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234 ANTENNA BASICS

frequency dependable complex amplitudes of these fractional signals. Furthermore, then
and there the sophisticated array feeding algorithm should be applied to evaluate the
multiple pattern directivities and beam shapes. Reader can find more detailed information
turning to the specialized literature [43].
5. The surge of atmospheric absorption of mm-waves depicted in Figure 5.3.9. For example,
the attenuation due to absorption in water vapor is about 0.1-0.2 dB/km in 27-37 GHz range
and rushes to 8-10 dB/km around 64-70 GHz. Meanwhile, at 0.7 GHz an attenuation is just
on the order of 0.01 dB/km. Such greater path losses might be overcome by higher beam
directivity, sophisticated signal processing, and reducing the separation between BSs. The
increased hardware and software cost due to the use of large-scale antenna arrays and
denser network should pay off handsomely since 5G terminals would have access to
different wireless technologies and wide range of services at the same time (see Table 5.3).
All good ideas and innovations will be implemented very quickly and on a large scale [39].

5.4 ANTENNA ARRAY FACTOR

5.4.1 Introduction

Antenna theory and design are based mainly on solving the synthesis problem, meaning how to
properly arrange some set of elemental or close to elemental radiators in space and time and

c)
a) b) Azimuth Electronic Elevation Electronic
or Mechanic Scan or Mechanic Scan

Direction of
incoming
aircraft

d) e) f)

Figure 5.4.1 Exemplary antenna patterns

develop an antenna structure and geometry as well its feed. These radiators can include an
electrical dipole, a magnetic dipole or a Huygens’ element. We have to be sure that the designed
antenna system has the far field pattern of a particular shape, certain input impedance and loss,
handles power without breakdown and satisfies many other requirements like mass and cost
based on system designation. At first glance, this task appears nor so challenging and
straightforward because we have comprehensive information about elemental radiators. Despite
this, the synthesis problem is a tough theoretical and technical challenge belonging to a class of