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-µm GaAs pHEMT process with 32–52 GHz RF bandwidth for Atacama Large Millimeter / sub-millimeter Array (ALMA) band-1 application. The down-conversion mixer using triple cascade 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 cascade structure to close to 50 Ω and the RF 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.