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antenna and generator question

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Mica188

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Hello,

A generator gives a 100 volts output in 3 secondes and it connected to an dipole antenna (assuming no loss in connection). What will be the fequency of this output that can radiated this maximum energy? Because a dipole its lenght is lamda/2 to radiate the maximum energy. How can you find the frequency of this generator?

Thanks,

Mica
 

jian

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Hi, Micca:

From your description, I am not sure whether you are interested in a time domain signal or a time harmonic signal. For 3 seconds, you can consider it as time harmonics if your signal is a sine wave. However, it is also possible you can put a purlse with the peak at 100 V for a period of time for a time domain signal.

From what I see, when you apply the pulse to an dipole antenna, the antenna will filter out the frequency for you. Only those spectrum fall into the resonances will be radiated out. At other frequency ranges, most of the power will be reflected back. Normally, a dipole antenna has very high efficiency (such as 98% net input power radiated out). Anyway, the radiated pulse will be of different shape as the original excitation due to either the mismatch and the radiation efficiency. Hope you can get some information from my comments.

Regards.
 

Mica188

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Thanks for your response.

What is the difference when you apply an impluse to your dipole and a sine wave? Correct me if I'm wrong, an impluse have a large spectrum of frequency then a sine wave which have a single frequency. So, if my antenna is a dipole, it is not necessarily to have an impluse because its frequency is related to its lenght. A dipole is a narrow band antenna.

Thanks again,

Mica
 

jian

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Hi, Micca:

You can apply an impulse or a sine wave to a dipole. Certainly, a dipole is not a very wide band antenna, if you apply an impulse to it, the radiated wave will havfe deformation on the waveform because the radiated energy will have different magnitides and phases at different frequencies. Basically, a dipole antenna is a filter and its passband is not wide, if you apply an impulse on it, the waveform will change. Regards.
 

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