Coaxial Electrical Connector

The connectors are a coaxial circular waveguide filled with a dielectric . The connector has two coaxial (English coaxial ) contacts: internal and external.

Depending on the form of internal contact, coaxial connectors are divided into two types: plug and socket. The internal contact of the plug is a pin. At the outlet, this pin is a socket. The external conductor inside has a cylindrical surface shape.

The line impedance depends on:

• on the ratio of the diameters of the inner conductor and the inner diameter of the outer conductor;
• from dielectric material.

Standard impedance values ​​are 50 ohms and 75 ohms .

Dielectric Materials:

• ftoroplast ( polytetrafluoroethylene (teflon));
• polyethylene ;
• polystyrene .

Socket contacts of connectors used in the microwave range or for measurement purposes are made of bronze and coated with a thin layer of silver or gold .

Sealed connectors have a design that, in the articulated position, prevents gas or liquid exchange through the insulator and seals in quantities exceeding the permissible values.

• By the method of articulation, the connectors are:
  • threaded ;
  • bayonet mounts ;
  • cut.
• According to the design of the connectors are:
  • cable (installed on the ends of coaxial cables);
  • dashboards;
  • instrument-cable;
  • connectors mounted on printed circuit boards .

Russian Connectors

• 1st element (two characters): the letters "CP" - with radio frequency coupler.
• 2nd element (optional): the letter "G" - hermetic design .
• 3rd element (two signs): nominal value of wave impedance :
  • 50 to 50 ohms ;
  • 75 - 75 ohms ;
• 4th element: hyphen ( - ).
• 5th element (an indefinite number of characters): serial number of the development.
• 6th element: indication of dielectric material:
  • "P" - polyethylene ;
  • “F” - fluoroplast ( polytetrafluoroethylene );
  • "C" - polystyrene ;
  • "K" - ceramics ;
  • "B" - high-frequency press powders.
• 7th element (optional): the letter "B" - in all climatic modifications.

Some special types of connectors have their own special designations.

International Connectors

Global manufacturers of coaxial connectors use different naming systems. In one of the most common systems, ^{[1] the} designation of connectors consists of the following parts:

• letter;
• three-digit number;
• letter.

For example: “B-212 ° F,” where the first letter indicates the series of connector.

BNC

Connector type BNC ( BNC is the abbreviation of the English. B ayonet N eill- C oncelman ) - an electrical connector with a bayonet joint. Named after the developers: Paul Neill from the Bell Labs lab and Carl Concelman from Amphenol . Serves for connecting a coaxial cable with a wave impedance of 50 Ohms or 75 Ohms and a diameter of up to 8 m . Losses in such a connector usually do not exceed 0.3 dB .

Cables with BNC connectors are used to connect electronic devices ( measuring generators , oscilloscopes, and other devices), as well as to build Ethernet networks using 10BASE2 technology.

In BNC connectors of different designs, the central core and braid of the coaxial cable can be fixed in three ways:

Installation of the internal and external (braids) of the coaxial cable conductor to the connector can be carried out in three ways:

• soldering ;
• wrapping;
• crimp connector parts on the cable.

The shape of the BNC connectors is divided into straight and angular.

The abbreviation BNC is sometimes deciphered as “ b aby N eill- C oncelman ”, “ b aby n c onnector ”, “ b ritish n aval c onnector ”, “ b ayonet n ut c onnector ”.

BNC Subtypes

• BNC (at the end of the cable is either soldered or crimped).
• BNC-F (with threaded mount).
• BNC-T ( T-connector ; connects a network cable to a computer network card using 10BASE-2 Ethernet technology).
• BNC-I and BNC-buffer ( I-connector ; used for splicing two segments of a “thin” coaxial cable).

TNC

TNC type connector (TNC stands for t hreaded N eill- C oncelman ) is a threaded version of the BNC connector. The connector has an impedance of 50 Ohms and is suitable for frequencies up to 11 GHz . More efficient for microwave frequencies than the BNC connector. Developed in the late 1950s and named after the developers: Paul Neill ( Eng. Paul Neill ) from the Bell Labs laboratory and Carl Concelman ( Eng. Carl Concelman ) from the Amphenol company. It is used in radio and wire technology.

SMA

SMA type connector (SMA is an abbreviation of English ub-iniature version A ) - a connector for connecting a coaxial cable with a wave impedance of 50 Ohms . Designed in the 1960s . Used in microwave devices. It has increased reliability and durability. It has a 1/4 ” -36 threaded connection (approximately equivalent to M 6 × 0.75). The plug has a 0.312 ” ( 7.925 m ) hex nut , female thread, and protruding contact. The SMA connectors use polytetrafluoroethylene dielectric .

SMA connectors are designed for 500 joint cycles provided that the nut is properly tightened. For the correct tightening, you need to install a _5/16 - inch torque wrench :

• from 0.3 to 0.6 Nm for copper connectors;
• from 0.8 to 1.1 Nm for steel connectors.

SMA connectors are designed for AC operation up to 18 GHz , but some versions are rated up to 26.5 GHz .

For other frequencies , connectors similar to SMA connectors are used:

• 3.5 m connectors designed for frequencies up to 34 GHz ;
• 2.92 mm connectors (also known as type K connectors or 2.9 mm connectors), designed for frequencies up to 46 GHz .

These connectors, like SMA connectors, have an external thread (they can connect to SMA), but they use air as a dielectric . When connected to low-quality SMA connectors, connection life is reduced.

RP-SMA connectors ( r everse p olarity SMA ) - SMA connectors in which the conductors are interchanged: the external cable conductor is connected to the connector pin, and the internal cable conductor is connected to the external connector pin (connectors with reverse polarity, inverted SMA- connectors).

RP-SMA and RP-N connectors are used to protect equipment and measuring equipment from direct electric current , which can be transmitted via cables, for example, to power an external (outdoor) module, amplifier or transceiver. Due to the presence of such current, equipment that does not have built-in protection (not ready for the presence of constant voltage, and equipped with conventional connectors) may fail. The intentional incompatibility of the RP series with the regular one prevents an erroneous connection.

The voltage on the central core of the cable can be:

• for household devices: +12 V (less often +24 V );
• for operator devices: -60 V ... -48 V (negative voltage, since a positive voltage will inevitably lead to cable corrosion ).

SMB

SMB type connector ( English s ubm iniature version B ) - connector for connecting a coaxial cable with a wave impedance of 50 Ohms or 75 Ohms . Designed in the 1960s . SMB connectors are smaller than SMA connectors. Designed for two types of cables:

1. cable 2.6 / 50 + 75 S (external diameter 3 m ; internal diameter 1.7 m );
2. 2/50 S cable (external diameter 2.2 m ; internal diameter 1 m ).

The SSMB connector is a reduced SMB connector. Characteristics:

• impedance : 50 ohms ;
• current : constant ;
• working frequency: 12.4 GHz .

SMC

SMC type connector ( English ub-iniature version C ) - connector for connecting a coaxial cable with a wave impedance of 50 Ohms or 75 Ohms . Designed in the 1960s . It features a low noise level. Characteristics:

• current : constant ;
• frequency : up to 10 GHz ;
• Coaxial cable diameter: from 2 m to 3 m .

SMC connectors are thread-locked . The number of threads : from 10 to 32. A layer of gold , nickel , silver or other metals can be applied to the connectors. They are used to connect Wi-Fi equipment with antennas and in microwave devices with increased requirements for protection against vibration .

FME

Connector type FME - connector for connecting a coaxial cable with a wave impedance of 50 ohms . Designed to operate at frequencies up to 2 GHz inclusive.

They are used to connect the end devices of mobile communication systems, radio extenders, cellular terminals, etc. with mobile antennas. In particular, they are used to connect GSM antennas.

Adapted to UHF, Mini UHF, TNC, BNC and N.

The design of the connector socket ( eng. Rotating nipple ) allows the cable to rotate 360 ° ; a thread is provided for fixing the connection with a union nut (convenience of connecting mobile communications equipment).

There are modifications for coaxial cables RG-58 , RG-59 , RG-174 .

F

Type F connector . Designed for television equipment. Today it is the cheapest connector for high frequencies (HF). The central core of the cable is used for connection. It works with frequencies up to 2150 M Hz .

F connectors are typically rated for coaxial cables up to 7 m in diameter . In connectors for cables with a diameter of up to 11 m , special inserts and nozzles on the central core are used .

In F connectors, inch thread : 3/8 " -32UNEF, 32 threads per inch .

Coaxial Transitions

Coaxial junction ^[2] (adapter) is a combination of two coaxial connectors connected by a short rigid piece of coaxial line. The transitions are designed for splicing coaxial cables between themselves or for joining coaxial paths with different channel cross-sections.

In addition to coaxial, there are coaxial-waveguide and coaxial-strip transitions used for joining coaxial channels with waveguides or with strip lines .

Transition classification

• Transitions of one connecting row are called single-channel , of different connecting rows - inter - channel .
• Transitions by scope:
  • general purpose;
  • measuring (precision) (increased requirements for path heterogeneity and transition resistance are imposed on such passages).
• Transitions by design (different designs are released for ease of use):
  • direct (measuring transitions are only direct);
  • corner (L-shaped).

Transition approval

• Interchannel junctions, as a rule, have connectors with the same wave impedance ( 50 Ohms or 75 Ohms ). Simple (inconsistent) transitions with connectors of different resistance exist, but are rarely used (usually at low frequencies ).
• Sometimes, when matching transitions with different wave impedances , a high-frequency resistor is connected to the ends of the conductors. Disadvantages: such a transition has coordination only in one direction; power dissipation (loss) on the resistor . More often, resistors use quarter-wave or exponential transformers - special junctions containing a wire with a variable diameter. In quarter-wave transformers, the wire cross-section varies in length in steps, and in exponential ones, it changes smoothly.

Russian measuring transitions

Coaxial Tees

• Coaxial tees are used to branch the electromagnetic signal into two channels. Simple tees do not provide coordination in the line (due to the fact that two loads are connected in parallel), so they are used in cases where the mismatch is insignificant.
• For branching of electromagnetic energy at microwave frequencies, sometimes special tees are used, in which the shoulders are made in the form of matching quarter-wave segments of the line, however, such devices can only work in the narrow frequency range for which they are intended.
• There are special tees for branching part of the energy from the main channel, in which one of the arms is connected to the main path either through the structural capacity or through a communication loop, however, more often in such cases a directional coupler is used .

• The first UHF connector was created by EC Quackenbush from American Phenolic Co (later renamed Amphenol ) in the early 1940s .
• In 1958, J. Cheal from Bendix research laboratory (USA) developed the first miniature connector with a limiting frequency of 10 GHz for an active Doppler radar system (with an operating wavelength of 5.5 s m ). This connector is called BRM ( eng.b endix r esearch m iniature ). As a result of its improvement by the company “M / A-COM Omni-Spectra” (USA) in 1962, the OSM connector appeared.
• The N-connector was developed by Paul Neill of the Bell Labs laboratory and is the first connector that most fully meets the requirements of the microwave range.

• Rated impedance ;
• Nominal cross-sectional area of ​​the channel and its permissible deviations;
• Upper limit frequency ;
• Limit coefficient of a standing wave (SWR);
• Insulation strength;
• Voltage range;
• Contact resistance ;
• Insertion loss.

• Electrical connector
• RCA type connector
• Coaxial cable
• Coaxial transformers

Literature

• Handbook of elements of electronic devices: Ed. V. N. Dulina et al. - M .: Energy, 1978
• A quick reference to the designer of CEA. Ed. R. G. Varlamova - M .: Sov. Radio, 1972
• Dzhurinsky K. B. Coaxial new generation radio components for microelectronic microwave devices. Reference materials on electronic technology - ONTI, 1996
• Dzhurinsky K. B. Miniature coaxial radio components for microwave microelectronics: connectors, coaxial microstrip junctions, adapters, microwave inputs, low-frequency inputs, isolation racks, interference filters - Technosphere, 2006
• Savchenko V.S., Melnikov A.V., Karnishin V.I. Radio-frequency coaxial connectors - M .: Sov. Radio 1977, 48 pp.

Regulatory and technical documentation

• GOST 20265-83 . Radio-frequency coaxial connectors. The connecting sizes.
• GOST 13317-89 . Elements for connecting microwave paths of radio measuring instruments. The connecting sizes.
• GOST RV 51914-2002. Elements for connecting microwave paths of electronic measuring instruments. The connecting sizes.
• GOST 21962-76 . Electrical connectors. Terms and Definitions.
• GOST 18238-72 . Microwave transmission lines. Terms and Definitions.
• OST4-G0.364.024-71. Transitions are coaxial. Selection guide.
• OST5-8772-86. Transitions are waveguide-coaxial. Design, dimensions, specifications, acceptance rules and test methods.
• ChTU VR0.364.016 TU-65. Cable plugs, transitions, sockets and tees with threaded connection.
• TU 11-AG0.364.204TU-80. Connectors RF coaxial plugs and sockets.
• TU 107-VR0.364.060TU-88. Radio frequency coaxial connector.
• TU 88-NTDI.004TU-91. Radio-frequency coaxial connectors of type RC.00.
• VRO.364.049 TU. Radio-frequency coaxial connectors. Technical conditions
• IEC 60169. Radio frequency connectors. Parts 1-36.
• IEC / TR 61141 (1992). Coaxial RF connectors. The upper limit of the frequency.

• Miniature coaxial connectors SMA, SMB and SMC for microwave electronic equipment // Electronic Components, 2001, No. 1.
• The most common coaxial RF connectors
• Elements of radio frequency transmission lines