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• W121209482 abstract "Ground Surveillance Radar (GSR) requires a phased array, conformal cylindrical antenna solution that has specific features (electronically scan the azimuth and elevation, with angular width of ca. 6° in both directions, and dimensions of ca. 30 cm in radius and height), working between 10 GHz and 10.5 GHz. The task is to prepare the requirements and specifications for the antenna in cooperation with the system user, then conduct a study and simulate the resulting performance where analysis are carried out in CST Microwave Studio, and MATLAB. Then the results are evaluated in relation to the required specification. Efforts seek to define the optimal parameters for the antenna. With that in mind, the suitable antenna structure was chosen to be a microstrip patch. These antennas have the advantages of light weight, high gain, conformability to various surfaces, low cost of fabrication, and versatility in terms of input impedance. Their ability to integrate with microwave integrated circuits, plus their low profiles makes them an unmatched rival for other antenna types. As the first step, a single element, single layer rectangular microstrip patch antenna was designed and simulated. Next, a planar array consisting of these single elements was optimized and synthesized. Antenna simulations in this work have been mainly carried out in CST Microwave Studio, and some of them in MATLAB. The studies began by calculating the necessary dimensions for the single element patch antenna, and then parameterizing the CST with the obtained dimension values, and simulation in CST. As in any practical system, there is always a deviation between the theoretical values and the practical results. Thus some changes had to be done in the antenna dimensions, so that it fitted the system requirements and needs; requirements such as return loss value (S11) and the resonance frequency (10.25 GHz) of the antenna. The simulation values based on the theoretical calculations, were S11=&#8208;9.59 dB at 9.65 GHz. By adjusting and optimizing the dimensions of the patch, a reduction of return loss value was observed from &#8208;9.59dB to &#8208;47.32dB at the desired resonant frequency which was 10.25 GHz, indicating a great match at that frequency. Furthermore, some antenna parameters such as the substrate height (h), patch width (W) and length (L), and the metallic layer thickness (Mt) were also changed to see how each of these factors contributed to the overall antenna performance. As the next step in the design, an arbitrary 24×12 planar array was constructed, and elements were excited with different input excitation signals, and it was observed that the binomial signal gave the lowest SLL value of all excitation signals, but the 3dB angular width of the beam (both in &#952; and &#966; directions) was too wide to be used in the array. The lowest values of angular width were obtained by the uniform excitations, which was ideal, but the SLL value was too high (just &#8208;13.2 dB), which again was outside the specification boundary of at least &#8208;20dB. All of the input excitation signals exhibited roughly the same amount of directivity. Thus, based on the results, Chebyshev excitation was chosen that had an SLL value of &#8208;30 dB, and an angular width of 6.1° and 8.2°. On top of all these requirements, the appearance of grating lobes on the radiation pattern had to minimized as much as possible, as they represented the unwanted radiation in directions other than the direction of interest. In the final stage, after choosing the suitable input signal waveform, the optimization of the spacing?s between the antenna elements was carried out, to have the lowest value of SLL (obtained: &#8208;22.5dB) and lowest possible angular width (obtained: 6.1° and 6.5° in the &#952; and &#966; directions respectively). Both these values were within the boundary of the specifications and thus were satisfying. Furthermore the effect of parasitic mutual coupling in the simulated planar array was studied, and it was shown that it degraded the array performance by changing the single element antenna input impedance (Zin), which resulted in a mismatch between the feed and the antenna itself, which ultimately caused a different antenna performance and behavior, e.g. the S11 value changed dramatically. One of the requirements of this antenna solution was its shape and ability to be phased steered. It was supposed to be a conformal, cylindrical, phased array antenna. Unfortunately due to some problems with the CST program, and not having the sufficient and required information to be able to connect and log in to its website (to use the online help, tutorials and instructions, provided by the CST producers on how to bend, and phase steer the planar structures), the writer, was not able to bend the planar array structure to a cylindrical form. Therefore an octagonal (rather than cylindrical) multi&#8208;beam antenna (MBA) was constructed. Just to have a comparison, a linear array in CST is rather easier to be bent, because it extends in only one direction, and on top of that, one does not necessarily need to design the feed network for the antenna elements, as they can be fed by the already&#8208;defined discrete ports in CST from the feed entrance of the antenna elements, with desired amplitude distribution and phase to the elements to form a linear phased array antenna. Thus bending the structure becomes much easier than in the planar structure case. A planar array however, extends in both x and y directions, and therefore it needs special knowledge of the CST program to feed the elements (with the suitable amplitude and phase distribution) and bend the structure. However, despite all these difficulties, one can rely on the works done in the previous studies [5,6] that basically have bent the microstrip patch antenna and concluded that the curvature of the antenna resulted in a significant influence on the fringing fields of the antenna, and consequently, an impact on the &#949;reff, which ultimately led to a change in antenna performance. For a given cylindrical antenna with radius R, it was shown in [5,6] that fresonant changed very little, so it could be considered untouched compared to the planar single element antenna. Furthermore decreasing R resulted in a reduction in resonant resistance and Q factor, while the antenna efficiency and its bandwidth increased and the radiation pattern widened." @default.
• W121209482 created "2016-06-24" @default.
• W121209482 creator A5054191663 @default.
• W121209482 date "2013-01-01" @default.
• W121209482 modified "2023-09-24" @default.
• W121209482 title "Design of a Conformal Ground Surveillance Radar (GSR) Antenna" @default.
• W121209482 hasPublicationYear "2013" @default.
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