An RF coaxial cable is defined as a cable featuring two concentric conductors, wherein both the inner conductor and the shielding layer share a common central axis.
The insulating material within an RF coaxial cable consists of physically foamed polyethylene, which serves to isolate the central copper conductor. Surrounding this inner insulation layer is a second, annular conductor-known as the outer conductor. This outer conductor (or shielding layer) may be constructed using formed, welded, and corrugated copper tape; an aluminum tube structure; or a braided wire configuration. Finally, the entire cable assembly is encased within a protective jacket typically made of polyvinyl chloride (PVC).
There are two primary categories of commonly used RF coaxial cables: 50-ohm (50Ω) and 75-ohm (75Ω) cables.
RF coaxial cables with a characteristic impedance of 75Ω are frequently utilized in CATV networks-hence their designation as "CATV cables." These cables offer a transmission bandwidth capable of reaching up to 1 GHz, with a typical operating bandwidth of 750 MHz for standard CATV applications.
RF coaxial cables with a characteristic impedance of 50Ω are primarily employed for baseband signal transmission, covering a bandwidth range of 1 to 20 MHz. Generally, "thin" 50Ω coaxial cables have a maximum transmission distance of 180 meters, while "thick" coaxial cables can extend this range up to 1,000 meters.
The name "RF coaxial cable" is derived directly from its structural design. Furthermore, RF coaxial cable remains one of the most prevalent transmission media utilized in Local Area Networks (LANs). The pair of conductors responsible for transmitting information is constructed in a specific configuration: a cylindrical outer conductor encases an inner conductor (typically a thin central core), with an insulating material separating the two. Because the geometric center of the outer conductor aligns perfectly with the central axis of the inner core wire, the cable is aptly named a "coaxial" cable. This specific design architecture serves a critical functional purpose: to prevent external electromagnetic waves from interfering with or distorting the transmission of signals.
