Radio frequency will never be unemployed, because the communication system is constantly developing, such as cell phones 2G \ 3G \ 4G, every upgrade generation, the frequency is elevated, because the higher the frequency of electromagnetic waves to transmit data faster, the more data can be transmitted.
As the frequency changes, so do the antennas and filters. Because the design of antennas and filters is based on the frequency wavelength design, different frequencies can not be common.
Communication system upgrade every generation, the operator save invested a lot of money to build communication base station, is those antennas. You then look at Huawei how rich. You will know how the prospects of RF.
Of course, engage in radio frequency is not just the design of cell phone antenna, it can be said that as long as it is through the wireless technology to transmit data to the electronic equipment, there are antennas, there are filters, such as the wireless mouse, wifi, bluetooth and so on. People are not satisfied with the existing demand, for example, there are always people complaining about the signal is not good, that most of the reason is that the antenna design is not good, the coverage is not enough, the gain is not good, so to design a better RF device.
You should have studied electromagnetic fields electromagnetic waves, those things are difficult or not, you should also know.