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Implementation of a phased array antenna for the 2.45 GHz ISM band

Implementation of a phased array antenna for the 2.45 GHz ISM band. Presented By: Alejandro Fuentes 260725 Ricardo Pérez 260769. Undergrad thesis. National university of Colombia GMUN - CMUN group 2008. Conrad project and our project logos. http://gmun.unal.edu.co/cmun.

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Implementation of a phased array antenna for the 2.45 GHz ISM band

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  1. Implementation of a phased array antenna for the 2.45 GHz ISM band Presented By: Alejandro Fuentes 260725 Ricardo Pérez 260769 Undergrad thesis National university of Colombia GMUN - CMUN group 2008 Conrad project and our project logos. http://gmun.unal.edu.co/cmun

  2. Block diagram for field test setup Source: [1] UNAL 2008  Page 2

  3. Measurements of radiation patterns Use standard spherical coordinate system for antenna measurements. Source: [2] UNAL 2008  Page 3

  4. Basic antenna-range configurations Fixed-line-of-sight Movable-line-of-sight • The source antenna is moved trough to the circumference centered at the phase center of the test antenna. The test antenna is rotated about a appropriate axis. UNAL 2008  Page 4

  5. Antenna radiation field characterization UNAL 2008  Page 5 Characterize completely measure: relative amplitude, relative phase, polarization and power gain. Characterize is function of space coordinates. R is fixed and θ,Φ are variables in a given radiation pattern. Frecuency of operation is a parameter.

  6. Considerations UNAL 2008  Page 6 The coupling between source and test antennas. The transverse and longitudinal amplitude taper of the illuminating wave front. The phase curvature of the illuminating wave front. Interference from spurious radiating sources.

  7. FAR-FIELD MEASUREMENTS UNAL 2008  Page 7

  8. Elevated range (free-space) Source: [4] • Use when test and source antennas are located on roofs or towers, etc. • Design over a flat area. UNAL 2008  Page 8

  9. Slant range (free-space) Source: [2] • Use less land than elevated range. • Be careful with materials of tower. UNAL 2008  Page 9

  10. Compact range (free-space) Source: [4] Create uniform plane wave in short distances. UNAL 2008  Page 10

  11. Ground reflection range Source: [4] Use reflections to create constructive interference. UNAL 2008  Page 11

  12. Considerations • Elevation range is common in medium size antennas measurement. • The compact range is limited by antenna size and low operation frequency range. • In outdoor ranges external signals cause measurement errors, this effects can be eliminated by sharp filters. UNAL 2008  Page 12

  13. NEAR-FIELD MEASUREMENTS UNAL 2008  Page 13

  14. Types • Separation between source and test antenna about 4 or 10 wavelengths. • Use small RF antenna as source antenna. Planar near-field Cylindrical near-field Spherical near-field UNAL 2008  Page 14

  15. Planar near-field measurement Source: [4] • Scan in X and Y coordinates. • Source antenna moves with precision at the XY plane. UNAL 2008  Page 15

  16. Cylindrical near-field measurement Source: [4] • AUT (Antenna Under Test) gives ΔΦ. • Source antenna moves linearly. • Accurately angular coverage for pattern. UNAL 2008  Page 16

  17. Spherical near-field measurement Source: [4] • AUT gives ΔΦ around Z axis for variable θ. • Source antenna is fixed in space. UNAL 2008  Page 17

  18. ANECHOIC CHAMBER UNAL 2008  Page 18

  19. Anechoic chamber Overview Purpose • Simulate free-space without electromagnetic contamination. • Ideal measurement: uniform plane wave. Types • Rectangular anechoic chamber • Tapered anechoic chamber Free-space ranges: null effects of surroundings Reflections ranges: use reflections to produce plane wave. UNAL 2008  Page 19

  20. Types • Rectangular anechoic chamber • Tapered anechoic chamber UNAL 2008  Page 20

  21. Rectangular anechoic chamber • Free-space conditions • Reflect energy to test region • No part of Main lobe is incident upon sidewalls, ceiling and floor. Where: R: Separation between source and test antennas W: Width or height of chamber Source: [2] UNAL 2008  Page 21

  22. Tapered anechoic chamber • Reflections from sidewalls contribute to field. • Source antenna position is determined experimentally • High frequencies become more difficult to place source antenna near to the apex. Where: ht: Perpendicular distance from source antenna to chamber wall R: Separation between source and test antennas hr: Perpendicular distance from test antenna to chamber wall λ: Wavelength Source: [2] UNAL 2008  Page 22

  23. References • M. Golio, “The RF an microwave handbook,” CRC press LLC, 2001, ch. 6, sección 6.9. • Antenna standards committee, "IEEE standard test procedures for antennas," ANSI/IEEE Std 149-1979, 19 Dec 1979. • Orbit/fr Inc, “Intorduction to antenna measurement,” http://www.home.agilent.com/upload/cmc_upload/All/ORFR-Theory.pdf • J. A. Fordham, “An Introduction to antenna test ranges, measurements and Instrumentation,” Microwave instrumentations technologies, http://www.lehman-inc.com/pdf/mag.pdf UNAL 2008  Page 23

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