RF connectors types and cables

Intro

There are very wide variety of RF connector and even more developed and added every year. RF are usually used to make low VSWR coaxial connections. Most RF and high-frequency systems use 50 Ω characteristic impedance, but some other values, such as 75 ohms used as well. All RF connectors described below have specified impedance, frequency range and size listed.

Few notes on precision RF connectors usage

While some of connectors, like SMA, 3.5mm, 2.92mm, 2.4mm are mechanically and physically compatible, there is hidden cost, in impedance mismatching and impedance consistency. This means that amplitude accuracy and signal waveform repeatability of mismatched connector path would be reduced. Millimeter-wave signals can’t be transmitted without having loss and phase errors.

Even simple connector savers, which are essentially feed-thru adapters, usually a good practice working with RF expensive equipment, also degrade signal integrity due to differences in mechanical interfaces. One of the solutions is simply to have cable attached to instrument at all times, so connectors would not see frequent connection cycles. It’s important to also consider cable length and cable quality carefully, especially for frequencies over 3 GHz. Quality cables can be expensive but may be the required item to ensure measurements accuracy and repeatability.

Coaxial connectors – overview

Type / name Frequency range Impedance, Ω Dielectric Year Description
BNC DC – 4 GHz 50 PTFE
SMA DC – 26 GHz 50/75 PTFE 1960’s Sub-miniature type A, threaded
SMB DC – 4 GHz 50 PTFE Sub-miniature type B, a snap-on subminiature connector
SMC DC – 10 GHz 50 PTFE Sub-miniature type C, a threaded subminiature connector
SSMA DC – 38 GHz 50 PTFE Smaller version of SMA
N (Neill) DC – 11 GHz (18GHz) 50/75 PTFE 1940’s Named for Paul Neill of Bell Labs. Cheap and heavy-duty
BMA or OSP DC – 22 GHz 50 PTFE “Omni Spectra push-on”, blind-mate connector with zero detent
C (Concelman) DC –
Dezifix (used by Rohde & Schwarz) DC –
F DC – 75
GR
Musa
OSX, MCX , PCX DC – 6 GHz 50/75 PTFE
MMCX 50 PTFE Usual for wireless industry due to small size and cost
NMO
NMD from HP, 3.5mm DC to 34 GHz Used by HP/Agilent/Keysight RF gear
NMD from HP, 2.92mm DC to 40 GHz Used by HP/Agilent/Keysight RF gear
NMD from HP, 2.4mm DC to 50 GHz Used by HP/Agilent/Keysight RF gear
NMD from HP, 1.85mm DC to 70 GHz Used by HP/Agilent/Keysight RF gear
NMD from HP, 1.0mm DC to 110 GHz Used by HP/Agilent/Keysight RF gear
OSMT DC – 6 GHz 50 PTFE SMT connector
OSSP DC – 28 GHz 50 PTFE Smaller version OSP connector
OS-50P DC – 40 GHz 50 Smaller version OSP blind-mate connector
GPO, OSMP , SMP DC – 40 GHz 50 PTFE “Gilbert push-on”
TNC DC – 15 GHz 50 PTFE Threaded BNC, to reduce vibration issues
APC , 7 mm DC – 18 GHz 50 PTFE 1960’s Sexless connector, which provides the lowest VSWR up to 18 GHz
3.5 mm DC – 26.5 GHz 50 Air A precision (expensive) connector, compatible with SMA connectors
2.92 mm DC – 40 GHz 50 Air 1974 Precision connector, compatible with SMA and 3.5 mm
K DC – 40 GHz 50 Air 1974 Mass-marketed 2.92 mm connector, Named the “K” connector, as it covers all K frequency bands
2.4 mm DC – 50 GHz 50 Air 1986 2.4 mm and 1.85 mm will mate with each other without damage
1.85 mm DC – 60 GHz 50 Air 1986 Mechanically compatible with 2.4 mm
V DC – 60 GHz 50 Air 1986 Anritsu’s name for 1.85 mm connectors, as it span V frequency bands
1 mm DC – 110 GHz 50 Air 1989 The ultimate connector

Even though some connector combinations like SMA and 2.92mm connectors are thread-compatible, plugging one into the other can damage the sleeve in the receptacle side due to differences in the diameter tolerance. So it can be OK to plug a 2.92mm plug into an SMA jack, but NOT OK to put an SMA plug into a 2.92mm jack. The jacks are usually more fragile port of connection.

SMA connector system

The SMA connector is very common in the RF and microwave industry. Design uses a 4.2 mm diameter outer coax, filled with PTFE dielectric. Upper frequency limit is anywhere from 18 to 26 GHz, depending on the tolerances maintained in machining SMA connectors. Outer nut sized to fit a 5/16” wrench. These connectors have male and female genders.

Lot of SMA connectors are gold-plated, but it is not always best, as thin gold plating can chip off and cause shorts and problems. The best connectors usually with stainless steel on their outer jackets.

SMB and SMC connector systems

http://www.microwaves101.com/encyclopedias/smb-connectors

High-frequency connectors

NEVER rotate these connectors when tightening. Use a 8 inch/lb torque wrench and a smaller wrench to hold the other connector during mating.
Never, ever connect a SMA to a 3.5 or 2.92 mm ports, VNA cables, or any other expensive 3.5 mm device. Use the jack savers, which are adapters with SMA on one side and 3.5/2.92mm on other.

3.5 mm type

This type connector using air dielectric, meaning central conductor is hold in center by spacers only. The 3.5 mm connector is the next upgrade from using SMA, it performs well up to 26 GHz. Outer nut sized to fit a 5/16” wrench.

2.92 mm type

The 2.92 mm connector works up to 40 GHz. The K is Anritsu version of the 2.92 mm connector. Outer nut sized to fit a 5/16” wrench.

2.4 mm type

Outer nut sized to fit a 5/16” wrench.

1.85 mm type

The 1.85 connector is often referenced as V type. Outer nut sized to fit a 5/16” wrench.

1 mm type

This is highest frequency coax connector. Requirements for it’s precision can drive cost of single 1 mm connector over $1000 USD!

NMD versions of connectors

NMD connectors are rugged version of same standard geometry connector, such as 3.5mm, 2.4mm and such. Usually these connectors used on GHz-frequency network analyzers, signal generators, oscilloscopes. Few examples covered in this blog post by Keysight.

Coax cable types

Cable Type Mil Designation Impedance, Ω Dielectric OD (Inches) Shield Construction
RG-87 50 PTFE 0.425 Braid
RG-141 50 ST 0.190 Braid
RG-174 50 PE 0.100 Braid
RG-122 /54 -RG122 50 PE 0.160 Braid
RG-178 /93 -RG178 50 ST 0.072 Braid
RG-142 /60 -RG142 50 ST 0.195 Braid
RG-188 50 PTFE 0.105 Braid
RG-188 Double Braided 50 PTFE 0.105 Double Braid
RG-196 50 PTFE 0.072 Braid
RG-303 /111-RG303 50 ST 0.170 Braid
RG-213 /74 -RG213 50 PE 0.405 Braid
RG-214 /75 -RG214 50 PE 0.425 Braid
RG-223 /84 -RG223 50 PE 0.211 Double Braid
RG-225 50 PTFE 0.430 Braid
RG-304 /112-RG304 50 ST 0.280 Braid
RG-316 /113-RG316 50 ST 0.102 Braid
RG-316 Double Braided 50 ST 0.102 Double Braid
RG-393 /127-RG393 50 ST 0.390 Braid
RG-400 /128-RG400 50 ST 0.195 Braid
RG-9 51 PE 0.420 Braid
RG-8 52 PE 0.405 Braid
RG-55 53.5 PE 0.200 Braid
RG-58 /28 -RG58 53.5 PE 0.195 Braid
RG-179 /94 -RG179 70 ST 0.100 Braid
RG-59 /29 -RG59 73 PE 0.242 Braid
RG-140 75 PTFE 0.233 Braid
RG-179 Double Braided 75 ST 0.125 Double Braid
RG-187 75 PTFE 0.105 Braid
RG-302 /110-RG302 75 ST 0.201 Braid
RG-62 93 PE 0.242 Braid
RG-180 /95 -RG180 93 ST 0.140 Braid
RG-210 93 PTFE 0.242 Braid
RG-195 95 PTFE 0.450 Braid

Waveguides – overview

Most of waveguides are made to order, with various shapes and lengths featuring precision machining from solid alloy, often with gold plated finish and a choice of flanges.

WG type

WG DESIGN FREQ RANGE, NOTE WAVEGUIDE CUT OFF Attenuation dB/30m Material Band DIMENSIONS,mm
WG00 0.32 – 0.49 GHz 0.256 GHz 0.051 – 0.031 Alum B 584 × 292
WG0 0.35 – 0.53 GHz 0.281 GHz 0.054 – 0.034 Alum B,C 533 × 267
WG1 0.41 – 0.625 GHz 0.328 GHz 0.056 – 0.038 Alum B,C 457 × 229
WG2 0.49 – 0.75 GHz 0.393 GHz 0.069 – 0.050 Alum C 381 × 191
WG3 0.64 – 0.96 GHz 0.513 GHz 0.128 – 0.075 Alum C 292 × 146
WG4 0.75 – 1.12 GHz 0.605 GHz 0.137 – 0.095 Alum C,D 248 × 124
WG5 0.96 – 1.45 GHz 0.766 GHz 0.201 – 0.136 Alum D 196 × 98
WG6 1.12 – 1.70 GHz 0.908 GHz 0.317 – 0.212 Brass D 165 × 83
WG6 1.12 – 1.70 GHz 0.908 GHz 0.269 – 0.178 Alum D 165 × 83
WG7 1.45 – 2.20 GHz 1.157 GHz D,E 131 × 65
WG8 1.70 – 2.60 GHz 1.372 GHz 0.588 – 0.385 Brass E 109 × 55
WG8 1.70 – 2.60 GHz 1.372 GHz 0.501 – 0.330 Alum E 109 × 55
WG9A 2.20 – 3.30 GHz 1.736 GHz 0.877 – 0.572 Brass E,F 86 × 43
WG9A 2.20 – 3.30 GHz 1.736 GHz 0.751 – 0.492 Alum E,F 86 × 43
WG10 2.60 – 3.95 GHz 2.078 GHz 1.102 – 0.752 Brass E,F 72 × 34
WG10 2.60 – 3.95 GHz 2.078 GHz 0.940 – 0.641 Alum E,F 72 × 34
WG11A 3.30 – 4.90 GHz 2.577 GHz F,G 59 × 29
WG12 3.95 – 5.85 GHz 3.152 GHz 2.08 – 1.44 Brass F,G 48 × 22
WG12 3.95 – 5.85 GHz 3.152 GHz 1.77 – 1.12 Alum F,G 48 × 22
WG13 4.90 – 7.05 GHz 3.711 GHz G,H 40 × 20
WG14 5.85 – 8.20 GHz 4.301 GHz 2.87 – 2.30 Brass H 35 × 16
WG14 5.85 – 8.20 GHz 4.301 GHz 2.45 – 1.94 Alum H 35 × 16
WG15 7.05 – 10.0 GHz 5.26 GHz 4.12 – 3.21 Brass I 29 × 13
WG15 7.05 – 10.0 GHz 5.26 GHz 3.50 – 2.74 Alum I 29 × 13

WR type

WR DESIGN WG EQUIVALENT Freq range Band Standard Flange Inner DIMENSIONS (inch)
WR340 WG9A 2.20 – 3.30 GHz D 3.400 × 1.700
WR284 WG10 2.60 – 3.95 GHz S 2.840 × 1.340
WR229 WG11A 3.30 – 4.90 GHz E 2.290 × 1.150
WR187 WG12 3.95 – 5.85 GHz G 1.872 × 0.872
WR159 WG13 4.90 – 7.05 GHz F 1.590 × 0.795
WR137 WG14 5.85 – 8.20 GHz C 1.372 × 0.622
WR112 WG15 7.05 – 10.00 GHz H 1.122 × 0.497
WR90 WG16 8.2 – 12.4 GHz X 0.900 × 0.400
WR75 WG17 10.0 – 15.0 GHz X-Ku 0.750 × 0.375
WR62 WG18 12.4 – 18.0 GHz Ku 0.622 × 0.311
WR51 WG19 15.0 – 22.0 GHz K 0.510 × 0.255
WR42 WG20 18.0 – 26.5 GHz K 0.420 × 0.170
WR28 WG22 26.5 – 40.0 GHz Ka UG 599/U 0.280 × 0.140
WR22 WG23 33 – 50 GHz Q UG 383/U 0.224 × 0.112
WR19 WG24 40 – 60 GHz U UG 383/U 0.188 × 0.094
WR15 WG25 50 – 75 GHz V UG 385/U 0.148 × 0.074
WR12 WG26 60 – 90 GHz E UG 387/U 0.122 × 0.061
WR10 75 – 110 GHz W UG 387/U-M 0.100 × 0.050
WR8 90 – 140 GHz F UG 387/U-M 0.080 × 0.040
WR6 110 – 170 GHz D UG 387/U-M 0.065 × 0.0325
WR5 140 – 220 GHz G UG 387/U-M 0.051 × 0.0255
WR4 170 – 260 GHz UG 387/U-M 0.043 × 0.0215
WR3 220 – 330 GHz UG 387/U-M 0.034 × 0.0170
WR2 325 – 500 GHz Y UG 387/U-M 0.020 × 0.0100
WR1.5 500 – 750 GHz UG 387/U-M 0.015 × 0.0075
WR1 750 – 1100 GHz UG 387/U-M 0.010 × 0.0050

http://www.everythingrf.com/tech-resources/waveguides-sizes

Author: Illya Tsemenko
Published: Feb. 25, 2016, 4:17 p.m.
Modified: Nov. 16, 2016, 2:31 p.m.

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