This paper describes cryogenic broad-band amplifiers with very low power consumption and very low noise for the 4-8-GHz frequency range. At room temperature, the two-stage InP-based amplifier has a gain of 27 dB and a noise temperature of 31 K with a power consumption of 14.4 mW per stage, including bias circuitry. When cooled to 15 K, an input noise temperature of 1.4 K is obtained at 5.7 mW per stage. At 0.51 mW per stage, the input noise increases to 2.4 K. The noise measurements have been repeated at different laboratories using different methods and are found consistent.

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This paper explores the potential of metallic 3-D printing technology for millimeter-wave (mmWave) applications. It uses the selective laser melting (SLM) technology to melt the Cu-15Sn powder layer by layer to build up rectangular waveguides at E-(60-90 GHz), D-(110-170 GHz), and H-band (220-325 GHz). Different from nonmetallic 3-D printed waveguides, SLM Cu-15Sn waveguides are printed once in a whole piece. Postelectroplating and assembling are not necessary. Besides, the SLM waveguide also outperforms the nonmetallic 3-D printed waveguide in mechanical robustness. Compared with nonmetallic 3-D printed and commercial metallic waveguides, SLM waveguides demonstrate comparable performance at E-band with averaged dissipative attenuation 7.51 dB/m and 7.76 dB/m for 50-and 100-mm waveguides, respectively. The attenuation of SLM waveguides is acceptable up to D-band.We prove the potential of the SLM technology for mmWave applications in both prototyping and mass production.