With the integration of RF coaxial connectors with sensors, a new type of 5G RF connector suitable for 5G wireless connections has been launched. In order to implement wireless connections on a global scale, the cost of customized parts for 5G wireless devices will be lower in the future and reliability It should be further strengthened. The naming model of the RF connector is generally located by the internationally used main name model. The naming model of the structure of different products should be formulated in accordance with the detailed standard specifications. How much do you know about the basics of RF connectors?


Overview of RF coaxial connectors:
Coaxial connector, (some people also call it a radio frequency connector or RF connector, in fact, strictly speaking, the radio frequency connector is not completely equivalent to the coaxial connector. The radio frequency connector is from the perspective of the frequency of the connector. Coaxial connectors are classified from the structure of the connector. Some connectors are not necessarily coaxial, but they are also used in the radio frequency field. Coaxial connectors can also be used in low frequencies, for example, very common audio Headphone plug, the frequency does not exceed 3MHz. From a traditional point of view, radio frequency refers to the MHz category. Nowadays coaxial connectors are often used in the microwave field. In the GHz category, the term “radio frequency” has always been used, overlapping with the “microwave” one. Above the word) is a branch of the connector, which has the commonality of the connector and its particularity.

The coaxial connector has an inner conductor and an outer conductor. The inner conductor is used to connect the signal wire and the outer conductor is not only the ground wire of the signal wire (reflected on the inner surface of the outer conductor), but also plays a role in shielding the electromagnetic field (shielding the internal electromagnetic waves from the outside The interference acts on the inner surface of the outer conductor, and the shielding of the external electromagnetic field from the internal interference acts on the outer surface of the outer conductor. This feature gives the coaxial connector a lot of space and structural advantages. The outer surface of the inner conductor of the coaxial connector and the inner surface of the outer conductor are basically cylindrical-special cases are often required for mechanical fixation and have a common axis, so they are called coaxial connectors.

Among the several forms of transmission lines, coaxial cables are commonly used due to their outstanding advantages (simple structure, high space utilization, easier manufacturing, superior transmission performance…), the coaxial connector was born. Due to the superiority of the coaxial structure, the continuity of the characteristic impedance of the (coaxial) connector (compared to other connectors) is more easily guaranteed, the transmission interference and interference (EMI) are very low, and the transmission loss is almost unique. The ground is used in radio frequency and microwave fields. And because it is almost absolutely used at high frequencies, some electrical performance requirements are different from other connectors.

The radio frequency connector is connected with a coaxial cable, a microstrip line or other radio frequency transmission line to realize the electrical connection and separation of the transmission line or the original part of the transfer of different types of transmission lines. It belongs to a mechatronics product and acts as a bridge.

The model of RF coaxial connector consists of two parts: the main name code and the structure code, separated by a dash “-” in the middle. The main designation code The main designation code of the radio frequency connector adopts the main designation code commonly used in the world, and the naming of different structures of specific products shall be specified by the detailed specifications. Structure code of the structure of the radio frequency connector.

According to the structure of the connection interface:

  • bayonet type (internal bayonet, external bayonet): BNC
  • Thread type (right-hand thread, left-hand thread): L29 (7/16), N, F, TNC, SMA, SMC, SSMA, SSMB, FME, L9 (1.6/5.6), 7mm, 3.5mm, 2.4mm, K (2.92mm), 1.85mm, 1mm;
  • Push type (in-line, self-locking): SMB, SSMB, MCX, MMCX, SMP, SMI, BMA, SAA;
  • Flange connection type

Classified by size:

  • Standard type: UHF, N, 7/16, 7mm;
  • Small size: BNC, TNC;
  • Subminiature: SMA, SMB, SMC, MCX, BMA, SAA, 3.5mm;
  • Micro: SSMA, SSMB, MMCX, 2.4mm, K (2.92mm), 1.85mm, 1mm;

Third, the main specifications of the RF connector

  1. Impedance: Almost all RF connectors and cables are standardized to 50Ω impedance. The only exception is that 75Ω systems are commonly used in cable TV installations. It is also important that the RF coaxial cable connector has the characteristic impedance of the matching cable. If this is not the case, a discontinuity is introduced and loss may result.
  2. VSWR (Voltage Standing Wave Ratio): Ideally, it should be unity, and good design and implementation can keep VSWR below 1.2 within the range of interest.
  3. Frequency range: Now most of the radio frequency work is in the range of 1 to 10GHz, therefore, the connector must have low loss in this area. For the case above 10GHz-there is a lot of work, now things in the 10 to 40GHz range-there are newer connectors among them to choose. They are expensive because of the cable itself.
  4. Insertion loss: This is the connector loss in the frequency range of interest. The loss is usually between 0.1 and 0.3 decibels. Determine how critical per watt (or fractional watt) is in most designs. Even such a small loss must be minimized and included in the link loss budget. It is in the low-noise front end, especially when the signal strength and signal-to-noise ratio are low.
  5. Operation cycle: How many connection/disconnection cycles can be connected and endured and still meet its specifications? This is usually in 500 or 1000 cycles. For threaded connectors, the tightening torque specified by the supplier is an important factor in maintaining performance and reliability.
  6. Power: Power handling is determined by two resistance losses (heating) and insulation breakdown. Although even decades of design are mainly pre-processing tens of watts, today’s design community focuses on low-power devices such as mobile phones, picocells and femtocell base stations, video interfaces, RF and gadgets. These are in the sub 1W range, so the connector can be much smaller and its power rating is a smaller constraint.

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The radio frequency connector is defined as a separable component that is usually installed on a cable or device for electrical connection of a transmission line system. It can be seen from this definition that it has the common feature of the “detachable element” connector. “Transmission line system” refers to the microwave transmission system. The common structure of transmission line is shown in the figure below:

Signal transmission principle

Take the commonly used coaxial line as an example, the main mode of the coaxial line is TEM wave, and the field distribution is shown in the figure below:

The electromagnetic wave transmitted is an oscillating particle wave derived from the same phase and perpendicular electric field and magnetic field in space. It is an electromagnetic field propagating in the form of wave and has wave-particle duality.

Electromagnetic waves move in the form of waves by electric and magnetic fields that oscillate in phase and are perpendicular to each other. The electric field direction, magnetic field direction, and propagation direction of electromagnetic waves are perpendicular to each other. Electromagnetic waves have no longitudinal components and are transverse electromagnetic waves.

Classification and main technical parameters

RF connectors are mainly divided into three categories: RF coaxial connectors, RF triaxial connectors and dual-core symmetrical RF connectors. The main uses are as follows:

  • RF coaxial connector: mainly used to transmit transverse electromagnetic waves (TEM waves);
  • Radio frequency triaxial connector: mainly used in occasions with higher requirements for shielding efficiency, to transmit transverse electromagnetic waves (TEM waves) or transmit pulse waves;
  • Dual-core symmetrical radio frequency connector: mainly used to transmit digital signals with a low speed.

The main performance parameters of radio frequency coaxial connectors

Including characteristic impedance, operating frequency, return loss, insertion loss, isolation, radio frequency leakage, phase consistency, third-order intermodulation, etc.

Commonly used materials and coatings for RF coaxial connectors

The radio frequency connector is mainly composed of outer conductor, inner conductor and insulating support medium and other parts. The commonly used materials are as follows:

  • Outer conductor: stainless steel passivation, copper alloy gold plating, copper alloy nickel plating, copper alloy plating ternary alloy, etc.;
  • Inner conductor: copper alloy plated with gold, copper alloy plated with silver, etc.;
  • Insulation support medium: PTFE, PEI, LCP, etc.

Dosin Hardware Electronics Co., Lrd. produces more than 30 series of RF connector products, such as SMA, SSMA, BMA, SBMA, SMP, SMPM, N, TNC, 2.92, 2.4, 1.85 and other products.

The maximum operating frequency of the product reaches 65GHz. The first sample of the 1.0 series millimeter wave connector with a working frequency of 110 GHz has been successfully developed. It is the first to introduce the L7 series radio frequency coaxial connector with a characteristic impedance of 75Ω and an operating frequency of 6GHz to meet the new needs of the military and civilian products. Products are widely used in weapons and equipment, communications, rail transit and medical fields.

The simpler thing instead the easier it is for consumers to accept, which is the inevitable trend under the development of modern high-tech, so more and more products begin to develop in the direction of refinement and miniaturization, such as wire-to-board connector is one of them. The integrated wire-to-board connector can not only compress the contact, but also has three advantages as below.

First, realize the connection of local gold-plated auxiliary board and increase the flexibility of design. In the past, the wire-to-board connectors are clumsy, although they can complete the docking, but the flexibility is not enough. The integrated wire-to-board connectors are widely used in digital cameras, mobile devices and GPS and other fine industries through the compression of contacts, the improvement of the efficiency and area of the connection with the local gold-plated auxiliary board, and the enhancement of flexibility.

Second, high temperature thermoplastics are used to achieve greater accuracy. It is understood that the contact area of the integrated wire-to-board connector has many protrusions, which can avoid the damage caused by accidental dropping, and further reduce the thickness of solder paste to achieve maximum accuracy.

Third, Simple design makes the integrated wire-to-board connector more convenient to use. Wire-to-board connector manufacturers point out that this product uses a special automation design, which can achieve the connection between primary and secondary printing, but also achieve a balanced state, small wear and tear, long use time, high refinement, so it is popular with mobile device manufacturers.

The FPC full name is Flexible Printed Circuit board. Popularly speaking, That PCB is made of soft materials (foldable and bendable materials). It is widely used.

There are many kinds of connectors on mobile phones, among which FPC is one of them. The product categories can be divided into internal FPC connectors and board-to-board connectors, external connected I / O connectors, battery connectors and Camera Socket, etc.

FPC Connector

FPC connector is used to connect LCD display screen to drive circuit (PCB). At present, 0.4mm pitch products are the main products, and 0.3mm pitch products have been widely used as well. In the long run, the FPC connector is expected to be integrated with other mobile phone components into the framework of the mobile phone or its LCD modaule in the future.

Board-to-Board Connector

The development trend of the board to board connector in mobile phone is more and more smaller of the Pin spacing and height that the 0.4mm pitch is the main products, and it will develop to 0.35mm or less, and the subsequent request the lower height and with shielding in the future. At same time, the height of BTB ( Board to Bard connector ) will reduce to 0.9mm as well.

I/O Connector

I/O Connector is one of the most important in-and-out channels on the mobile phone, included the connection of the power and signal, volume reduction and Product Standardization will be the main development Direction in the Future. Then the connector is required to be thinner, the visual effect and the waterproof function are provided.

Battery Connector

The battery connector can be divided into elastic sheet type and knife type. The technical trend of the battery connector is mainly the miniaturization, the new battery interface, the low contact resistance and the high connection reliability.

Thus it can be seen, the connector is the essential part for the electronic engineering industry, the different function and use make the users in the industry see its function and impact on our life and production. In the future, we need to carefully consider and understand the choice and use of different connectors as users. Dongguan Dosin hardware Electronics Co., Ltd., as a company with many years of production and R & D experience, deserves the recognition and trust of the majority of users.

Mis-insertion is a kind of wrong behavior caused by carelessness in the operation process of the staff, which will not only lead to the normal operation of the equipment, but also may lead to the circuit short circuit in serious cases, so the requirements on the prevention of anti-missing insertion are very high.

The prevention of misplacement mainly starts from the following aspects:

On the one hand, the line of wire connector itself, rotate one hundred and eighty degrees, if misalignment error can lead to signal an error, so at this time requires attention as far as possible choose lines to prevent mistaken insertion of the connector, it can avoid this kind of error, but also can avoid the equipment damage, can also by adjusting the line to line the relative position in the connector configuration only.

On the other hand, when the manufacturer USES the same connector, it is very likely to plug A into B socket, this situation needs special attention, because once this happens, the consequences will be very serious, must be connected to AB interface for different socket can be.

And the use of wire to wire connector can avoid this kind of situation to a certain extent, so it is suggested that in order to reduce the types of materials, or to save costs of manufacturers, in the process of use, must choose reliable and safe wire to wire connector products, so that their equipment can be well protected.

Although the anti-misplacement effect of wire-to-wire connector cannot be completely solved now, with the development of science and technology and the update of products, we believe that solutions will be found in the future.

Connectors are important components that connect two devices,Used to transmit or receive signals and is an essential item,With the development of domestic science and technology and continuous improvement,Domestic connector has gradually replaced the foreign connector,Become the brand type that domestic consumer likes quite.

Domestic connectors in the use of the process of a total of three advantages, respectively as follows:

First, it is easy to maintain and can improve the production process.

Because of the existence of domestic connectors, not only simplify the process of mass production, improve the work efficiency of the enterprise, at the same time when a certain component problems, but also can be replaced quickly, so as to reduce the loss caused by the damage of parts.

Second, upgrading is more convenient.

For the equipment, the upgrade may be slow, but for the domestic connector components, it is easier to upgrade, and the connector upgrade will naturally drive the change of other equipment, so as to achieve the effect of enterprise upgrading equipment.

Third, the design is more flexible.

According to statistical data, since there is a domestic connector, China’s designers in the design process, flexibility than before 20%, and this saves 20%, not only improve work efficiency, but also save a lot of cost expenditure, for enterprises kill two birds with one stone.

Since the products that need to use the connector are developed in the direction of appearance refinement, installation simplicity and long service life, the existence of the pin probe connector has well solved the needs of the connector manufacturer, the pin probe connector. Therefore, it has become the favor of many connector manufacturers. After a large number of related tests, the factors affecting the life of the pin probe connection are as follows.

1. Frictional corrosion

The friction of the pin probe connector during operation and the corrosion of various corrosive substances in the working environment are important factors for greatly reducing the life of the pin probe connector.

2. Electrical accident

This type of fault generally refers to the connection between the wire and the terminal and is a factor that directly affects the life of the pin probe connector. In order to solve this problem effectively, a new type of reinforced crimping technology has emerged, which is an upgraded version of the previous crimping technology. After testing, this technology can greatly reduce the occurrence of electrical faults, and has gradually begun to be applied in actual production.

3. Plugging problem

The problem of plugging and unplugging the pin probe connector has always been an important factor in the failure. The control of the insertion force is difficult, and it is easy to fall off when it is small, and it will be damaged when it is large. This has always been a big problem in this respect, so many designers can’t think of any good way. The more methods used now are to control different insertion and extraction forces depending on the place of use. Although the application of a part of the pin probe connector can be guaranteed to some extent, this problem cannot be completely solved.

Currently, the board-to-board connector used on mobile phones has the following characteristics:

First, “soft”, flexible connection, and has a strong corrosion resistance; secondly, no welding is required, installation is convenient, and there is no fire hazard, which also saves space.

In order to improve the combined force of the socket and the plug, a simple locking mechanism is adopted in the fixed metal part and the contact part, which not only improves the combined force, but also makes the locking more realistic. The connector minimizes the thickness of the product to achieve the purpose of connection, which has more and more ultra-thin mobile phones on the market.

The pitch of the pins is also narrower and narrower. At present, the main focus is 0.4mm pitch. The 0.35mm pitch should be the industry’s narrowest pitch-to-board connector. The 0.35mm pitch is currently used mainly for Apple mobile phones and domestic high-end machines. Type, its application will be the trend of the past two years, it has the advantages of the smallest volume, the highest precision, high performance.

Today, consumers are demanding more and more demand for product thickness and feel. Ultra-thin, ultra-narrow connectors put new demands on the electroplating process. On products with a height of 0.6mm and a single product of less than 0.4mm. How to ensure the gold plating thickness of the product and the tin effect does not climb the tin, which becomes the most critical problem of the miniaturization of the connector. At present, the common practice in the industry is to remove the gold plating layer by laser to block the upper tin path.

The waterproof rf coaxial connector is usually working in the water.and they are waterproof.The power cable and net cable can be put in their internal.They can not only provide normal and reliable power,single transmission,but also can be waterproof ans dust-proof.

At present.The standard for waterproof is according to IP waterproof grade standard.You can see the number XX after IPXX to estimate the waterproof performance, The first number X is from zero to six.the maximum is 6,The second number is from zero to eight,so the maximum waterproofing grade is IP68.

With the development of technology,We use many application in our daily life.And the thing with electric are not very good at our safety.so It’s very important if the the application is waterproof.The waterproof connector has excellent sealing performance,reliable waterproof performance,For example,some device need to be fixed in the water or at the button of the water,Then if we use waterproof rf coaxial connectors,we don’t need to worry about the water especially the water contains many chemical substances destroy the devices.

The appearance of waterproof connector can be said to be a great blessing for us,It is widely used,We use waterproof rf coaxial connectors in many areas.Like in an industrial environment,LED lighting, urban outdoor lighting project, lighthouse, cruise ship, aviation, industrial equipment, cable, sprinkler and so on.which are all use waterproof connectors.Military field due to the application of strict requirements,Many waterproof connector are used, such as submarine connector, submarine-launched missile connector and so on.