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ECE 1100: Introduction to Electrical and Computer Engineering

ECE 1100: Introduction to Electrical and Computer Engineering. Spring 2008. David R. Jackson Professor, ECE Dept. Notes 13. Transmission and Reception of Waves. Power In Electromagnetic Wave. x. E x [V/m]. z. power flow. H y [A/m]. y. “intrinsic impedance of free space”. x.

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ECE 1100: Introduction to Electrical and Computer Engineering

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  1. ECE 1100: Introduction toElectrical and Computer Engineering Spring 2008 David R. Jackson Professor, ECE Dept. Notes 13 Transmission and Reception of Waves

  2. Power In Electromagnetic Wave x Ex [V/m] z power flow Hy [A/m] y “intrinsic impedance of free space”

  3. x Ex z power flow Hy y Power In Electromagnetic Wave (cont.)

  4. Example The AM radio station KFCC (1270 KHz) transmits 50 [kW] of power equally in all directions above the earth (hemisphere pattern). • a) What is the power density 30 [km] away? • What is the magnitude of the electric field 30 [km] away? • Describe mathematically the electric field that an observer would see at this distance. 30 [km] observer

  5. Example (cont.) 30 [km] observer

  6. Example (cont.) Also, So or

  7. Example (cont.) x From previous calculation: Hence we have 30 [km]

  8. Ex Hy Receive Voltage Receive antenna wire is in x direction z = zR z h + v(t) - earth

  9. Ex Hy Receive Voltage (cont.) h For a monopole antenna: + v(t) - earth z = zR

  10. Example Assume that the incident electric field for the AM radio station KFCC has a magnitude of Calculate the received voltage if the vertical antenna wire is 3 meters high. so

  11. Example (cont.) (from previous calculation of  and k) So we have: This is the received voltage at the terminals of the monopole antenna.

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