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Mobile System Antennas

Part of system Propagation effects Environment Platform Manufacturing Performance. cannot be isolated diversity control pattern to match body effects / hazards exploit new technology reliable / user friendly. Mobile System Antennas. DESIGN CONSIDERATIONS. SYSTEM. ANTENNA.

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Mobile System Antennas

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  1. Part of system Propagation effects Environment Platform Manufacturing Performance cannot be isolated diversity control pattern to match body effects / hazards exploit new technology reliable / user friendly Mobile System Antennas DESIGN CONSIDERATIONS

  2. SYSTEM ANTENNA PROPAGATION ENVIRONMENT

  3. Size and Weight Trends in Mobiles & Pagers weight Mobiles 700g 87 97 Pagers 100g 87 97 10g Volume 100cc 1000cc

  4. Size now becoming limited by practicality of use rather than technology Mobiles Pagers 97 2002 Volume 100cc 1000cc

  5. Antenna Gain • Achieved by focussing (Directivity) • Inversely proportional to beamwidth • Expressed relative to “isotropic” source or “dipole” source • Proportional to “effective” aperture • Inversely proportional to wavelength squared • Gain = Efficiency x Directivity =

  6. Polarisation • Defined by the direction of the E-Field • For a dipole is in line with the dipole axis • Can be linear (V/H), circular (RH / LH) or elliptic (RH / LH) • Dual polarisation can be used for diversity

  7. Radiation Hazards? • Basic safe power density level ˜ 50W/m2 • NRPB recommended maximum Specific Absorption Rate (SAR) = 0.1W in any 10g of head tissue • ANSI controlled exposure limit = 0.4mW/g (averaged over the body); 8mW/g peak (over 1g); averaging time 6 min.

  8. Antenna gain is given by: • Ae is the effective aperture • Ae< physical aperture (eg dish) • Ae> physical aperture (eg dipole)

  9. Gain is achieved by focussing. The focussing is described by beamwidth & directivity. • Directivity increases as beamwidth reduces. • The beam gets narrower as the antenna is made larger. • Beamwidth is inversely proportional to antenna dimension

  10. Directivity is inversely proportional to beamwidth: • Gain is: • efficiency x directivity

  11. Radiation pattern for a rectangular aperture (3l by 2l) in dB magnitude polar form:

  12. Radiation pattern for a rectangular aperture (3l by 2l) in linear magnitude Cartesian form:

  13. Radiation pattern for a 3l by 2l planar array with beam steering, in linear magnitude polar form:

  14. Radiation pattern for a 3l by 2l planar array with beam steering, in linear magnitude Cartesian form:

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