Ultrawide Band Antenna and Filter Design
Ultrawide Band Antenna and Filter Design
Ultrawide Band Antenna and Filter Design
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13<br />
The basic of antenna input impedance <strong>and</strong> radiation resistance<br />
Input impedance Zi→If you see antenna as a circuit,<br />
it is circuit constant characteristics of antenna<br />
when you see antenna part from I/O port<br />
Zi=Rr+Rl+jX<br />
Radiation resistance Resistance loss reactance<br />
e.g. half-wave dipole antenna<br />
73.13Ω<br />
As it gets bigger, heat loss will be increasing,<br />
<strong>and</strong> radiation efficiency of an antenna will be<br />
decreasing.<br />
Radiation efficiency =<br />
Rr<br />
Rr+Rl<br />
As Rr gets small, Rl cannot be ignored<br />
2005/11/3
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