AN IMPROVED DRONE TRACKING CONTROL SYSTEM TRANSPONDER

Abstract

Improved performance has been achieved in the new Herley design of the Model MD700C-1 Drone Tracking and Control System, C-band Command and Control Transponder. The approach for obtaining better radio frequency rejection, automatic gain control, local oscillator stability, and power supply efficiency is described. New hybrid microwave integrated circuit application techniques were used to design a small local oscillator, tunable over the 5400 to 5900 MHz range with a frequency drift of less than ± 1 MHz. This low frequency drift allowed the use of a 4 pole immediate amplifier filter, 60 dB down, at 40 MHz bandwidth, which, when coupled with the three cavity radio frequency preselector filter, provides 7 pole out of band rejection for unwanted radar signals operating at close frequencies. To augment the out of band rejection, a new form of 75 dB dynamic range automatic gain control was used, which combines signal attenuation with a circuit that reduces immediate frequency noise with increasing signal. This allows rejection of the radars own in-band multipath signals by reducing the gain and threshold sensitivity. To reduce power consumption and heat while operating over a wide voltage range, a switching mode regulator and a nonsaturating core power supply was designed to operate at 80% efficiency. Compared to units in field use over the past 10 years, the new design shows improvements of 400 percent in local oscillator frequency stability, 30 percent in out of band frequency rejection, 66 percent in the automatic gain control dynamic range, and 60 percent in power supply efficiency. The MD700C-1 was developed by Herley Industries for the USAF SMALC, and is currently in production.