A technique for reducing the grating lobes of the Molonglo Observatory Synthesis Telescope

The grating ring response of the Molonglo Observatory Synthesis Telescope can be reduced by the installation of 60-deg phase switches into each of 176 signal paths of the antenna. A suitable voltage-controlled UHF phase switch has been designed and tested at 843 MHz. It consists of two varactor diodes in series with a microstrip. Although designed to provide only two phase states, the device works well as a continuous phase shifter with a coefficient of about 3 deg per volt. Details of the design, performance, and application to the radio telescope are given.