Question

Antenna Input (load) A cell phone antenna has an input 500 admittance Yi(0.015j0.015) S that operates at a frequency of 1 GHz. It has been proposed that this antenna can be matched using a shunt impedance next to the load followed by a quarter wavelength transformer; as shown in Fig. 3(a) Ys 0.1 Fig. 3. Matching network for cell phone antenna tower antenna a. Compute the required shunt impedance (Y) so that the combined parallel admittance Yi and Ys has only a real component (Hint: Smith Chart is not needed to answer this). (5 points) b. After computing Y, indicate if you can achieve it with an inductor or a capacitor and compute the value of the element 5 points) Compute the required quarter wavelength ( achieve matching to 50 Q and the input port. (10 points) c. ) impedance that you need to place after the shunt admittance Y to

Answer 1

Given y_L = 0.015 * j (0.15) y_s = unknown z_L = y_L = 0.15 - j (0.015)/2 [0.015]^2 = 33.3 - j (33.3) z_s = unknown = 1/y_s If y_s & y_L are in parallel then z_s & z_L will be in series y_s y_L/y_s rightarrow y_L = z_s + z_L = real (from given condition) 33.3 - j (33.3)+ z_s = real Then z_s = + j (33.3) \r\n The obtained impendence is an imaginary value therefore it can be either induction or capacitor it inductance j w L = j (33.3) L = 33.3/6.28 times 10^- 9 H = 5.30 times 10^- 9 H L = 5.3 intersection H w = 2 pi f = 2 times 3.14 times 10^9 (f = 10^9 H) = 6.28 times 10^9 H_z it capacitance j/w_c = j (33.3) c = -1/w times 33.3 capacitance can ' t be negative, so the compound will be of inductor from the