Analyzing and designing of a dual band active antennas

A study has been done to analyze and design dual band active antennas. Dual band is accomplishing by combining two forms of helical antennas, i.e cylindrical and conical. The antenna has resonant frequencies of 860 MHz and 1800 MHz based on IMT-2000. An empirical equation has been suggested to calculate the resonant frequency of the antenna. Discussions also include the design of a four-port circulator for a resonant frequency of 2 GHz. This circulator has been used to isolate transmit and receive signals using the same antenna. The gain of the dual band antennas was amplified by using a Hewlett Packard MGA 86563 amplifier. The MGA 86563 is a MMIC (monolithic microwave integrated circuit) that offers a low noise figure and excellent gain so that this antenna can act as an active antenna. Using MMIC techniques, the circulator and amplifier can be combined together to be reduced to a small size which is suitable for any mobile communication systems.