# Antenna Theory and Design, 2nd Edition by Warren L. Stutzman

By Warren L. Stutzman

Hugely revered authors have reunited to replace the well-known 1981 version that's nonetheless hailed as the most effective in its box. This version comprises contemporary antenna suggestions and functions. It encompasses a succinct therapy of the finite distinction, time area (FDTD) computational method. it's also the 1st textual content to regard actual thought of diffraction (PTD).

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At large distances from an antenna, called the far-field region, all power is radiated power. , the radiation pattern) is independent of distance from the antenna. Field regions and the distance away from an antenna where the far field begins are discussed further in Sec. 3. 7 RADIATION PATIERNS We briefly introduce the radiation pattern in Sec. 3 as a description ofthe angular variation of radiation level around an antenna. This is perhaps the most important characteristic of an antenna. In this section, we present several definitions associated with patterns and develop the general procedures for calculating radiation patterns.

Z e-i {3r. z e-i {3r 2'1Tf3 r3 () a - 1'1/ - - - - cos () r A • A (1-76b) These are referred to as the near fields of the antenna. Actually, the magnetic field of (1-76a) which varies as 1Ir2 is that of a short, steady or slowly oscillating current, that is, an induction field. z apart. , indicating reactive power. Z)2 . 2 ()rA + cos () sm . () aA) =--2 - 51 (sm f3 4'1T r (1-77) Note that this power density vector is imaginary and therefore has no time-average radial power flow. The radiation fields, in contrast, are in-phase giving a real-valued Poynting vector that is radially directed; see (1-72) and (1-74).

For an arbitrary z-directed current density, the vector potential is also z-directed. If we consider the source to be a collection of point sources weighted by the distribution lz, the response A z is a sum of the point source responses of (1-56). This is expressed by the integral over the source volume v': Az = III -j{3R JLlz IJ' ~ R dv' (1-57) 7T. Similar equations hold for the x- and y-components. The total solution is then the sum of all components, which is A - i III = . -jfJR JLI ~7TR dv' (1-58) V This is the solution to the vector wave equation (1-46).