265AHW1Winter09

265AHW1Winter09 - ECE 265A Homework #1 (TA:...

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ECE 265A Homework #1 (TA: tgathman@ucsd.edu) Due Thursday Jan. 29, 2009 In-Class. No late homeworks accepted. 1) 50 pts. A wideband CDMA (a 3G cellular standard) power amplifier is designed as shown in Fig. 1 using the “Level-0” BJT model to drive the antenna, which has a 50 impedance. The dc collector current is 250 mA, and when the output power is maximum, the collector current varies sinusoidally from 0 to 500 mA at a frequency of 1950 MHz. a) What value of load impedance ZL must be presented to the collector if the voltage swing at the collector is limited to 6V p-p at maximum output power? 10 pts b) Design an L-match circuit to provide the appropriate transformation from the collector to the antenna impedance using L1 and C1. What is the Q of the match, and what is the power delivered to the antenna? 8pts c) The transistor has an T (gm/Cbe) = 2 *50*10 9 rad/sec and rb=1 . Design an L-match circuit using L2 and C2 to conjugately match the base
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265AHW1Winter09 - ECE 265A Homework #1 (TA:...

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