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Poynting's Theorems and Their Relationship to Antenna Power, Q, and Bandwidth
Poynting's Theorems and Their Relationship to Antenna Power Q and Bandwidth Author:D. J. White, P. L. Overfelt This is a NAVAL AIR WARFARE CENTER WEAPONS DIV CHINA LAKE CA report procured by the Pentagon and made available for public release. It has been reproduced in the best form available to the Pentagon. It is not spiral-bound, but rather assembled with Velobinding in a soft, white linen cover. The Storming Media report number is A000763. The abstrac... more »t provided by the Pentagon follows: In this report a number of the basic ideas and assumptions involved in the analysis of electrically small antennas is considered. Poynting's theorems in both the time and frequency domain cases are derived, and the conditions under which they are mathematically applicable are examined. Their relationships with stored energy, both time dependent and time average, are derived. Resistive and reactive power flow into circuits is examined and compared with the power flow across a closed surface surrounding an antenna. It is found that while using this approach to find the input or radiation resistance of a single port antenna can be justified, using the same approach to obtain the antenna input reactance cannot be justified. The antenna quality factor (Q) concept is considered from first principles, various forms of Q are explored for series and parallel circuits, and the relationship of the Q to the antenna bandwidth is discussed. A consistent theoretical foundation and a physical understanding of the radiation and stored energy properties of general antennas are constructed to determine the performance limits on electrically small antennas.« less