Antenna Measurement techniques indoor and outdoor

Antenna Measurements

1. ANTENNA MEASUREMENTS

2. Fundamental Antenna Parameters RADIATION PATERN DIRECTIVITY GAIN

3. RADIATION PATERN R adiation pattern  defines the variation of the power radiated by an antenna as a function of the direction away from the antenna and observed from the antenna's far field.

4. Radiation Pattern- Types Radiation Pattern-Linear Scale Field Pattern- Plot of Electric or Magnetic field vs. Angular space Power Pattern- Plot of square of Electric or Magnetic field vs. Angular space Radiation Pattern- Logarithmic Scale Power Pattern- Plot of Electric or Magnetic field in dB vs. Angular space

5. Radiation Pattern-Linear Scale Field Pattern Power Pattern

6. Radiation Pattern- Logarithmic Scale

7. Radiation -Types Isotropic-a hypothetical antenna having equal Radiation pattern in all direction Directional-Radiating/Receiving radiations more effectively in some direction Omni directional-Non directional Pattern in a given plane and directional Pattern in any orthogonal plane

8. Isotropic Radiation

9. Omni Directional Radiation

10. Directional Radiation

11. Directivity Ratio of radiation intensity in a given direction to the radiation intensity averaged over all directions (Total Radiated Power)

12. Partial Directivity For Antennas with orthogonal Polarization components Total Directivity is the sum of Partial directivity for any two orthogonal Polarization

13. Partial Directivity Part of the radiation intensity corresponding to a given polarization divided by radiation intensity averaged over all direction

14. Partial Directivity

15. Gain Ratio of radiation intensity in a given direction to of radiation intensity that would be obtained if power accepted by the antenna were radiated isotropic ally

16. Relative Gain The ratio of Power Gain in a given direction to Power gain of a reference antenna in a reference direction(lossless isotropic source)

17. Gain-IEEE Standards Gain does not include losses arising from impedance mismatch and Polarization losses

18. Absolute Gain Gain that includes losses arising from impedance mismatch and Polarization losses

19. Partial Gain Part of the radiation intensity corresponding to a given Polarization divided by radiation intensity of an Isotropic antenna.

20. Why measure Antenna Characteristics? To check whether the designed Antenna confirms to the design specification. Electromagnetic Interference (EMI) Electromagnetic Compatibility (EMC)

21. Antenna Measurements

22. Antenna Measurements Test Antenna in receiving mode Reciprocity- received signal characteristics identical to that of transmitted one Large out door distance-Far field region Matched Polarization with a sense of rotation Uniform Plane Wave

23. Out door Antenna Measurements Uncontrolled Environment and Seasonal Variation of capability Reflections and unwanted Interferences from other sources Logistics issues for large Antennas Enormous time Requirement Expensive

24. Antenna Measurements Reflection Ranges Free Space Ranges Elevated Ranges Slant Ranges Anechoic Chambers Compact Ranges Near Field Ranges

25. Antenna Instrumentation Source Antenna and Transmitting Antenna Receiver Antenna Positioning System Recording System Data-Processing System

26. Antenna Instrumentation

27. Antenna Instrumentation Source- Polarization control, Frequency control, Spectral Purity, Power level and Modulation Receiver- Detector, Amplifier, Recorder, Greater Sensitivity, Precision, Dynamic range and Heterodyning Recorder linear Plot, Polar Plot, Relative plot and Absolute Plot.

28. Antenna Measurements

29. Mounting Structures

30. Antenna Instrumentation

31. Gain Measurement Gain depends on frequency Absolute Gain-requires a priory knowledge of Antennas-Two antenna , Three Antenna method Gain Transfer-a standard Gain Antenna used in conjunction to find absolute Gain of AUT

32. Gain Measurement

33. Gain Measurement

34. Two Antenna method

35. Three Antenna method

36. Gain-Transfer Method Utilizes a Standard Gain Antenna Initially a Relative Measurement is taken Compared with gain of a standard Antenna

37. Directivity Measurement Measure the two principle E & H Pattern of Test antenna Determine HPBW of E & H Pattern

38. Anechoic Chamber Indoor Facility High Isolation from External Environments Suitable for Highly Sensitive measurements Indoor enclosures made up of EM absorbing materials Carbon impregnated polyurethane foam pyramids

39. Anechoic Chamber

40. Anechoic Chamber

41. Reference “Antenna Theory : Analysis & Design”, 3/e C.A.Balanis , Wiley Interscience , 2005.