## 1 Introduction  
In ultra-high-field magnetic resonance imaging (MRI) systems, radio frequency (RF) power combiners serve as critical components between RF coils and RF power amplifiers,with their core elements including transmission lines, inductors, and capacitors [1]. These combiners must exhibit exceptional power-handling capabilities: 1.5T MRI RF power amplifier (RFPA) systems require combiners to withstand pulse powers exceeding 20 kW, while 3.0T systems demand handling capacities of up to 40 kW [2]. Consequently, the key components in high-power MRI combiners must endure large currents and high voltages, resulting in increased physical dimensions and elevated losses. Current mainstream solutions widely adopt microstrip lines or lumped-element components combined with Wilkinson structures [3], yet they face persistent challenges, such as excessive size, high losses, poor parameter consistency, and difficulties in integrating with printed circuit boards (PCBs). For instance, in 3.0T MRI systems, a conventional one-quarter-wavelength microstrip line segment measures 0.6 m, and a four-way combiner requires six such segments totaling 2.4 m [4]. This not only leads to volumetric expansion but also exacerbates conductor losses due to increased line resistance. On the other hand, lumped-element solutions, while reducing size, necessitate high-current-tolerant inductors--typically implemented as air-core or magnetic-core structures--which suffer from complex fabrication processes and persistent size constraints [5]. The existing research has predominantly focused on bridge configurations and Wilkinson structures, with the former commonly used in RF coils and the latter in RFPA [6]. However, the operating frequency of the MRI system ranges from tens to hundreds of MHz and meets the requirements of high-power output [7]. The microstrip-based implementation method has a large size and high loss due to the long line length, making it difficult to meet power capacity requirements. The lumped component method faces challenges such as discrete circuit parameters and difficulty in the heat dissipation of various devices. In the traditional design of combiners based on \(\lambda\)/4 microstrip transmission structures, conductor loss and dielectric loss can be effectively reduced by, respectively, increasing the line width of the microstrip and selecting low-loss dielectric materials. However, in high-power, MHz-range (from tens to hundreds of MHz) MRI applications, the quarter-wavelength (\(\lambda\)/4) microstrip lines exhibit excessive physical length, leading to oversized dimensions and significant conductor losses [8]. For lumped-parameter combiners, enlarging the wire diameter of inductors introduces similar challenges [9]--increased size, elevated thermal dissipation, and inconsistent inductance values--all of which degrade combiner performance. Reference [10] achieved low-loss coaxial combiners under high-bandwidth conditions, but this method remained confined to narrowband, low-power scenarios and is ineffective for MRI systems. Reference [11] proposed a lumped-element model and tuning technique for narrowband RF combiners, reducing impedance distortion and achieving ultra-high efficiency (13.56 MHz, 1 kW); however, its reliance on ferrite cores introduced consistency challenges and severe heating-induced nonlinearities at 3.0T MRI frequencies. Reference [12] underscored the critical need for compact, low-loss multi-channel RF combiners in 7.0T systems employing parallel transmission (pTX) technology, emphasizing the growing demand for miniaturization and efficiency in ultra-high-field MRI environments, and the proposed design demonstrated superior performance in this scenario, achieving both loss reduction and compact multi-channel integration that enhances clinical system practicality.