5 Mins Guide of What SMA Connector Is and Used For

SMA (Sub Miniature version A) connectors are most widely used coaxial RF connectors nowadays. The small size, outstanding durability and reliable performance make SMA connector favorite choice for RF engineers.
 
In the following, we would like to provide the insight of SMA connectors and indicate features of Chin Nan's SMA connectors.
 

Table of content:

• Introduction of SMA series
• What is SMA 27GHz connectors
• What is 3.5 mm connectors
• What is 2.92 mm connectors
• SMA series comparison

Introduction

SMA connectors feature an impedance of 50 Ω and a 1/4-inch diameter, 36-thread-per-inch threaded interface with a screw-on coupling mechanism.
 

MIL-STD-348B of Chin Nan

Chin Nan SMA connectors are built in accordance with MIL-STD-348 interface which latest version is MIL-STD-348B. Besides conforming to the interface, Chin Nan upgrades the performance for MIL-STD-348B connectors in the meantime.
 
There are several high frequency connectors which apply the same outside thread as SMA could potentially mate with SMA connectors, such as 3.5 mm connector, frequency rated to 34 GHz and 2.92 mm connector, frequency rated to 40 GHz.
 

SMA 27GHz Connectors

SMA connectors operate up to 18 GHz, but in order to respond to the growth of the communication system, there is an extended version that operates up to 27 GHz for higher frequency applications. 
 

SMA 27GHz Connectors

Chin Nan SMA 27 GHz connectors feature stainless steel construction and passivated or gold plating. 
 
They maintain the same mechanical characteristics and are able to mate with standard SMA connectors.
 
Chin Nan offers an extensive line of SMA receptacles and cable connectors for semi-rigid and flexible coaxial cables.
 
SMA has a wide range of applications, such as telecommunications, wireless communications, measurement, and microwave systems (filters, attenuators, and oscillators). Besides, Chin Nan provides various solutions such as non-magnetic, sealed and reverse-polarity in SMA series.
 

What Is 3.5 mm Connectors

SMA was designed to be an economical miniaturized system connector. It was designed to be used in semi-rigid cable assemblies and the parts not needing repeated connection or disconnection.
 
SMA is not a precision connector used in the laboratory. It has limited number of connection cycles in the measurement and calibration applications. Its durability only rated for 500 times of connect/disconnect operations.
 
The 3.5 mm connector, which utilizes air dielectric for higher frequency is a precision connector known for its durability. 3.5 mm was designed as the test connector for the network analyzer operating at higher frequency up to 34GHz.
 

What Is 2.92 mm Connectors

SMA 2.92mm Connectors

2.92 mm, also known as K, SMK or K type, are designed with SMA footprint to provide the connector performance up to 40 GHz in 1970's.
 
2.92 mm connectors feature an air dielectric for higher frequency operating in the range DC to 40 GHz. The 2.92 mm male connector is designed with a shorter center contact in order to prevent the damage happened while mating. 
 
2.92 mm connectors have excellent performance and are also mechanically compatible to SMA and 3.5 mm connectors. Those advantages make 2.92mm connectors quickly recognized by the majority of manufacturers. 2.92mm became one of the most widely used millimeter wave connectors in the world.
 
Chin Nan has the expertise to design and build 2.92mm connectors for semi-rigid cable assemblies, 2.92mm receptacles, four hole flange and 2.92mm precision adapters to satisfy various demands.
 

SMA Series Comparison

The SMA and SMA 27 GHz connectors have an outer diameter of approximately 4.13 mm, while the 3.5mm and 2.92mm connectors have outer diameters of 3.5 mm and 2.92 mm, respectively.

3.5mm vs. SMA Connectors

The main difference between 3.5mm and standard SMA connectors is the dielectric material—3.5mm connectors use air, whereas SMA connectors typically use PTFE. Additionally, 3.5mm connectors have a thicker outer contact, enhancing their mechanical durability and electrical performance compared to SMA. Due to these advantages, 3.5mm connectors are widely used in measurement and calibration devices.

2.92mm vs. SMA Connectors

The key difference between 2.92mm and SMA connectors is the male center contact—the 2.92mm male has a shorter center pin than both SMA and 3.5mm. This design ensures that the outer conductor engages before the center contacts mate, reducing the risk of damage.

Although 2.92mm connectors are compatible with both SMA and 3.5mm connectors, they offer higher electrical performance and operating frequency due to their air dielectric and smaller inner diameter of the outer conductor.

SMA 27 GHz Connectors

While air is an ideal insulator for high-frequency performance, connectors still require materials to support the center contact and maintain a stable dielectric constant. For applications requiring higher frequency operation, SMA 27 GHz connectors with PTFE dielectric provide an optimized solution.

Is the SMA connector the right choice for your application, or is SMB a better fit? Explore the 4 key differences between SMA and SMB connectors to make an informed decision!

If you have diverse requirements or questions about other applications, feel free to contact CHIN NAN for assistance! (service@chinnan.com.tw)