An SMP connector is a compact 50-ohm RF interface used for cable-to-board, module-to-module, and blind-mate board-to-board connections. The main selection decision is the retention style. Full detent provides the highest retention, limited detent provides medium retention, and smooth bore provides the lowest retention for slide-on or floating connections. After choosing the retention style, confirm the frequency range, mounting method, cable or PCB interface, and mating-cycle requirement for the exact connector combination.
SMP Connector Selection Starts With the Connection Path
Before comparing detent styles, identify how the RF signal will pass between the cable, PCB, and module. A cable-to-board connection, a direct cable-to-module connection, and a blind-mate board-to-board connection use different connector combinations.
An SMP cable connector normally mates directly with a receptacle mounted on a PCB, panel, or RF module. This arrangement is suitable when the signal needs to be routed through a coaxial cable between two separated positions.
In a board-to-board system, two mounted receptacles are commonly joined through an in-series adapter called a bullet. The bullet completes the RF path when the boards or modules are assembled together without requiring access to each connector during mating.
How an SMP Interconnect Is Built
An SMP interconnect needs to be considered as a complete mating path. Depending on the equipment layout, the path may contain a cable connector, PCB receptacle, panel receptacle, bullet adapter, or several of these components.
Cable-to-board connection: An SMP connector terminated to a coaxial cable mates with a receptacle on the PCB or RF module. The connector direction, cable group, termination method, and available strain-relief space all affect the finished assembly.
For routed connections between separated modules or between different RF interfaces, a custom SMP cable assembly can combine the required SMP end with the selected cable type, cable length, and opposite connector.
Board-to-board connection: Two PCB or module receptacles are joined by a bullet adapter. Bullet length and engagement depth need to match the final board spacing and the mechanical tolerance of the assembled equipment.
Module-to-module connection: Flange-mounted receptacles, thread-in receptacles, or multiport structures may be used when several RF signal paths need to mate during one module installation process.
Full Detent, Limited Detent, and Smooth Bore
SMP retention styles control how strongly the mating parts remain connected. They are different mechanical options for different assembly conditions and are not quality levels.
Full detent provides positive engagement with the highest retention among the three standard options. It is suitable where the connector needs to resist vibration, movement, or accidental separation. The higher insertion and removal force also needs to be considered when the connection will be serviced repeatedly.
Limited detent provides positive engagement with medium retention. It is often used where the connection needs some mechanical retention but still needs to be separated more easily than a full detent interface.
Smooth bore provides the lowest retention and uses a slide-on connection. It is commonly selected for floating blind-mate arrangements where the equipment structure controls the final board position and the connector needs to accommodate movement during assembly.
Stronger retention does not automatically make a full detent interface suitable for every connection. A cable connection exposed to movement may need full detent retention, while a floating board-to-board path may need a smooth bore interface. Limited detent covers the middle range between these two conditions.
| If the connection needs… | Start with… |
|---|---|
| Stronger retention against cable movement or vibration | Full detent |
| Medium retention with easier separation | Limited detent |
| Low retention for a floating blind-mate path | Smooth bore |
These are starting points rather than universal part-selection rules. Confirm the mating force, mating-cycle rating, and complete mechanical arrangement for the exact SMP parts being used.
How SMP Blind-Mate Connections Work
In a blind-mate board-to-board connection, the SMP interfaces are connected as one PCB, module, or equipment section is inserted into another. The individual RF connectors do not need to be reached and connected by hand.
A common arrangement uses two mounted receptacles and a floating bullet. The bullet bridges the RF signal path while allowing limited movement between the two mounting positions. This movement reduces side loading caused by PCB position differences and accumulated mechanical tolerances.
One possible floating configuration uses limited detent retention on one side and smooth bore on the other. The limited detent side retains the bullet when the modules separate, while the smooth bore side allows easier sliding movement during mating.
Where SMP Connectors Are Used
SMP connectors are suitable for compact RF paths where a threaded coupling nut would occupy too much space or could not be reached during module assembly.
Board-to-board RF modules: A floating bullet can join two PCB receptacles as the modules are installed. This structure is used in stacked boards, replaceable RF modules, and compact internal assemblies.
Cable-to-board transitions: An SMP cable assembly can route a signal from an internal PCB or module to another RF interface while occupying less connector space than many threaded interfaces.
High-density multiport systems: Several SMP interfaces can be held in one controlled mechanical structure so multiple RF paths mate during one module installation operation.
Communication, radar, satellite, and phased-array equipment: SMP interfaces can support compact internal connections where high-frequency performance and module integration are required.
FAQ
Conclusion
SMP connectors support compact cable-to-board, board-to-board, and module-level RF signal paths, but the SMP interface name alone does not confirm compatibility. Confirm the retention style, receptacle and bullet combination, board spacing, allowable misalignment, frequency range, PCB mount, cable specification, and required test data before selecting the assembly. For a configuration review, share the mating drawing, operating frequency, board spacing, cable type, retention requirement, and expected mating cycles with the Bafitop team.