Cryogenic W-band LNA for ALMA band 2+3 with average noise temperature of 24 K

A cryogenic low noise amplifier that operates across the E and W-bands, from 65 GHz to 116 GHz, has been developed using 0.1-μm InP HEMT technology. Such wideband performance makes this work suitable for the ALMA telescope where two of its bands, 67-90 GHz of Band 2 and 85-116 GHz of Band 3, can be combined into one. At an ambient temperature of 5.5 K, this W-band LNA demonstrates an average noise temperature of 24.7 K with more than 21 dB gain and +/-3.0 dB gain flatness from 65 GHz to 116 GHz. To the best knowledge of the authors, this combination of bandwidth, gain flatness and noise temperature has not been demonstrated before.

I. Introduction

In this work, InP process has been utilized to develop this wideband cryogenic low noise amplifier. The development of this LNA is aimed to cover two separate ALMA bands, Band 2 and Band 3, which range from 67 GHz to 90 GHz and 84 GHz to 116 GHz, respectively. Currently, InP is the chosen receiver technology for operating ALMA at Band 2, and SIS mixer is baselined for Band 3 [6]. Our work demonstrates achievable performance at Band 3 with InP HEMT which can eventually replace the SIS mixer at this frequency range. HEMT technology is more convenient to build receivers on and does not required cryogenic temperatures as low as 4K at which SIS mixers operate. The presented LNA demonstrates such wideband response as to cover both Band 2 and Band 3. Thus, this technical achievement can ease the receiver complexity by combining Band 2 and Band 3 into one single band [7]–[8].