Antenna radiation control using electronic magnetic band gap

The ever growing wireless technologies pose new challenges for the design of antenna systems. The challenges can be related to the mechanical and electrical properties of the antenna, such as dimensions, compactness and low profile with the improvement of power directivity, gain and efficiency. The antenna design have experienced enormous advances in the last decades and still undergoing massive developments. Many new technologies have emerged including the development of the metamaterial structures. Electromagnetic band gap (EBG) structure can be considered as a metamaterial that possesses some interesting properties of high impedance and artificial magnetic conducting surface. This work is focused on developing EBG structures to control the surface wave propagation around the antenna. The sectorized EBG has been utilized to steer the beam around the microstrip patch antenna. The flexible beam directive antenna with an operating frequency of 2.2GHz has been achieved by integrating a TM01 mode microstrip patch antenna with an EBG. The circular EBG elements are arranged in six sectors with group of pin vias. Switching pin vias in and out from each sector has steered the beam into that sector. The flexible beam scanning antenna with a stable reflection coefficient has been achieved. In modern wireless communication, compact systems with high gain and efficiency are always needed. To achieve these requirements, a compact array utilizing the miniaturized capacitive loaded EBG with a total period of λ/36 has been developed. Pin vias been used to alter the EBG surface impedance, which controls the propagation of surface waves within the array elements. Switching pin vias on has increased the surface impedance to be infinite, which suppress the surface waves, whereas switching the pin vias out has reduced the surface impedance and altered the surface to become the artificial conductor. These EBG have ii isolated and propagated the signal within the array elements accordingly. The application of EBG to control and channel the signal within the array elements has been demonstrated. The other EBG application to control the radiation has been described for the phased array antenna. Large array of microstrip phased array antenna with a high gain and a directive beam has the problem of scan blindness with losses of power at a certain direction. This is due to the surface waves, which is bound to the array surface, which stores some of the energy. The array return loss near 0dB at the angle has demonstrated the severity of the problem. Miniaturized EBG which is placed within the array elements has efficiently suppressed the surface waves and improved the scan blindness problems. The simulation results using CST software has illustrated the EBG characteristics on controlling the antenna and array radiation. The novel finding of EBG characteristics in controlling the antenna radiation pattern by suppressing and propagating of surface waves is the main contribution of this research