rf power combiners are core passive devices in radio frequency communication, microwave testing, base station networking and industrial wireless transmission systems. They are mainly used to integrate multiple RF signals into a single output to realize power synthesis and link integration, and are widely applied in various high-frequency RF scenarios such as 5G communication, private network radio frequency, satellite measurement and control, and precision testing. Most engineering selections tend to focus on conventional electrical parameters such as frequency band, loss and isolation, while ignoring the decisive role of materials in the overall performance, service life and working condition adaptability of devices. In fact, the impedance stability, power bearing limit, heat dissipation capacity, anti-interference performance and environmental resistance of rf power combiners are all determined by the core material system including cavity alloy, internal conductors, dielectric base materials and coating protection. Different material formulas and processing technologies directly distinguish the quality gap between ordinary civil-grade and industrial high-performance combiners. From the perspective of materials, this paper deeply analyzes the performance characteristics, adaptation advantages and engineering application specifications of various core materials of rf power combiners, providing professional references for RF engineering selection, scenario adaptation and long-term operation and maintenance.

　　The cavity shell material is the basic core material that determines the structural strength, electromagnetic shielding and heat dissipation performance of rf power combiners. At present, the industry’s mainstream materials include aluminum alloy, brass and stainless steel, adapted to different working conditions and power levels. Lightweight aviation aluminum alloy is a common material for commercial and medium and low-power combiners. It has the advantages of low density, easy processing, good thermal conductivity and controllable cost, meeting the usage requirements of conventional indoor normal-temperature and medium-low power scenarios. It can quickly dissipate basic heat generated during device operation and maintain stable electrical parameters. Brass materials are mostly used for high-end industrial-grade rf power combiners, with far better conductivity and thermal conductivity than ordinary aluminum alloys, denser metal structure and excellent electromagnetic shielding performance. It can effectively block external stray electromagnetic interference and prevent internal high-frequency signal leakage, adapting to complex RF scenarios with intensive superposition of high-frequency, high-precision and multi-signal signals. Stainless steel materials feature high strength, corrosion resistance and impact resistance, with mechanical strength far exceeding alloy materials. They are not easy to deform, wear or vibrate, and are specially designed for harsh working conditions such as outdoor exposure, vehicle and airborne applications and industrial heavy load, ensuring the structural integrity of devices against external impact and long-term environmental erosion.

　　The internal conductor material is the key core material affecting the signal transmission efficiency, loss index and power bearing capacity of rf power combiners, which directly determines the upper limit of device electrical performance. The conductivity purity, uniformity and oxidation resistance of conductor materials are directly related to insertion loss, standing wave ratio and power transmission stability. Ordinary low-end combiners on the market mostly adopt ordinary copper alloy or copper-plated iron materials, which have poor electrical conductivity, high resistance, large high-frequency signal transmission loss, and are prone to heat generation under high-power working conditions. They are also easy to oxidize and rust, resulting in parameter drift and signal distortion during long-term operation. In contrast, high-performance industrial-grade rf power combiners adopt high-purity oxygen-free copper as internal transmission conductors, with extremely low impurity content and excellent electrical conductivity. They have minimal high-frequency signal transmission loss, can retain signal power to the greatest extent and ensure the integrity and purity of signals after multi-channel combining. Meanwhile, oxygen-free copper has good ductility and stable structure, and is not prone to nonlinear distortion under high-frequency and high-voltage working conditions with excellent third-order intermodulation indicators, perfectly adapting to high-power and high-precision RF synthesis scenarios and serving as the standard conductor material for high-end combiners.

　　Dielectric support materials and insulating materials are important supporting materials for rf power combiners to ensure stable impedance, prevent leakage and crosstalk, and adapt to high-frequency transmission. The interior of RF power combiners requires dielectric materials to support the conductor structure, fix the circuit layout, and achieve electrical isolation to prevent signal short circuit and channel crosstalk. Mainstream dielectric materials include PTFE, high-density PE and ceramic dielectrics with significant performance differences. PTFE is a special high-quality dielectric material for high-frequency rf power combiners, featuring stable dielectric constant, ultra-low high-frequency loss, high temperature resistance, corrosion resistance and excellent insulation. Its dielectric parameters are almost stable in the range of DC-18GHz or even higher frequency bands, which can accurately maintain a constant 50Ω standard impedance and avoid impedance offset and signal reflection under high-frequency working conditions. High-density PE materials are mostly used for low-frequency ordinary civil combiners with low cost but large high-frequency loss, only suitable for simple low-frequency networking scenarios. Ceramic dielectric materials have high hardness, high temperature resistance and strong dielectric stability, mostly used for military and aerospace-grade high-precision rf power combiners. They can withstand ultra-high power and extreme temperature working conditions without performance attenuation during long-term operation, maximizing the accuracy of high-power and high-frequency signal combining.

　　The surface coating protection material is the key protective structure to improve the aging resistance, oxidation resistance and corrosion resistance of rf power combiners, determining the service life and complex scenario adaptability of devices. Exposed metal cavities and conductors are prone to oxidation and corrosion in humid, high-temperature, acid-base and dusty environments, leading to increased contact resistance, sharp rise in signal loss, deteriorated standing wave ratio and finally system failures. Therefore, industrial-grade combiners adopt precision coating protection processes, with mainstream coating materials including silver plating, gold plating and nickel plating. Silver plating has excellent electrical conductivity and strong oxidation resistance, which can further reduce conductor contact loss and improve high-frequency transmission performance, serving as the mainstream coating solution for commercial industrial-grade combiners. Gold plating has extremely stable chemical properties with no oxidation, corrosion resistance and high and low temperature impact resistance, delivering top-level protection performance. It is applied in high-precision scenarios such as military industry, precision testing and aerospace, ensuring no parameter drift of devices for more than ten years. Nickel plating features high hardness, wear resistance and collision resistance with balanced protection performance, mostly used for outdoor industrial combiners to balance protective effect and cost performance, adapting to various complex outdoor working conditions.

　　Reasonable material matching and selection are the core principles for engineering adaptation of rf power combiners, and exclusive material combination schemes are required for different scenarios. For conventional indoor light-load scenarios, a conventional material combination of aluminum alloy cavity, oxygen-free copper conductor, nickel plating and PTFE dielectric can balance performance and cost. For harsh outdoor and frequently vibrating working conditions, stainless steel cavity matched with gold plating is required to improve structural strength and corrosion resistance. For high-power and high-frequency precision testing scenarios, a high-end material scheme of brass cavity, high-purity oxygen-free copper conductor and composite silver and gold plating must be adopted to ensure low loss, high stability and low intermodulation transmission effect. Ignoring material adaptation and blindly selecting low-cost combiners with inferior materials will easily cause problems such as excessive loss, signal crosstalk, device overheating and burnout, and short-term aging failure, seriously affecting the stability of RF systems. In conclusion, materials are the core foundation of rf power combiners performance. By accurately identifying the performance advantages of various materials and selecting models scientifically combined with working condition requirements, the combining performance of devices can be maximized, improving the transmission accuracy, stability and service life of RF systems, and building a solid hardware foundation for the stable operation of various RF projects.