A radial power combiner is a high-bandwidth, low-loss and high-power RF synthesis device based on the radial waveguide spatial synthesis principle. Different from traditional planar combiners, it adopts a radial spatially symmetric structure with the core advantages of wide frequency band, large power capacity, excellent heat dissipation and high synthesis efficiency. It is widely used in radar transmission systems, millimeter-wave communication, high-power solid-state RF power amplifiers, satellite ground base stations and other high-end high-frequency RF scenarios. In engineering applications, the explicit performance indicators of the device such as insertion loss, power capacity and frequency range are relatively stable, making operation and maintenance personnel ignore various recessive problems. These hidden deviations will not cause equipment downtime immediately, but will erode the performance of RF systems for a long time, resulting in progressive attenuation of power synthesis efficiency, hidden signal distortion, and reduced link stability. From the recessive perspective, this paper deeply analyzes the hidden working characteristics, causes of recessive faults, drift rules of hidden parameters and standardized avoidance schemes of radial power combiners, solving the problem of hidden performance attenuation in the long-term operation of high-end RF systems.

　　1. Unique Recessive Technical Characteristics of Radial Power Combiner

　　The recessive risks of radial power combiners stem from their unique spatial radial transmission structure, which is essentially different from the linear transmission logic of conventional coaxial and microstrip combiners, with multiple undetectable hidden characteristics. Firstly, there is the recessive impedance mutation characteristic of the central node. Multiple input ports are evenly arranged in a radial shape, and the central convergence node will generate subtle hidden impedance drift. When multiple channels work at full load simultaneously, the node impedance drifts slightly with power load changes, which cannot be captured by conventional single-port static detection, becoming a hidden inducement for signal reflection and reduced synthesis efficiency. Secondly, high-order modes are easily and implicitly excited. The radial waveguide bifurcation is prone to arouse high-order spurious modes under high-frequency and high-power working conditions. It will not cause explicit faults, but continuously produce hidden clutter loss and reduce power synthesis efficiency, which is the core hidden reason for low system efficiency in millimeter-wave frequency bands.

　　Meanwhile, the device has hidden defects in channel isolation. Compared with Wilkinson combiners, radial power combiners have no obvious disadvantages in explicit isolation performance, but the mutual coupling interference between channels will increase implicitly under dynamic working conditions. When the power of multi-channel signals is unbalanced, intermodulation clutter accumulates quietly, affecting the purity of RF signals for a long time. In addition, the transition structure of coaxial and waveguide has hidden matching blind spots. Subtle matching deviations occur at the high and low frequency ends under broadband working conditions, which cannot be covered by conventional detection, resulting in excessive hidden loss at the frequency band edges.

　　2. High-Frequency Recessive Fault Types and In-Depth Causes in Engineering

　　Based on the operation and maintenance experience of high-end RF engineering, the recessive faults of radial power combiners are mainly divided into three categories: hidden parameter drift, structural hidden loss and working condition hidden deterioration, featuring concealment, accumulation and hysteresis. The first category is hidden parameter drift. After long-term high-power continuous operation of the device, the temperature gradient of the radial cavity is unevenly distributed, and the dielectric properties of the radiation branch circuit change slightly, leading to gradual offset of the amplitude and phase consistency of each channel. There is no equipment alarm in the early stage, only manifested as slight attenuation of synthetic power and subtle rise of background noise, and obvious signal distortion and power imbalance faults will occur after long-term accumulation.

　　The second category is cumulative structural hidden loss. Due to the special physical characteristics of the radial radiation structure, subtle processing tolerances and assembly gap deviations of the cavity will not appear in static tests. However, under high-frequency and high-power transmission, problems such as electromagnetic leakage and micro-reflection in gaps exist continuously, forming hidden transmission loss. At the same time, the central output coaxial structure is limited by power capacity, resulting in hidden power saturation under high-duty-cycle working conditions, gradually reducing the peak power margin of the device and greatly shortening the service life of equipment. The third category is hidden deterioration of working conditions. In outdoor, airborne and industrial high-temperature vibration scenarios, subtle problems such as cavity stress deformation, interface micro-oxidation and asymmetric wiring will continuously cause deviation of channel transmission delay, resulting in hidden imbalance of vector synthesis and inducing irregular intermittent system signal fluctuations with extremely high difficulty of fault detection.

　　3. Cascading Hazards of Recessive Faults to High-End RF Systems

　　Although the recessive problems of radial power combiners have no immediate destructive impact, they will cause cascading performance degradation of high-end RF systems and seriously affect the operation accuracy of precision equipment. Firstly, the implicit reduction of power synthesis efficiency. High-order mode excitation and central node impedance drift will continuously consume effective RF power, leading to reduced utilization rate of power amplifier output, increased equipment energy consumption, insufficient effective radiation power of radar and satellite systems, and reduced detection distance and communication coverage, which affects the core equipment performance after long-term accumulation. Secondly, hidden signal distortion. The gradual offset of channel phase and amplitude consistency will cause unbalanced vector superposition of multi-channel signals, generate hidden intermodulation interference and spurious signals, lead to deviation of test data in precision test scenarios and clutter misjudgment in radar systems, and greatly reduce system accuracy.

　　At the same time, hidden mutual coupling interference will reduce the anti-interference ability of the system. After the dynamic deterioration of channel isolation, cross-penetration of signals of different frequencies occurs, and clutter accumulation becomes more serious in broadband working scenarios. Most importantly, hidden loss and power saturation will accelerate device aging, cause irreversible performance attenuation, and eventually lead to sudden device burnout and link interruption, resulting in downtime faults of high-end equipment and greatly increasing operation and maintenance costs and equipment loss risks.

　　4. Accurate Detection and Long-Term Avoidance Schemes for Recessive Risks

　　To solve various recessive problems of radial power combiners, it is necessary to break through the limitations of conventional static detection and establish a dynamic and full-cycle hidden risk management and control system. Firstly, optimize the selection and adaptation logic. For high-frequency millimeter-wave and high-power continuous working scenarios, prioritize radial combiners with high-order mode suppression structure and multi-stage impedance matching design to avoid hidden matching deviation and spurious mode interference at frequency band edges, and reserve sufficient power margin to prevent hidden power saturation. Secondly, innovate detection methods, abandon single static parameter detection, add full-load dynamic working condition tests, focus on verifying the phase consistency, dynamic standing wave ratio and full-band loss fluctuation during multi-channel synchronous operation, and accurately capture hidden drift problems that cannot be found in static tests.

　　In terms of installation and operation and maintenance, unify the wiring length and cable specifications of each radiation branch to eliminate artificial hidden delay deviation; ensure uniform heat dissipation of the cavity to avoid parameter drift caused by local high temperature; regularly detect interface micro-oxidation and cavity gap deformation to eliminate hidden loss risks in advance. At the same time, establish a periodic calibration mechanism for long-term operating equipment, regularly calibrate channel balance and impedance matching parameters, timely correct hidden performance deviations, and fundamentally avoid fault accumulation, so as to ensure the long-term stable and high-precision operation of radial power combiners.

　　5. Conclusion

　　The core hidden hazards of radial power combiners do not lie in substandard explicit parameters, but in various easily ignored hidden deviations and cumulative faults. While its unique radial spatial synthesis structure brings the advantages of low loss and high broadband, it also accompanies exclusive problems such as hidden impedance drift, high-order mode clutter, dynamic isolation deterioration and structural hidden loss. Accurately recognizing the hidden technical characteristics of devices and implementing full-process management and control of dynamic detection, accurate calibration and standardized operation and maintenance can completely avoid the risk of long-term hidden performance attenuation, give full play to the performance advantages of radial power combiners in high-power and high-bandwidth RF systems, and ensure the long-term, high-precision and stable operation of radar, satellite communication and precision RF equipment.