Lect30TwoHertzian_1

# Lect30TwoHertzian_1 - ECE 3030 Electromagnetic Fields and...

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1 ECE 3030 Electromagnetic Fields and Waves Fall 2009 Lecture 30 2009/11/6 Two Hertzian Dipole Arrays Interference Patterns Fa Field Gain y z x 1 J 2 J 1 Swartz 06/5/25 Electromagnetic Fields and Waves – Fall 2009 Lecture 30: Instructor: Dr. Wesley E. Swartz Far-Field Gain Reflecting Planes Antenna Arrays Defined An antenna array consists of multiple sub-antennas. Usually the sub-antennas are all the same (only case we will consider here). We will call these sub-antennas “ elements ”. Why have multiple elements? How is gain or beam pattern affected? More power can be sent in one direction versus some other direction. 2 Swartz 06/5/25 Electromagnetic Fields and Waves – Fall 2009 Lecture 30: Nulls in pattern can be placed to reduce interferrence. The Jicamarca example: Basic element: a dipole. 64 th : an array of 12 dipoles by 12 dipoles. Full antenna array: 8 – 64 ths by 8 – 64 ths , i.e., 64 – 64 ths , all over a reflecting screen. Review: Hertzian Dipole Characteristics (1) For a Hertzian dipole the gain is:  2 2 sin 2 3 4 ˆ . , , r P r t r S G rad 0 , p 0 90 30 60 0 , p 3 Swartz 06/5/25 Electromagnetic Fields and Waves – Fall 2009 Lecture 30: Antenna Radiation Pattern: For a Hertzian dipole the radiation pattern is: 2 max sin , , G G p (degrees) 180 120 150 Review: Hertzian Dipole Characteristics (2) Radiation pattern in 3D: 2 max sin , , G G p 4 Swartz 06/5/25 Electromagnetic Fields and Waves – Fall 2009 Lecture 30: , p Review: A Single Hertzian Dipole Antenna Not at the Origin (1) What if one has a Hertzian dipole sitting at some arbitrary point? y z h r d I z r J 3 ˆ r h h r k j o r r k j o e h r Id z r A dv e r r r J r A  4 ˆ ' ' 4 ' ' If one is interested in radiation far-fields only, then assume: 5 Swartz 06/5/25 Electromagnetic Fields and Waves – Fall 2009 Lecture 30: r h d   2 , h r r h r 2 1 r h r 2 r h r 2 r r h r 2 h h r r h r 2 2 h r k j o e r 4 Id z ˆ  h k j r k j ff e e sin r 4 Id k j ˆ r H h k j r k j o ff e e sin r 4 Id k j ˆ r E Additional phase factor x h r k j o e h r Id z r A 4 ˆ So we get: Review: A Single Hertzian Dipole Antenna Not at the Origin (2) Example: x a h ˆ e e sin r 4 Id k j ˆ r E h k j r k j o ff Suppose: y z   h r d I z r J 3 ˆ x r a h k j r k j ff e e sin r 4 Id k j ˆ r H 6 Swartz 06/5/25 Electromagnetic Fields and Waves – Fall 2009 Lecture 30: z ˆ cos y ˆ sin sin x ˆ cos sin

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## This note was uploaded on 11/26/2009 for the course ECE 3030 at Cornell.

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Lect30TwoHertzian_1 - ECE 3030 Electromagnetic Fields and...

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