A Novel Broadband Active Balun

We have developed a novel broadband active balun. It consists of series-connected common-gate FETs and a common-source FET. The active balun achieved broadband characteristics by using series-connected common-gate FETs with the same gradient as the phase performance of the common-source FET. From 500 MHz to more than 10 GHz, the fabricated active balun shows a phase error of less than 5 degrees. A fabricated single balanced mixer using the proposed active balun had LO suppression of more than 40 dB over an LO frequency range of between 1 and 5 GHz.