The technological developments pioneered at the Korean VLBI Network for designing and implementing simultaneous multfiband (SMB) receivers paved the way to extending phase calibration and phase referencing techniques to the frequency space. Numerous advantages of this extension have been convincingly demonstrated at the KVN, and the time is now right to explore them on a larger scale. This would enable reaching an astrometric accuracy of ~10 microarcseconds, performing relative astrometric measurements at multiple frequencies, and increasing the dynamic range of mm-VLBI observations by factors of 20-50. A possible extension of the frequency-phase transfer (FPT) to 230 GHz is likely to bring a critically needed improvement of the quality of EHT imaging. Scientific potentials of implementing the SMB for mm- and sumnn-VLBI on a global scale will be discussed in this presentation.

Potential astrometric and astrophysical applications of simultaneous multiband receivers are discussed in the context of global VLBI observations at frequencies of 22/43/86 GHz and up to 230 GHz.