Coaxial cable loss problem

Coaxial cable is widely used in the industry, and its loss has always been concerned. CONNEXIONS is a professional coaxial cable processing company that will provide you with the best quality coaxial cable products.


The higher the frequency of the coaxial cable, the greater the loss, the reasons are as follows

a. The higher the frequency of the signal, the stronger the skin effect, and the more concentrated the transmission on the metal surface, the smaller the transmission cross-sectional area, so the greater the impedance, the greater the loss. In order to reduce the loss, the radio frequency line uses precious Metals (high electrical conductivity, precise manufacturing processes, etc.).

b. Coaxial line loss is divided into dielectric loss and metal conductor loss, among which dielectric loss is mainly required. Generally, the relative dielectric constant is required to be low, and the dielectric loss angle factor is small, so that the attenuation is small. The medium requires a consistent structure to ensure uniform impedance. The higher the frequency, the more difficult it is to keep the impedance consistent and continuous, and the reflection loss will be larger.

      1. Dielectric loss: When the frequency is very high, the dielectric constant is a function of the frequency due to the dispersion of the medium. The fundamental reason is that the charged particles change differently with the alternating electric field. The dielectric coefficient should have a maximum value with frequency, but since the coaxial wire insulation is a highly non-polar material, the dielectric coefficient dispersion is very weak from low frequency to high frequency.

       2. Conductor loss: Strictly speaking, conductor loss can actually be divided into two parts: heat loss and electromagnetic leakage caused by incomplete shielding. The same shielding rate has different shielding effects on electromagnetic waves of different frequencies, and the shielding effect on high frequencies. Not as good as the low frequency ones (of course, this is not the main part of the loss).

c. Skin depth δ=1/πfuσ ; cross-sectional area of transmission current s=π[(r+δ)²-r²] ; transmission resistance R=1/σs;

  Conclusion:-----The thicker the wire, the larger the cross-sectional area, and the smaller the transmission resistance;

         -----The greater the conductivity, the smaller the skin depth, the smaller the cross-sectional area, the greater the transfer resistance; the greater the conductivity, the less the transfer resistance; from the two considerations, the latter is dominant, so the conductance The greater the rate, the smaller the resistance;

         -----The higher the frequency, the smaller the skin depth and the greater the transmission resistance.

d. The thinner and longer the coaxial cable, the greater the loss, the higher the signal frequency, the greater the loss.



Attachment: The general method of judging the quality of the coaxial cable:

Observe the roundness of the insulating medium

Detect the consistency of the insulating medium of the coaxial line

Braided mesh for detecting coaxial wires

Check the quality of aluminum foil

Check the extrusion tightness of the outer sheath

Observe the shape of the coaxial line in the loop