How does it affect the impedance and radiation pattern of Archimedean Spiral antenna if the width of the turns are wider, if no. of turns gets increased or the spacing between the turns increased or decreased. Please help me understanding this concept.
Thankyou smriti. I read these papers but still not clear on my question. Can you guide more please?
An archimedian spiral antenna should be more than a wavelength in circumference and/or with matched loads at the circumference so that it behaves as a travelling wave antenna with only an outgoing wave. Otherwise the signal is reflected at the circumference and the impedance is not well behaved. If the arms are about as wide as the gaps the impedance will be about 188.5 ohms (half that of free space) and if the metal is thinner it will be a higher impedance and if it is thicker it will be a lower impedance.
Thankyou Malcolm, One more question: will there be any affect on impedance if the number of turns are more or less?
The number of turns does not affect the impedance, if the antenna is big enough. It radiates from the radius where it is a wavelength in circumference so it needs several turns after that so there is not much power left to be reflected.
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