15-60 GHz asymmetric broadside coupled balun in 0.18 μm CMOS technology

A 15-60 GHz asymmetric broadside coupled balun fabricated in the standard TSMC 0.18 μm CMOS process is demonstrated. Using the broadside tight coupling technique, the balun is achieved with wide bandwidth and low insertion loss and utilises the inherent three-dimensional multilayer structure in CMOS technology. The balun achieves bandwidth of over 120%, the minimum insertion loss is better than 1.1 dB, amplitude difference is less than 1 dB and phase difference is less than 5deg (15-60 GHz). The occupied chip area is only 0.06 mm².