## 1 Introduction  
In communication systems, the power amplifier is the most critical component but also the most energy-consuming component. Therefore, the performance of the designed power amplifier directly affects the performance of the entire system [1; 2; 3; 4]. Up to now, envelope tracking technology (ET) [4; 5; 6; 7] has been the main technology used to improve the efficiency of power amplifiers. The basic architecture of ET technology is shown in Figure 1. The baseband signal is up-converted after delay correction as the input signal of the power amplifier. The baseband signal of the other channel is used as the input signal of the power modulator after envelope detection and envelope processing. The power supply modulator is the key to ET technology, and its output voltage should track the input signal of the envelope well. The power supply modulator has high conversion efficiency to improve the efficiency of the entire power amplifier system. In order to enhance the efficiency and bandwidth of power supply modulators, various methods have been proposed. Power supply modulators come in three main forms, switching converters [8; 9; 10], linear amplifiers [11; 12; 13; 14; 15], and hybrid power modulators [16; 17; 18; 19; 20; 21; 22]. When switching converters process relatively wide information, the frequency of the switching transistor of the switching converter is required to be 5-6 times that of the processing envelope signals. This increases losses and reduces efficiency. Wide band-gap device technology has been proposed to improve the efficiency of switching converters [23; 24; 25]. Multi-phase structure and multi-level structure have also been achieved [26; 27]. For linear amplifiers, it is easy to introduce losses and decrease the efficiency with the increase of peak-to-average ratio. The hybrid power supply modulator mainly includes switching converters, linear amplifiers, and controllers. This structure makes switching convertersprocess information to improve efficiency, while the linear amplifiers process information to improve linearity. In order to improve efficiency, the controller is a tradeoff between efficiency and bandwidth. The hybrid power supply modulator has more advantages than other structures. The characteristics of linear amplifiers in hybrid power supply modulators are wide band, small output impedance, high gain, and large swing [28; 29; 30]. The common control methods are PWM control [31] and hysteretic control [32]. Switching converter structures are multi-phase [31; 33] or multi-level [34]. Controlling multilevel switching converters is a challenge. More levels need more complicated circuits to be designed [35]. In [16], the bandwidth of a dual-mode hybrid power supply modulator, which consists of a hybrid power modulator and an average power tracking, is limited to 40 MHz. In [31], a hybrid power modulator composed of a class-AB linear amplifier and a two-phase switching converter is proposed, but it only tracks 4 MHz rectified sine waves. In [36], an ac-coupling of the outputs of the linear amplifier is proposed to improve the efficiency of a hybrid power supply modulator; however, the output method requires a large coupling capacitance, resulting in increased area. In [37], tracking and controlling the current of a linear amplifier optimizes the current distribution which results in limiting bandwidth. It can be seen from the studies cited above, although different structures have been tried in attempts to implement power supply modulators, it is challenging to design a highly efficient and wide bandwidth hybrid power supply modulator. In communication systems based on envelope tracking technology, a mismatch between the envelope and the phase reduces Error Vector Magnitude (EVM). Thus, it is also important to increase the bandwidth of a hybrid power modulator. In this paper, an efficiency-86% hybrid power modulator for 5G New Radio (NR) is proposed. A current-mirror amplifier with current reuse is introduced, which is followed by a class-AB buffer.