Min-Yu Huang

Millimeter-wave (mm-Wave) receiver (RX) array systems are widely employed to address a plethora of applications for telecommunication, radar sensing, localization, imaging, and weather monitoring. Many future mm-Wave arrays need to operate in increasingly dynamic and mobile scenarios with complicated electromagnetic (EM) environments. With their wide deployment, they are more likely to be exposed to strong interferences with unknown angle-of-arrival (AoA), frequency, and modulation schemes. In this work, we propose and implement a 23–37-GHz autonomous 2-D multiple-input and multiple-output (MIMO) RX array system with rapid full field-of-view (FoV) spatial filtering and beamforming to manage interferences and signals from unknown direction-of-arrival (DoA). The implemented RX array system architecture provides multiple deep spatial notches to relax the dynamic range requirement of downstream analog-to-digital converter (ADC) circuits and is also extendable to a larger 2-D array. The implemented RX array system includes a broadband mm-Wave frontend and two autonomous spatial filter stages (ASFs) in cascade without losing MIMO capability. A prototype is demonstrated in a 45-nm RF CMOS silicon on insulator (SOI) process. The broadband mm-Wave frontend achieves $S_{11}$ $<$ $-$ 10 dB from 26 to 36 GHz with 23–37-GHz 3-dB bandwidth and 4.9-dB minimum noise figure (NF) within the operating band. Our autonomous MIMO array demonstrates $>-$ 2.4 dB normalized array factor over full FoV and spatial notch with $>$ 27.1 dB cancellation. With two ASFs stages in cascade, we demonstrate two individual spatial notches, each with $>$ 28.3 dB spatial cancellation on unknown blockers. Furthermore, co-channel wideband modulated blockers are autonomously rejected, and the desired signal is successfully demodulated for 2.4-Gb/s 64 QAM (highest speed) with $-$ 22.02-dB error vector magnitude (EVM) rms (25% interference/signal co-channel overlap), for 0.6-Gb/s 64 QAM with $-$ 26.32-dB EVMrms (50% co-channel overlap) and for 1.2-Gb/s 64 QAM with $-$ 26.16-dB EVMrms (25% co-channel overlap).

Next-generation millimeter-wave (mm-Wave) power amplifiers (PAs) need to support multistandard communication systems with wide bandwidth, complex modulation, and high energy efficiency. Most existing mm-Wave PA architectures with power backoff (PBO) efficiency enhancement, such as Doherty and outphasing PAs, typically only support limited carrier bandwidth. In this work, we propose and demonstrate that a 180 $^{\circ}$ coupler balun structure can serve as an extremely wideband active load modulation network for broadband PBO efficiency enhancement and further realize a coupler balun load-modulated PA (CBMA). Moreover, compared to load-modulated balanced amplifiers (LMBAs), the proposed CBMA supports natural single-ended-to-differential balun conversion, differential power cells, and wideband capacitive neutralization, ideal for integrated mm-Wave PAs. Furthermore, we propose a continuous-mode CBMA operation with role exchanges to attain a nearly 3:1 carrier bandwidth. A prototype CBMA is designed and fabricated in a 45-nm RF CMOS SOI process, which achieves an OP $_{\mathrm{1\,dB}}$ PAE of 39.9%–20.4% with OP $_{\mathrm{1\,dB}}$ of over 21.6–18.3 dBm from 26 to 60 GHz. The PA also achieves a 32.8%–13.4% 6-dB PBO (from OP $_{\mathrm{1\,dB}})$ efficiency with its best 1.75 $\times$ /3.51 $\times$ efficiency enhancement over an ideal Class-B/-A PA. Using a single-carrier 64-QAM signal with 0.5 GSym/s (3 Gb/s), the PA supports an average $P_{\mathrm{out}}$ of 15.8–11.3 dBm with an average PAE of 27.15%–8.58% with $-$ 23-dB rms error vector magnitude (EVM) over 26–60 GHz. The PA also supports 5G NR modulation using 5G new radio (NR) FR2 200-MHz 1-CC 64-QAM signals, achieving 18.22%–6.55% average PAE at 10.72–7.1-dBm average $P_{\mathrm{out}}$ with rms EVM of $-$ 23 dB over 26–60 GHz.

This article presents a wideband millimeter-wave (mmWave) receiver front-end that covers the frequency range from 43 to 97 GHz, supporting the operation in the major parts of the V-, E-, and W-bands. The front-end incorporates a passive mixer-first topology to achieve high linearity and wideband performance. The front-end adopts I/Q generation at the RF port, using a coupled-line coupler (CLC), rather than at the local oscillator (LO) port to mitigate the crosstalk of the overlapping I/Q LO signals especially present at high frequencies. The CLC at the RF input facilitates ultrawide band input matching. The front-end implements the multi-gate gm3 cancellation technique at the IF amplifiers to preserve the linearity and provide gain at the IF section. Image rejection capabilities using a current mode transformer-based IF 90° coupler are implemented on chip and demonstrated with measurements. The front-end prototype is fabricated on the GlobalFoundries 22-nm FD-SOI CMOS process and it demonstrates an ultra-wideband performance across the frequency range 43-97 GHz (2.25:1 bandwidth) with image rejection of up to 32 dB, IIP3 of 1.6-5.2 dBm, and gain of 15 dB. The implementation used is low-IF topology with 3.8-GHz IF frequency and 1-GHz bandwidth. Furthermore, the measurement results show that the front-end supports high-speed modulated signals of up to 6-Gbps 64QAM modulation data.

This article presents a millimeter-wave (mm-wave) transmitter (TX) front-end employing a new inverse outphasing architecture with current-mode power amplifiers (PAs). This study on the conventional outphasing operation reveals its strong dependence on its voltage-mode driving source assumption and thus exhibits major limitations at mm-wave, since efficient and linear mm-wave PAs often behave as current sources. To address this challenge, we propose a current-mode inverse outphasing architecture that employs current-mode driving sources and is inherently compatible with mm-wave linear PAs. Moreover, the conventional series outphasing combiner is replaced by a much simpler and low-loss parallel power combining scheme. Closed-form mathematical expressions are derived for both the outphasing and inverse outphasing operations, including the active load modulation, Chireix compensations, and outphasing efficiency, which fundamentally explains the limitations of the conventional approach and the advantages of the inverse outphasing architecture. Further theoretical analysis discovers a circuit duality relationship between outphasing and inverse outphasing architectures, which offers unique circuit intuitions. As a proof-of-concept, we implement a 28-GHz TX front-end using cascode PAs, based on the inverse outphasing architecture. In the measurement, the TX achieves 22.7-dBm saturated output power with 42.6% PA drain efficiency. The TX exhibits effective PA efficiency enhancement at 6-dB power back-off (PBO), validating the high-efficiency inverse outphasing active load modulation. Modulation tests with high-order quadrature amplitude modulation (QAM) signals demonstrate that the TX supports >10-Gb/s high-fidelity complex signals and achieves the state-of-the-art modulation performance.

An autonomous beamformer demonstrates multi-beam and multi-band signal transmission and reception with wide field-of-view (FoV) self-steering beam-tracking/-forming for future extreme broadband and dynamic mm-Wave fronthaul applications operating in 5G new radio (NR) frequencies. The experimental results show the novel autonomous beamformer system covering full FoV beamforming (180o) with a wideband 22-40GHz home-designed antenna array, demonstrating simultaneously multi-band (24.75 and 37 GHz) signals receiving with enhanced mobile multi-Gb/s transmission. A system testbed is further implemented to achieve a mm-Wave bi-directional link between remote radio unit (RRU) and user equipment (UE) in a fiber-wireless integrated network. A wide FoV autonomous signal sensing for angle-of-arrival (AoA) information in receiver is fed forward for mirror-reversed multi-Gb/s signal transmitting over a 10-km fiber and 0.56-m wireless link, addressing fast-changing complex 5G transceiver alignments. To the best of our knowledge, this is the first demonstration of an integrated autonomous beamformer for mm-Wave multi-beam and multi-band mobile applications in a fiber-wireless integrated radio access network.

Antenna load impedance variations typically cause significant power amplifier (PA) performance degradation, including output power, large-signal linearity, and peak/average PA efficiency, which are especially critical for modern millimeter-wave (mm-Wave) communications with spectrally efficient complex modulations. To address this problem, we propose a reconfigurable hybrid series/parallel Doherty PA with a 90°-coupler-based active load modulation network. By reconfiguring the series/parallel Doherty operation modes, the strengths of the Main/Auxiliary PAs, and their relative phase, linear output power (OP1 dB), as well as peak output power (Psat) and energy efficiency (PAEpeak and PAE1 dB) of the PA can be largely restored under full-span 360° antenna impedance variations. The theoretical analysis and design guidelines are both presented in this article. As a proof of concept, a 39-GHz reconfigurable hybrid series/parallel Doherty PA is fabricated in the Global Foundries 45-nm RF CMOS silicon on insulator (SOI) process with a 2-V PA supply and 1-V driver supply. At 39 GHz, the PA achieves a 33.3% peak power-added efficiency (PAE) at 20.8-dBm Psat and 32.2% PAE1 dB at 20.2-dBm OP1 dB at a nominal 50-Ω load. The reconfigured PA demonstrates an 18.5-19.12-dBm OP1 dB with a high PAE1 dB of 20.6%-25.3% at 3:1 antenna voltage standing wave ratio (VSWR) over 360° angles. The PA achieves an rms error vector magnitude (EVM) of -23.6 dB/-22.8 dB/-23.1 dB at an average Pout of 13.8 dBm/12.2 dBm/11.5 dBm with 100 MSym/S/500 MSym/S/1 GSym/S single-carrier 64-quadratic-amplitude modulation (QAM) signal, respectively, at a nominal load of 50 Ω. A greater-than 11.2-dBm average Pout is achieved at an rms EVM of -24 dB under a full-span 3:1 antenna VSWR with a 100-MSym/S 64-QAM signal.

An autonomous beamformer covering 24-37 GHz for fiber-wireless network demonstrates multi-beam and multi-band signal transmission with wide-FoV (110^o-180^o) self-steering beam-tracking/-forming over a 10-km fiber and 56-cm wireless link for future dynamic 5G-NR fronthaul applications.

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 mm²) 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.