The SMB connector is used in applications where a quick mating sub-miniature RF connector is required for RF frequencies up to frequencies of a few GHz.
The SMB connector derives its name as it is termed a Sub-Miniature version B connector. It was developed as a result of the need for a connector that was able to connect and disconnect swiftly. It does not require nuts to be tightened when two connectors are mated. Instead the connectors are brought together and they snap fit together. Additionally the connector utilizes an inner contact and overlapping dielectric insulator structures to ensure good connectivity and a constant impedance.
The SMB connector is not as robust as the SMA connector, and although they perform well under moderate levels of vibration, they are not suitable for harsh environmental conditions where the levels of vibration rise.
SMB connector impedance
The SMB connector is specified in two impedances:
- 50Ω: The 50Ω version of the SMB connector is possibly more widely used. The connectors are often specified up to 4 GHz.
- 75Ω: The 75Ω version of the SMB connector is often only specified to a maximum frequency of 2 GHz, although 4 GHz versions are available. To achieve the different impedance the ratio of the inner to outer diameters is different
The connectors are available in variants for the different types of thin coax available. The cable entry areas need to be able to accurately accommodate the coax cable.
SMB coaxial connectors are not as widely used as their SMA counterparts. They are used for inter board or assembly connections within equipment, although they are not widely used for purchased microwave assemblies in view of their inferior performance.
Applications for SMB connectors can include:
- Base Stations
- Radio Boards
Although the SMB connector is not as widely used as its SMA cousin, large quantities are nevertheless used. The connector is much easier to connect and this can be a distinct advantage in applications where its performance is sufficiently good. As a result the SMB connector is a very successful design and used for many applications.
Typical SMB connector specification
Although the specifications for SMB connectors will vary considerably between manufacturers, a typical specification may give some guidelines for what can be expected.
|SMB Connector Typical Specifications|
for use as a guide
|Impedance||variants available for 50Ω and 75Ω|
|Frequency range||0 - 4 GHz, but often usable to 10 GHz with higher reflection and reduced specification|
|Contacts resistance||Centre conductor: 6.0mΩ,|
Outer conductor 1.0mΩ
results taken before environmental testing).
|VSWR||Varies according to connector and coax size used but normally better than 1.35+0.04f(GHz)|
|Insertion loss||Varies according to connector and coax size used but normally better than 0.3dB for straight conenctor and 0.6dB for right angled at 1.5GHz|