A High LO-to-RF Isolation 32-52 GHz Triple Cascode Down-Conversion Mixer with 2-12 GHz IF Bandwidth for ALMA Band-1

This paper presents a wide IF bandwidth (2-12 GHz) down-conversion mixer fabricated in 0.15-mu m GaAs pHEMT process with 32-52 GHz RE bandwidth for Atacama Large Millimeter / sub-millimeter Array (ALMA) band-1 application. The down-conversion mixer using triple cascode structure enhances LO-to-RF isolation about 19 dB from the conventional cascode mixer. This mixer achieves a wide IF bandwidth and high conversion gain by applying a modified bias line which converts high IF output impedance of triple cascode structure to close to 50 Omega and the RE amplifier stage in triple cascode mixer. It demonstrates measured conversion gains of 5.2-8 dB, 4-6.8 dB, 3.5-6.9 dB with different LO frequencies (30/35/40 GHz). The LO-to-RF, LO-to-IF and RF-to-IF isolations are greater than 37 dB, 37.7 dB and 21 dB.