A TE011Ka-band tunable filter with a stable and continuous tuning performance is presented in this paper. Both bandwidth and center-frequency tunability are demonstrated by cascading six-pole pseudo-low-pass and pseudo-high-pass tunable filters. A novel mode-splitter resonator and coupling configuration enabling cross-coupled planar TE011 filter realization is introduced in this paper. The concept can be applied to back-to-back coupled TE011 resonators as well. The filter design is verified through fabrication of multiple tunable filters that demonstrates 500 MHz of tuning range with a stable RF tuning performance.