108年 - 108 國立中山大學_碩士班招生考試_電機系(戊組)、電波領域：電磁學#108273

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1. (25%) In free space, the electric field intensity is E = (6cx+8)a_x -(8cy+9y)a_y+(7cz)a_z and the volume density of free charges isρ_v= 0 (C/m³). Please find the value of the constant c.

2. (25%) A small square loop with side d carries a direct current I as shown in Fig. 1. Please determine the magnetic flux density at a point P at a distance R from this loop. Fig. 1

3.(15%) Derive the attenuation constant, phase constant, complex intrinsic impedance, phase velocity, and group velocity of low-loss dielectric.

4.(15%) As shown in Fig. 2, for a coaxial line operated in the TEM mode, find the EM fields, surface current density on the inner and outer conductors, and the characteristic impedance.

(a) (5%) Voltage at the input terminal and at the load.

(b) (5%) Voltage standing-wave ratio and the average power delivered to the load.

(a) (5%) Dipole antenna and antenna array.

(b) (5%) Antenna gain and half-power beamwidth.