I know this is something easy to do but I am kind of stuck on it.I have antenna with impedance changing with frequency,I have matlab function that will give me a microstrip tapped lines dimensions if I have a real impedance which is not my case.I know I can match this antenna simply on a single frequency so the question is how can I do this on broadband antenna?If I can get away of imaginary part of antenna impedance over my frequency of interest,then i can use my matlab function.
Anyone with relevant papers or suggestions?
Hi Jean,
until 9.8GHz you obtained a negative reactance, thus you can try to calculate an plot the equivalent capacitance. If it is not changing too much in the band you will just need to compensate with an inductance.
good luck
If the solution above does not work, I suggest you to work with Smith chart. Plot the curve in the full bandwidth and try different LC matching circuit and see how the curve behaves (using calculations for middle and limit frequencies).
Dear Jean,
Some important question!. How your imaginary impedance varies with frequency. From the basic point of view imaginary impedance's are reactances which vary with frequency. The capacitive reactance decreases with the frequency while the inductive reactance increases with the frequency. Can you display the reactance as a function of frequency? As matter of principle, capacitive reactants are compensated by inductive reactance and vice verse.
Best wishes
Thanks everyone for your input,I appreciate.@Zekry I have attached the graph of imaginary part of z.
The shown dependence of the antenna reactance points out that your antenna is equivalent to a series resonance circuit that has a resonance at about 9.6 GHz. If you want to broaden the bandwidth using matching circuit., this is possible by adding a parallel resonance circuit . By adding such matching parallel resonance one realize three resonance frequencies one of them is the original one of the antenna and two others which are displaced by an appreciable amount of frequency deviation around the the original resonance frequency.
Also the real part will be transformed to an other value. This method of broad band matching is treated in full details in the paper at the link:http://upcommons.upc.edu/bitstream/handle/2117/20022/05504933.pdf
Best wishes
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