Dual track filters with response folding

A concept of folding the transducer response is reported, detailed study of the properties of such structures and on the feasibility of their implementation is discussed. The prototype filter time domain response is assumed to be symmetrical. In this case an ideal reflecting element may be placed in the middle of the transducer, and only one half of the transducer is left, while the other half may be removed. This ideal reflector must be infinitely thin, frequency independent and 100% reflecting. However as real reflecting elements often make use of reflection arrays and different multistrip mirrors, there is not enough place to dispose such elements. In this approach the effective center of the lengthy reflecting element is placed in a second track parallel to the main track, in a position corresponding to the transducer center. Thus the transducer length can be decreased by an amount depending on the sidelobes number. This suggestion has been subjected to extensive modeling of different variants of reflecting elements including different reflecting arrays, transducers, combinations of tracks with multistrip couplers and truncation approaches