Page 41 - Complete Wireless Design
P. 41
Wireless Essentials
40 Chapter One
Figure 1.48 Waveguide microwave transmission line.
Figure 1.49 The width of a
waveguide should be half a
wavelength.
Figure 1.50 Voltage, current, and impedance distribution on a matched
line, with no standing waves.
easily calculate a wireless device’s gain, return loss, stability, reverse isola-
tion, matching networks, and other vital parameters.
S parameters, or scattering parameters, are effective for small-signal design
in linear, Class A amplifiers. Typically practical only in amplifiers running
under 1 watt, they are not considered useful in most power amplifier designs
(RF power amplifiers operate at 1 watt and above). As intimated above, pow-
er is only one of the aspects that determine whether an RF amplifier can be
designed and described with S parameters: The amplifier must also be oper-
ated within its linear region. This would leave out any amplifier, even under
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