Broad and Narrow-Band Frequency Discriminators using Dual Gate GaAs Field Effect Transistors

The use of a dual-gate gallium arsenide FET as a broad-band (and narrow-band) frequency discriminator is described. Such a circuit has use in IFM systems and phase locked loops respectively. The discriminator employs a GaAs FET amplifier used as a limiter followed by a dual-gate device whose phase angle differences between the first and second gate to drain transmission coefficients with frequency can be employed as a frequency sensitive element. The paper describes the biasing needed of the device to achieve optimum performance and details the results of a full X-band discriminator using the methods outlined.