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This article presents a fully integrated stand-alone narrowband Internet-of-Things (NB-IoT) and global navigation satellite system (GNSS) system-on-chip (SoC). It aims for an all-in-one system to integrate all necessary blocks such as an RF transceiver, a power management system (PMIP), and a clock management system and to save a bills-of-material (BOM) cost. An RF transceiver is integrated to support multi-band cellular IoT and GNSS with a CMOS RF power amplifier transmitting 23-dBm output power. A PMIP, including bucks, a boost, and low-dropout regulators (LDOs), is integrated to support coin cell or AAA battery and to support a wide input supply voltage range from 2.5 to 5 V. In addition, clock management system is embedded with a digitally controlled crystal oscillator (DCXO), a relaxation oscillator (RCO), and temperature sensor units (TSUs). It is fabricated in a standard 28-nm CMOS process and its size is 24.6 mm2. The power consumption of always-on-block is 15 $\mu \text{W}$ , and the sleep current consumption is less than 10 $\mu \text{A}$ at 3.8 V.

Envelope tracking (ET) is a key technology improving efficiency of RF power amplifiers (PAs) and battery lifetime in mobile handsets. It has been commercialized since 4G LTE era, and is also being employed in 5G NR handsets. A supply modulator (SM) is a circuit generating power supplies of RF PAs for ET and average power tracking (APT) operations. Currently, the maximum channel BW and supported ET BW of 5G NR handset is 100MHz [1]–[4]. In a short time, over 100MHz BW will be necessary to support intra-band contiguous carrier aggregation cases of n77C/n78C/n79C in 3GPP standard [5]. The required instantaneous maximum output power of SM is about 10W which is calculated by the following parameters: 26dBm output power by power class 2 (PC2), 2dB loss of RF front-end module (FEM) due to complex operating band combinations (EN-DC for non-standalone mode, NE-DC, 2CA/3CA), 6dB higher instantaneous power due to peak-to-average power ratio (PAPR) at 1 resource block (RB), 1dB margin, and poor PA efficiency of around 33% (worst example) due to high carrier frequency of 5GHz at n79 band. The poor PA efficiency can be relaxed by high voltage PA design beyond 5V. In [1], a supply modulator with boosted output larger than battery voltage $(V_{BAT})$ is proposed, and the designed PA with 30% higher voltage shows 10% higher efficiency and broader BW owing to low impedance transformation ratio from $50 \Omega$ and small parasitic output capacitance of power cell. The challenge is how to design a supply modulator for 5G NR that can achieve both wide ET BW and high output voltage/power capability, while satisfying high efficiency, low receiver-band noise, short transition time, and multi-mode/standard operation.

In recent years, buck-boost converters have been widely utilized for battery-powered mobile systems such as RF power amplifiers, battery chargers, and LED drivers. However, in a wide battery voltage range, they face challenges including dynamic voltage scaling (DVS), wide load current range, and dynamic line/load transients while ensuring reliability for an industrial usage. To resolve these issues, the conventional buck-boost (CBB) converter should overcome the characteristic of discontinuity in the output transfer current (OTC) which causes degradation of loop dynamics and transient response. Several past works with continuous OTC have been proposed to resolve these problems, but their voltage conversion ratios are limited [1], [2]. Moreover, in [3], [4], a high-voltage (HV) process, which necessitates large active area and incurs high fabrication cost, is required to withstand voltage stresses over 10V (2×V IN ) applied across power switches. To overcome the above challenges, this paper proposes a voltage-tolerant three-level buck-boost (TLBB) converter. The TLBB has continuous OTC and uses only normal 5V CMOS devices for its switches. In addition, a voltage-tolerant dual channel-interleaved three-level buck-boost (DTLBB) converter is suggested for applications [5] requiring a wide range of load current and high conversion ratio while supporting fast DVS transition.

Due to extensive application prospects and huge market potential of narrowband internet-of-things (NB-IoT), there is growing demand for low-power and low-cost system-on-chips (SoCs) and a massive number of wireless devices. For a low-cost solution, the most challenging blocks such as an RF transceiver, an RF power amplifier (RF-PA), and a high-power switching converter have to be integrated to eliminate the need for expensive multichip components. To support power scenarios of NB-IoT, low-power circuits and highly efficient power regulators are needed simultaneously [1]. This work aims for an all-in-one system to integrate all necessary blocks. An RF transceiver is integrated to support multiband cellular IoT and the global-navigation satellite system (GNSS) with a CMOS RF power amplifier. A power-management system (PMIP) including bucks, a boost, and low-dropout regulators (LDOs) is integrated to support coin-cell or AAA battery supply and operate over a wide-input supply voltage from 2.5V to 5V. In addition, a clock-management system is embedded with a digitally controlled crystal oscillator (DCXO), a relaxation oscillator (RCO), and temperature-sensor units (TSUs) [2].

The 5G-New-Radio (NR) standard in millimeter wave (mm-wave) bands requires a low-cost antenna module consisting of a phased-array transceiver with beamforming [1], an antenna array, and a power management IC (PMIC). Since a typical on-chip mm-wave CMOS power-amplifier (PA) arrays have poor power efficiency due to the lossy substrate and the low maximum available-gain frequency of CMOS processes, they cause serious thermal issues due to the high power density and reduce battery life in a mobile handset. Recently, supply-modulation (SM) techniques, such as an envelope tracking (ET) and an average-power tracking (APT) instead of a direct battery-connected supply, have been introduced to enhance PA efficiency [2]. However, these techniques have few challenges, such as limited ET tracking bandwidth and APT transition time, to support new requirements of the 5G NR standard. In order to manage the power effectively of a phased-array module, a special SM technique named symbol-power tracking (SPT) is proposed for the power management in this work. The SPT controls the supply voltage of mm-wave PA arrays every few micro-second (symbol to symbol), which is much faster than that of APT, which adjusts the output voltage every one millisecond (sub-frame to sub-frame).

In the recent 3GPP standard, 5G New Radio (NR) in the sub-6GHz frequency band supports up to 100MHz bandwidth (BW) for uplink channel and requires fast on/off transition below $10 \mu \mathrm {s}$ to support short transition-time interval (TTI). Thus, it forces the supply modulator (SM) to track the NR-100MHz envelope signal for power saving of an RF power amplifier (RF-PA) and requires a fast dynamic voltage-scaling (DVS) transition. For the 3G/LTE uplink, the SM has to satisfy low receiver-band noise (RxBN) for LTE-FDD bands [1] and a boosted output for Power Class 2 high-power user equipment (HPUE) in TD-LTE [2], [3]. In order to support the 100MHz envelope tracking (ET) BW, the SM must have a 3dB bandwidth of at least 125MHz while keeping sufficient phase margin in the presence of few-hundred-pF load capacitance. Furthermore, a typical linear-assisted SM topology has maximum efficiency limitation due to the AB bias current, sinking- and sourcing-current of the linear amplifier. In this work, a voltage-buffer-compensated (VBC) Class-AB linear amplifier (LA) and a feed-forward fast-switching (FFFS) buck converter are proposed to achieve the 100MHz ET BW and high system-power efficiency.

Uplink carrier aggregation (UL-CA) and high-power user equipment (HPUE) are proposed in the recent 3GPP standard [1]. UL-CA increases data-rate by aggregating intra-or inter-band carriers, and requires a supply modulator (SM) IC to generate two independently modulated supply voltages for the separate transmitter (TX) paths. Power Class 2, a new HPUE standard intended for TD-LTE Band41, allows 26dBm output power, which is 3dB higher than typical Power Class 3. To achieve 26dBm output, an SM must provide an RF power amplifier (PA) with larger current and boosted voltage above battery range. However, conventional Sm-ICs support only Power Class 3 PAs with intra-band contiguous CA up to 40MHz bandwidth in an envelope-tracking (ET) operation [2]. In order to support non-contiguous intra- and inter-band CA, a typical ET system needs two SMs with double the external components, occupying great PCB area in a cellular handset. This paper presents a single-chip SM-IC with two independently controlled TX outputs supporting Power Class 2. In this way, the SM-IC saves the BOM cost and the PCB area while achieving high system-power efficiency and low receiver-band noise.

Envelope tracking (ET) prolongs the battery life by modulating the supply of a power amplifier (PA) according to the signal envelope. With this emerging technology, the PA efficiency is greatly improved, whereas the supply modulator (SM) itself needs to provide efficient and accurate envelope tracking for the overall performance of the SM-PA combined system (PA module). The ET technique, meanwhile, has seen limited use in high-power transmission due to the reduced SM efficiency for low output power originating from the linear stage in hybrid structures [1].

The dehydrogenation behavior of the LaCo 5 –H 2 system was studied by in situ X-ray diffraction (XRD) under a hydrogen pressure of 5 MPa in the temperature range of 433–505 K. A new hydride phase (LaCo 5 H 2.2 ) which is formed between the α phase (solid solution) and the β phase (LaCo 5 H 3.4 hydride) has a hexagonal structure and the crystal lattice expands mainly along the a -axis during the transformation from the α phase to the LaCo 5 H 2.2 phase. To elucidate the effect of the substitution of aluminum for a part of cobalt in LaCo 5 on the phase transformation behavior in the LaCo 5 –H 2 system, the hydrogenation and dehydrogenation behavior of the LaCo 4.75 Al 0.25 –H 2 system was studied by the pressure differential scanning calorimetry (PDSC) under a hydrogen pressure of 0.1–5 MPa in the temperature range of 323–593 K. In the heating and cooling runs of the LaCo 4.75 Al 0.25 –H 2 system under a hydrogen pressure of 0.1 MPa, one endothermic and one exothermic peaks were observed, respectively. These PDSC peaks were due to the transformation between the α phase and the β phase. Under a hydrogen pressure of 0.2 MPa both peaks divided into two peaks. Combining the PDSC with the P – C isotherms, the division of the PDSC peaks is attributed to the formation of the LaCo 4.75 Al 0.25 H 2.7 phase between the α phase and the β phase above 383 K in the LaCo 4.75 Al 0.25 –H 2 system, whereas the LaCo 5 H 2.2 phase is formed above 465 K in the LaCo 5 –H 2 system. By the substitution of aluminum for a part of cobalt in LaCo 5 , the formation temperature of a new hydride phase lowers. The substitution of aluminum makes the β phase stable and the γ phase (LaCo 5 H 4.5 hydride) unstable.

The phase transformation in the La(Co x Ni 5− x )–H systems ( x = 2, 3, 5) were investigated using in situ X-ray diffraction (XRD). La(Co x Ni 5− x ) ( x = 2, 3) formed α, β, γ and δ hydride phases with increasing hydrogen content while LaCo 5 formed only α, β and γ hydride phases. The metal lattice of each phase is hexagonal in P 6/ mmm symmetry (α), orthorhombic in Cmmm symmetry (β) and orthorhombic in Im 2 m symmetry (γ), commonly observed for x = 2, 3, 5. The δ phase observed for x = 2, 3 has a hexagonal structure with P 6/ mmm symmetry, which was characterized for the first time in this study. The lattice expansion accompanied by the phase transformation was anisotropic for Co-rich compositions ( x ≥ 2) compared with Ni-rich compositions ( x = 0, 1). The lattice parameters changed with increasing hydrogen solution in the γ and δ single-phase regions for x = 2 and 3. Anisotropic lattice strain related with dense dislocations was not introduced through formation of any hydride phases. The isotropic strain increased upon formation of the δ phase but disappeared in subsequent phase transformation.

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