In this paper we report the development of a loadbearing outer surface that enhancedantenna performances, and is termed CSS for ‘composite smart structure’. A CSS is amultilayer composite sandwich structure in which antenna layers are embedded. Two typesof CSS are designed. One uses a direct-feeding stacked patch antenna and theother an aperture-coupled patch antenna for electrical performances. The designprocedure is presented including structure design, material selection and design ofantenna elements in order to achieve high electrical and structural performances.Antenna design is processed at a central frequency of 12.2 GHz and a bandwidthover 1 GHz. Honeycomb thickness under the outer facesheet is selected for themost efficient electrical performances. A high gain can be obtained by placing anouter facesheet at a resonance position of the radiated field, which is half thewavelength distance from the spot which the radiation originates from. Measuredelectrical performances show that CSSs have a wide bandwidth over 10% and ahigher gain than the antennas before they are embedded, and no doubt theyhave excellent structural performances due to sandwich effects by compositesand honeycomb cores. With the CSS design concept, antenna efficiency can beimproved with structurally effective materials of high electrical loss. The CSSconcept can be extended to give a useful guide for manufacturers of structural bodypanels as well as antenna designers, promising innovative future communicationtechnology.