Adaptive spectrum exchange and modification using multirate filters

This paper presents adaptive spectrum exchange and modification methods using multirate filters. An input signal may be decomposed into a number of subsignals, and their spectrum may be exchanged and modified on a specified time-frequency plane in real time processing. The multirate filters are constructed based on well-known QMF bank structures. In our structure, once QMF banks are designed, adaptive processing may be realized with a simpler procedure. In a design, by introducing bifrequency maps, we formulate the multirate filters design completely. Design examples and experimental simulations are shown. One example includes an adaptive spectrum scrambling filter which can be applied in vehicle telephones for more secure communication