Back To Basic: A Guide To RF/Coaxial Connector Interface Types & Applications

In this article, we would like to introduce you some common interface types of RF /coaxial connectors and differences between them. Based on sizes, all RF/coaxial/microwave connectors are divided into 4 categories.

<Standard>

• UHF Connectors
• 7/16 Connectors
• N Connectors

<Miniature>

• BNC Connectors
• TNC Connectors
• Mini-UHF Connectors
• FME (SAP) Connectors

<Sub-Miniature>

• SMA Connectors
• SMB Connectors
• SMC Connectors
• SSMA Connectors
• SSMB Connectors
• 1.0/2.3 Connectors

<Micro-Miniature>

• MCX Connectors
• MMCX Connectors
• SMP Connectors
• SMPM Connectors
• SMT Connectors

The above 4 types represent the development of the design concept of the coaxial connector from 1930 to 1980. The Standard connectors are larger than Subminiature and Micro-miniature connectors.

UHF connectors are invented by Amphenol in 1930 and applied to radio broadcasting systems. Because of its unstable impedance, its frequency rate is limited to 300 MHz and classified as a low-cost connector.

UHF connectors are mainly applied in low-frequency communication equipment such as CB radio and public communication system.

7/16 connectors are designed for 50 ohm impedance to conform to the DIN standards, featuring excellent power-handling capability and low VSWR up to 7.5GHz. 7/16 connectors are named for its dimensions. The diameter of inner conductor contact is 7 mm and the internal diameter of outer conductor is 16 mm.

7/16 connectors provide superior performance on return loss and intermodulation distortion. These connectors are ideal for vibration resistance and environmental protection, such as radio base stations and broadcast communication application.

N connectors are still commonly in use nowadays. Applications include local area networks (LANs), test equipment, broadcast, satellite and military communications equipment. 

N connectors have threaded coupling and standard 50/75 ohm impedance. N connectors with 50 ohm impedance can perform to 11GHz, while some connector suppliers offer versions that perform to 18 GHz.

BNC connectors are widely used in test and measurement equipment. BNC is a reduced size version of C type connector. BNC series has 2 levels of impedance, which are 50 & 75 ohm. They can be compatible with each other without damaging their structures.

TNC connectors were designed in 1950. The origin of TNC series is 50 ohm BNC connectors then change coupling design into threaded interface. Typically, the frequency range of TNC series is up to 11GHz. These connectors can be used in vibrating environments. These are often be applied in military and aviation industry.

Mini-UHF connectors were designed to cover a frequency range of DC to 2.5 GHz. The size of Mini-UHF makes them able to provide excellent RF performance and impedance that matches 50 ohm cable because. Crimp, twist-on and solder terminations are available with the Mini-UHF series.

FME (For Mobile Equipment) is a miniature 50Ω RF connector series offering performance on frequency from DC to 900MHz. These are primarily assembled with RG-58 or RG-174U type cables. The mating of FME connectors is screw-lock.

People call FME as SAP connectors sometimes. The applications of FME (SAP) connectors are mainly telecommunications and wireless.

SMA (Sub-Miniature-A) connectors were originally designed to fit the .141 semi-rigid cables (RG-402). Some sophisticated SMA connectors are able to perform as high as 26.5GHz.

SMA connectors with cables are designed for 50 ohm impedance and coupled with threaded interface.

The maximum frequency of SMA connectors is determined by the type of cables they installed with. Suitable microwave system components include amplifiers, attenuators, filters, mixers, oscillators, switchgear, and more.

SMB (Sub-Miniature-B) connectors are sub-miniature connectors that are designed for quick connection and disconnection. The structure of SMB connectors has shrapnel between its body, housing and overlapping insulator.

This makes SMB easy to bite another connector has good efficiency under moderate vibration. SMB connectors with 75ohm impedance cannot be compatible with SMB connectors with 50ohm.

SMC (Sub-Miniature-C) connectors have a similar design to SMB. They both have the same center and overlapping insulating structure, but SMC uses a threaded coupling instead of a spring bite contact.

SSMA connectors are micro miniature RF connectors with a screw-coupling, which are similar to SMA series but designed for smaller diameter semi-rigid cable. They provide repeatable electrical performance and perform from DC to 38 GHz.

SSMB connectors are smaller version of standard SMB connectors. SSMB series provides excellent electrical performance in a micro miniature footprint while the snap-on mating interface allows quick installation and dense packaging.

The design of SSMB connectors have straight and right angle cable versions, and printed circuit board styles that are available for crimp, clamp and receptacle termination types. The common applications for SSMB connectors are radio systems, video equipment, telecommunications and GSM.

1.0/2.3 connectors are smaller in size with frequency up to 4 GHz. These are reliable in broadband performance and popularly used in telecommunication system. With high mechanical strength, high durability, and the push-pull on coupling match, 1.0/2.3 connectors provide better solution to prevent accident disconnection.

MCX connectors were designed in Europe in 1980. These provide repeatable performance on frequency from DC to 6 GHz. The design has taken into consideration the need for size reduction, low weight; durability and reliable performance.

MCX connectors enable a 30% space reduction over similar SMB/SMC types. MCX is available for affixment to industry standard cable and as printed circuit board device. The "snap-on" connection feature between devices offers users an ease of assembly in dense packaging layouts. Applications of MCX connectors are GPS, wireless communications (WLAN and mobile) and automotive, especially where size, weight performance and ease of assembly are the demanding consideration.

MMCX connectors are designed for the smallest dimensions. These provide repeatable performances on frequency from DC up to 6 GHz. The locking has reliable snap-on mechanism which is responsible for delivering excellent electrical parameters during usage. Because of the non-slotted outer conductor of MMCX connectors, the RF-leakage is much lower.

SMP connectors provide repeatable electrical performance from DC to 18GHz with semi-rigid cable. The adapter extends the frequency range of the device up to 40GHz. SMP connectors use a snap-on connection. Because of the vibration-proof design of SMP connectors, they are suitable and applicable for mobile applications.

The small package size of SMP connectors are made for high-density board-to-board applications. The standard designs of SMP series include cable connectors, straight and right angle, for .047 and .085 semi-rigid cable, full detent, limited detent, and smooth bore mating shrouds that are bulkhead or flange mounted.

SMPM push-on, blind-mate connectors provide a micro-miniature interface that maximizes performance. Even in the most compact spaces, SMPM and SMP connectors are capable of reducing system weight and deliver superior reliability at the same time. SMPM connectors are compatible with GPPO, SSMP, and Mini-SMP series. SMPM has high reliability and excellent electronic performance on frequency from DC to 65GHz.

SMT connectors are designed to be ultra-small surface-mount RF/coaxial connectors. They are widely acknowledged as a standard in the industry. The characteristic impedance is 50 ohms. SMT connectors are commonly used in applications that has limited space, such mobile phones, wireless communication devices, instrumentation, test points, GPS, Bluetooth and all applications requiring a compact, high frequency (6 GHz), coaxial connection.

The plugs are also available on cable assemblies with a variety of coaxial cables. These assemblies can be configured in SMT plug to plug, SMT pigtail, and SMT plug to multiple standard connector options like SMA, MCX, MMCX and others. A wide variety of conversion adapters are available for this series. Chin Nan's SMT connectors are compatible with U.FL, MHF and UMCC connectors.

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