METHOD OF CONVERTING FREQUENCY TO VOLTAGE USING A SURFACE ACOUSTIC-WAVE DEVICE

A simple sampling technique for frequency to voltage conversion is described, using a surface acoustic wave (SAW) linear FM chirp filter as the central signal processing component. Results are exemplified for a 70-MHz FM discriminator with 18 MHz bandwidth, using a doubly-dispersive chirp filter. The measured nonlinearity of the conversion characteristic in this case is less than 1.8 percent of the full band excursion. Detection errors, resulting from variations in the amplitude of the output pulse from the chirp filter, are minimized using a zero-crossing detector. The application of the circuit as an Fm demodulator is also demonstrated. In principle, the method can be applied to such conversions at frequencies in the range from about 10 MHz to 1 GHz, while using the inherent wide-band capability accompanying the use of a chirp filter. Copyright © 1979 by The Institute of Electrical and Electronics Engineers, Inc.