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coaxial cable (COAX)

Coaxial cables (COAX) are coaxially constructed high-frequency cables. They have an asymmetrical design and consist of the signal-carrying inner conductor surrounded by the dielectric, the shielding and the cable sheath.

Coaxial cables are used wherever high-frequency signals have to be transmitted or signals have to be shielded against interference. For example, in antenna technology, in community antenna systems, in broadcasting technology, in broadband cable networks, broadband networks and also - at least in the past - in local area networks( LAN).

The most important parameters of coaxial cables

Important parameters of coaxial cables are impedance, bandwidth, attenuation and return loss. InRF technology, impedances of 50 ohms are predominantly used, while bandwidths cover the entire UHF range and extend up to 12 GHz for various coaxial cables. For such frequencies, the attenuation is correspondingly high, which is frequency-dependent for all coaxial cables.

Structure of coaxial cables

Structure of coaxial cables

As an example of the attenuation values, a MIL-standardized RG ultrahigh-frequency cable is given: Attenuation for the RG-223 cable cited is 10 dB/100 m at 50 MHz, 30 dB/100 m at 400 MHz, 50 dB/100 m at 1 GHz, and 180 dB/100 m at 5 GHz.

Attenuation behavior of different coaxial cables

Attenuation behavior of different coaxial cables

There are also some important specifications regarding the type and number of shields, which are reflected in the shielding effectiveness and have a direct influence on the coupling resistance or shielding effectiveness. Furthermore, there are specifications on the diameter of the inner conductor and the shielding, which are included in the installation-related criteria such as the bending radius or the tensile load. Coaxial cables are nationally and internationally standardized by the International Electrotechnical Commission( IEC) under 61196-1, as a European standard( EN) under 50117 and as a Mil standard under MIL-C-17F.

Known coaxial cables

Coaxial cables have an outer shield that protects the cable from external radiation and internal radiation. The shielding can be a braided or foil shielding, or a Kpombination of both. Thanks to the high bandwidth, data rates in the gigabit range can be transmitted via coaxial cable.

Double-shielded RG-6 cable, photo: Computercablestore.com

Double-shielded RG-6 cable, photo: Computercablestore.com

Coaxial cables are available for data transmission technologywith impedances of 50 ohms, 75 oh ms(cable TV, broadband systems), 93 ohms( 3270 terminals) and 105 ohms twinaxial cables (5250, AS/400, /36, /38). Well-known coaxial cables formerly used in data communications and networks include RG-6 cable, RG-58 cable, and RG-62 cable.

Among the better known high frequency cables are RG-174, RG-188, RG-213, RG-214, RG-223 and RG-316.

Informations:
Englisch: coaxial cable - COAX
Updated at: 04.11.2013
#Words: 390
Links: frequency (f), signal, conductor, dielectric, shielding
Translations: DE
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