Ultra Broadband Low-Power 70 GHz Active Balun in 130-nm SiGe BiCMOS

This paper presents an ultra broadband low-power single-ended to differential active balun. The balun has been fabricated using IHP SG13S SiGe 130-nm BiCMOS technology, which features an ft of 250 GHz and an fmax of 340 GHz. Conversely to other works, the designed circuit is based exclusively on two transistors in common-emitter and common-base configuration, fed by a current source with a high output impedance. Moreover, the design does not employ inductors accommodating a compact form-factor. A theoretical analysis demonstrates a single-ended to single-ended identical gain in amplitude for both outputs with opposite phase. Small-signal measurements validate the proposed work up to 70 GHz achieving a maximum phase and amplitude imbalance of 3.2° and 0.65 dB, respectively. Furthermore, a peak gain of 2.3 dB and a 3-dB bandwidth of 57 GHz are shown. Large-signal measurements show an input 1-dB compression point (IP1dB) better than −7dBm along the whole 3-dB bandwidth, together with a power consumption of 37 mW. The occupied silicon area is 0.42 mm2, pads included.