A K-band area-saving marchand balun integrated with low-noise amplifier in 0.18-μm CMOS

A new topology of Marchand balun with a compact area is demonstrated in 0.18-μm CMOS technology. The lengths of coupled windings are reduced significantly from quarter wavelength compared to the conventional ones. The coupling coefficient between windings is designed for specific impedance matching. The S-parameters of the differential outputs are tested. The proposed balun is first fabricated without and with matching networks to verify the properties, and later integrated with a single-input differential-output low-noise amplifier (SIDO LNA). It is shown that the proposed balun is well suited to integrate with an amplifier that it not only serves as a DC-block but also provides a compact impedance matching. The balun shows an insertion loss within 6 dB from 20-30 GHz, amplitude and phase imbalances within 0.4 dB and 4
^o
, respectively. The LNA shows a differential gain of 15.8 dB and noise figure (NF) of 6.4 dB at 25 GHz.