| Emerging air vehicle designs and applications are placing an increasing emphasis on reducing the size, weight, and power consumption of on-board electronic systems, sensors, and apertures. These requirements are especially acute for military aircraft where time on station, innovative aerodynamic designs and high performance sensors tend to push the designs in conflicting directions. Although the analysis and synthesis of conformal arrays have been studied for many years, only more recently have technological advances emerged that are increasing the push toward conformal arrays. Conformal array apertures have great potential for providing high performance, low weight, low power consumption systems with little or no impact to aerodynamic design. Thus, it is of interest to characterize the signals, analyze the performance, and investigate pattern synthesis techniques for conformal array geometries typical of airborne vehicles. A comprehensive performance analysis of conformal conical arrays for a notional airborne radar application is presented. The conical array geometry was chosen for its similarity to an aircraft or missile nosecone. The approach taken to achieve the performance analysis was to model an array of slot radiating elements on the surface of a right circular cone. The co- and cross-polarization element patterns were defined, along with shadowing caused by the curvature of the array. Then several array configurations were defined in terms of the element spacings, the total number of active elements, and the area occupied by the active elements. Scan volume and grating lobe performance were discussed in detail as well as the effect of element orientation on cross-polarization return. For sidelobe control a synthesis algorithm based on optimizing directivity subject to constraints of sidelobe levels was adapted and extended in several ways for the conformal conical array. Key among these was inclusion of the co- and cross-polarization element pattern components and the capability to apply the prescribed radiation patterns anywhere within the visible region. The performance capabilities were analyzed for a number of antenna performance parameters including grating lobes, sidelobe levels, scan volume, beamwidth, directivity, element count, and cross-polarization. The results are documented and causal relationships are analyzed. |
