Cryogenic low noise amplifier for phased array antenna

We have developed a cryogenic low noise amplifier (LNA) for phased array antenna. By using this cryogenic LNA, a low noise receiving antenna can be easily available for wireless applications such as radar systems, communication systems, and so on. In this paper, we describe an S-band cryogenic LNA with an RF interfaces having both low loss characteristic and thermal isolation characteristic. The RF interface is realized by coupling resonators with vacuum gap of 1 mm and also has narrow band characteristic. The noise temperature of the cryogenic LNA at 77 K was improved to less than 1/5 as compared with the noise temperature of the same LNA at room temperature.