Introduction to RF connectors: Types, Uses and Applications

Radio frequency (RF), in essence, is the range of oscillation rates between 3 kHz and 300 GHz. The energy of the alternating current radiates outwards from the conductor in this frequency range. In the field of telecommunications, RF signals are widely used. Different RF connectors can be used in many applications to connect radio frequency cables and equipment to reduce signal loss. This introduction will help you learn more about RF Connectors.

What is RF connector ?

In radio frequency transmission systems, RF connectors establish electrical connections. They are commonly used with coaxial cable, and are therefore also called RF Coaxial Connectors. A typical RF plug is made up of a center and outer conductors, as well as insulating materials. These components work together to maintain shielding on coaxial cables. The RF connector is usually equipped with a spring and a mechanism for fastening it. This helps reduce the insertion force.

Both female and male RF connectors are available and widely used for radio broadcasting, TV receivers, communications and radar. They can also be found in medical devices, measuring tools, aerospace and other fields. These connectors can be used for non-RF applications due to their superior shielding abilities.

Some RF connectors need to be thoroughly cleaned and inspected before use. They also require meticulous mating in order to minimize any possible effects on the system due minor mechanical variations. Cleaning air-dielectric connectors involves the use of clean, dry, air.

RF Connector Gender

The male connector of standard polarity (SP), has a pin in the center, while the threads on the housing are located outside. The female connector is similar, but has a middle hole to match the male, with the threads being located outside.

In reverse polarity (RP), RF connectors, the gender configuration is different. The male connector for RP RF has a thread inside the housing instead of a pin. The female connector, on the other hand, has an external thread and a center pin.

There are also sexless connectors. Gender-neutral plugs are mounted flush, rather than mating. These connectors are usually similar in housing and can be paired with any other connector.

Types of RF Connectors

There are many different types of coaxial connectors. They differ in terms of size, mate mechanism, frequency, application, etc. This section will explore some of the more common types.

BNC connector s

In the 1940s the miniature-size Bayonet Neil-Concelman connector (BNC), was developed. It is still one of the most common and popular RF connectors. BNC connectors are simple in structure, with a bayonet mount locking mechanism for quick connection/disconnection.

Features:

· Maximum Frequency: 4 GHz

· Maximum Voltage: 500 Volts

· Impedance Characteristics: 50 Ohm and 75 Ohm

· Coaxial Cables Often Used Together: RG59, RG6, RG11,...

· Common applications: amateur radio, video signals, timing signals, test equipment and instrumentation.

SMA connector

 

SMA RF Connector, KH-N-SMA-Z

The SubMiniature Version A (SMA), a subminiature connector, is an RF connector that has a screw type coupling. It's commonly used for high-frequency applications. Be careful when checking the polarity of RP SMA connectors. The SMA connector has a 500-cycle rating.

Features:

· Maximum Frequency : 18 GHz. Some can operate at up to 26.5"

· Characteristic impedance: mainly a 50 Ohm

· Applications: handheld radios and antennas for mobile phones, Wi-Fi, radio astronomy etc.

IPEX / U.FL Connectors

 

IPEX RF Connector, KH-IPEX3-2020

The IPEX (also known as U.FL or MHF) is an ultra-miniature RF connector commonly used on PCB-mounted wireless modules. Its compact size makes it ideal for space-constrained designs.

Features:

· Maximum Frequency: up to 6 GHz

· Characteristic Impedance: 50 Ohm

· Coaxial Cables Often Used: 1.13mm, 1.37mm, RG178

· Common Applications: Wi-Fi modules, Bluetooth modules, LTE modems, GNSS antennas

MCX connectors

Micro Coaxial (MCX), a connector with a similar design, is smaller than SMB connectors. This small snap-on RF connector can be installed in tight spaces. The MCX is also available in a smaller version known as the MMCX.

Features:

· Maximum Frequency: 6 GHz

· Characteristic Impedance : primarily 50 Ohm

· Coaxial Cables Often Used Together: RG316 RG174 RG188

· Common Applications: cellular telecom equipment, GPS receivers, data telemetry, tuners, etc.

MMCX Connectors

The MMCX (Micro-Miniature Coaxial) connector is an even smaller variant designed for ultra-compact RF equipment. It provides a snap-on connection similar to MCX but in a reduced form factor, making it suitable for densely packed devices.

Features:

· Maximum Frequency: typically up to 6 GHz

· Characteristic Impedance: 50 Ohm

· Coaxial Cables Often Used: 1.13mm, RG178, RG174

· Common Applications: portable wireless modules, IoT devices, wearable electronics, antenna pigtails

FAKRA Connectors

FAKRA connectors are automotive-grade RF connectors built on the SMB interface and enclosed in color-coded plastic housings. The keying structure ensures secure mating and prevents accidental mismatching.

Features:

· Maximum Frequency: up to 6 GHz

· Characteristic Impedance: 50 Ohm

· Common Applications: automotive GPS antennas, 4G/5G telematics, rear-view camera systems, AM/FM and DAB radio modules

Five Things to Consider when Selecting RF Connectors

Let's clarify the selection process now that you know more about RF connectors. When choosing the right RF plug, you need to consider several factors. These include coupling mechanisms, electrical performance and environmental suitability. Let's explore these factors.

Material and Construction

Commercial RF connectors are usually made of cheaper materials than those that meet military standards. Brass, copper alloys and stainless steel are commonly used as conductor materials. They can be plated in gold, silver or nickel. Insulation materials include PTFE and PP. The right connector material can have a significant impact on performance and durability. The dielectric and conductor insulation can have an impact on the signal degradation.

There are many sizes of RF connectors, such as standard, mini, submini, micro etc. Connectors that match the cable diameter minimize reflections of signals, while miniature connectors may be more suitable for smaller devices but are less durable when used frequently. If you need RF connectors to connect RF equipment, select connectors that are able to withstand mating cycles of thousands.

There are also RF connectors available with different coupling mechanisms to suit various needs. These include bayonet, screwed, snap-on, push-on and quick-lock types. The push-on and bayonet types allow for a fast connection while the snap-on and quick-lock types increase the reliability and firmness of the connection. The threaded coupling is most common for RF connectors. It is also highly resistant to vibration.

Electrical Parameters

When selecting a connector, it's important to take into account the frequency of your application. SMA connectors are a great choice for many applications due to their wide frequency range.

Impedance considerations are also important for different applications. To achieve optimal transmission, the characteristic impedance should match the cable and system. BNC and F connectors, for example, are commonly used in 75-ohm applications.

Environmental Factors

Temperature of the RF connectors is affected by ambient temperature as well as the temperature of the connected devices. To avoid damage, ensure that the RF connectors are operating at the correct temperature. Choose these connectors that are resistant to moisture and corrosion for outdoor use. This will ensure durability and reliability.

Standard and Compatibility

Be sure to check that the RF connector is compatible with the existing connectors and devices. This includes the mechanical structure as well as the electrical parameters. When mating connectors, be careful and use an adapter if needed to convert between connector types.

RF connectors may be required to meet specific standards for different projects, including MLC, DIN BS, IEC and IEEE. You should also ensure that the RF connector complies with the standards for the entire system.

Cost

When choosing RF connectors, it’s also important to consider cost. IPEX (U.FL) and MMCX connectors are usually the most affordable because they are small and widely used in consumer electronics. BNC and MCX connectors are moderately priced and offer good reliability. SMA connectors can cost a bit more, especially for high-frequency or precision types. FAKRA connectors are generally the most expensive since they are made for automotive use and come with coded housings.

Summary

There are many types of RF connectors, and they are used widely in high-frequency applications. It is important to have the right knowledge for selecting and using the correct RF connectors. Maintaining your RF connectors is also important.