2025-11-11 14:24:15
High-frequency cables, also known as high-frequency signal cables, are core carriers for transmitting high-frequency signals in modern electronic equipment. They are widely used in communications, aerospace, medical care, industrial and other fields. Their performance directly determines the stability, integrity and anti-interference capability of signal transmission, which relies on sophisticated structural design, high-quality material selection and precise adaptation to different scenarios. This article provides a comprehensive and in-depth analysis of high-frequency cables from the perspectives of core structure, segmented types, key performance, special scenario adaptation, and installation & maintenance.
The excellent performance of high-frequency cables stems from the scientific nature of their layered design. Each structural layer undergoes strict material screening and process optimization to minimize loss and interference during signal transmission.
As the core of signal transmission, the inner conductor material directly affects conduction efficiency and loss control. Mainstream products use oxygen-free copper (OFC) with a purity of ≥99.99%, which reduces conductor loss during signal transmission due to its extremely low resistance. In high-end scenarios such as radar and satellite communications, silver-plated oxygen-free copper (Ag-plated OFC) is used, with a silver layer thickness controlled between 5-15μm. This effectively reduces the impact of the skin effect on high-frequency signals and further improves conductive performance.
The insulation layer serves to isolate the inner conductor from the outer conductor, preventing signal leakage and short circuits, while also requiring low dielectric loss. Currently, widely used insulation materials include polytetrafluoroethylene (PTFE), fluorinated ethylene propylene (FEP) and polyethylene (PE). Among them, PTFE is the first choice for ultra-high-frequency scenarios due to its wide temperature resistance range (-200℃~+260℃) and low dielectric constant (εr=2.1). FEP combines the temperature resistance of PTFE with better processing fluidity, making it suitable for the production of cables with complex structures. PE materials, on the other hand, are used in medium and low-frequency general scenarios due to their cost advantages.
The outer conductor undertakes the dual responsibilities of conducting reverse current and shielding external electromagnetic interference. Its structural design directly determines the cable's anti-interference capability. Common outer conductors are divided into braided type and aluminum foil + braided composite type: the braided layer uses tinned copper wires with a braiding density of ≥95%, achieving a shielding efficiency of over 95dB at 1GHz. High-end high-frequency cables adopt a double-layer braiding + aluminum foil wrapping structure, which can increase the shielding efficiency to 100dB and effectively resist interference signals in strong electromagnetic environments.
As the "protective layer" of the cable, the sheath material is selected based on the application environment. Polyvinyl chloride (PVC) sheaths are used in conventional indoor scenarios, with a temperature resistance range of -15℃~+70℃, low cost and easy processing. For outdoor or harsh environments, polyethylene (PE) or polyurethane (PU) sheaths are used: PE has excellent weather resistance and anti-aging properties, while PU has advantages in wear resistance and oil resistance, making it suitable for complex industrial or outdoor working conditions.
With the diversification of application scenarios, high-frequency cables have gradually formed multiple segmented categories. Each type is optimized for specific frequency, environment and performance requirements.
High-frequency Coaxial Cables are currently the most widely used category. Based on impedance characteristics and structural differences, they can be further divided into RG series and LMR series. RG-58 (50Ω) is a common model in the radio frequency communication field, with a conductor diameter of 0.81mm and an insulation outer diameter of 2.95mm, suitable for short-distance signal transmission. RG-6 (75Ω) is mainly used for cable TV and broadband networks, with a conductor diameter of 1.02mm and an insulation outer diameter of 4.57mm, providing better signal-carrying capacity. The LMR series focuses on low-loss performance; for example, the LMR-400 (50Ω) has an attenuation of only 0.4dB/m at 1GHz, making it widely used in base station-to-antenna connection scenarios.
Semi-rigid and semi-flexible cables are designed for the installation needs of precision equipment, complementing each other in structural stability and flexibility. The outer conductor of semi-rigid cables is made of seamless copper tubes, with impedance stability controlled within ±1Ω. Its shape remains fixed after bending, which can effectively avoid impedance fluctuations during signal transmission, making it suitable for scenarios with extremely high signal stability requirements such as radar and satellite equipment. The outer conductor of semi-flexible cables is made of braided tinned copper wires, which can be manually bent and shaped. It balances structural stability and installation flexibility, making it an ideal choice for test instruments and precision electronic equipment.
Microwave cables focus on ultra-high-frequency signal transmission, with an operating frequency usually ≥10GHz. To reduce dielectric loss, microwave cables mostly use foamed PTFE as insulation material. By optimizing the insulation layer structure, signal attenuation is reduced, while excellent impedance consistency is maintained. They are mainly used in high-end fields such as microwave communications and aerospace.
The performance of high-frequency cables is evaluated through a series of quantitative indicators, which directly determine their adaptability and effectiveness in different scenarios.
The attenuation coefficient is a core indicator for measuring signal transmission loss, affected by conductor materials, insulation materials, cable structure and other factors. Industry standards stipulate that the attenuation of ordinary 50Ω cables at 1GHz should be ≤1.5dB/m, while high-end low-loss cables require ≤0.5dB/m. Tests must be conducted in a standard environment of 23℃±2℃ to ensure data accuracy. A smaller attenuation coefficient means less signal loss during transmission, making it more suitable for long-distance transmission scenarios.
The consistency of characteristic impedance is one of the key performances of high-frequency cables. High-frequency signals are extremely sensitive to impedance fluctuations; once impedance mismatch occurs, signal reflection will be generated, affecting transmission quality. Typically, the test frequency range for characteristic impedance is 1kHz~1GHz, measured using an impedance analyzer. In precision scenarios, the impedance deviation should be controlled within ±1Ω, while in general scenarios, it should be ≤±2Ω. Common standard impedance values are 50Ω (for radio frequency and microwave equipment) and 75Ω (for cable TV and broadband networks).
The Voltage Standing Wave Ratio (VSWR) is an important parameter reflecting the degree of impedance matching. Ideally, VSWR=1; in practical applications, it should be controlled within ≤1.3. If it exceeds 1.5, severe signal reflection will occur, even affecting the normal operation of equipment. Insulation resistance is related to the cable's insulation performance, tested using a 500V megohmmeter. For a 1km length, the insulation resistance should be ≥5000MΩ・km, which can effectively prevent leakage, avoid signal interference and safety hazards.
Weather resistance indicators are mainly for cables used in outdoor or harsh environments. They need to pass a series of environmental tests such as high-low temperature cycle testing (-40℃~+85℃), salt spray testing and ultraviolet aging testing. This ensures that the cables can work stably in extreme temperatures, humidity, corrosion and other environments, with a service life usually requiring ≥10 years.
The usage environment and performance requirements vary significantly across different fields. High-frequency cables need to achieve scenario adaptation through customized design. The following are adaptation requirements for several typical fields:
The aerospace field has extremely high requirements for cable lightweight, radiation resistance and high-temperature resistance. To meet the weight control requirements of spacecraft, the cable weight should be ≤100g/m. At the same time, it needs to have radiation resistance with a total dose of ≥100krad to resist radiation interference in the space environment. The sheath material uses fluoroplastics, with a flame retardant grade of V0 to ensure safety in extreme environments.
High-frequency cables in the medical equipment field must comply with biocompatibility standards, prohibiting the release of harmful substances to avoid harm to the human body. Meanwhile, to prevent cable signals from interfering with the normal operation of medical equipment, the shielding efficiency should be ≥99dB, ensuring undisturbed signal transmission in complex medical environments.
In industrial control scenarios, cables need to cope with harsh conditions such as oil pollution, vibration and high-low temperatures. The sheath material uses oil-resistant PVC, which has good oil resistance and wear resistance. At the same time, it needs to pass vibration testing (vibration frequency 10-2000Hz, acceleration 10g) to ensure stable operation in the high-frequency vibration environment of factory automation equipment, without joint loosening, insulation layer damage and other issues.
The installation quality and maintenance cycle of high-frequency cables directly affect their performance stability and service life, requiring strict compliance with industry standards and operating requirements.
The bending radius is an important consideration during installation. Different types of cables have different bending radius requirements: semi-rigid cables require a bending radius ≥10 times the cable outer diameter, semi-flexible cables ≥5 times, coaxial cables ≥12 times the outer diameter for outdoor installation, and ≥5 times for indoor installation. If the bending radius is too small, the insulation layer and outer conductor will be damaged, leading to impedance fluctuations, signal attenuation and even cable breakage.
The standardization of connection processes is crucial to signal transmission quality. Cable joints need to be fixed using crimping or welding methods. For crimping, the pressure should be ≥500N to ensure tight bonding between the joint and the conductor, avoiding poor contact. The welding temperature is controlled at 350℃±20℃ to prevent damage to the insulation layer due to high temperatures while ensuring the conductive performance of the welding point. After joint installation, a VSWR test should be conducted to ensure impedance matching at the connection.
In terms of wiring specifications, high-frequency cables should avoid parallel routing with high-voltage cables, with a spacing of ≥30cm between them. A 90° crossing should be used when crossing to reduce electromagnetic interference generated by high-voltage cables. At the same time, excessive stretching and twisting of the cable should be avoided during laying to prevent damage to the conductor and insulation layer.
The maintenance cycle should be adjusted based on the usage environment: outdoor cables, which are exposed to the natural environment for a long time, need to have their insulation resistance and VSWR tested every 2 years to detect aging, damage and other issues in a timely manner. For indoor equipment cables, the tightness of the joints should be inspected annually to prevent joint loosening caused by equipment vibration, which affects signal transmission.
As the core carrier of high-frequency signal transmission, the structural design, material selection, performance indicators and scenario adaptation of high-frequency cables are directly related to the operating efficiency and stability of electronic equipment. From sophisticated layered structures to diversified segmented types, from strict performance indicators to customized scenario adaptation, every detail of high-frequency cables reflects the in-depth integration of technology and applications. With the continuous advancement of technology, high-frequency cables will develop towards lower loss, higher stability and lighter weight, providing more reliable support for technological upgrading in communications, aerospace, medical care, industrial and other fields.
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