Ultrawide Band Antenna and Filter Design
Ultrawide Band Antenna and Filter Design
Ultrawide Band Antenna and Filter Design
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Variety <strong>and</strong> principle of ultra wide b<strong>and</strong> antenna<br />
log-periodic antenna<br />
20<br />
β<br />
α<br />
Although structure is self-complementary,<br />
it has wide b<strong>and</strong>width characteristics for<br />
infinite spread. Therefore in principle<br />
b<strong>and</strong>width characteristics is smaller than<br />
self-complementary antenna.<br />
It is practical structure than<br />
self-complementary antenna<br />
Its structure is that antenna characteristics<br />
repeat periodically in proportion to log of frequency.<br />
Invented by DuHamel in 1955<br />
α+β=90°→self-complementary condition<br />
Rn+1<br />
Rn =τ(constant)→ log-periodic condition<br />
Element that is L distance from feed point<br />
decide resonance frequency.<br />
Maximum dimension decide<br />
adjustment resonance frequency.<br />
Input impedance=189Ω<br />
When α=45°τ=0.5, b<strong>and</strong>width is 5:1<br />
2005/11/3
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