Multi-Port Connectors: High-Density Interconnection Solutions

Multi-Port Connectors: High-Density Interconnection Solutions

Definition and Overview

Multi-port connectors integrate multiple coaxial contacts into a single connector module, enabling higher interconnection density while reducing installation time. These connectors also reduce overall system footprint and complexity. When selecting a multi-port connector, factors such as required frequency range, signal integrity, and space constraints must be considered – these are key elements for application-specific selection.

System Advantages and Standardization

Because multi-port RF/coaxial cable assemblies feature standardized contact cavities, they allow flexible integration of RF (coaxial, twinax, triax, etc.), fiber optic modules, and non-RF signal contacts within the same connector, depending on contact size. For example, Amphenol SV Microwave's DC to 40 GHz high-frequency coaxial D38999 contacts enable continued use of D38999 connectors while extending their application to microwave transmission lines.

Intermating Concerns and Test Progress

In his IMS2024 report, David Shaff, RF/Microwave Director at Bishop & Associates, noted that although "the trend for multi-port multi-coax assemblies is either linear (continuous) or as coaxial inserts installed in multi-cavity connectors," and interfaces such as SMPM and SMPS/SMP3 have been standardized, concerns about intermating remain due to differences in coaxial recess/interface depths among manufacturers. However, he added: "Several suppliers have successfully performed intermating tests on D38999 assemblies that use SMPM interfaces for size 16 contacts (and possibly larger cavity sizes) involving vibration, etc. Reports are not yet public, but the suppliers will be common suppliers to VITA67 and SOSA." Furthermore, coaxial solutions for small size 20 contact cavities (operating up to 110 GHz) in MIL-PRF-24308, MIL-DTL-38999 (all four series), and even the new MIL-DTL-32689 circular connector, are still considered sole-source.

Major Suppliers and Product Forms

Multiple companies, including Radiall, Amphenol SV Microwave, Amphenol CIT, Southwest Microwave, SOURIAU (Eaton), and TE Connectivity, offer coaxial cable connector assemblies for multi-port applications, covering circular MIL-STD-38999, rectangular MIL-DTL-24308, and even ARINC-600 types that can be installed by knowledgeable users. In addition, many suppliers such as Samtec, HUBER+SUHNER, and Rosenberger primarily offer multi-port products as pre-assembled units. The figure below shows a typical stand-alone multi-port coaxial cable from Radiall.

Design Considerations

• Standards: Multi-port connectors used in high-frequency military and avionics systems must meet or exceed the electrical, mechanical, and environmental specifications of the traditional coaxial connectors they replace. Designing around industry-standard military connector specifications has led to the use of MIL-DTL-38999 connectors in commercial assemblies, as well as versions using standard and custom 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 their non-coaxial equivalents, which vary by connector series. Panel-mount multi-ports may feature PC terminations. Note: RF signals are generally not suited for 90° terminations, and PCB trace impedance must be considered. Alternatively, they may route connections to other locations on the PCB or to internal components, requiring knowledge of the electrical performance of these connections.

• Mating: Multi-port mating is the same as standard mating. It can be achieved via in-line blind mating, screw coupling, or push-pull mechanisms. This is a key advantage, as only one connector pair is mated instead of many individual RF connector pairs.

• Frequency Range: Frequency performance depends on the cables and PCB used. By itself, multi-port coaxial cabling typically covers DC to 20 GHz; however, unique (often miniaturized) assemblies with appropriate components and cables can achieve operation up to 125 GHz.

• Impedance: Most multi-port connectors are 50 Ω.

• Port Positions and Count: Board-level connectors are available in 2‑port, 4‑port, and 6‑port configurations, with various size options.

• Ruggedization: Multi-port connectors used in MIL/Aero applications must withstand high shock and vibration, wide temperature ranges, and operate under near-vacuum conditions at high altitudes.

• Quick-connect example: Amphenol CIT's multi-port quick-connect cable harnesses feature push-on RF interfaces designed to reduce integrator time and cost without compromising reliability or performance. They support the same critical operating frequency, return loss, and RF shielding specifications as traditional single-point threaded interfaces such as SMA and SMK/2.92 mm.

Markets and Applications

Multi-port connectors are widely used in military/aerospace, datacom/telecom, medical, and industrial fields. Commercial applications include military and avionics systems, cable TV and internet services, industrial automation, instrumentation, and test equipment.

Representative Product: Times Microwave Multi-Port Series

Times Microwave Systems' Multi-Port (M8) and Mini Multi-Port (MMP) connectors are high-density interconnection solutions designed for robust performance in extreme environments, meeting MIL-T-81490 and MIL-C-87104 standards. The M8 connector supports frequencies up to 20 GHz, while the MMP extends to 40 GHz. Both feature sealed housings, spring-loaded interfaces, and jackscrew coupling systems, providing excellent shielding, low insertion loss, and high reliability under vibration and thermal stress. They are ideally suited for airborne systems and other high-durability applications.