an idt produces a saw when excited by a single electrical pulse and can be fabricated to embody a code , which code provides for a passive autocorrelation of a saw input to the idt and thereby lends itself to further application as a signal generator in a communication device . however , internal dimensions of idts are inversely proportional to operating frequency , such that high frequency idts present significant manufacturing difficulties . fabrication of idts for high frequency applications is simplified by exploiting a harmonic frequency saw generated by idts . an idt may therefore be designed according to fundamental frequency internal dimension criteria but can operate at a multiple of the fundamental frequency , thereby providing much higher frequency operation than conventional saw systems . operation of a second harmonic saw system at 2 . 4 ghz based on a fundamental frequency of 1 . 2 ghz is contemplated .