7. (10%) Analyze the performance of a right-hand circularly polarized wave received respectively by linearly or circularly polarized antennae.

3.(10%) In the following configurations, Fig. 2, assuming both grounds are perfect conductors, current directions are as indicated (the solid arrows)； the image current for both cases are shown. Using an✖H = J, H is the magnetic field intensity on the ground, an is the normal vector of the top surface of the grounds, determine the direction of the currents on the top surface of the grounds.Current relative to the ground. Considering both the original current and its induced current on the ground, which one, left or right, is likely to be an effective antenna structure, why?

4.(5%) Using the Method of Image, wite down the potential distribution, V(x, y,  z), for an observing point P(x, y,  z) in the space, Fig. 3. The dielectric constant of the space is ε0. Q is a positive point charge of Q Coul.

5.(10%) 下圖 Fig. 4 之 magnetic flux density B can be found as, 簡化上列之Bas a function of,o and @ when ＞. In cylindrical coordinate system,.Show that∇•B=0.

6.(5%) What are the permittivity e and permeability μ of Copper, a very good conductor? Provide your reasoning.

8. (15%) As shown in Fig. 5, a waveguide filled with a material whose εr = 2.25 has dimensions a = 2 cm and b = 1.4 cm. If the guide is to transmit 13.5 GHz signals, what possible modes can be used for the transmission? Please respectively calculate the cutoff frequencies of the possible modes.

(a) (6%) Open-circuit termination, and also plot the reactance-line length diagram

(6) (6%) Short-circuit termination, and also plot the reactance-line length diagram

(c) (3%) Quarter-wave section 

10. (10%) As shown in Fig. 7, calculate the average power transmitted into the infinite 150 Ω line. The λ/2 line is lossless and the infinitely long line is slightly lossy. (Hint: The input impedance of an infinitely long line is equal to its characteristic impedance so long as the line is not lossless)

1.(20%) The radius of the solid inner conductor and the inner radius of the very thin outer conductor of an air coaxial transmission line are ri and ro, respectively. A uniform current I flows in the inner conductor and returns via the thin outer conductor in the other direction. The permeability of free space μ0 is H/m. Determine the stored magnetic energy per unit length of the line.