350lect10 - 10 Antenna gain, beam pattern, directivity A...

Info iconThis preview shows pages 1–3. Sign up to view the full content.

View Full Document Right Arrow Icon
10 Antenna gain, beam pattern, directivity Adipoleantenna(oracloselyrelatedmonopoletobestudiedinLecture 18) is a “near perfect” radiator for purposes of “broadcasting” — that is, sending waves of equal amplitudes in all directions to reach out multiple targets or receivers. However dipole is a poor choice when the objective is to radiate the power P rad in a speciFc direction (i.e., towards a speciFc receiver), as in –commun ica t ion with deep space probes or orbiting satellites, or with –rada rbeacon s where the objective is to determine the direction of a moving target. In such applications we need high-gain and directive antennas, as opposed to low-gain and non-directive antennas such as a single dipole. Qualitatively speaking, gain and directivity of an antenna measures its ability to conFne its radiated wave Felds within a narrow Feld of view called the antenna beam or beam pattern . when a narrow antenna beam is achieved, and all the radiated power
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Arrays of dipoles can serve as high-gain antennas needed in beaming applications as we will learn in the next lecture. In this lecture we will focus on the deFnition of antenna gain and directivity as well as the related concept of beam solid angle. Quantitatively, the gain of an antenna is simply the average power density ratio G ( θ,φ ) E ( r ,t ) × H ( r ,t ) ²| P rad 4 πr 2 where the denominator is what the transmitted power per unit area at distance r would have been if the antenna radiated isotropically. Thus, antenna gain is a comparison of the strength of the average Poynt-
Background image of page 2
Image of page 3
This is the end of the preview. Sign up to access the rest of the document.

This note was uploaded on 09/27/2011 for the course ECE 450 taught by Professor Staff during the Fall '08 term at University of Illinois, Urbana Champaign.

Page1 / 8

350lect10 - 10 Antenna gain, beam pattern, directivity A...

This preview shows document pages 1 - 3. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online