Asymmetric CMOS switch for Dicke radiometer in millimeter-wave imaging system

An asymmetric Dicke switch implemented in bulk complementary metal-oxide-semiconductor (CMOS) technology is proposed to achieve high isolation and low insertion loss in the D-band. A Dicke switch eliminates the noise in the signal transmitted from the antenna, providing a high signal-to-noise ratio at the receiver front end. The proposed Dicke switch employs an asymmetric configuration for the signal transmission path and the reference noise incidence path, which overcomes the trade-off relationship between the insertion loss and isolation characteristics. The proposed asymmetric structure presents an optimum impedance in the reference component to achieve the same characteristics as those of the noise incident from the antenna port. The Dicke switch is fabricated using the 65-nm RFCMOS process with a chip size of 350 × 490 μm², including all the pads. The measurement results in the D-band present an insertion loss below 2.8 dB in the on-state and isolation above 22 dB in the off-state. The minimum insertion loss and maximum isolation were measured to be 1.7 dB at 155 GHz and 29 dB at 122 GHz, respectively.