Radio Frequency (RF) cables carry signals between the antenna and the transmitter and/or receiver for technologies such as cellular, Global Navigation Satellite Systems (GNSS), Wi-Fi, and Bluetooth. That means they play a critical role in the performance and reliability of the application that uses those signals.
An obvious example of this role is ensuring that the signal gets from the antenna to the device or vice versa. But RF cables also can provide design and installation flexibility.
For instance, GNSS applications work best when their antenna has a clear view of the sky. That can be difficult to achieve with an antenna that’s embedded in the device. An RF cable enables those two components to be separated. Now the GNSS antenna can be installed in a location where it’s always looking up at the sky.
In the case of cellular, an RF cable can enable the antenna to be installed in a location that provides a ground plane. An example is a terminal mount monopole antenna that needs to sit atop a large metallic surface — such as a vehicle’s roof or trunk lid — so it has a ground plane to radiate efficiently.
RF Cable Types
There are several types of RF cables. The choice comes down to application requirements such as signal loss, interference resistance, and frequency range. If the cable is used for transmitting signals, then another important consideration is a cable’s power handling capacity to avoid overheating, failure, and damage to nearby components.
- Coaxial cable is the most common type. It’s good for applications that use high-frequency signals and need low loss.
- Twinaxial and triaxial cables have two or three central conductors, respectively. Both types provide extra protection and reduce signal interference.
- RF cable assemblies have factory-installed connectors at both ends to facilitate installation. For example, the Taoglas MCA3.J0915J coaxial assembly has 2.92 mm connectors, with other types available.
RF cables all typically have four main components:
- Center Conductor: Typically made of copper or aluminum, it carries the signal.
- Dielectric Insulator: Separates the center conductor from shielding and helps signal efficiency.
- Shielding: Surrounds the insulator, blocking outside interference.
- Outer Jacket: Protects the cable from physical damage.
How Cables Protect RF Signals
These components also illustrate the functions of an RF cable. Besides carrying the signal, they protect it from interference from other RF sources. An RF cable also physically protects the signal with its onion-like layers of insulation, shielding, and jacket.
It’s important to consider each of these functions when choosing an RF cable. Take the example of a GNSS antenna mounted on a vehicle roof. The RF cable will run past electrical wiring and electrical motors, all of which can interfere with the signal. As a result, the quality of the RF cable’s shielding plays a major role in ensuring that the signal isn’t undermined by the time it reaches the GNSS receiver in the dashboard navigation head unit.
Meanwhile, the outer jacket ensures that the shielding, insulator, and conductor are all protected against environmental conditions such as water and physical damage that can lead to signal loss. The application design also can help the jacket do its job. One best practice is to route the cable away from pinch points, heat sources, and other hazards that could weaken the jacket and cause it to fail, exposing the shielding, insulator, and conductor.
Testing Verifies That Requirements are Met
Testing is critical for verifying that an RF cable meets requirements such as performance and reliability.
- Voltage Standing Wave Ratio (VSWR) measures signal reflection and transmission efficiency.
- Insertion loss measures signal loss as it travels through the cable.
- Return loss is the amount of signal reflected back toward the source, such as the transmitter.
This is a lot to consider, which is why savvy device manufacturers, systems integrators, and end users rely on trusted cable experts for highly reliable solutions. The Taoglas line of RF coaxial cable assemblies is specifically designed to meet the demands of wireless telecommunications applications, including 5G/LTE, Wi-Fi®, and IoT devices. These cable assemblies are precisely manufactured and rigorously tested to ensure the highest quality and performance.
