dipole loaded with a fast switching element. Time-variation of antenna structure is achieved by operating the switch via a message signal that has the overall effect of transferring a modulated carrier to antenna currents for subsequent radiation.
Time-domain integral equation and linear state-space theory is used to understand the dynamics of the radiated waveform and the antenna input current. It is demonstrated that the antenna has capabilities of radiating waveforms with an information bandwidth that is an order of magnitude greater than possible with an electrically small traditional antenna. Effect of switch parameters such as the finite OFF resistance and finite switching times relative to the time period of the RF carrier on the operation of the antenna are also presented.
For more information, contact:
Raoul O. Ouedraogo, raoul.ouedraogo@ll.mit.edu or
Wajih Elsallal, welsallal@mitre.org, Phone:(319) 775-5296
Direction to MITRE:
Refer to the link below. Please use the lobby at C-building.
WebEx instruction:
Please login at 2.45pm to give yourself enough time for troubleshooting connection problem.
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Meeting information
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Topic: Operating Electrically Small Antennas for High Information Bandwidths
Date: Tuesday, May 20, 2014
Time: 3:00 pm, Eastern Daylight Time (New York, GMT-04:00)
Meeting Number: 596 891 596
Meeting Password: (This meeting does not require a password.)
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