Methods of improving the resolving power of quadrupole mass analyzers were studied theoretically. The results showed that use of two AC powers on top of the main radio-frequency(RF) supply enabled appropriate modification of the first stability diagram for mass filtering by creating a narrow and long stable band along the X boundary near the tip of the first stability region. These newly developed X-band stability regions are similar to higher stability regions, featuring high mass resolution and fast mass separation. They allow many of the normal operational limitations of quadrupoles to be overcome while maintaining the advantages of using the first stability region. The new operating mode can have mass resolving power of 10000 with ion residence time of only 100 RF cycles. Additionally, the ion transmission efficiency is not only affected by use of the X-band, but is higher than that of the normal operation mode. The proposed mode features one-dimensional mass filtering(X-direction only), and is insensitive to nonlinear field distortions, particularly for quadrupole mass filters built using circular rods. Faster mass separation was confirmed through simulations and theoretical computation of the exponential increment of trajectory instability. Because the X-band is located near the tip of the first stability region, the mode retains the benefits of traditional techniques(delayed DC ramping) to overcome fringe field effects and improve ion transmission efficiency. Simulations showed that the proposed method does not require any mechanical structure modifications, and only requires a slightly more sophisticated electrical application method.