IMPLEMENTATION OF KAISER FUNCTION ON POWER WEIGHTING DISTRIBUTION METHOD FOR ANTENNA ARRAY PERFORMANCE ENHANCEMENT

• Main Author: Mistialustina, Hartuti
• Format: Dissertations
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/77859
• Institution: Institut Teknologi Bandung

The need for antenna array in various telecommunication applications has been triggering the development of antenna array design technology. Mainly, performance metrics of antenna arrays are gain requirements, pattern requirements, and other requirements based on their application. To satisfy the performance metrics, especially in pattern requirement, one of the methods is the weighting power method. Weighting in antenna arrays can be implemented based on the power of signal excitation of each array elements, whether on amplitude, phase, and a combination of both. Amplitude weighting is implemented by distributing the current in specific configuration, so it has an impact in power distribution on each element. The features in performance metrics related to radiation pattern that are satisfied by power-weighted antenna arrays are mainly about Sidelobe Level (SLL) suppression and other features of pattern requirement based on their application. The development of power weighted antenna array method is basically dominated by window .function as a weighting coefficient and its modification using specific techniques or an algorithm. Modifications to the use of power weighting distribution method are dominated by algorithm for coefficient optimization and other simple-to-more complex techniques. The use of these techniques enhances metrics performance achievement in some features other than SLL suppression, for example, Width of Mainlobe (WML), polarization, gain enhancement, etc. The results of some prior research show that the use of Chebyshev window .function is still a favorite window in the power weighting distribution method. The average SLL suppression using this window.function is about 25 dB. There are many opportunities to use other window functions. Kaiser .function is a good alternative. Some references show that the use of Kaiser .function as weighting coefficient gives SLL suppression greater than 25 dB. The Kaiser function also has similar flexibility as the Chebyshev function. The implementation of Kaiser function in the design of antenna array can be an interesting starting point for exploration, considering that the opportunity to make various modifications based on the performance metrics requirement is still very wide. It is expected that the results of this study can be a contribution to the field of antenna array design by providing exposure and proof of the Kaiser .function implementation as an alternative weighting coefficient with performance in the SLL suppression based on the target. The nature of performancemetrics that are iii prioritized is in terms of SLL suppression and then other properties according to the needs of supported applications. In this study, a theoretical as well as an experiment approach have been carried out to investigate the performance of linear antenna arrays with Kaiser function weighting or Kaiser linear array (KLA). Modifications are made in KLA design simulation in forms that can be realized into prototypes. Observations from simulation results and measurements of realization results are carried out on several parameters, including gain, S11 (reflection coefficient), and radiation patterns (SLL, WML, front-to-back ratio (FBR)). The proposed design uses the Kaiser function as a weighting coefficient with a Kaiser parameter value (/J) of 2 for an SLL target of 29 dB, with a total of 8 elements (N) at the frequency of 3 GHz, and a modified design of the antenna array, especially in the feeding network structure. The simulation results from the KLA (P=2), which is proposed to give an SLL suppression value of24.54 dB-25.24 dB in the simulation results and 27.96 dB- 33.3 dB in the measurement results from the prototype, are taken at the frequency value of 3.11 GHz. The performance of KLA (P=2) is also compared with linear array antennas with uniform distribution or uniform linear array (ULA). ULA development is carried out with the shape of antenna similar to the KLA (P=2) antenna structure. ULA gave SLL suppression of 13.38 dB for the simulation results and 7.65 dB - 15.99 dB for the measurement results, which both are taken at frequency of 3.15 GHz. In addition to linear antenna array, this study also developed 4x8 planar antenna array by compiling KLA (P=2) as many as 4 pieces, where the feeding network is a uniform distribution or also called planar array uniform-Kaiser, P=2 (PAU-K, P=2). The application of uniform distribution and Kaiser weighting has an influence according to the axis coordinates of the application carried out. In the PAU-K (P=2) radiation pattern on x-axis (rp=0°), the SLL suppression is 22.43 dB- 22.98 dB, while on the y-axis (<p=90°), the SLL suppression is 13.56 dB -15.81 dB. The measurement results are confirmed by pattern multiplication, both for KLA (/3=2), ULA, and PAU-K (P=2). Confirmation of KLA (P=2), ULA, and PAU-K (P=2) shows similar results although not entirely the same, considering pattern multiplication using an array factor calculated under ideal conditions. This confirmation process is proven by the realization results that has been carried out. Overall, the results of this study show that the Kaiser.function is proven to be an alternative weighting coefficient that can provide SLL suppression values based on the target, either on linear antenna array or planar antenna array. Other parameters such as gain, WML and FBR were also observed in the performance evaluation of variations in the type of feeding network, N and the distance between elements (d).