What is an SMB Connector?

SMB connector is one kind of coaxial RF connectors which are smaller in size than SMA connectors and were designed in the 1960s with snap-on coupling. The snap-on design permits rapid connection and disconnection in limited spaces.

SMB connectors are available either in 50ohm or 75ohm impedance. 50ohm SMB connectors are usually specified up to 4GHz, and 75ohm SMB connectors are specified for only 2GHz.

SMB connectors are originally designed with female contacts in male bodies or male contacts in female bodies. These connectors are popularly used in telecommunications and automotive applications.

Mechanical Feature:

SMB male

  1. Snap-on coupling.
  2. Six slots radially spaced outer contact inside the shell.
  3. Shell is fixed and cannot be rotated.
  4. Female center contact.
  5. Insulator surrounds the female center contact completely for 50ohm SMC male.
  6. An air gap between the female center contact and outer contact for 75ohm SMB male.

SMB female

  1. Snap-on coupling.
  2. A groove for securing the mating connector after a smooth area with a diameter of 3.7mm, located 3.0mm from the mating end.
  3. Male center contact.
  4. Insulator fully nestles against the outer contact, with an air gap between the insulator and the male center contact for 50ohm SMB female.
  5. Reduced insulator amount, with an air gap between the male center contact and the outer contact for 75ohm SMB connector.

How to judge SMB connectors’ feature from outline:

SMB connector – Male/Plug

The SMB male connector has an outer contact with 6 slots radially spaced inside the shell.

SMB male connector, 50 ohm V.S. 75 ohm

SMB connector – Female/Jack

A significant trough (groove) for mating purposes, with a diameter of around 3.70mm.

SMB female connector, 50 ohm V.S. 75 ohm

SMB male, SMB female right angle type

The cable entry or PCB termination is at a 90-degree angle to the coupling direction.

SMB male, SMB female straight type

The cable entry or PCB termination is in line (180-degree) with the coupling direction.

SMB female/jack bulkhead type

Besides the mating trough, there is an outer thread on the body, which defines this SMB connector as a bulkhead type.

Rear mount type bulkhead
The SMB bulkhead connector passes through the panel mounting hole from the inside of the device to the outside and is secured with a washer and nut from the outside.

Front mount type bulkhead
The SMB bulkhead connector passes through the panel hole from the outside of the device to the inside and is secured with a washer and nut from the inside.

SMB male, SMB female PCB connector

PCB type SMB connectors normally have leg lengths of 2.9mm or 3.9mm. Four legs and one conductor go through the PCB vertically and are soldered on the rear side of the PCB.

SMB female/jack edge mount

An SMB edge mount type connector will be mounted on the PCB from the board's edge.