It's a fact that separable interconnects are the least reliable parts of systems, yet they're indispensable for a variety of reasons. Considerations for using them include modularity and ease of partitioning, access for testability, the ability to adapt between connector types, and the capacity to upgrade and/or repair only portions of a system.
RF connectors are essential for these reasons, but they do add a dimension of complexity. RF coaxial connectors, unlike power connectors, or low-frequency small-signal connectors, must provide and maintain dimensional stability to ensure impedance continuity. They must also ensure adequate shielding. Many must work outdoors or in hostile environments. Others must ensure quick-disconnect operation.
Thousands of Types
Regardless of the constraints, RF connector makers offer an extremely wide variety of products. It's fair to say that thousands upon thousands of different RF connector products are available. Need proof? Just look at the Pasternack Enterprises catalog
of coax connectors and related products. It includes 18,700 different types. Ditto for United Microwave Products' extensive catalog
of microwave connectors and cables.
In step with the diminishing size of today's nomadic and portable products, many of the latest RF connectors are sub-miniature in size. Still others are ruggedized for industrial, military, and aerospace applications.
OEM demand for connectors makes it a vibrant and flourishing corner of the industry. Indeed, connector research firm Bishop and Associates indicates
the RF connector marketplace will reach more than $2 billion by 2010. In particular, vendors are supplying connectors to meet the needs of RF systems operating at ever-higher frequencies. Innovation is the name of the game. Let’s look at some examples.Anritsu
is one company offering microwave-compatible connectors. Its K connectors, for example, serve applications to 40 GHz. These coaxial connectors are compatible with standard SMA, WSMA, and 3.5-mm connectors, too.
The company's V connectors and IV connectors, based on the 1.85-mm geometry endorsed by the IEC (International Electromechanical Commission) and meeting the IEEE-Std-287-2007 specs
, can route signals at frequencies as high as 65 GHz. The latest addition to Anritsu's connector family is its W1 connector. Based on the 1-mm geometry specified by IEEE-287, it can be used at frequencies as high as 110 GHz.Trompeter Electronics
also offers RF connectors for coax, twinax, and triax. Significantly, Trompeter's products typically meet or exceed standards such as NEBS, MIL-C-49142, MIL-STD-1553B, MIL-C-39012, and GR 326.
A recent innovation at Trompeter is a line of miniaturized high-reliability BNC connectors. The company's patented UPL250 Series BNC high-rel types are slated for voice-data-video network equipment, where they also offer a density advantage. UPL250 BNCs give you a 40% gain in connector density in a given area.
The plug connector in a UPL250 connector is also 60% smaller than a full-size BNC. Nonetheless, they're applicable wherever the venerable BNC workhorse is used, and they can be attached with industry-standard installation tools.
The UPL250 Series includes straight and right-angle plugs, bulkhead cable jacks, and straight and right-angle circuit board-mounted jacks. All are available in nickel or gold-plated versions. Various between-series adaptors are also available. Significantly, Trompeter's miniaturized BNCs maintain a 75-Ω impedance throughout their entire frequency range. Like the company's standard-size BNCs, these down-sized connectors include rear-view indicator notches that provide visual inspection to ensure proper alignment and full engagement when mated to a jack. Trompeter company also provides cables and pre-terminated cable assemblies, as well as a line of termination tools.Ready-to-Go Assemblies
Another company offering pre-assembled coaxial cables with connectors is ITT Interconnect Solutions
. ITT is now shipping coaxial RF connectors along with as many as a dozen phase-matched RF cable assemblies. The semi-rigid cable sets ensure phase-matching within 2° (at 3 GHz).
Considered as a system, ITT's phase-matched assemblies feature press-fit contacts the company says are suitable for sustained operation at temperatures as high as 250°C for a lifespan of an astounding 25 years. That's just the ticket for use in military and industrial applications where reliable performance at high temperatures for a prolonged period of time is mandated.
"Since some of these applications only reach 200°C, these RF cable assemblies are available with a choice of dielectric materials to meet cost requirements," notes Keith Teichmann, ITT Interconnect's director of marketing. For operation up to 250°C, ITT cable assemblies use silicon-dioxide dielectric material. For applications to 200°C, the assemblies use PTFE dielectric.Different Appearance
Breaking with tradition, Tyco’s recently-introduced QSL RF connector system
is a low profile high-reliability RF interface that can handle signals at 6 GHz and higher. As replacements for conventional BNC, SMA, and similar RF connectors, Tyco's QSL line comprise low-profile surface-mount interconnects that don't look like conventional circular connectors.
Designed to terminate smaller-sized RG-174 and RG-316 coaxial cables, these Tyco connectors, with their stamped and formed contacts, are expandable to accommodate multiple ports. In spite of rectangular contact arrangements, Tyco specifies them for low insertion-loss and low VSWR.
Ultra-small coaxial connectors are also available from a number of vendors. Many are eminently suitable for today’s pint sized cellular handsets. I-Pex’s subminiature MHF Series plugs and board-level receptacles, for example, accommodate subminiature coaxial cables as small as 0.032 inches in diameter.Multi-Port Connectors
A company offering multi-port connectorization products is Molex
. Its multi-port SSMCX (below) is an 8-position coaxial connector block designed for cable-to-board applications. It's available in 4-port and 8-port flavors. These board-level RF connectors come in either right-angle types that can be used out to 6-GHz. Straight versions are good for making RF connections as high as 10-GHz.
Molex’s coax connectors can be specified in surface-mount or through-hole configurations, too. Contacts are available for 0.8-mm coax up to RG-178 size. For even higher frequency applications, semi-rigid compatible contacts are available to accommodate up to RG-405 (0.086-inch diameter) cables.
WLANs (wireless local area networks) are also impacting the need for RF connectors, as WLANs supplant or act as alternatives to UMTS systems or wired LANs. N, TNC, and SMA connectors are typically used as the interfaces for connecting WLAN components such as antennas and access points.Reverse-Sex Connectors
As a means of preventing incorrect or improper components from being connected to a WLAN, the use of reverse-polarity TNC and SMA connectors is emerging. Reverse-sex connectors are standard-sized cable plugs, but they contain female center contacts instead of standard male contacts. Conversely, mating receptacles also contain non-standard male center contacts instead of female center contacts. The photo shows an example of some reverse-sex coax connectors from Telegartner.
FCC (Federal Communications Commission) rules have led to a proliferation in the use of these reverse-sexed RF connectors. For unlicensed users there's a requirement that equipment manufacturers ensure that unauthorized antennas can't be connected in attempts to increase range. As a result, most connectorized antenna designs now call for reversed-polarity connectors.
These non-standard connectors are now used for the interfaces on antennas, access points, and WLAN circuit cards, making it necessary for the mating connectors to be compatible. A number of connector vendors now offer reverse-polarity TNC and SMA connectors for WLAN applications. These connectors often include an R designation in their part numbering scheme, to indicate reverse-polarity, such as R-SMA.Responding to Your Needs
Obviously, time and space limitations in this article limit our analysis and scope, but the basic information above indicates how RF coaxial connector makers are innovating in response to the needs of RF systems developers and designers. Vendors also offer a variety of hardware and software tools to help users select and assemble RF connectors, and properly terminate cables.
We’ve presented just the tip of the iceberg. To explore product offerings, go to the Web sites for RF coaxial connector makers such as Amphenol, Aviel Electronics, Bomar Interconnect, Conec, Conectec International, Crown Electronics, Delta Electronics Manufacturing, Digicon, Empower RF Systems, Foxconn, Hirose, Honda Connectors, Hosiden, Huber and Suhner, I-pex, JAE, Kings, Nemal Electronics International, Radiall, RF Industries, Rosenberger, Samtec, SMK, Souriau, SRI Connector,and Telegartner, to name just a few.