This paper presents a circularly polarized Corporate-Fed Radial-Line Slot Antenna (CF-RLSA) operating in Ka-band and realized in low-cost, low-profile printed circuit board (PCB) technology. The radiating aperture is fed by a corporate feed network based on a broadband pillbox-like circular transition. The proposed feeding system results in a 67% gain bandwidth improvement compared to classical center-fed RLSA designs. Pattern stability versus frequency is also achieved. The bandwidth improvement provided by the corporate-feed topology is analytically derived for the general case of circular apertures with uniform amplitude illumination. This predicted improvement is confirmed by measurements. The prototype is optimized using a dedicated numerical tool, then fabricated and characterized. A good agreement is obtained between simulated and measured gain bandwidths, with a demonstrated relative bandwidth of 6.9% at 29 GHz for a maximum gain of 35.5 dBi and a 260 mm diameter for the radiating aperture.