An original coaxial structure allows operation of packaged MESFET at top noise and gain performance up to 24 GHz

An original mechanical solution allows a packaged MESFET to be used at least up to 24 GHz. Three radioastronomical bands can be tuned in with very little effort by the same unit, while physically larger unit copes with the 5 GHz band. The two intermediate frequency bands, subjected to more accurate investigation, showed outstanding performances after cooling at 20 K, as the gain rose to 15 dB while the noise temperature dropped to less than 40 K. Input return loss was about 5 dB across a 500 MHz bandwidth while output return loss was better than 15 dB over a similar frequency range. At 24 GHz an amplifier cooled at 77 K produced a gain of 5.5 dB and a noise temperature of about 70 K. It is concluded that coaxial techniques seem particularly suited for the full exploitation of MESFET potentialities even at frequencies beyond the manufacturers' limits.