Signal lines

RF lines specifically designed for cryogenics

Tackle your cryogenic cabling challenge. Bringing many channels to your cold stage, signal lines provide a simple and elegant solution for a wide range of applications.

General Specifications

Connector TypeSMA female / SMP
Connector MaterialGoldplated Brass/BeCu/PEEK/PTFE
Connector HousingGoldplated O2-Free Copper
Flex length200 to 1100 mm
Amount of channels8 Channels
Flex Thickness0.3 mm
Flex MaterialsPolyimide & Silver (Ag) or NbTi
Transmission typeStripline
Minimum bending radius5 mm
Required length for longitudinal rotation10 cm / 180° rotation
Vacuum Feedthrough Leak rate<10-9 mbar L s-1
Compatible vacuum connections​KF25/40, ISO 100
side and top loader ports

Cable overview

Signal lines are the most simple ways to get your i/o to your cold stage. Whether you go for the Silver (Ag)-platform or go superconducting (NbTi), it is suitable for many situations. Find out more about the plain Cri/oFlex® signal solutions below.

sma cables with vacuumfeedthrough in packaging box

Used to

Optimised for

Key Features​


All measurements shown on this page are based on a flex cable containing eight channels without components. The mean is shown with a thick line and the spread of all channels is shown with the transparent area.

Transmission properties

The transmission of Cri/oFlex® can be as low as 1.5 dB/m at 6 GHz for NbTi. For our Silver (Ag) platform a typical 6 dB/m at 6 GHz at low temperatures is normal. In the field these losses are denoted as insertion losses.

On the graph the Silver transmission is plotted for different temperatures. 

Below the transmission are the S11 reflections graphs shown. These are known in the field as reflection losses, as they appear as reflections for the system. The Cri/oFlex® is overall well below 15 dB for each reflection. For more information contact our engineering team.


A common concern for high-density microwave signaling is crosstalk. Our multichannel Cri/oFlex® 3 allows for high line density with good isolation. On the right, the near-end crosstalk (NEXT) and equal level far-end crosstalk (EL-FEXT) between channels in a room-temperature 20 cm long Ag Cri/oFlex® 3 with a 1 mm channel pitch are plotted. The solid line is the average of all channel combinations and the semitransparent the area shows the best (furthest) and worst case (nearest channels) of an 8-channel flex. Even in the worst case, crosstalk is below -60 dB for signals up to 10 GHz. NbTi Cri/oFlex® has comparable performance.

The microwave signal lines include an SMA/SMP connector block to interface the room temperature electronics. In case you aim to get Wideband and maximum power at your cold stage, bare signal lines are the way to go.

How to


Cri/oFlex® into your system?

Cri/oFlex® can fit in your system in many ways and Delft Circuits has multiple approaches to find a perfect fit for your wishes, options range from a one-stop-shop in cabling solutions or a full service I/O provider designing a specific solution for your I/O challanges.

Need some help picking the right option?

First questions to ask yourself is how your system is currently wired. Do you have a port available or full loader you would like to install, upgrade or add wiring to?

For ports Delft Circuits recommends choosing from our wiring ports solution, if you want to fill a single port with more cables or get a lower heatload etc. etc. and already know exactly what cables you want pick the Wiring ports option. if you want a hassle free solution with installation, service, calibration. We recommend going for the turn-key solution and see what else we can do for you.

Delft Circuits recommends

Wiring ports

Delft Circuits recommends


For ports Delft Circuits recommends choosing from our wiring ports solution, if you want to fill a loader with more cables or get a lower heatload etc.. If you want a hassle free solution with installation etc. etc. we recommend going for the turn-key solution and see what else we can do for you

Delft Circuits recommends

Delft Circuits recommends

If you are building a new system we recommend looking at everything we have to offer for you, next to just I/O we can help you design, help you optimize, do cryogenic calculations, calibrations and much more.

Delft Circuits recommends

Dive deeper into

Cri/oFlex® technology

Learn all about what makes our technology specially fitted for the quantum industry

Get in touch

Questions or curious what we can do for you?

Use our contact form for all information requests or contact us directly using the contact information below.

Feel free to get in touch with us via email or phone



+31 153010607

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2627 AN Delft
Schieweg 15A 

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