A STUDY OF ELECTRONICALLY TUNABLE MICROWAVE (X-BAND) GENERATORS.

A completely solid-state X-band transmitter has been breadboarded and demonstrated and has achieved a power output of 175 milliwatts from a total DC power of 8 watts. The DC-to-RF efficienty of this device is approximately 2.2. It is important to note that each element in the transmitter had a greater efficiency when operated as an individual unit than when operated as a cascaded device. For example, the transistor oscillator multiplier had an efficiency of 30 with a power output of 2.25 watts at 1.25 Gcs. The varactor doubler from 1.25 to 2.5 Gcs had an efficiency of 60 throughout the required tuning range. Hence, the power delivered to the final bimode quadrupler should have been in excess of 1.3 watts. The bimode quadrupler had an experimental efficiency of 30. The reason for the reduction in efficiency when all units were cascaded is that a broken connection occurred in the varactor doubler, thereby greatly reducing its overall efficiency. It is expected that when the doubler is repaired the overall X-band transmitter will have a 190-milliwatt power output and an overall efficiency of between 5 and 5.4.