This preview shows pages 1–2. Sign up to view the full content.
This preview has intentionally blurred sections. Sign up to view the full version.
View Full Document
Unformatted text preview: ECET 512 Winter 2007 : Homework #4 Midterm Practice Problems March 11, 2007 1 25.4.3 a)For the Friis law to hold, the separation of the two antennas should be at least one Rayleigh distance apart. Rayleigh distance is calculated as: d R = 2 L 2 a , where L a is tha largest dimension of the antenna. In our case, L a = 15 m , and = 0 . 3 m (1 GHz carrier frequency), so Rayleigh distance is d R = 1500 m > 90 m , so for the specified distance, the Friis law cannot be used. b) The effective area of a parabolic antenna is A eff = 0 . 55 A , where A is the physical area. So, in our case, A eff = 0 . 55 r 2 = 97 . 193 m 2 . The antenna gain is then given as: G = 4 A eff 2 = 13570 . 70 = 41 . 33 dB . If the Friis law was used for the link budget, then the received power would be calculated as: P RX = P TX G TX G RX 2 (4 d ) 2 P RX dB = P TX dB + G RX dB + G RX dB + 20 log( lambda 4 d P RX dB = P TX dB + 82 . 66 71 . 53 P RX dB = P TX dB + 11 . 13 dB ....
View
Full
Document
This note was uploaded on 02/09/2010 for the course ECET 512 taught by Professor Dand during the Spring '09 term at Drexel.
 Spring '09
 Dand

Click to edit the document details