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RF coaxial connectors:Classification, Size and Application

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The RF coaxial connector is a subdivision of electronic connectors and a hot topic. Below, Superlink Technology (SLK) will provide some professional introductions to the classification, size and application of RF coaxial connectors.

RF coaxial connectors are divided into four categories based on their form factor: standard, miniature, sub-miniature, and micro-miniature. Early coaxial cables were much larger than the coaxial cables that are commonly used today, so early RF coaxial connectors were large, and this classification reflects the evolution of coaxial connectors.

Standard (standard):

UHF (Ultra-High-Frequency, RF) coaxial connectors were invented by Amphenol engineers E. Clark Quackenbush in the 1930s and used in wireless broadcasting. The UHF male is often referred to as the PL-259 connector (US Army Standard Part No.). UHF uses a threaded interface and its characteristic impedance is not fixed. Because the characteristic impedance is not constant, UHF can only be applied within 300MHz. It is commonly used in lower frequency communication devices such as CB radio broadcast and cable broadcast systems, and is a lower cost connector.

The N-type RF coaxial connector was invented by Paul Neill of Bell Labs, the first in the history of RF coaxial connectors to be used in the microwave field. The N connector is available in a threaded connection and is available in 50 and 75 ohm versions. The 50 ohm N head can be used in 11 GHz applications, and the precision N head is even applied to the 18 GHz environment. Typical applications include LAN, test equipment, satellite and military communication equipment.

The C series was successfully developed by Concel. It is connected by internal bayonet. The internal nominal size and working frequency are the same as those of the N series, but there is no N series.

Other standard RF coaxial connector series include SC, HN, 7/16, APC-7.MinDin.

Small RF coaxial connector:

BNC RF coaxial connector was invented in the 1940s and is one of the most popular RF coaxial connectors. BNC is the abbreviation of Bayonet-Neill-Concelman. Bayonet indicates that the interface is connected by bayonet. Neill and Concelman respectively. It is the inventor of N-type and C-type RF coaxial connectors. The BNC is actually a small version of the C-type connector, and the C-type connector is a bayonet version of the N-type connector. The biggest feature is that the connection is convenient, and it is generally connected by rotating the connection sleeve less than one turn. Suitable for frequent connection and separation, it is the most versatile and cheap product. The BNC is available in 50 and 75 ohm versions and is compatible with each other. The 50 ohm BNC can be used in 4 GHz applications, such as flexible networks, inspection equipment, computer peripheral connections, monitoring systems, especially in the field of instrumentation, network and computer information.

The TNC RF coaxial connector was invented in the 1950s. TNC is the abbreviation of Threaded-Neill-Concelman, Threaded indicates that the interface is threaded, and Neill and Concelman are the inventors of N-type and C-type RF coaxial connectors, respectively. The TNC was invented because the BNC produced noise in a vibrating environment. It is a threaded version of the BNC. It is applied at frequencies up to 11 GHz. It is often used in vibration environments. Military and aerospace are typical applications. F head, 75 ohm threaded RF coaxial connector, standard connector of CATV system, mainly connected with RG59, RG6 and RG11 RF coaxial cable, mainly one-piece (without crimping tube) and two-piece structure (with pressure) take over). The joint has good economy, low cost and convenient installation, especially a one-piece structure. Other small RF coaxial connector series include SHV, MHV, and Mini-UHF.

Ultra-small RF coaxial connector:

SMA (Sub-Miniature-A) RF coaxial connector was invented in 1958 by James Cheal of Bendix Corporation of the United States. It was used to solve the problem of TEM mode conversion between coaxial and microstrip because of its small size and structure. Simple, high-frequency bandwidth, high reliability, and so on, it is widely used in aerospace systems, microwave communications engineering, military weapons. At present, SMA has become the most versatile RF connector with the most versatile specifications and the largest amount in the world, and its inventors have won the World Microwave Application Award. SMA operating frequency 0 ~ 18GHz, adapt to 3 ~ 5mm soft, semi-flexible, semi-rigid cable. The SMA was developed for the 141 (RG402) semi-rigid cable, so the inner conductor of the RG402 coaxial cable can be directly used as the inner conductor of the SMA. This structure has excellent transmission performance. The SMA is threaded and precision grades can be used up to 26.5 GHz. Its maximum frequency of use is limited by the cable to which it is connected. The advantages of SMA are high frequency of use, small size, and stable connection. SMA is widely used in the microwave field: coaxial cable to waveguide, coaxial cable to PCB microstrip, SMA can also be seen in amplifiers, attenuators, filters, mixers, crystals and switches.

SMB (Sub-Miniature-B) RF coaxial connector is a push-in connector with a stopper. It is developed according to the market demand for quick insertion and removal of the connector. The center positioning function and overlap of the outer conductor shrapnel The insulator makes the SMB easy to buckle and maintain good performance in a vibrating environment. It has the advantages of small size, convenient insertion and removal, good vibration resistance and small footprint. It is widely used in working frequencies from 0 to 4 GHz. Communication equipment, instrumentation and navigation systems, application of RF or digital signal connections between PCB boards and PCB boards... SMB is available in 50 ohm and 75 ohm versions, some connector manufacturers are 50 ohm SMB and 75 ohm Can be matched, and some manufacturers are not.

SMC (Sub-Miniature-C) RF coaxial connector is similar in structure to SMB. It is a threaded deformation of SMB. Its internal structure is the same as that of SMB. The operating frequency is 0 to 11 GHz. The inner conductor and the overlapping insulator structure and SMB. It is identical, but the SMC uses a threaded connection instead of a snap. The more precise control of the position of the inner conductor and the insulator and the connection structure of the thread allow the 50 ohm SMB to operate at a frequency of 10 GHz, and the SMC is a good choice for environments with small size requirements and high vibration. SMC is commonly used in microwave telephony and non-military communication equipment, and is commonly used in military equipment such as radar and navigation. Other ultra-small RF coaxial connector series include SMK/K (2.92mm), 2.4mm, 3.5mm, BMA (Blind Insert).

Ultra-miniature RF coaxial connector:

With the trend toward miniaturization of connectors, ultra-small connectors have been further reduced, and connector suppliers have developed ultra-miniature coaxial connectors.

MCX (Micro Coaxial) was developed in Europe in the 1980s. The structure is very similar to that of SMB. The inner conductor and the overlapping insulator structure are identical to those of SMB. They also use a snap-fit ??connection structure, but it flips the center positioning structure of the outer conductor shrapnel. Looking outward, this makes the head much smaller. The reliability of the MCX is no less than that of the SMB, but the shape and body are about 30% smaller than the SMB. The 50-ohm MCX can operate in the 6 GHz environment. It can work in the traditional SMB and provide more space. Its basic functions are similar to those of SMB, and there is a trend to replace SMB. Applications for MCX include GPS (Global Positioning System), automotive, mobile, and data communications.

MMCX (Micro-MCX) was developed in Europe in the 1990s and is also used for quick insertion and removal, but it is 45% smaller than SMB, and the male and female connectors can rotate freely relative to 360° during operation. Intermittent, ideal for applications such as miniature antennas.

BMA series, also known as blind plug connector, operates at 0 to 22 GHz. The internal nominal size and cable are the same as SMA. The fixed socket has a certain amount of floating in the axial and radial directions, which can realize modular building, modular whole machine system and fast blind plug replacement, mainly used for military products and CDMA communication equipment.

The SAA series (DIN47297) is a push-in self-locking connector available in 50Ω and 75Ω. At present, there are a large number of applications in communication systems such as program-controlled switches and optical transceivers.

The SSMA series features similar features to the SMA, but with a smaller size and operating frequency up to 40 GHz, it is the only standard millimeter-wave connector available.

The SSMB series features similar features to SMB and is smaller in size and is commonly used in military radio stations.

Other ultra-miniature RF coaxial connector series include: SSMC, SMP, MC-card, MHF.
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