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How to Select RF and Microwave ConnectorsHow to Select RF and Microwave ConnectorsHow to Select RF and Microwave Connectors

Type N. Type BNC. Type MMBX

Image Credit: Aeroflec | TE Connectivity | Huber + Suhner 

 

Radio frequency (RF) and microwave connectors are used to connect the ends of cables in systems that operate in the radio frequency or microwave spectrum. Microwave refers to electromagnetic energy with a frequency higher than 1 gigahertz and a wavelength shorter than 30 centimeters. Radio frequency refers to alternating current which generates an electromagnetic field suitable for wireless broadcasting and/or communications if the current is input to an antenna. An RF connector can be found in transmission systems and allows for the coupling or uncoupling of system components. A mated pair consists of a plug and a jack.

 

Connector Classifications

There are three basic ways to categorize RF connectors:

  • Cable connectors include plugs and jacks which terminate cables.
  • Receptacles include plugs and jacks which terminate to printed circuit boards.
  • Equipment chassis and adapters are used to join multiple incompatible units in, or between, series. 

They include threaded or bayonet-style couplings that snap, screw, or push into place.

 

How to Select RF and Microwave Connectors

Bayonet - style coupling.

Image Credit: SPI

 

Types of RF and Microwave Connectors

There are many types of RF and microwave connectors. Please see the tables below.

how to select RF and microwave connectors

MMCX. Image Credit: Samtec

 

 

Micro- miniature RF and microwave connectors

 

Name

Description

Size

Frequency Range

Impedance

Application

Micro-Miniature

MMCX
 

Micro-miniature coaxial (MMCX) connectors feature a more robust interface for greater durability. 

Micro-miniature - smaller than MCX

6GHz

50Ω

Ideal for high volume, wireless SMT or PCMCIA applications in cellular base stations, cellular phones and personal communicators. MMCX connectors are also used in global positioning systems (GPS) and wireless LAN (WLAN) applications.

 

how to select RF and Microwave connectorshow to select RF and microwave connectorshow to select RF and microwave connectors

SMA. MCX. SSMB

Image Credit: AerFlex | Digi-Key | Radiall

 

 

Sub-miniature RF and microwave connectors

 

Name

Description

Size

Frequency Range

Impedance

Application

Sub-Miniature

1.0 / 2.3
 

1.0 / 2.3 coaxial connectors require sub-miniature 50Ω slide-on or screw-on connectors.

 

 

50 Ω and 75Ω

Designed telecommunications systems

MCX
 

Miniature coaxial (MCX) provide good electrical performance and are used to address the rapid implementation of the U.S. digital cellular PCN infrastructure.
 

Miniature

Provide broadband capability through 6 GHz

50 Ω and 75Ω

Used in applications where weight and physical space are limited. MCX connectors are also used in global positioning systems (GPS) and wireless LAN (WLAN) applications.

SSMB
 

Sub-SMB (SSMB) connectors are 30% smaller than SMB connectors. 

30% smaller than SMB connectors

35GHz

50Ω

Well-suited for board-to-board applications and are designed for use with semi-rigid cables.

SMA
 

Subminiature-A (SMA) directly interface the cable dielectric without air gaps. They are not intended for permanent connections.
 

 

DC to 18GHz

50Ω

SMA connectors are intended for use on semi-rigid cables in components.

SMC
 

Subminiature C (SMC) connectors accept flexible cables with diameters as large as 3.17 mm or 0.125". 

Smaller than SMA connectors

7 to 10 GHz.

50Ω or 75Ω devices

Base stations, telecom, GPS, radios, WLAN, automotive

SMB
 

Subminiature-N (SMB) connectors are snap-mount connectors.

 

DC to 4GHz.

Either in 50Ω or 75Ω impedances.  

Base stations, telecom, GPS, radios, WLAN, automotive

SSMA
 

Sub-SMA (SSMA) connectors are 30% smaller than standard SMA connectors. 

Miniaturized SMA

 

50Ω

Military radio

BMA / BMMA 

BMA connectors feature a push-on interface and a threadless outer ground connection. They can withstand both radial and axial misalignment. 

Miniature BMA connectors.

 0 – 22GHz

50Ω 

Equipment racks and modular instrumentation

QMA
 

QMA connectors are quick-disconnecting devices that have the same internal construction as SMA connectors. 

 

Up to 6GHz

 

Wireless applications

Type F
 

Type F connectors have a screw-type coupling. 
 

 

Up to 1.5 GHz.

75Ω

Applications include CATV, TV, and antennas.

Type G
 

Type G connectors are 75Ω impedance devices with snap-on coupling. 

 

 

75Ω

Well-suited for CATV applications

 

how to selet RF and Microwave connectorsRF and microwave connectorshow to select RF and microwave conenctor

BNC Connector. TNC Connector. MHV Connector

Image Credit: TE Connectivity | Digi-Key | Huber + Suhner

 

Minature RF and microwave connectors

 

Name

Description

Size

Frequency Range

Impedance

Application

Miniature

BNC
 

Bayonet Neil-Councilman (BNC) BNC connectors have a slotted outer conductor and a plastic dielectric that causes increasing losses at higher frequencies. Both 50Ω and 75Ω BNC connectors are available. BNC connectors are also known as bayonet navy connectors or baby Neil connectors. 

 

Usable above 4 GHz as long as the slots radiate signals; however, these devices may not be mechanically stable to 10 GHz.

50Ω and 75Ω 

Designed for military applications, but are used widely in video and RF applications up to 2 GHz.

MHV
 

MHV connectors are compact, high-voltage devices with a two-stud bayonet coupling. 

Similar in size to, but not interchangeable with, BNC connectors.

 

NM

 

Mini-UHF
 

Mini-UHF connectors feature a threaded coupling mechanism for reliable mating. With crimp cable termination for low installation costs, these connectors provide excellent RF performance in applications through 2.5 GHz. 

Miniature version of the original UHF connector.

Through 2.5 GHz

 

Designed for use in cellular mobile telephone systems where size, weight and cost are critical. 

TNC
 

Threaded Neil-Concelman (TNC) connectors feature a threaded coupling nut for applications that require performance to 11 GHz. TNC connectors are durable, reliable devices.  

Similar in size to BNC connectors

11 GHz

50Ω and 75Ω

Widely used in the cellular and mobile communication industry for equipment cabling and antenna interfaces.

 

how to select RF and microwave connectorshow to select RF and microwave connectorshow to select RF and microwave connectors

Type N. 2.4 connector. 7-16 connector

Image Credit: AeroFlex | AeroFlex | Digi-Key

 

Standard RF and microwave connectors

 

Name

Description

Size

Frequency Range

Impedance

Application

Standard

Type N
 

Type N connectors include an integrated gasket to protect against environmental ingress and create an air gap between the center and the outer conductor.  

 

11GHz

Primarily 50Ω impedance, but 75Ω versions for CATV are available.

 

7-16
 

7-16 connectors are designed for use in medium to high power communication systems. These connectors perform exceptionally well in multi-channel cellular systems where power levels approximate 100 watts per channel. 

 

 

 

Designed for both flexible as well as corrugated cables, these connectors are used in a variety of cellular base station and broadcast communication applications.

2.4 mm
 

2.4 mm connectors are metric devices that derive their name from the length of the inside diameter of their outer conductor. 

 

DC to 65 GHz

50 Ω

 

2.92 mm
 

2.92 mm connectors are metric devices that derive their name from the inside diameter of their outer conductor. They mate with SMA and 3.5 mm connectors. 

 

Provide mode-free performance to 40 GHz.

50 Ω

 

3.5 mm
 

3.5 mm connectors are metric devices that derive their name from the inside diameter of their outer conductor.  

 

Up to 34 GHz.

50 Ω

 

7 mm
 

7 mm connectors are metric devices that derive their name from the inside diameter of their outer conductor. Compared to other 18 GHz connectors, 7 mm devices provide the lowest reflection coefficient and the most repeatable measurements. 7 mm connectors are also known as ACP-7, an acronym for Amphenol precision connector, 7 mm.

 

18 GHz

50 Ω

 

 

 

how to select RF and microwave connectorshow to select RF and microwave connectorshow to select RF and microwave connectors

FME connector. Twinax connector. Type C

Image Credit: Comtelco | TE connectivity | Radiall

 

 

Other common types of RF and microwave connectors

Name

Description

Size

Frequency Range

Impedance

Application

Type C
 

Type C connectors are weatherproof devices with a two-stud bayonet coupling.
 

Medium-size

Provide constant 50Ω impedance and may be used with 75Ω cable below 300 MHz

50Ω

 

FME
 

With adapters, FME connectors can also be used in place of UHF, Mini-UHF, TNC, BNC, and Type N connectors.  

 

 

 

Used in mobile antenna applications. 

SC
 

Subscription channel (SC) connectors are coaxial.

Medium-size devices- larger than BNC connectors, but about the same size as Type N devices.

0 to 11 GHz.

Constant 50Ω impedance

 

Triax
 

Triax connectors are used with triaxial cables where maximum RF shielding and minimum noise radiation is required. 

 

 

 

 

Twinax
 

Twinax connectors feature polarized key and keyway construction as well as threaded coupling. 

 

 

 

Used with twinaxial cables for balanced low level and high sensitivity circuits.

UHF / PL259
 

Ultra high frequency (UHF) connectors are economical, all-purpose connectors designed with non-constant impedance for use in comparatively low voltage and low frequency applications such as citizens' band (CB) communications systems.  

 

300MHz to 3,000MHz (3GHz)

 

Used in public address systems, closed circuit television (CCTV), civil defense, landing systems, ground control apparatus, ship-to-shore communications, and mobile radio equipment hookups between antennae and transmitters or receivers.

1.6 / 5.6
 

1.6 / 5.6 connectors are mechanically sturdy devices that feature a coupling mechanism. They are often used with equipment that requires resistance against environmental and mechanical stress.  

 

 

 

Suitable for handling RF analog and digital signals in telecommunications systems.

1.85 mm
 

1.85 mm connectors are metric devices that derive their name from the length of the inside diameter of their outer conductor.  

 

DC to 65 GHz

 

 

Images for each type of RF and microwave connector can be found here.  

 

Cable Variations

RF and microwave connectors vary in terms of gender, geometry, and cable type.

 

Cable Type

Coaxial cables are transmissions lines consisting of two concentric conductors insulated from each other.

 

how to select RF and microwave conenctorshow to select RF and microwave connectors

Conformable cable.  Flexible cable. Sem-ridge cable

Image Credit: ITT | Delphi | VidaRFConnectors

  • Semi-rigid cables - The connectors have a solid outer conductor made of aluminum or copper. Semi-ridge cables perform better, electrically, than flexible cable with an extended frequency range. The center is usually solid silver plated copper.
  • Flexible - The cable has either a solid or stranded center conductor surrounded by a dielectric. A braid is woven around the dielectric. This forms the outer conductor and an additional plastic covering is placed on top. Flexible cables are able to handle the tight bending radii and physical stresses associated with moving applications.
  • Conformable cables - Conformable cables have a center conductor of various types of metallic braid. Semi-ridge connectors can be used with a conformable cable and it will retain its shape once bent.

Gender

  • Male connectors or plugs are often called header or free connectors. In coaxial RF connections, the plug is normally movable and usually attached to a cable. In shell-type, multiple-contact connectors, the plug contains the socket contacts and mounts on the rack or “hot” side of the system.

  • Female connectors or jacks are connecting devices into which plugs are inserted to make circuit connections.

Connector gender.

 

Geometry

In terms of device geometry, RF and microwave connectors are either straight or right-angled. The geometry of the connector is based on the system in which it needs to fit.

 

 

Mounting Styles

There are several mounting styles for RF and microwave connectors. 

Bulkhead. PC Mount.

CableEnd. JamNut

 Aeroflex | DigiKey

Huber + Suhner | TE Connectivity

Specifications

Performance specifications for RF and microwave connectors include:

  • Impedance- Impedance is a characteristic property of a transmission line describing the ratio between the electric and magnetic field. Most RF and microwave connectors provide a nominal resistance of 50 or 75 ohms (Ω). Some connector series come in both 50Ω and 75Ω. Fifty ohms connectors on 75Ω cables should be used at frequencies below 500 MHz (and vice versa). This practice is done since 50Ω connectors are generally less expensive due to their greater usage.
  • Size of cable- The connector size (diameter) should match the cable diameter as closely as possible. This will help reduce reflections which hinder performance. Reflections will generally increase as a function of frequency, and smaller connectors will generally perform well at higher frequencies.

how to select RF and Microwave connectors

Connector diameter. Image Credit: Bixmart

  • Frequency range- Frequency and cable range are the primary factors when selecting a connector. This specification helps identify the connector series used. It is recommended to use push-on or bayonet style connectors at low frequencies (below 6GHz) and threaded connectors for high performance, low noise applications.

how to select RF and microwave connectorshow to select RF and microwave connectors

Bayonet style connectors are used for low frequencies and threaded connectors are best for high performance.

Image Credit: Norgren | Xmultiple

  • Power- Power handling is limited by the cable's power specification and is determined empirically. Higher power applications require large diameter connectors. Power handling capability will diminish as a function of frequency and altitude.
  • Working voltage - Working voltage is the maximum operating voltage of the connector
  • Operating temperature - Operating temperature is the full-required range of ambient operating temperature.
  • Insertion loss - Insertion loss (in dB) is the total RF power transmission loss resulting from the insertion of a device in a transmission line. It is defined as the ratio of signal power at the output of the inserted device to the input signal power at the input of the inserted device.

  • Voltage standing wave ratio (VSWR) - Voltage standing wave ratio (VSWR) is a unit-less ratio that ranges from one to infinity and expresses the amount of reflected energy at the input of the device. A value of one indicates that all of the energy passes through. Any other value indicates that a portion of the energy is deflected. There are many online calculators available to determine this ratio.

Features

RF and microwave connectors are available with many different features to ensure that the device fits the application.

  • Moisture or oil resistant - Gaskets or seals protect the connector against moisture, oil, and other contaminants.
  • Hermetically sealed - A hermetic seal is impervious to air or gas. They can also be used to protect against internal moisture.
  • Hospital grade - Hospital grade connectors must conform to rigorous safety standards associated with official Hospital Grade certification. The testing for this certification includes prevention of inadvertent plug disengagement from outlets and increased shock and impact ratings.
  • Environmentally resistant - Environmentally resistant connectors can be used in hazardous chemical environments.

 

Resources

RF & Microwave Solutions Guide


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