How High-Frequency Coaxial Cable Supports Cleaner Signals in Advanced Imaging Probes

Transmitting these highly complex signals—including those used in IVUS ultrasound imaging, ICE intracardiac imaging, and high-definition (HD) endoscopy systems — requires highly sensitive analog signal transmission from the probe transducer to the imaging processor. Most of these signals operate above 5 MHz, with some exceeding 50 MHz, enabling the high-resolution imaging required to identify potential abnormalities and support accurate diagnosis and intervention. However, high-frequency signal transmission is susceptible to attenuation, impedance mismatch, phase distortion, and electromagnetic interference, all of which can reduce image clarity. At Hotten, we manufacture high-frequency coaxial cable assemblies for advanced imaging probes. The following four core technologies enable reliable signal transmission and support high-quality diagnostic imaging.

Why Do Advanced Imaging Probes Require High-Frequency Coaxial Cable?

Direct Answer

Advanced imaging probes place several demanding requirements on the cable at the same time.

The cable may need to transmit weak or high-frequency signals through a compact, shielded and mechanically constrained path while maintaining controlled impedance, low attenuation, stable phase characteristics and reliable environmental performance.

The cable therefore needs to be designed as part of the complete imaging signal path.

If → the probe transmits weak high-frequency signals over a limited physical distance

Then → evaluate conductor loss, dielectric loss and total cable attenuation

Why → even relatively small transmission losses can affect the available signal at the receiving electronics.

If → the imaging system uses controlled-impedance signal paths

Then → control conductor/dielectric geometry and the cable-to-connector transition

Why → impedance discontinuities can introduce reflections into the signal path.

If → multiple channels must operate together for phased-array or multi-element imaging

Then → evaluate phase matching, electrical-length consistency and channel-to-channel construction

Why → differences between signal paths can affect the timing relationship between channels.

If → the probe operates in a high electromagnetic-noise environment

Then → evaluate individual and overall shielding, shield termination and grounding structure

Why → external interference and channel coupling can degrade sensitive imaging signals.

If → the probe or cable is repeatedly moved during normal operation

Then → evaluate RF performance together with flexibility and mechanical durability

Why → mechanical movement can alter the physical signal structure or stress the termination area.

The current HOTTEN article specifically addresses these four areas—dielectric loss, impedance matching, phase stability and shielding—for IVUS, ICE and endoscopic imaging systems.

For customized High-Frequency Coaxial Cable, HOTTEN can develop cable structures around application-specific signal and mechanical requirements.

For finished assemblies, see RF Coaxial Cable Assembly.

Ultra-Low-Loss Dielectrics for Minimal Attenuation Across Frequency Bands

Signal attenuation of coaxial cable depends on the frequency due to the skin effect and loss of signal in the dielectric of the cable. Low-level return signals from deep tissue can experience more than 1.5 dB/m of signal loss when transmitted through conventional cables at 20 MHz. Advanced low-loss dielectric materials, such as expanded PTFE (e-PTFE) and microporous polyethylene with a dissipation factor below 0.0005 at 10 MHz, are used by Hotten. These materials help maintain weak reflected signals above the noise floor in IVUS and ultrasound probe cables while achieving an insertion loss below 0.3 dB/m at 30 MHz. The permittivity is very stable even in the e-PTFE's porous microstructure, thus avoiding attenuation drift during the course of a long scanning session. This directly contributes to improved image resolution and enhanced tissue penetration.

Precision Impedance Matching to Eliminate Signal Reflections

Discontinuities in characteristic impedance at cable splices, connector interfaces, or due to manufacturing variations can introduce image artifacts, including ghosting and range sidelobes. Every component is verified using Hotten’s patented closed-loop extrusion control and time-domain reflectometry (TDR) systems, which will achieve an impedance tolerance of less than 2% (when used in medical imaging, it is considered 50 ohm nominal cable). Our attention is also focused on the interface of the cable to the internal flex circuit of the probe for our ICE catheter cables and endoscope imaging harnesses—as we custom design the transition boards to match the impedance of the cable, instead of a sharp transition. The continuity in impedance eliminates ring down artifacts that could be confused with disease. All measurements show a VSWR of < 1.2:1 for the entire band.

Phase-Stable Construction for Consistent Delay Characteristics

The relative phase alignment of multiple signal paths within phased-array or multi-element imaging probes is critical for accurate beamforming. With a varying geometry and/or material of the cable between channels, the reconstructed image will be misregistered and/or blurred because of the differences in the timing of arrival of the signal. Hotten achieves phase stability through three key approaches: (1) High dielectric constant uniformity within each production batch; (2) High-precision signal path length matching of signal path (e.g. tolerances within ±1 mm) for multi-coaxial bundles; (3) A dense braid shield provides uniform capacitance, even when flexed. We also do thermal equalization on our robotics wire harnesses for automated imaging systems in order to remove internal stresses that may lead to phase drift. This provides coherent beamforming, with phase errors of less than 2° at 10 MHz.

How Should OEM Engineers Select High-Frequency Coaxial Cable for Imaging Probes?

For an OEM imaging project, selecting a high-frequency coaxial cable should begin with the imaging architecture and signal requirements, not simply with a request for “low-loss coaxial cable.”

A useful engineering sequence is:

Imaging Requirement → Frequency → Signal Level → Attenuation → Impedance → Phase / Channel Matching → Shielding → Mechanical Constraints → Connector Transition → Validation

The exact priorities depend on the imaging system.

1. Define the Imaging Signal Before Selecting the Cable

Different imaging systems can impose very different electrical requirements.

Typical engineering inputs include:

If → the system uses multiple imaging channels

Then → define channel-to-channel electrical requirements before selecting the cable construction

Why → the cable must preserve consistency between signal paths, not only meet the specification of one individual coaxial channel.

2. Low Loss Should Be Evaluated Across the Required Frequency Range

A cable is not simply “low loss” in absolute terms.

Attenuation can depend on:

• conductor resistance
• skin effect
• dielectric loss
• cable length
• operating frequency
• cable geometry
• connector interfaces

If → the imaging system operates across a defined frequency band

Then → evaluate attenuation across that band rather than at one frequency only

Why → a single attenuation value may not represent the cable's behavior throughout the operating range.

If → the receiving signal is very weak

Then → evaluate the complete loss budget from the probe to the receiving electronics

Why → cable loss is only one part of the total system transmission path.

The current HOTTEN article specifically links dielectric selection to attenuation performance in high-frequency imaging applications and discusses low-loss dielectric materials such as ePTFE.

3. Dielectric Selection Is a Key Design Decision

The dielectric influences more than insulation.

Relevant properties may include:

• relative permittivity
• dissipation factor
• dielectric loss
• dimensional stability
• moisture sensitivity
• flexibility
• manufacturability

If → attenuation is a major system limitation

Then → evaluate lower-loss dielectric structures

Why → dielectric losses contribute to total high-frequency transmission loss.

If → the same cable must also tolerate repeated bending

Then → evaluate dielectric structure together with mechanical flexibility

Why → electrical optimization and mechanical optimization can create competing requirements.

For micro and ultra-fine coaxial structures, this connects naturally to:

How to Select the Right Foaming Technology for Micro Coaxial Cable Insulation?

and:

How Micro Coaxial Cable Design Ensures Signal Integrity in Medical Devices

4. Impedance Continuity Matters Through the Complete Imaging Path

The nominal impedance of the cable is only one part of the design.

The actual signal path may be:

Probe Element

→ Cable

→ Termination

→ Connector

→ Flex Circuit / PCB

→ Imaging Electronics

If → the cable has the specified impedance but the connector transition is not controlled

Then → evaluate the complete transition

Why → local impedance discontinuities can create signal reflections.

If → the cable connects to an internal flexible circuit or transition board

Then → design the interface around the cable's controlled transmission structure

Why → a large geometry change at the transition can create a localized mismatch.

This is especially relevant to the current HOTTEN article because it already states that transition boards can be customized to avoid an abrupt transition between the cable and internal flex circuitry.

The related technical foundation is:

What Is Cable Impedance and Why Does It Matter in High Frequency Cable Assemblies?

5. Phase Matching Becomes Important in Multi-Channel Imaging

For multi-element and phased-array systems, signal paths may need to remain closely matched.

Relevant variables can include:

• cable length
• dielectric consistency
• conductor geometry
• capacitance
• propagation characteristics
• temperature response
• channel-to-channel variation

If → multiple channels are combined for beamforming or image reconstruction

Then → evaluate the electrical length and phase consistency between channels

Why → differences between signal paths can change signal arrival timing.

If → the cable contains many individually shielded coaxial channels

Then → control cable construction consistently across channels

Why → small differences in geometry or material can create channel-to-channel variation.

The current HOTTEN article specifically discusses signal-path length matching and dielectric consistency for phase stability.

6. Shielding Has Two Different Jobs

For advanced imaging probes, shielding can be considered from two perspectives:

External Noise Rejection

and

Internal Channel Isolation

Relevant considerations include:

If → multiple sensitive channels are tightly packed

Then → evaluate individual-channel shielding as well as overall shielding

Why → channel-to-channel coupling may need to be controlled separately from external EMI.

If → the probe is used near other RF or electrosurgical equipment

Then → evaluate the complete shielding and grounding architecture

Why → the external electromagnetic environment may impose additional interference-control requirements.

The existing HOTTEN article describes multi-layer shielding and a stranded ground return structure for certain IVUS and ICE applications.

7. Cable Diameter and Channel Density Create a Mechanical Constraint

Advanced imaging probes often have limited internal space.

This creates a design trade-off among:

Channel Count

vs.

Cable OD

vs.

Shielding

vs.

Flexibility

vs.

Electrical Performance

If → channel count increases without increasing available space

Then → evaluate a higher-density cable architecture

Why → conventional cable constructions may not fit the available routing envelope.

If → the cable OD must be reduced

Then → evaluate conductor size, dielectric structure, shielding and channel arrangement together

Why → reducing one dimension may increase electrical loss or reduce mechanical robustness.

HOTTEN's current ultrasound cable portfolio includes customized high-density and micro coaxial constructions, including configurations with different channel counts, conductor sizes and jacket materials.

8. Mechanical Movement Can Affect RF Performance

A high-frequency imaging cable may need to move repeatedly during operation.

Potential mechanical effects include:

• local bending
• torsion
• connector movement
• shield deformation
• conductor displacement
• strain-relief stress

If → the cable is repeatedly bent during probe operation

Then → compare relevant RF measurements before and after representative flex testing

Why → electrical performance should remain within the application's acceptance criteria after mechanical stress.

If → failures are concentrated near the connector

Then → investigate strain relief, termination geometry and local bend radius

Why → the connector transition can experience higher local mechanical stress.

This connects directly to:

How Flex-Life Testing Helps Medical Cable Assemblies Maintain Performance After Repeated Bending

9. Different Imaging Applications Need Different Cable Priorities

The cable should be designed around the actual imaging system.

IVUS

If → the cable is used inside an intravascular imaging system

Then → prioritize compact structure, signal integrity, shielding, electrical consistency and the mechanical constraints of the catheter system

Why → the cable operates inside a highly space-constrained imaging architecture.

HOTTEN currently lists customized IVUS cable solutions for intravascular imaging applications, including ultra-thin cable structures and configurable conductor, insulation and shielding materials.

See IVUS Cable.

ICE

If → the cable is used in an intracardiac imaging system

Then → consider high-frequency transmission, impedance transition, compact routing and application-specific mechanical requirements

Why → the cable is part of a compact catheter-based imaging system.

Ultrasound

If → the cable connects a high-channel-count ultrasound probe to imaging electronics

Then → consider channel count, capacitance, impedance, shielding, cable OD and flexibility together

Why → ultrasound probe cables often combine dense signal routing with strict mechanical constraints.

HOTTEN currently offers ultrasound probe cable configurations with high channel counts and micro coaxial structures, including 132-channel low-capacitance configurations.

See Ultrasound Probe Cable.

Endoscopic Imaging

If → the cable is integrated into a miniature endoscopic imaging system

Then → evaluate cable OD, flexibility, attenuation, shielding, termination and connector space together

Why → the available routing space is limited while the cable may experience repeated movement.

10. What Should an OEM Include in an Advanced Imaging Probe Cable RFQ?

A useful RFQ should define both the electrical performance and the physical integration requirements.

If → the RFQ only states “high-frequency coaxial cable”

Then → add frequency, impedance, attenuation, cable length, connector, OD and environmental requirements

Why → otherwise different cable constructions may all satisfy the same general description while producing different system-level results.

Practical Advanced Imaging Cable Selection Logic

A useful engineering sequence is:

Imaging Requirement

→ Frequency / Bandwidth

→ Signal Level

→ Channel Count

→ Impedance / Capacitance

→ Attenuation

→ Phase Matching

→ Shielding

→ Cable OD

→ Flexibility

→ Connector / Transition

→ Prototype Testing

→ Mechanical / Environmental Validation

→ Production Verification

For an advanced ultrasound probe:

High Channel Count

→ define frequency range

→ determine acceptable attenuation

→ establish impedance and capacitance requirements

→ determine available routing space

→ select conductor and dielectric construction

→ define shielding architecture

→ establish channel matching requirements

→ define connector / flex-circuit transition

→ validate the finished assembly

→ perform representative mechanical testing

→ verify production consistency.

For an IVUS system:

Miniature Catheter

→ define available cable envelope

→ establish electrical requirements

→ define signal path length

→ select ultra-fine cable construction

→ control shielding and return structure

→ define termination

→ perform electrical validation

→ perform application-specific mechanical validation.

Related HOTTEN Engineering Resources

How Micro Coaxial Cable Design Ensures Signal Integrity in Medical Devices

Design Factors in Medical Cable Assemblies That Protect Signal Integrity in Clinical Devices

How Flex-Life Testing Helps Medical Cable Assemblies Maintain Performance After Repeated Bending

What Is Cable Impedance and Why Does It Matter in High Frequency Cable Assemblies?

How RF Coaxial Cable Assemblies Control Impedance and Loss for Reliable High-Frequency Signals

How to Select the Right Foaming Technology for Micro Coaxial Cable Insulation?

Why Low Capacitance Is Critical in Ultrasound Probe Cable Design

How Low-Noise Medical Cable Assemblies Support More Accurate Diagnostic Signals

RF Cable

RF Coaxial Cable Assembly

Ultrasound Probe Cable

IVUS Cable

Medical Equipment

Comprehensive Shielding for Rejection of External and Internal Noise

In a few instances imaging probes are employed together with other radiative technologies including electrosurgical systems and the well-known device causing noise in poorly-shielded coaxial cables, the fluoroscopes. Other causes of noise could be generated internally as in, for example, the effects produced in cables due to movements being picked up. By using a three-layer shielding design, Hotten protects your device with a combination of a semiconductive layer inner (retaining triboelectric charges), a highly braided silver-plated copper shield (95% shielding effectiveness, reducing magnetic interference from external sources) and an outer shield foil (100% shielding of electrical field coupling). In order to reduce common mode currents, a stranded ground return conductor for the IVUS and ICE cable of intravascular catheters is provided. The overall result is transfer impedance of less than 3 mΩ/m at 30MHz providing for clean signals that will yield high contrast, artifact-free images.

Conclusion

Not only do the advanced imaging probes yield cleaner signals, they are the result of careful selection of the dielectric material, the impedance control applied and design of the phases and shields of the probes. High-frequency coaxial cable assemblies are utilized in ultrasound probes, ICE catheters, IVUS harnesses, and endoscope systems to preserve the integrity of acoustic and optical signals at the probe tip. We have developed more than 400 cable variants and operate over 40 cable production lines annually, with more than 10,000 meters of manufacturing capacity dedicated to supporting imaging systems that enable accurate clinical diagnoses and achieve excellent patient outcomes.