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Abstract-A comprehensive study of the effects of the reflection phase profiles on dipole antennas is presented with the ultimate objective of designing ultrathin printed dipoles (as thin as one hundredth of the wavelength). Dipole driving-point impedance and bandwidth are studied as function of various electromagnetic bandgap (EBG) reflection phase profiles. It is demonstrated that although many different reflection phase profiles can be generated for a certain antenna height, it is the profile that satisfies a specific range of reflection phase angles that is required to achieve good antenna performance. Such optimum EBG phase profiles are generated for a number of antenna heights and their influence on a dipole antenna impedance and bandwidth are also studied. Finally, an actual EBG structure and a printed dipole antenna are designed, fabricated and tested. The overall antenna height for this case was 0 03 . The computed and measured results show that efficient printed dipoles on ultrathin grounded dielectric substrates can be developed that will substantially reduce the sizes and weight of large arrays.Index Terms-electromagnetic bandgap (EBG), input impedance, low-profile, reflection phase.

V. CONCLUSIONSThe dual-band and wide-band designs for a square-ring patch antenna with four shorting walls are presented. Three resonant modes with conical radiation patterns can be excited in the proposed antenna. The key parameters which affect the resonant frequencies of the three modes are studied, and it is found that these modes can make the antenna with the dual-band or wide-band operation if the width of the shorting walls is properly selected. For the dual-band design, the experimental results show the impedance bandwidths at lower and higher operating frequencies are 42 and 8%, respectively. The broad bandwidth at the lower operating frequency is due to the coupling of two resonant modes. Moreover, the two operating frequencies of the dualband antenna can be further coupled together and form a wide-band operation. Several prototypes with the wide-band operation are constructed and measured, and an impedance bandwidth of around 70% is realized. Also, the antenna can provide stable conical radiation patterns within the obtained impedance bandwidth. Therefore, the proposed designs are suitable for the applications of the present wireless communications. Abstract-A new low-cost smaller unit-cell planar electromagnetic bandgap (EBG) structure operating at the lower GHz frequencies (below 6 GHz) is proposed. EBG structures based on this new geometry are designed on a number of commonly available substrates. Characteristics of such structures, such as bandgap and reflection phase profile are analyzed. A simple empirical model is proposed to predict the surface wave stopband frequency of the proposed EBG structure. Finally, a low-profile dipole antenna is designed and tested for operation on the EBG structure. REFERENCES

Abstract-A new smaller unit-cell planar electromagnetic bandgap (EBG) structure is proposed on low dielectric constant low-cost substrate (TMM: r = 4 5 thickness = 25 mils) that has a stopband frequency at around 4 GHz. The proposed structure when placed in between a two-element printed dipole array results in over 13-dB reduction in mutual coupling and a significant improvement in antenna return loss bandwidth and gain pattern.Index Terms-Antenna array, mutual coupling, planar electromagnetic bandgap (EBG), surface wave.

A survey was conducted in different districts of Barisal division in Bangladesh during May-June, 2008 to assess the production, consumption and marketing of livestock and their products. A total of 114 farmers were interviewed, of which 26, 24, 21, 10, 10 and 9 % were in Patuakhali, Barisal, Barguna, Bhola, Jhalakati and Pirojpur districts, respectively under Barisal division of Bangladesh. The livestock keeping patterns of farm household’s were cattle, buffalo, goat, chicken or duck or any combination of these. Cattle and chicken population was high in all farm categories and due to marshy area duck was higher in number compared to other region. Cattle and buffaloes were also reared by share system. Average milk production per cow was found 2.25 liter per day. The small and large farmers sold the highest portion of the product and the medium farmers consumed most of their products. On an average, all farm households spent 29, 18 and 19 % income generated through livestock for their daily expenses, agricultural inputs and food, respectively. On an average, health and veterinary expenditure per household was 6.95 US$ (1US$=70BDT). Black quarter (23 %) and Foot and mouth disease (35 %) in cattle, Diarrhoea (39 %) and PPR (29 %) in goat, ranikhet (40 %) and fowl pox (34 %) in poultry were the common disease.