RF Coax

High frequency signals may be brought into the cold space via a side panel on the sample chamber base or via one of the unused optical ports.


The side plate is a convenient place to feed through the coax, as it remains fixed at the base and allows the user to still easily remove the housing side and radiation shield for sample access. An SMA connector mates to the outside, with an SMP connector on the inside. A small coax is routed up to the sample area and thermally lagged at the radiation shield.

The image below shows a typical side panel installation.


The coax cables may be brought in through an optical port, but this makes it difficult to remove the side housing with the cables in place, as the radiation shield and vacuum housing need to be removed together to take off the coax. We offer a single SMA connector through a 30mm port (Fig. A), or four SMA connectors through a 50mm optical port (Fig. B).

Fig. A - 30mm Port Fig. B - 50mm Port

Interface extension housing

In applications where the Montana Instruments magnet is used, RF coax and other options are typically routed through a vacuum housing spacer as the base side panels are often inaccessible by the magnet. More information on this can be found in the Interface Extension Housing Option page.


Several types of coax cables are available. For lower frequency applications < 1GHz, flexible coax is used. This allows simple connections and cable removal and connects to your samples or boards easily. For higher frequency applications up to 20GHz, semi rigid coax is typically used. This is most conveniently connected from the side plate on the base and run up into the cold space. If it is necessary to connect these to moving stages, this can be done by reconnecting the semi rigid coax to flexible lines for a short distance.

Refer to the Coaxial Cable Options Chart for a description of the various options.


Whether the cables come in through the base or through the port, the cables must be thermally lagged to dissipate the room temperature heat. This is done by running them under a clamp at the base of the radiation shield. More information on this can be found in the Thermal Lagging How-To Article.