The attenuation of radio frequency cable is related to conductor, medium, structure size, process level and frequency of operation.
1, below 50MHz attenuation constant is too large or ultra poor, while the high margin, often is the aluminum plastic composite belt is too thin. When the frequency is low, the penetration depth is less than the thickness of aluminum matrix or with the frequency of R is too large, resulting in a. According to the theoretical calculation, the penetration depth of aluminum layer was about 12.2 f=50MHz M. Generally take the aluminum 12~15 M can solve this problem. (of course, if the shielding attenuation requirement is taken into account, it can be properly thickened)
2, select PE in the use of frequency within the tan delta is larger, such as X * 10-3 level, will lead to insulation structure of tan delta increases, so that the attenuation of the cable increases. So we should pay attention to 2 issues, one is to be small (such as tan delta tan delta in 400MHz is 2~4 * 10-4, the smaller the better), is a process of performance (such as melt index 0.5~10) should adapt to the extrusion and insulation, melt index of different temperature.
3, the external conductor weaving general 60%-80% is appropriate, too large, to reduce attenuation effect is not obvious.
4, the die design and processing of insulation production is also the key, and it should ensure the product to achieve a better uniform structure, so that the equivalent dielectric constant to meet the design requirements.
5, the physical foaming PE attenuation in low frequency is qualified, and the high frequency (more than 800MHz) when the ultra poor, most of the dielectric loss tangent and the equivalent dielectric constants is too large, or with the outer conductor braiding density is too small, the inner conductor of smaller diameter relationship. In addition, the attenuation constant also depends on the degree of foaming. In the range of impedance and echo, the degree of foaming can be increased (by increasing the degree of foaming, increasing the impedance and decreasing the attenuation) It is helpful to improve the attenuation constant of cable, and it can also reduce the cost.