This paper is concerned with extending the energy transfer filters (ETFs) designs to a more general case where the design requirement is to focus signal energy from different input frequency bands into a desired output frequency range. ETFs are a class of non-linear filters recently proposed by the authors to employ non-linear effects to transfer signal energy from one frequency band to a different frequency location. The new ETF designs considered in the present study involve the development of an algorithm for determining output frequencies of non-linear systems subject to an input the frequency components of which are located in two separate frequency intervals and a new procedure for the implementation of the filter design. The results achieved provide an effective approach to the solution to a more general ETF design problem.