RF & Microwave Connectors, Adapters and Cables

Tailored to Your Needs
All parts will be manufactured on customer request. This enables us to provide all cables exactly tailored to the customers demand (any user specified length and bend is available) while keeping the delivery time at 3 weeks.

Phase & Lengths Matching
Optionally we offer phase or delay matched versions of any cable. These extremely accurate manufactured cables are the ideal tool for transmitting complementary data streams or achieving a well defined bit delay, e.g. for decorrelation of data streams in DQPSK applications. The phase matching is possible to any reference value (e.g. bit delay, reference cable or transmission time).

Cryogenic Applications
Some of our coaxial components are designed and approved for cryogenic and vacuum environments. An example for custom designed semi-rigid cables for cryogenic applications can be found here.

• Brochure: Passive RF Components

• Tutorial Note 2 – Microwave Connectors
  Types of connectors, compatibility, specifications, care and cleaning.

The table below shows IEEE-std-287 RF connector standards. The combinations with a check mark share the same specifications for the dimensions  c, d, e, f, g  and the thread type. Thus, these are mechanically compatible.

SMA: SMA, 3.50 mm, 2.92 mm

3.50 mm: SMA, 3.50 mm, 2.92 mm

2.92 mm: SMA, 3.50 mm, 2.92 mm

2.40 mm: 2.40 mm, 1.85 mm,  1.00 mm

1.85 mm: 2.40 mm, 1.85 mm,  1.00 mm

1.00 mm:  1.00 mm

Although mechanically compatible, the different interfaces still have different dimensions of the inner and outer connector (the dimensions a and b). Mechanically, this means that a conductor with a larger diameter connects with a smaller diameter conductor. The junction is not as smooth as if two connectors of the same type would mate. This “impurity” does influence the electrical performance. However, practically this influence is very small. In particular for data signals it is not noticeable.

IEEE-std-287 defines the interface names according to the inner diameter of the outer conductor  (dimension b). Some manufactures, however, designate parts with their own names. These are not different connector standards; just different names. Thus they mate perfectly. The list below shows which designations are essentially referring to the same interface.

2.92 mm = K

1.85 mm = V

1.00 mm = W1

SMPM = Mini-SMP = GPPO™ = SSMP

The basic performance of an RF and microwave coaxial cable is determined by the connector diameters.

At low frequencies, electrical signals propagate in coaxial lines in the TEM (Transversal Electro Magnetic) mode. If the frequency of a signal into a coaxial line is chosen too high waveguide modes of the electromagnetic field (such as the H₁₁) may exist.  To ensure that only the TEM mode propagates, thus keeping the signal clean, the frequency needs to stay below the cut-off frequency fc.

The cut-off frequency is not exactly the same as the specified upper frequency limit. In fact, the standards leave some margin as shown below.

3.50 mm:
Upper Frequency Specification: 26.5 GHz
Cut-Off Frequency fc: 34 GHz

2.92 mm:
Upper Frequency Specification: 40 GHz
Cut-Off Frequency fc: 45 GHz

2.40 mm:
Upper Frequency Specification:50 GHz
Cut-Off Frequency fc: 55 GHz

1.85 mm:
Upper Frequency Specification: 65 GHz
Cut-Off Frequency fc: 71 GHz

1.00 mm:
Upper Frequency Specification: 110 GHz
Cut-Off Frequency fc: 133 GHz

The characteristic for the onset of the 1^st moding frequency is the occurrence of a null (a drop in signal) in the frequency transfer characteristic. If the application is for broadband communication signals (i.e. PRBS or similar type of data) the impact of this first frequency null might be negligible. In fact, in case a cable with a lower cut-off frequency is chosen, one may not suffer from the potential moding, but benefit from less attenuation due to the bigger diameter.

However, the first mode is potentially damaging the signal if the system is supposed to transmit narrowband RF signals at or around the moding regime.

• Cost: very small connectors are difficult to manufacture and therefore tended to be more costly
• Loss: smaller the connector geometry, higher the over-all cable loss caused by  skin effect

Attenuation of the TCF flexible cable assemblies series (click/touch to enlarge)

So, in particular for longer cables one might consider sacrificing bandwidth to minimize over-all loss of the transmission path. For example, SHF delivers its 64 Gbps Bit Pattern Generators with 2.40 mm cable assemblies although a cable with 1.85 mm connectors might provide more bandwidths.

The Totoku cable line up below shows that some connectors can be attached to different cables. If above rule always applies, why would one do that?

1.
Because a cable can be equipped with two different connectors (like an adapter). The TCF280, for example, can be equipped with a 2.92 mm on one end and a 2.40 mm on the other end. Bearing in mind that such a combination results in the attenuation of a 2.40 mm cable while providing only the bandwidth of a 2.92 mm connector, such a cable can perfectly be used to omit an adapter.

2.
Because mechanical restrictions in the setup restrict the use of a bigger diameter cable.

Other than that, there is no reason to choose the thinner cable.

Totoku cable line up (click/touch to enlarge)