Experimental Rotary Transformers For Antenna Power Supplies and Control [Antenna Designer's Notebook]

Rotary transformers can be effectively used for low-noise amplifier (LNA) or down-converter power supply and control signal transmission in scanning-antenna applications. Three air-core designs, utilizing a square wave at audio frequencies, using HCMOS logic and giving a 5 V/0.6 A dc power feed, are discussed. The constructions allow further installation of RF rotary joints or other coaxial hardware up to a diameter of 100 mm. They add about 30 to 80 mm to the overall height of the antenna, depending on application and requirements. Bearing replacement with such a transformer is also possible, if adequate tolerances are met and suitable coil-support materials are selected.