Design and implementation of squared and octagonal W‐band CMOS marchand baluns for W‐band communication systems

Abstract

ABSTRACT An enhanced squared and an enhanced octagonal W‐band CMOS Marchand baluns for direct‐conversion transceiver are reported. These Marchand baluns can be applied to an up‐conversion mixer for converting the single local oscillator input signal into differential signal, and converting the differential RF output signal to single signal. They can also be applied to a subharmonic down‐conversion mixer for converting the single RF input signal into differential signal. Instead of the traditional Marchand balun structure that uses three sections of thin (0.53 μm) M 5 interconnection lines (underneath the thick (2.34 μm) M 6 main structure), the proposed balun structures use only one section of thin M 5 interconnection line to improve S 21 and S 31 . The squared Marchand balun occupies a small chip area of 0.0313 mm 2 , and achieves S 21 of −4.19 to −4.53 dB, S 31 of −4.28 ∼ to −4.42 dB, magnitude of amplitude imbalance (MAI) smaller than 0.11 dB and deviation of phase difference (DPD) smaller than 4.3° for frequencies 75 ∼ −85 GHz. The octagonal Marchand balun occupies a small chip area of 0.0288 mm 2 , and achieves S 21 of −4.56 to −5.03 dB, S 31 of −4.56 to −4.86 dB, MAI smaller than 0.18 dB and DPD smaller than 2° for frequencies 75–85 GHz. The state‐of‐the‐art results of these proposed baluns indicate that they are suitable for W‐band communication systems. © 2014 Wiley Periodicals, Inc. Microwave Opt Technol Lett 56:2205–2211, 2014