Controlled attenuators are key elements in a phased array's beam forming network and generally in all those systems requiring accurate control of the RF signal's amplitude and phase. Therefore the realisation of constant- phase digital attenuators is essential to obtain advanced system performance. A reactive element has been inserted in the traditional T topology digital attenuator to obtain equiphase condition and design equations have been inferred for optimum design. A MMIC X-Band 5-BIT constant-phase attenuator system has been designed and realised as a test vehicle for the proposed methodology.