In Ground Based Augmentation System (GBAS), non Gaussian tails are created by ionosphere when detecting a satellite payload fault with the Code Carrier Divergence (CCD) ground monitor. Ionosphere can also trigger alarms which is not distinguishable with the payload fault. Using multi-frequency observations which would be available in future supporting GBAS Approach Service Type F (GAST-F), a new CCD monitor is proposed with influence of ionosphere removed. The improved performance is shown with the empirical data and simulated scenarios. The worst case is concluded for analysis of compliance with the integirty requirement