Types of Coaxial Cables and Selection Guidelines for 5G Communications and Medical Applications

Coaxial cables are essential in various industries, including base station communications and precision medical equipment. Selecting the right coaxial cable ensures optimal signal transmission, minimizes interference, and protects sensitive equipment.

This article aims to help engineers properly match electrical parameters and reduce signal loss. If you are seeking high-frequency transmission solutions for a new project, please feel free to contact the WIRES team at any time for professional technical support and rapid prototyping quotes.

How Does Coaxial Cable Work?

Coaxial cable is a waveguide structure that uses a combination of concentric inner and outer conductors to directionally transmit high-frequency electromagnetic signals.

When analyzing coaxial cable, a thorough understanding of its internal spatial configuration is crucial for circuit design.

A coaxial cable consists of four basic components, from the inside out: the center conductor, the dielectric insulator, the outer shielding layer, and the outer jacket.

• The center conductor is typically made of solid copper wire or tinned copper wire and is primarily used to carry high-frequency electrical signals.
• The dielectric insulator surrounds the center conductor, providing physical isolation and maintaining the conductor’s concentricity.
• The outer shield is usually composed of a metal braid or aluminum foil, which blocks external electromagnetic interference.
• The outermost jacket provides environmental protection, ensuring the cable’s physical durability against abrasion and moisture.

Electrical signals propagate forward inside a coaxial cable in the form of transverse electromagnetic waves (TEM mode).

The electric and magnetic fields are completely confined within the insulating medium between the inner and outer conductors, giving coaxial cables excellent resistance to interference.

The characteristic impedance of a coaxial cable is determined by the ratio of the diameters of the inner and outer conductors and the relative permittivity of the insulating material:

• D: Inner conductor inner diameter
• d: Outer conductor outer diameter
• εr: Relative permittivity of the insulating material

Therefore, the impedance of a coaxial cable is not randomly determined but is jointly determined by the conductor dimensions and the dielectric material. If, during manufacturing, the concentricity of the conductors is insufficient, the insulation thickness is uneven, or dimensional tolerances are poorly controlled, this will cause the impedance to deviate from the design value (such as 50Ω or 75Ω), leading to signal reflection, increased return loss, and degraded transmission performance.

This is why high-quality coaxial cables require strict control over conductor dimensions, dielectric uniformity, and manufacturing tolerances to ensure stable impedance characteristics and excellent high-frequency transmission performance.

How to Scientifically Select the Right Coaxial Cable

In the face of diverse commercial communication cabling and precision medical signal transmission, correctly distinguishing and selecting coaxial cables is the foundation for ensuring system stability.

Different types of coaxial cables vary significantly in electrical loss, shielding effectiveness, and physical mechanical hardness.

RG Series Coaxial Cables: Versatile and Reliable

RG series coaxial cables are currently the most widely used standard general-purpose cable type, extensively deployed in residential, commercial, and general industrial environments.

These cables come in a variety of models, each optimized for specific impedance, gauge, and transmission distance.

Understanding these differences helps in matching the appropriate transmission equipment for cable TV systems, broadband networks, and RF communications.

Common types and their applications include:

• RG-6/U: Ideal for cable TV, satellite TV distribution, and residential broadband internet connections.
• RG-8/U: Commonly used for high-frequency equipment cabling, two-way radio communication systems, and base station interconnections.
• RG-11/U: Due to its thicker gauge, it is best suited for long-distance cable TV cabling and high-frequency backbone signal transmission.
• RG-59/A/U: Suitable for closed-circuit television (CCTV) surveillance and low-frequency analog video signal transmission.

The table below shows the key physical and electrical specifications for common RG series coaxial cable types:

Rigid Coaxial Cable: Designed for High-Power Signals

Rigid coaxial cables use a solid metal tube (such as a round copper or aluminum tube) as the outer conductor and shield, resulting in a very robust structure.

Their physical design is intended to significantly reduce signal loss and withstand high continuous electrical power and external physical stress.

This unique construction makes rigid coaxial cables ideal for high-power RF transmitters, radio broadcast towers, and cellular network backbone infrastructure.

They are capable of operating safely over long periods in extremely harsh outdoor environments, ensuring efficient transmission of high-power signals.

Semi-rigid and hand-formed coaxial cables: Precision cables for specialized applications

Semi-rigid coaxial cables use a solid copper jacket instead of traditional metal braiding, providing exceptional shielding performance. Once formed, the cable cannot be bent, but it exhibits extremely low attenuation and excellent electrical stability in the high-frequency range.

The hand-formed version allows engineers to freely bend the cable into specific shapes during installation, significantly improving cabling convenience in complex, compact spaces while maintaining high shielding performance.

Applications include:

• High-frequency RF measurement systems
• Network analyzers
• Advanced medical imaging equipment (e.g., MRI scanners)

Their excellent phase stability and low power loss ensure that weak signals remain clear and undistorted even in complex electromagnetic environments.

Dual-axis and Tri-axis Cables: Providing Additional Shielding Layers for Sensitive Signals

Dual-conductor cables contain two independent center conductors instead of the traditional single conductor, making them ideal for transmitting differential signals.

This dual-conductor configuration effectively suppresses low-frequency electromagnetic noise and ground loop interference, and is widely used in high-speed computing networks in data centers and in avionics.

Triple-conductor coaxial cables feature an additional layer of mutually insulated metal braiding outside the outer conductor of a standard coaxial cable.

This additional shielding layer is typically grounded separately, protecting the internal core transmission link from interference caused by strong electromagnetic fields.

Triple-shielded cables ensure high signal-to-noise ratios in professional broadcast cameras, precision laboratory test equipment, and high-resolution medical imaging systems.

Low-Loss Flexible Coaxial Cables: Balancing Transmission Performance and Physical Flexibility

Low-loss flexible coaxial cables are an upgraded version of traditional RF cables, typically utilizing advanced foamed dielectrics and multi-layer optimized shielding structures.

They are designed to significantly reduce signal attenuation over long distances while ensuring the cable remains sufficiently flexible and easy to bend and install.

These cables play a central role in wireless network deployments requiring long-distance cabling, vehicle-mounted antennas, and portable electronic systems.

The common LMR series is a typical representative of low-loss flexible coaxial cables:

• LMR-100: Suitable for short-distance wireless device interconnections and portable antenna extension cables.
• LMR-200: Commonly used in indoor Wi-Fi distribution systems and GPS antenna connections.
• LMR-240: Suitable for mobile antenna feeders and amateur radio station cabling.
• LMR-400 / Ultraflex: The most widely used low-loss flexible specification in high-frequency, high-power wireless communications.
• LMR-600: Specifically designed for long-distance base station antennas, offering extremely low operating loss.

The table below compares the key technical parameters of common LMR low-loss coaxial cable types:

Finding the Perfect Connector for Coaxial Cables

Regardless of the type of coaxial cable, it must be physically and electrically terminated at the device interface using a coaxial connector.

If the wrong connector is selected, significant signal reflection and loss will occur at the connection point, even with high-quality cable.

Common connectors include:

• BNC: Features a bayonet-style connection and is widely used in medical equipment, video surveillance, and traditional laboratory testing instruments.
• SMA: Features a threaded connection and compact size; it is the standard interface for 5G cellular networks, wireless antennas, and GPS devices.
• F-Type: An inexpensive threaded connector commonly found in cable TV set-top boxes and satellite receivers.
• MCX / MMCX: Micro snap-on connectors suitable for micro wireless modules and compact electronic circuit boards.

Key Considerations for Choosing Coaxial Connectors

When selecting a coaxial connector, engineers need to pay attention to several important factors:

• Impedance Matching: The connector’s impedance, such as 50Ω or 75Ω, should align with the cable’s impedance. Mismatches can cause reflections, signal loss, or even damage sensitive RF components.
• Operating Frequency: Make sure the connector supports frequencies beyond your system’s requirements to maintain signal integrity.
• Insertion Loss: High-quality connectors minimize signal attenuation at the connection point, ensuring the signal remains strong.
• VSWR (Voltage Standing Wave Ratio): This value indicates how much signal is reflected due to impedance differences. Ideally, a VSWR close to 1.0 shows excellent matching and minimal power reflection.

Proper evaluation of these parameters helps guarantee stable, low-loss performance, especially in high-frequency RF systems or precision medical equipment.

If the crimping process does not meet standards or there is a mismatch in specifications, the VSWR will increase, and the reflected energy will cause downstream chips to overheat and age prematurely.

When assembling high-frequency components, WIRES uses precision terminal crimping fixtures and tests every finished product with a vector network analyzer to ensure the VSWR complies with industry standards.

Types of Custom Coaxial Cables Provided by WIRES

As new commercial equipment places increasingly stringent demands on internal installation space and weather resistance, standard off-the-shelf coaxial cables on the market often fail to meet these requirements directly. With 28 years of experience in custom wire harness manufacturing, WIRES offers comprehensive coaxial component customization services based on your engineering drawings.

• Micro-coaxial cable assembly manufacturing: Suitable for highly integrated applications such as medical endoscopes and ultrasound probes.
• Multi-channel signal backbone harnesses: Capable of precisely combining multiple micro-coaxial cables as small as 42 AWG into a compact structure.
• High-precision terminal processing: Our in-house technical team, certified through professional qualification assessments, performs laser stripping and micro-welding under high-magnification microscopes to ensure secure and reliable connections.
• Customized Specialty Sheath Materials: We offer modified materials such as PTFE, FEP, and LSZH, balancing excellent dielectric properties, resistance to high-pressure sterilization, and outdoor salt spray corrosion resistance to significantly extend equipment lifespan.

WIRES’ custom coaxial solutions ensure signal stability and cable reliability in miniaturized, high-density, and harsh environments, meeting the stringent requirements of medical, industrial, and high-end commercial equipment.

Frequently Asked Questions (FAQ) About Coaxial Cable Types

Q: Can 50Ω and 75Ω coaxial cables be used interchangeably?

A: Absolutely not.

• Impedance mismatch causes significant signal reflection at the interface, leading to waveform distortion and increased signal attenuation.
• In high-power RF applications, excessive reflected power can burn out the wireless transmitter chip.

Q: What should be prioritized during long-term operation of flexible coaxial cable harnesses used in outdoor base stations?

A: Focus on preventing moisture ingress and UV aging:

• Poorly sealed connectors allow moisture to enter the shielding layer, altering the dielectric constant and corroding the conductor, which leads to signal attenuation.
• WIRES’ custom outdoor coaxial assemblies feature a design with heat-shrink tubing over the connector ends, effectively blocking moisture intrusion and ensuring long-term stable operation.

Q: Why do high-frequency, multi-channel cable assemblies require custom phase matching?

A: In radar antenna arrays or synchronized medical data acquisition equipment, signal delays across all channels must be highly consistent.

• WIRES can trim finished coaxial cables to the micrometer level under precision instrument monitoring,
• controlling the relative signal phase tolerance between multiple channels to an extremely narrow range, ensuring data acquisition synchronization and system stability.

Conclusion

Properly evaluating and matching coaxial cable types and connectors is key to the stable operation of high-frequency communication and precision medical equipment.

WIRES strictly controls every step of the process—from conductor material selection and shielding control to precision terminal termination—to ensure stable and reliable signal transmission. Choosing custom cable assembly components reduces assembly and testing workloads, improving production efficiency and the competitiveness of end products.

Provide your operating frequency, wiring diagrams, or engineering drawings to receive a free technical evaluation and customized solution quote from WIRES, with a response within 8 hours.