This paper describes the performance analysis of a Ka-band Synthetic Aperture Radar (SAR) system working in joint mode, which is able to provide an adequate Cross-Track Interferometric (XTI) and Ground Moving Target Indication (GMTI) performance. The common major problem of joint mode is the low Pulse Repetition Frequency (PRF). To overcome this problem a long receive antenna is considered, which allows a reduction of the PRF, resulting in an increase of the swath widths. The receive antenna is constituted by nine equal reflectarray modules and the transmit antenna consists of two reflectarray modules, both antennas are able to work in narrow and wide swath modes.