A Multi-Band and High-IRR Down-Conversion Mixer for 5G NR FR2 Using Compact Transformer-Based Mutual-Image-Rejection Filter

This paper presents a multi-band 5G NR FR2 down-conversion mixer with high mutual image rejection ratio (IRR) and compact area, while relaxing the requirements for local oscillator (LO) bandwidth. To achieve a broadband mutual image rejection within a small area, this paper proposes an on-chip compact transformer-based mutual-image-rejection (MIR) filter with an area of only 0.023 mm², which exhibits the ability to track the pole and zero frequencies simultaneously, and realizes the broadband IRR. Moreover, the MIR filter also serves as the broadband impedance matching network between low noise amplifier (LNA) and down-conversion mixer, avoiding the use of additional matching network. To the best of our knowledge, this is the first on-chip mutual-image-rejection filter in the multi-band 5G NR FR2 system. Fabricated in a 65-nm CMOS process, the proposed multi-band down-conversion mixer achieves a maximum IRR of 70 and 60 dBc in 28- and 39-GHz band operations, respectively.