A coaxial connector is a device used to connect a coaxial cable or a coaxial transmission line to other electronic devices or another section of coaxial cable. They are very common in radio frequency (RF) and microwave communication systems because they effectively reduce signal loss and provide good shielding against electromagnetic interference (EMI).

Basic structure

The basic structure of the coaxial connector usually includes the following parts:

1. Center conductor: This is the metal conductor inside the connector that transmits the signal.

2. Insulator: Located around the central conductor and used to isolate the central and outer conductors while maintaining electrical characteristics.

3. Outer conductor or shield: A metal shield surrounding an insulator that protects a signal from external electromagnetic interference and provides a reference ground plane.

4. Housing: The connector's external protective housing, usually made of metal, provides mechanical support and protection and contributes to electrical shielding.

5. Coupling mechanism: This is the part of the connector used to fasten to the cable or device, and can be threaded, bayonet, push-in, or other types of connection.

Working principle

The working principle of the coaxial connector is based on the working principle of the coaxial cable. When a signal is transmitted through a coaxial cable, the signal travels over the central conductor, while the outer conductor acts as part of the shielding and ground loop. Coaxial connectors align and establish electrical continuity with the corresponding part of the cable through the center conductor and outer conductor inside them, thus allowing signals to be transmitted from one end of the cable to the other, or from the cable to the device, and vice versa.

Coaxial connectors are designed to take into account RF performance, such as impedance matching, voltage standing wave ratio (VSWR), reflection loss, and insertion loss, to ensure the efficiency and integrity of signal transmission. In addition, the connector also needs to have good mechanical stability and durability to adapt to different installation environments and repeated connect/disconnect operations.

What are the performance indicators of coaxial connectors?

Insertion loss (IL) : Insertion loss refers to the energy loss of a signal as it passes through a connector, usually in decibels (dB). The lower the insertion loss, the smaller the signal loss, and the better the connector performance. Ideally, the insertion loss should be as close to zero as possible.

Reflection loss (RL) or voltage standing wave ratio (VSWR) : Both reflection loss and VSWR are related to the impedance match of the connector. When the impedance of the connector does not match the transmission line, part of the signal will be reflected back, causing energy loss and signal quality degradation. The reflection loss is expressed in decibels (dB), and the larger the value, the smaller the reflection; The VSWR is the ratio of the maximum voltage to the minimum voltage on the transmission line, ideally 1:1, indicating a perfect match.

Power capacity: Power capacity refers to the maximum power level that the connector can safely handle. High power applications require the selection of connectors with sufficient power capacity to avoid overheating and potential performance degradation or failure.

Operating frequency range: The design and materials of the connector limit its effective operating frequency range. Different types of connectors are suitable for different frequency ranges, from low frequency to high frequency and even microwave frequencies.

Temperature range: Temperature affects the material properties and electrical characteristics of connectors. Connectors should be able to maintain their performance indicators over a specified temperature range, which is especially important for outdoor or extreme environment applications.

Voltage resistance: Voltage resistance refers to the highest voltage that the connector can withstand, beyond this voltage, the connector may be broken or damaged.

Mechanical stability: including connector plug life, vibration resistance and impact resistance. These characteristics are important to ensure that the connector maintains its performance despite multiple insertions and harsh environments.

Impedance: The impedance of the connector should match that of other components in the system to reduce signal reflection. The most common impedance values are 50 ohms and 75 ohms.

Shielding effectiveness: This metric describes the connector's ability to protect against external electromagnetic interference (EMI) and is important for maintaining signal quality and preventing crosstalk.

Materials and coatings: The materials and coatings used affect the corrosion resistance, electrical conductivity and long-term reliability of the connector.

Characteristics and differences of different types of coaxial connectors

There are many types of coaxial connectors due to their importance in radio frequency (RF) and microwave communications, each with its own unique design, performance parameters, and application scenarios. INFINITECH summarizes several common coaxial connectors and their characteristics and differences:

SMA (Subminiature A):

SMA connector is a small threaded coaxial connector with good mechanical and electrical properties.

Application scenario: Widely used in microwave equipment, test instruments and digital communication systems, especially in the need for high precision and reliability.

The difference: SMA connectors support frequencies up to 18 GHz, have low insertion and reflection losses, and are suitable for high frequency and precision measurements.

BNC (Bayonet Neill-Concelman):

Features: BNC connector uses bayonet type quick connection mechanism, easy to plug and remove, with high repeatability and reliability.

Application scenario: Commonly used in video transmission, test equipment, and low frequency RF applications such as amateur radio and networking equipment.

Difference: The operating frequency range of BNC connectors is generally below 4 GHz, which is suitable for occasions where frequent plugging is required.

N-Type:

Features: The N-type connector features a threaded locking mechanism that provides higher connection strength and better sealing for outdoor and harsh environments.

Application scenario: Widely used in mobile communication base stations, radar systems and satellite communications, as well as applications requiring high power processing capabilities.

The difference: The N-type connector supports frequencies up to 11 GHz and has good water and dust resistance.

TNC (Threaded Neill-Concelman):

Features: The TNC is a threaded version of the BNC, providing a more stable connection and lower reflection.

Application scenarios: Suitable for environments that require vibration resistance and more reliable connectivity, such as aerospace and military applications.

The difference: TNC connectors operate at frequencies up to 11 GHz, providing better electrical performance and mechanical stability than BNC.

7/16 DIN:

Features: This is a large-size connector with high power handling capacity and good mechanical strength.

Application scenario: It is often used in high-power mobile communication systems, such as large base stations and professional radio equipment.

The difference: The 7/16 DIN connector is suitable for frequencies up to 3 GHz and is specifically designed to handle high-power RF signals.

4.3-10:

Features: This is a new type of connector designed to provide a smaller and lighter solution than traditional connectors while maintaining high performance.

Application scenario: Suitable for modern mobile communication infrastructure, especially miniaturized and weight-sensitive applications.

The difference: The 4.3-10 connector offers excellent electrical performance and mechanical stability for frequencies up to 6 GHz and is easy to automate assembly.

What is the difference between polar, non-polar and reverse coaxial connectors?

Polar coaxial connector

Polar coaxial connectors are the most common type, and they have a clear yin-yang polarity, that is, there is a male head and a female head. The male head usually has a central contact pin, while the female head has a central contact hole. This design ensures correct electrical connections and avoids the possibility of misinsertion. The outer conductor of the polarity connector is connected by a thread or other holding mechanism, while the inner conductor is electrically connected by a central contact pin and hole.

Applications: Polar coaxial connectors are widely used in a variety of RF and microwave communication systems, including but not limited to mobile communication base stations, satellite communications, radar systems and test and measurement equipment. They are suitable for applications where correct polarity connections are required to avoid equipment damage or performance degradation due to misinsertion.

Non-polar coaxial connector

Non-polar coaxial connectors, also known as flat connectors, do not have a distinct male or female head distinction. This means that the ends of the connector are interchangeable, with no specific yin-yang polarity. The outer conductor of the non-polar connector is usually threaded and can be expanded and expanded back and forth, and can be defined as either a positive head or a negative head. The design of the inner conductor also allows it to achieve the correct electrical connection in any direction.

Applications: Non-polar coaxial connectors are mainly used for those who need to connect and disconnect quickly, and do not need to worry about polarity issues, such as some portable equipment, field test equipment or RF links that need to be plugged and unplugged frequently.

Reverse polarity coaxial connector

Reverse polarity coaxial connectors are relative to standard polarity connectors, they reverse the polarity of the standard connector. Specifically, what should have been a male head became a female head, and what should have been a female head became a male head. This is designed to prevent misplugging with other standard connectors, especially in dense RF environments, which can cause signal interference or equipment damage.

Applications: Reverse polarity coaxial connectors are mainly used where additional safety measures are needed to prevent misinsertion, such as in dense installation areas of RF modules or devices, or for connection points that may be incorrectly accessed and incompatible with systems, to ensure that only correctly configured cables can be inserted.

How to choose the right coaxial connector based on frequency range, impedance matching, standing wave ratio and other factors?

Frequency range, first determine the frequency range required for your application. Different connector types have their specific frequency caps, such as BNC connectors for lower frequencies, while SMA, N-type, 7/16 DIN connectors cover a wider frequency range. Taking into account possible future needs, select connectors with a frequency range slightly higher than the current application for a rainy day.

Impedance matching, the coaxial connector should match the impedance of your system, the most common are 50Ω and 75Ω. Impedance mismatch can cause signal reflection, increase the standing wave ratio, and reduce signal quality. Ensure that the connector selected is consistent with your coaxial cable impedance to maintain good signal transmission characteristics.

Standing wave ratio (VSWR), select a connector with a lower standing wave ratio to reduce signal reflection and energy loss. The ideal VSWR is 1:1, but practical applications may require a trade-off between cost and performance. When choosing a connector, carefully review the VSWR data provided by the manufacturer to ensure that it performs well in your operating frequency range.

If the application involves high power transmission, choose a connector that can handle the expected power level and avoid overheating or performance degradation.

Environmental factors, considering the use of the connector environment, such as temperature changes, humidity, corrosive gases or physical impact, choose a connector with the appropriate level of protection and material. If the connector will experience frequent plugging and unplugging or be in a vibration environment, choose a connector with a robust design and good mechanical stability. Evaluate the relationship between the cost and performance of your connectors and choose a cost-effective product without sacrificing key performance metrics.

Other considerations

• Connector type: Consider how the connector is connected (such as threaded, snap, push-pull) and whether a polarity or reverse polarity connector is needed to avoid misinsertion.

• Maintainability: If the connector needs regular maintenance or cleaning, choose a type that is easy to operate and maintain.

• Brand and quality: Choose reputable manufacturers to ensure product quality and after-sales service.

How to choose the right coaxial connector for different application scenarios?

In different application scenarios, choosing the right coaxial connector is very critical, because each application has its own specific frequency range, power requirements, space limitations, connection frequency and environmental conditions. The following are some recommended coaxial connector types for specific application scenarios:

Radio frequency communication

• SMA connectors: Suitable for RF communication systems, especially where miniaturization and high frequency performance are required, such as wireless communication devices, microwave RF components, and test and measurement equipment.

• N-type connectors: Suitable for medium to high power RF communication applications, such as mobile base stations, satellite communications and radar systems, operating at frequencies up to 11 GHz.

Microwave communication

• 2.92mm connectors: Suitable for microwave communications that require extremely high frequency performance, such as automatic test equipment (ATE), wireless devices and measuring instruments, up to 40 GHz.

• 3.5mm connectors: In the microwave frequency band, for applications requiring tighter connections and higher frequency performance, up to 50 GHz.

• 1.85mm connectors: up to 67 GHz in extremely high frequency microwave applications for laboratory testing and precision measurements.

Data transmission

• BNC connectors: Common in lower RF and video signal transmissions, such as surveillance systems, cable television, and simple data networks.

• F-type connectors: Widely used for signal transmission in cable TV systems, broadband Internet and home entertainment systems.

Test and measurement

• SMA connectors: In the field of test and measurement, SMA connectors are widely used because of their good frequency response and stability.

• 2.4mm connectors: Used in ultra-precision test equipment for measurements requiring extremely high frequency performance, up to 50 GHz.

• SMP/SMPM connectors: In automated test equipment, SMP (push-pull) and SMPM (micro-push-pull) connectors are very popular due to their fast connection and disconnection capabilities and high frequency performance.

Aerospace and military

• TNC connectors: In environments where vibration resistance and anti-loosening are required, such as aerospace and military applications, TNC connectors are favored for the stability of their threaded connections.

• 7/16 DIN Connectors: In high-power RF applications, such as military communications and radar systems, 7/16 DIN connectors are widely used due to their high power handling capabilities and rugged construction.

Mobile communication

• N-type connectors: In mobile communication base stations, N-type connectors are preferred because of their high power handling capacity and wide frequency range.

• 4.3-10 connectors: In recent years, 4.3-10 connectors have become popular in mobile communication infrastructure due to their compact design, high performance and easy automated installation.

When choosing a coaxial connector, in addition to the above recommendations, you should also consider the mechanical strength, environmental tightness, cost and availability of the connector, and whether it is easy to integrate with existing systems. In some cases, customized solutions may be required to meet special requirements.