Question

Calculate the radio-frequency ranges which would be suitable for transmission: (i) to a satellite, and (ii) between Australia and Singapore. Assume that the maximum electron concentration in the ionosphere is 102 m-and that in (ii) the angle of incidence with the ionosphere is 40°. Also remember, reflections from a surface will occur iff<fp/coso. (6 marks) In an intrinsic Ge crystal at 300 K which has a carrier concentration of (see the formula sheet), calculate (i) the conductivity, (ii) the proportion of the current carried by holes, and (iii) the resistivity of the material. (6 marks)

Answer 1

1023 N Concentration sol © Electron 46 f < fe coso fo a J 1012 a sna nman 11 9 xlo qm HZ 9x106 f < Cos40 fc 9x106 11.75 MHz 0.766 Radio frequency fc 11,75MHz transmission between Australia and for Singapore 2 . (is. (1) for satellite Communication it Showd be order of GHZ. T= 300k 2,5*10'3 / cm? Conductivity me u + P. eun em = 0.17 = 170 cm nec ue + M) = 2.5x10 x 1.6x10 19 [ 3600 +1700) 2.12 x 102 612-cm, -1 J = ne ut +PEME 2 2 Me 0 36 3600 cm V-5 V-S V-S cii). we have J 41,4 un 1700 0.32 32% Metun 5310 Jn 0.32J Shot on 112 WIDE VIVO Al camera Qi12xió 47.2 2-cm