A non-realtime modulation method, called time base modulation (TBM), has been studied and analyzed with computer simulations using fast fourier transforms (FFTs). Although TBM had been proposed and had the patents granted to the authors for constructing an analog modulation system with a bandwidth conversion technique for video signals, the characteristics had not yet been clarified. Using frequency analyses of correlations between sidebands of TBM and FM, in which TBM was not similar as it resembled FM, we confirmed that we could approximate frequency spectrum responses of TBM signals using Bessel functions with unique parameters different from modulation indexes of realtime modulation FM signals. The non-realtime modulation system can be applied not only to analog processing systems but also to new digital processing systems using digital coding modulation techniques with low noise characteristics similar to FM and time base conversion techniques of digital image information for high-speed transmittion systems.
