What are Quadrax Connectors?
Meet the Connector: Quadrax Connectors
Commonly used in aerospace, military, and industrial applications, quadrax connectors contain four conductors arranged in a quad configuration within a single connector housing, designed to carry high-speed Ethernet or other differential signals with minimal crosstalk.
Quadrax connectors evolved from the broader category of coaxial and triaxial connector technologies, which were developed to improve signal transmission and reduce interference in high-speed data applications. Companies including Amphenol and TE Connectivity were instrumental in refining and commercializing the quadrax design in response to aerospace and military needs for robust, high-frequency connectors. These companies contributed to the development of the quad configuration with four conductors, which allowed differential signal pairs to be transmitted with low crosstalk, thus laying the foundation for the quadrax connectors we see today.
Design Notes
Standardization
Multiple standards include quadrax connector variants, including:
MIL-DTL-38999: This military standard for circular connectors includes specifications for quadrax contacts, ensuring that quadrax connectors used in these systems meet strict requirements for ruggedness, environmental sealing, and electromagnetic compatibility (EMC).
ARINC 600 and ARINC 404: These aerospace standards outline requirements for quadrax connectors used in avionics equipment, particularly for high-speed data transfer in commercial aircraft.
IEEE 802.3: In applications like Ethernet, IEEE standards apply to the electrical characteristics of the differential pairs within quadrax connectors to ensure compliance with data protocols like 1000BASE-T (Gigabit Ethernet).
Mounting type or types: Panel mount, cable mount, or PCB mount
Mating cycles: At least 500 and as many as 1,500 mating cycles
Positions: Quadrax connectors typically have four conductors within a single contact, arranged in a quad configuration (two pairs) for differential signaling, such as Ethernet or high-speed data lines. In circular connectors, like those based on MIL-DTL-38999, quadrax contacts can be positioned within multi-position housings, allowing several quadrax contacts in a single connector shell.
Pins: Quadrax connectors typically have four pins within each quadrax contact, arranged in a square or diamond pattern. These four pins consist of two differential pairs (two positive and two negative pins) designed to carry high-speed data signals with minimal crosstalk.
In circular connectors, such as those following the MIL-DTL-38999 standard, multiple quadrax contacts can be housed in a single shell, allowing for several quadrax connections within one connector body.
Spacing (Pitch): Generally, the pins within each quadrax contact are spaced quite close, often around 1.27 mm (0.05 inches) apart center-to-center.
Height: The height of each individual pin within the contact is often around 3.5 mm to 5 mm (0.14 to 0.20 inches), but it can vary depending on the contact type and connector size.
Contact resistance: The contact resistance for a quadrax connector should be less than 5 milliohms (mΩ) per contact.
Termination: Crimp, solder, or IDC
Material specifications: Ruggedized materials help ensure the performance, reliability, and longevity of quadrax connectors, especially in demanding environments like aerospace, military, and high-speed data applications. The housing is typically made from thermoplastic or thermoset polymers, such as polyamide (nylon) or PBT (polybutylene terephthalate), for general applications. For rugged or high-performance environments, housings may be made from aluminum (often with a coating like chromate or anodized aluminum) or stainless steel for enhanced durability and environmental resistance.
Physical properties
Insulation: The insulation material surrounding the contacts is often made from polyethylene or PTFE (Teflon), which have low dielectric constants and good electrical insulating properties. This ensures minimal signal loss and high-speed data integrity.
Shielding: Electromagnetic shielding may be used to protect against EMI (electromagnetic interference). This shielding is typically made from tin-plated copper, aluminum, or stainless steel.
Locking mechanism: Bayonet, threaded, push-pull, latch, or clip-on latching mechanisms may be used to ensure a secure connection under demanding conditions.
Environmental properties
IP rating/Sealing mechanism: Quadrax connectors used in outdoor or harsh environments are rated for IP67 or IP68.
Ruggedization: A wide variety of ruggedization features may be specified with quadrax connectors, depending on the requirements of the application. Sealing, corrosion resistance, chemical resistance, electromagnetic interference, shielding, UV protection, and vibration, shock, and impact resistance are among the extra layers of ruggedization that may apply.
Temperature range: Quadrax connectors are designed to operate in a broad temperature range, often from -55 °C to +125 °C (-67 °F to +257 °F), depending on the specific connector and materials used.
Electrical properties
Voltage AC/DC: For military-grade or high-performance quadrax connectors, the voltage rating is typically around 250-500 V (volts) AC or DC, though this can vary depending on the manufacturer and the specific application.
For low-voltage, high-speed data transmission applications (e.g., Ethernet), the voltage rating may be lower, typically around 50-150 V.
Current (Amps): The current rating for most quadrax connectors typically ranges from 3 A to 10 A per contact. Some quadrax connectors are designed for higher current applications and can carry currents up to 20 A or more per contact, especially those used in power transmission or industrial applications.
Markets and Applications
Military and aerospace, Transportation, Industrial, Automotive, Datacom and Telecom, Medical, Test & Measurement
Quadrax connectors are commonly used in military and avionics systems; in radar, sonar, and other sensor systems; in satellite communications and space exploration; in telecom equipment; in energy and power generation; medical imaging, robotics, and wearables, and many more applications.
Suppliers
To learn more about companies that offer quadrax connectors, visit the Preferred Supplier pages for Amphenol Aerospace, Amphenol Pcd, binder, Harwin, Lumberg, Molex, Phoenix Contact, TE Connectivity, Radiall, Smiths Interconnect.
Related products
Triaxial/Triax connectors
Like this article? Check out our other Meet the Connector, High-Reliability and Ruggedized articles, our Mil/Aero Market Page, and our 2024 Article Archives.
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