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RF coaxial connector application

Author: Date:3/8/2019 7:32:55 AM
What is a RF coaxial connector:

 RF coaxial connectors (RF connectors) are generally considered to be components attached to a cable or mounted on an instrument as electrical connecting or separating elements of the transmission line. It belongs to mechatronic products. In simple terms: For example, if two objects need to be linked together, an intermediate is required, and the connector is the intermediate, the left and right of the bridge, and the two objects are linked together.




RF connector classification:

First, according to the connection interface structure is divided into:

1. bayonet style (inner bayonet, outer bayonet): BNC;

2. Thread type (right hand thread, left hand screw): 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;

3. Push-in (inline, self-locking): SMB, SSMB, MCX, MMCX, SMP, SMI, BMA, SAA;

4. Flange connection type.

Second, according to size classification:

1. Standard type: UHF, N, 7/16, 7mm;

2. Small: BNC, TNC;

3. Ultra-small: SMA, SMB, SMC, MCX, BMA, SAA, 3.5mm;

4. Micro: SSMA, SSMB, MMCX, 2.4mm, K (2.92mm), 1.85mm, 1mm;


RF connector main specifications:


1. Impedance: Almost all RF connectors and cables are standardized to 50 Ohm impedance, the only exception being the 75 Ohm system commonly used for cable TV installations, it is also important for RF coaxial connectors to have matching cables The characteristic impedance. If not, a discontinuity can be introduced and lost.


2. Voltage Standing Wave Ratio (VSWR): In ideal situations should be solidarity, good design and implementation can keep VSWR below 1.2 in the range of interest.


3. Frequency Range: Most RF work is now in the 1 to 10 GHz range, so the connector must be low loss in this area. For the case of more than 10GHz - there is a lot of work and things are now in the range of 10 to 40GHz - there are newer connectors to choose from. They are expensive because it is the cable itself.


4. Insertion loss: This is the connector loss in the frequency range of interest, typically 0.1 and 0.3 dB. Determining how critical each watt (or fractional watt) is in most designs, even such small losses must be minimized to account for the link loss budget. It is especially important in low noise front-ends when signal strength and signal-to-noise ratio are low.


5. Operating cycle: How many connection/disconnection cycles can be connected and still meet its specifications? This is usually at 500 or 1000 cycles.


6. Power: Power handling is determined by two resistive losses (heating) and insulation breakdown. Although even decades of design are mostly pre-processing tens of watts, today's design community focuses on low-power devices such as mobile phones, picocells and femtocells, video interfaces, RF and gadgets. These are in the sub 1W range, so the connector can be much smaller and its rated power is a smaller constraint.


Example of radio frequency connector model composition:

Example 1: MCX-JW3 indicates MCX bending type RF plug. The inner conductor of the plug is a pin contact and it is equipped with SYV-50-3, RG-58/U and other RF cables.

Example 2: BNC-KWE indicates that the BNC is bent to a 50Ω impedance RF socket on a printed circuit board.

Example 3: SMA-C-J1.5 indicates SMA straight type RF plug. The inner conductor is a pin contact and it is equipped with SFF-50-1.5-1, RG-174/U and other RF cables. The termination type is crimping. formula.


RF coaxial connector features:


1. Slow product replacement.


2. The parts processing is mainly turning machine processing, assembly manual work, it is difficult to automate the assembly.


3. Mechanical features ensure electrical characteristics, which are electromechanical integration products, and are essentially different from other low-frequency connectors.


4. Product reliability, failure modes and failure mechanisms are complex.


5. Many types of specifications: more than 20 international series, more variety specifications.


RF coaxial connector application:


1. Communications, communications and networks;


2. Traffic monitoring system;


3. Medical machinery;


4. Instrumentation connection.


Due to the characteristics of RF coaxial connectors, it is not only widely used in automobiles, information communications, communications and broadcasting, communications networks, instrument testing, medical, aerospace, transportation, and antennas, but also in security systems, civil aviation, microwave components, and radio frequency. Microwave switches, consumer electronics, defense, military and other occasions and equipment. The main technical characteristics of RF coaxial connectors fall into two categories: First, mechanical parameters and first, electrical parameters.


RF coaxial connector selection:


1. Interface mechanism type: The connection mechanism of the connector not only provides convenient and quick connection or separation of the coaxial transmission line, but also provides stable electrical performance and environmental protection devices. When there is not enough space for rotating the connection nut in the occasion of use, Non-twist type connection mechanism should be selected.


2. Termination: The connector can be used for radio frequency coaxial cable, printed circuit board, chassis drawer functional components and its connection interface. Before use, you must be familiar with the performance of the selected product and use it in strict accordance with the specified conditions. Overloaded use may cause failure of the coaxial connector. Special attention must be paid when attaching the cable connector. The assembly instructions provided by the supplier must be correct. Use a suitable attachment tool for operation.

3. Electrical performance: characteristic impedance, withstand voltage and maximum working efficiency.


RF coaxial connector development status:

 RF coaxial connectors (abbreviated as RFCs) are generally considered as components attached to a cable or mounted on an instrument as electrical connecting or separating elements of the transmission line. It belongs to mechatronic products. Simply speaking, it mainly serves as a bridge.

        RFCs have a shorter history than other electronic components. There are two arguments, one saying that the UHF connector that appeared in 1930 was the earliest RF connector. However, I believe that the UHF connector cannot be considered as a RF coaxial connector from its use occasion or its basic design. It can only be called a coaxial connector at most.

 In the second way, BNC is the earliest RF coaxial connector r. During World War II, due to the urgent needs of the war, the destruction of various types of carrier-borne airborne electronic equipment caused a large number of US air and sea combat weapons to be repaired. In order to compress repair time, the US Department of the Navy focused on some outstanding scientific researchers and engineers. Within a short period of time, the inventor of a quick-release and separate connector, the Bayonets-Navy® Connector (BNC), became the originator of RF coaxial connectors worldwide.  

With the development of radar, radio and microwave communications, N, C, TNC, and other series have emerged. After 1958, miniaturized products such as SMA, SMB, and SMC emerged. In 1964, the US military standard MIL-C-39012 was established. "RF coaxial connector general specification", since then, RFC began to standardize, serialization, general direction.

 In more than 60 years, through the joint efforts of professional technicians and engineers from various countries, RFC has formed an independent and complete professional system and has become an important part of the large family of connectors. It is an indispensable key component of the coaxial transmission system. The RFC research and development technologies in Europe and the United States are in a leading position. Their design, production, testing, and use technologies have become complementary and perfect. They not only form a complete standard system, but also have standardized raw materials, auxiliary materials, test systems, and assembly tools. And to carry out professional scale production.  

 In the aspect of assembly automation, RFCs generally use manual operation or semi-automatic due to the characteristics of multiple varieties, small batches, and discontinuities. The most outstanding is the French Radiale, which hasfully automated assembly of some production lines with huge production volumes and continuous production. Of course, the high wages and vacations of French workers are the original driving force for Radial’s automation.