Wideband active MMIC baluns -concepts and design

Abstract

For a wide range of circuits, within the RF and microwave design, balanced signals, consisting of two signals with equal amplitudes and with 180◦ phase difference, are preferred. One way of creating these is through the use of a balun, which converts an unbalanced signal into a balanced one. Active baluns are compact, wavelength independent circuits that can provide signal gain and a wide operational bandwidth. This work investigates three active balun designs operating between 2-18 GHz in 0.25 μm GaAs technology. The results are obtained from simulations in Keysight Advanced Design System using the UMS PH25-20 v.1.3.1 process design kit. The first concept combines a common-gate common-source with a differential pair, resulting in a balanced output with a common mode rejection ratio (CMRR) above 22 dB. The second concept combines three differential pairs, resulting in a CMRR of above 26.5 dB. The third concept consists of two parallel connected distributed amplifiers that create a matrix balun with a CMRR of above 22 dB. The simulated results indicate that the design concepts are suitable candidates for wideband active baluns implementations.