Multi-port connectors integrate multiple coaxial contacts into a single connector module, resulting in higher interconnect density while reducing installation time. Multi-port connectors also reduce form factor and overall system complexity. The selection of a multiport connector depends on the desired frequency range, signal integrity, and space constraints, all of which must be considered when selecting a multiport connector for a particular application. Because multi-port RF/coaxial cable assemblies have standardized contact cavities, they offer the system advantage that RF (coaxial, duplex, triaxial, etc.), fiber optic modules, and signal contacts (non-RF) can be used in the same connector, depending on the contact size.
Elecbee SV Microwave's DC to 40 GHz high-frequency coaxial D38999 contacts allow applications to continue to use the D38999 connector and expand uses to include microwave transmission lines.
In his IMS2024 story, David Shaff, director of RF/microwave at Bishop & Associates, explains that despite the “trend toward multiport multi-coaxial assemblies that are either linear (continuous) or as coaxial inserts mounted in multi-cavity connectors” and the fact that SMPM and SMPS/SMP3 interfaces have been standardized, intermateability concerns remain due to different coaxial recess/interface depths. However, he adds, “several vendors have successfully tested intermateability of D38999 components that use the SMPM interface for 16 gauge contacts (and possibly larger cavity sizes) involving vibration, etc. The report has not been made public, but the vendors will be common to VITA 67 and SOSA. coaxial cables for MIL-PRF-24308, MIL-DTL-38999 (all four series) with small size 20 contact cavities (operating up to 110 GHz), and even the new MIL-DTL-32689 circular circuits are still being considered as the only sources.
Typical stand-alone multi-port coaxial cable from Radiall.
A number of companies including Radiall, Amphenol SV Microwave, Amphenol CIT, Southwest Microwave, SOURIAU (Eaton), and TE Connectivity offer coaxial cable connection assemblies for multiport use including round MIL-STD-38999 or rectangular MIL-DTL-24308, and even ARINC-600 which can be installed by knowledgeable users. 38999 or rectangular MIL-DTL-24308, and even ARINC-600 which can be installed by knowledgeable users. many vendors, such as Samtec, HUBER+SUHNER, and Rosenberger, are now offering multiport primarily as pre-assembled units.
Design Notes
Standard: Multi-port connectors used in high-frequency military and avionics systems must meet or exceed the electrical, mechanical, and environmental specifications of the conventional coaxial connectors they replace. The use of industry-standard mil-spec connectors as the base design for multiport connectors has led to the use of MIL-DTL-38999 connectors for commercial assemblies, as well as the use of standard and customized versions of MIL-DTL-24308 connectors. Multi-shell solutions and solutions with linked inserts include stacked Combo-D (with MIL inserts) and ARINC assemblies.
Mounting: Connector housings are mounted according to non-coaxial cable equivalents, which vary by connector family. Panel mount multiports may have PC terminations. (Note: RF signals are typically not suitable for 90 degree terminations and require consideration of PCB circuit impedance. Alternatively, they may connect lines to other locations on the PCB or to internal components, and the electrical properties of these connections need to be understood.
Mating: Multi-port mating is the same as standard mating. This can be done via in-line blind, rotary coupling or push-pull. This is a distinct advantage because there is only one connector pair to mate, rather than many individual RF connector pairs.
Frequency Range: The results will depend on the cable and PCB used, but by themselves, multi-port coaxial cables are primarily DC to 20 GHz, although unique (and often miniaturized) assemblies can perform up to 125 GHz with the right components and cables.
Impedance: Most multi-port connectors have an impedance of 50 ohms.
Location: 2-port, 4-port, and 6-port board connectors in multiple sizes
Ruggedization: Multi-port connectors in MIL/Aero applications must be able to withstand high shock and vibration, wide temperature ranges, and operate in vacuum-like conditions at high altitudes.
Amphenol CIT's multi-port quick-connect harnesses with push-on RF interfaces are designed to reduce time and cost for integrators without compromising reliability or performance, and support the same critical operating frequency, return loss and RF shielding specifications as traditional single-point threaded interfaces such as SMA and SMK/2.92mm.
Markets and Applications
Military/Aerospace, Datacom/Telecom, Medical and Industrial
Commercial applications in military and avionics, cable and internet services, industrial automation, instrumentation and test.
Times Microwave Systems' Multi-Port (M8) and Mini-Multi-Port (MMP) connectors are high-density interconnect solutions designed for robust performance in extreme environments and are compliant with MIL-T-81490 and MIL-C-87104. The M8 connector supports frequencies up to 20 GHz, while the MMP extends to 40 GHz. Both feature sealed housings, spring-loaded interfaces, and top wire mating systems for excellent shielding, low insertion loss, and reliability under vibration and temperature stress. Ideal for airborne systems and other high endurance applications.