A 24.5–43.5-GHz Ultra-Compact CMOS Receiver Front End With Calibration-Free Instantaneous Full-Band Image Rejection for Multiband 5G Massive MIMO

This article presents an extremely broadband 24.5-43.5 GHz receiver (RX) achieving 32-56-dB instantaneous full-band image rejection (IR), which supports multiple major mm-Wave 5G bands at 24.5/28/37/39/43 GHz. A compact transformer-based I/Q network (0.14 mm
²
) is proposed to generate high-precision LO I/Q signals at millimeter-wave (mm-Wave) and provide built-in load impedance up-transformation for passive voltage amplification, boosting the LO swing for a higher RX conversion gain (CG). The high-quality differential I/Q generation is measured with phase/amplitude variation less than ±1.8°/±0.15 dB over an instantaneous wide bandwidth of 25-50 GHz without any calibration or switching/tunable elements. The RX is measured with a peak 35.2-dB CG and 18-dB gain tuning to accommodate complex EM environments. The RX modulation tests successfully demonstrate receiving 18-Gb/s 64-QAM and 14.4-Gb/s 256-QAM signals. In addition, the RX is tested with concurrent injection of a desired signal and an image, while the image uses the same wideband modulation scheme and data rate as the desired signal. The RX successfully rejects the wideband images and receives the desired signals of 12-Gb/s 64-QAM with -27.6-dB EVM and 8-Gb/s 256-QAM with -33.47-dB EVM. To the best of our knowledge, this article presents the first CMOS RX front end that covers 24.5-43.5-GHz mm-Wave 5G bands and supports instantaneous full-band IR with no calibration, switching/tuning elements, or external controls, enabling future wideband low-latency 5G MIMOs.