Mode Locked Surface Acoustic Wave Oscillator for Coherent Frequency Signal Synthesis.

Abstract : A new type of frequency synthesizer utilizing Mode Locked SAW oscillators, CZT transducers, and rapidly switchable nonlinear diodes was experimentally demonstrated to be both feasible and promising. The conclusions from this work with a first preliminary model are as follows: The Mode Locked SAW Oscillator (MLSO) is able to provide a set of synchronized and stable short rf pulses with lengths in the range of 50 to 100 nseconds. These pulses can efficiently drive a set of CZT transducers that are used for generating counter flowing SAW discrete chirp signals. By using the sum frequency, signals are synthesized directly at rf frequencies. The Chirp Z Transform approach to frequency synthesis is particularly attractive because it provides means for switching frequencies in a coded sequence within time intervals as short as 50 ns. This was achieved experimentally in the present program. Equally important is the fact that the frequencies are determined only by the physical position of the selected taps.