Guest tandrroman Posted November 21, 2013 Report Share Posted November 21, 2013 Hi all, I need some help on a coil antenna design. I have been tasked to design a small low frequency (24Hz) beacon. The design of the electronics is very simple. I am using a square wave generator that drives a low side MOSFET switch, which in turn used to drive the antenna. The MOSFET driver ON time is 0.025s and OFF time is 0.018s. If I understand correctly the coil antenna can be represented as an inductor connected to my MOSFET switch (please correct me if I am wrong). I am using the following equation to compute the peak current: VL = L di/dt, then L = VL dt/Ipeak. Ipeak current has to be around 0.1A and I am driving the coil with 12V square pulse. So, if I am using the correct equation L = 12V 0.025 / 0.1 = 3H. Next I need to determine all the parameters for the antenna. I have found the following web page which describes a very similar design: http://www.cnktechlabs.com/index_fil...ennaDesign.htm. According to the article presented on the site an antenna radiation depends of the area and the number of turns. I need to know how can I determine the number of turn to maximize the radiation efficiency of my antenna and at the same time to keep the peak current under 100mA (to conserve battery life). Can I trust those equations presented on the webpage? They compute number of turns by the following equation:Is that equation correct? Quote Link to comment Share on other sites More sharing options...

Hero999 Posted November 22, 2013 Report Share Posted November 22, 2013 24Hz? Are you sure you don't mean 24kHz?24Hz is far too lower frequency to be of any use. You'd need an enormous antenna. The wavelength is 12491km which is the approximate diameter of the earth. Quote Link to comment Share on other sites More sharing options...

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