Voice of the Engineer: Choosing the Right RF Connector for High-Frequency Applications

In high-frequency design, every detail matters. We spoke with Remco van de Griendt , Field Application Engineer at Wurth Elektronik , to explore what truly defines a precision RF connector - and why it’s critical for modern applications like IoT, Bluetooth, and industrial systems.

Why Precision Matters in RF Connectors

Precision RF connectors have become essential in high-frequency applications. As Remco explains, “Precision in RF connectors means ensuring minimal signal loss, which is critical when we’re working with signals up to 18 GHz or higher.” The goal is to maintain low insertion loss and maximize signal integrity across a range of environments.

Precision is especially important in RF connectors as they handle higher frequencies than standard connectors. At high frequencies, small design factors - such as the thickness of plating, the geometry of the connector, and the materials used - can significantly impact performance.

High-Frequency Requirements and the Role of Skin Effect

When dealing with high-frequency signals, designers must account for skin effect, where higher-frequency signals tend to travel along the surface of the conductor. Remco uses a simple analogy to explain:

"Think of a washing machine drum. At high speeds, the laundry is pushed outward, similar to how a high-frequency signal travels to the conductor’s surface. If the plating is too thin, you’ll have higher impedance and more signal loss.”

To combat this, thicker gold plating is essential for handling high-frequency signals with minimal loss. For instance, connectors with thicker gold plating can handle higher frequencies with greater efficiency, supporting applications like 5G and advanced industrial automation.

Edge Launch vs. Right-Angle Connectors: Which to Use?

A common challenge in RF design is deciding between edge launch and right-angle connectors. Remco explains that edge launch connectors generally offer better impedance matching than right-angle connectors, especially for frequencies above 6 GHz. Right-angle connectors can introduce signal reflection due to the bend, which may reduce performance if not carefully matched.

Edge launch connectors align directly with the PCB layout, allowing a smoother transmission path and better impedance control. In applications where signal purity is paramount, opting for an edge launch connector can make a measurable difference.

Choosing the Right Material: Beryllium Copper vs. Phosphor Bronze

Material selection plays a critical role in high-frequency applications. Remco highlights that beryllium copper outperforms phosphor bronze in durability and high-temperature tolerance, making it an ideal choice for centre contacts in RF connectors. Beryllium copper maintains its tensile strength and electrical properties over time, even in demanding environments.

Phosphor bronze, while flexible and suitable for some applications, shows a reduction in tensile strength over extended periods, particularly in higher temperatures. This degradation can lead to weaker contact force and increased signal loss. For designs that prioritize long-term durability and performance, beryllium copper offers the reliability needed in precision RF connectors.

Matching Impedance Across the Signal Chain

A consistent impedance of 50 ohms is vital for RF signal chains to prevent signal reflections and ensure optimal transmission. According to Remco, maintaining impedance goes beyond just selecting the right connector—it requires careful consideration of the entire signal chain. This includes the connector, cable, PCB layout, and antenna.

In high-frequency designs, even slight mismatches in impedance can lead to losses. Some manufacturers use CNC machining for connectors to ensure precise dimensional control, which helps maintain the 50-ohm impedance throughout the signal chain. Remco emphasizes, “For critical applications, CNC machining provides tighter tolerances and better matching, especially compared to die-cast connectors.”

Key Considerations When Choosing an RF Connector

Choosing an RF connector is complex, especially for high-frequency applications where details like harmonics, ambient temperature, and environmental conditions play a significant role. Here’s a summary of the factors Remco suggests keeping top of mind:

1. Frequency Range: Identify the primary frequency and consider harmonics. If designing for 2.4 GHz Bluetooth, ensure the connector can handle harmonics like 7.2 GHz without additional losses.
2. Material Selection: For high-frequency applications, prioritize materials with long-term durability, such as beryllium copper, which resists tensile strength degradation.
3. Plating Thickness: Ensure the gold plating is sufficiently thick to support the skin effect at high frequencies, maintaining signal integrity.
4. Impedance Consistency: Choose connectors and layouts that ensure 50-ohm impedance across the signal chain, particularly in edge launch designs where impedance matching is easier to achieve.
5. Environmental Conditions: Consider temperature and humidity variations that could impact connector performance, particularly in industrial settings.

Precision Connectors in IoT and Industrial Applications

High-performance connectors are integral to applications like IoT and industrial systems, where connectors often need to interface with metal housings. Many designs use coaxial connectors to connect internal components to external antennas, which can improve range and reduce power losses.

Remco points out that these applications require connectors that withstand environmental stressors, including temperature and humidity variations, without compromising signal quality. Precision connectors that handle frequencies up to 18 GHz allow designers to meet these requirements, making them essential for next-generation IoT and industrial applications.

In Summary

Precision RF connectors are more than just a design choice - they’re essential for ensuring signal integrity, especially in high-frequency and industrial applications. From thicker gold plating for managing the skin effect to CNC-machined parts for exact impedance matching, each detail in a precision connector is engineered to maximize performance.

As Remco concludes, “Choosing the right connector involves understanding not just frequency requirements but also environmental and material considerations. It’s the combination of these factors that leads to a design that truly performs.”

For more insights and to explore the range of precision RF connectors from Wurth Electronik , visit the RS website.

You can also watch the full DesignSpark Ask The Expert series interview with Remco below or at: https://www.rs-online.com/designspark/ask-the-expert-precision-rf-connectors-with-wurth-elektronik