Communication systems, test equipment and avionics are among the systems that often need to interconnect various RF modules with high performance coaxial cables. Semi-rigid cables have long been the traditional way to achieve the necessary VSWR performance at RF and microwave frequencies when delay lines or signal routing between modules call for customized cable connections.

Unfortunately, these cable types sacrifice their flexibility for the benefit of electrical performance and ruggedness. Semi-rigid assemblies may even lack mechanical integrity at the cable-to-connector solder joint. In systems with numerous RF cable interconnects, the effort to design and assemble a network of inflexible cables with fixed turns and bends can be both challenging and time-consuming. While flexible customized cables circumvent this problem, they often sacrifice ruggedness and electrical performance—until now.

Santron’s new eSMA connector features an innovative internal design for unprecedented performance from a flexible custom cable. These new cable connectors utilize a unique extended ferrule that addresses fragile solder joints associated with semi-rigid assemblies. This connector also features: failure-proof coupling nuts; EZ style, solder free, captivated center contacts; and a solder damming positive cable stop.

Electrical Performance

Santron eSMA connectors feature typical VSWR performance of 1.17 through 20 GHz or 1.10 up to 12.4 GHz for specific frequency ranges (see Figure 1). The eSMA assemblies demonstrate passive intermodulation performance of < –150 dBc typical (2 x 20 W carriers). They also weigh less and have comparable loss to standard semi-rigid coax.

Mechanical Considerations

Like the popular high performance subminiature SMA connectors which are generally intended for use with semi-rigid cables, the new eSMA connectors employ a screw type coupling mechanism and have precision-butted dielectric interfaces for consistently low VSWR values. The eSMA connectors are gold-plated brass with gold-plated center contacts. They are weatherproof and provide 50Ω constant impedance.

Cable assemblies, shown in Figure 2, are delivered with these eSMAs professionally installed on Times Microwave Systems TFlex™ cable. They can be bent firmly even up close to the connector, where many solder joints in hand-formable assemblies often break or lose electrical integrity.

The TFlex cable is a lightweight, FEP-jacketed, corrosion resistant, coaxial interconnect that is both phase and attenuation stable, while providing excellent shielding. The combined mechanical design of this new eSMA and TFlex cable assembly creates a unique solution when performance, cost and flexibility are key application requirements.

The mechanical construction of any connector is critical to ensuring good electrical performance, that is, low reflection coefficient. Several mechanical features in the internal design of the eSMA specifically address proper connector mating, such as the enhanced coupling nut captivation to prevent coupling failures as well as the EZ style center contact to ensure proper assembly and improve consistency of performance. The positive cable stop controls the RF structure and prevents solder contamination while the rigid support beyond solder wicking prevents ground failure at the brittle wick-line.

The flexible TFlex cables eliminate the need for hand or precision machine bending, allowing cables to be routed through the most convenient or desired path. eSMA assemblies are built-to-spec in desired lengths and delivered with short lead times. They are available in cable sizes 0.086" (TFlex 405) and 0.141" (TFlex 402). Prices start at $24.95 in one foot lengths in quantities of 10 to 50. Sample requests can be made online at

San-tron Inc.
Ipswich, MA (978) 356-1585

RS No. 302