IF I want to match the impedance of Archimedean spiral antenna with the components like R, L, C. The impedance of antenna is 180 ohms with plus minus 20 ohms reactance. Please suggest and help
Exactly what is your requirement?
Would you like to know the value of R,L and C?
Make a 50 to 180 ohm transformer. The reactance component is not significant and doesn't need to be matched unless you object to reflecting 1% of the power.
At higher frequencies the transformer could be a tapered line, which you may be able to put on one of the spiral arms and feed from the outside edge and thus get a balun at the same time, or at lower frequencies you could wind a transformer.
Thankyou. and If we want to use a resistance for this, what value of resistance would you suggest. Thankyou
If you use a resistance then you need 69 ohms in parallel with the antenna (i.e. across the antenna terminals) but over 72% of the power will be lost in the 69 ohm resistor and less than 31% will get to the antenna. It would be better to leave it unmatched which will reflect 32% of the power back to the generator, if the generator can stand it, and about 68% will go into the antenna. If you feed it with co-ax then it will probably be unbalanced which will change the impedance and may mess up the radiation too. A spiral antenna requires a balanced feed which is why a balun (or transformer) is needed if it is fed from co-ax.
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