Broadening the range of resonance tuning in multiband small antennas

Antennas for portable terminals are to be small and preferably mounted inside a case. Due to clustering of mobile system bands there is an urgent need for antennas providing wide bands amongst others (500 MHz or more). When the operation over the desired number of bands is met, it is necessary to provide required bandwidth in each of the designated bands. To achieve this suitable means of tuning an antenna in separate bands are required. This is not a simple task because the ratio between the lowest and the highest frequency can exceed the number of seven. The broad range of tuning is needed for keeping a small number of antenna types, so a manufacturer can take advantage of cost-effectiveness.