Firstly, volume resistivity is an electrical property of materials. For radio frequency (RF) cables, the volume resistivity at 20℃ reflects the ability of the cable's insulating material per unit volume to resist the flow of electric current at 20 degrees Celsius. It is determined by applying a voltage across the material, measuring the current flowing through the material, and then calculating the resistance according to Ohm's Law (R = U/I, where R is the resistance, U is the voltage, and I is the current), and finally combining it with the volume of the material.
Impact on Signal Transmission
Higher volume resistivity at 20℃ helps reduce signal attenuation. When RF cables transmit high-frequency signals, energy losses will occur due to the electrical conductivity of the insulating material. If the volume resistivity is low, it means that the insulating material has relatively strong electrical conductivity, and more current leakage will occur during signal transmission, resulting in a weakened signal strength. For example, in the RF cables used in some communication base stations, the insulating materials with high volume resistivity can enable the signals to maintain a relatively high strength after long-distance transmission, ensuring the communication quality.
In Terms of Signal Interference
Good volume resistivity can reduce signal interference. When the volume resistivity of the cable's insulating material is low, external electromagnetic signals can more easily penetrate the insulating layer and enter the inside of the cable, interfering with the normal transmission of RF signals. On the contrary, the insulating materials with high volume resistivity can effectively shield external interference signals. Just like in the industrial environment with a complex electromagnetic field, RF cables with high volume resistivity insulating materials can better resist the electromagnetic interference generated by surrounding motors, transformers and other equipment.
In Terms of Insulation Aging
Appropriate volume resistivity at 20℃ can slow down the aging rate of the insulating material. If the volume resistivity is not suitable, for example, if it is too low, under the long-term action of an electric field, partial discharge may occur inside the insulating material. This will lead to the gradual aging and damage of the insulating material and reduce the service life of the cable. Taking outdoor RF cables as an example, after experiencing long-term exposure to sunlight, rain and the action of an electric field, the insulating materials with high volume resistivity can better maintain their insulating properties and extend the service life of the cable.
In Terms of Performance Stability
Stable volume resistivity can ensure the stability of the performance of RF cables. Under different environmental temperature and humidity conditions, the insulating materials with relatively small changes in volume resistivity can keep the electrical properties of RF cables relatively stable. For example, in some aerospace equipment that requires high-precision signal transmission, the stability of the volume resistivity at 20℃ of the insulating materials of RF cables is of vital importance, as it can ensure the accuracy and reliability of signal transmission under the complex environmental conditions in space.
