Question

8. (6 points) A Hertzian dipole antenna in free space has /= 0.02. The following are in far-field: (a) What value of current I is necessary to radiate a total power of 60 mW? (b) What is the ratio of the magnetic field intensity, H, at the polar angles 0 = 10 degrees and 80 degrees (c) What fraction of the total radiated power is contained in the region 0 < 60 degrees (d) What is the radiation resistance, Rrad? (taken partly from problem 13.4, Sadiku)

Answer 1

Ansues Gven A Hesican clipole antenna in fee Spuce e S0 (a) hat Vahe of Cowent is wecessary to vadict total pves af 6o mh? TOt odiated poe& 6omw rad GoXlo Ho A o x q,3t x o02).T 60 xlo o-15 79.T0 2 6ox/o3 o1579 6.3799 bbt2 T0.6/6 aps

Therefre, TO tal Radiated pwes s - 0.616 aMPS What is the Yatio of the maghelic field intensity, H at the polaf angies = 10 degree and 0-30degtee tet, Haghetic field Intensity Høs Smo.e At the plas augle &-lo A-l the polaa ange 30 H ToR sih Noto Ratio o waqnetic field neteusity at O-f0° t 8= 80 o3 are sin lo 20.1763 Sing0 o.984 There fve, magueticfield utensity * O- lo The Ratio 763 e

hat fraction of the total vadiated powes degees S Contaied in the Yeqion 2Go et Povs ReEx To sine 2 This is due to Yadiatd fields on- e in far field Sgion Total POwes Poy Y2 Sih& ded To Asino YShe de dø HAY 지3 Y aC E 2 7 2 HA Sineli-casodo L-se Cas s 30 lo. 616 XA

o. 66 OI6 o.02 X O-02 * 30 o 209 9.3H Mm These fre Total Roes Jzq.3H MU CYaction of tue ttal adiated Powes s ortained in the Regicn 9.34 lo Ihat is the Ra diation Yesistance, Rrad let Radiatian resistance Rvad 0 30 xA 0.315 Theve fre Rrad 0.315JL