High Density Low Cost I/O Signal Connectors Cables

The purpose of designing the MRJ21 connector is to increase the packaging density of electronic devices, improve the performance of Gigabit Ethernet (GbE), and reduce its installation time. Recent developments in I/O connector technology can help solve many of the problems associated with network upgrades and new network designs. The two primary I/O interconnects used for networking and communications are the modular jack and the “25-pair” RJ-21 connector. There are many varieties of such products, among which RJ-45 and RJ-21 type connectors are the most common. These connectors provide the reliability and simplicity necessary to allow the device to operate within the 10/100 Base-T bandwidth.

However, as the application range of this Gbit Ethernet system becomes wider and wider, many deficiencies of the existing RJ-45 and RJ-21 interconnection devices are also increasingly apparent. In order to adapt to the great leap forward of communication network products to the era of Gbit Ethernet, existing electronic products have evolved in some aspects, and new I/O connectors have also emerged as the times require.

At present, people have designed a MRJ21-type I/O connector suitable for Gbit Ethernet applications, thereby expanding the density of the existing RJ-21 I/O connector to 3 times the original. Not only that, it is also beneficial to convert the existing network system to Gbit Ethernet, and realize further upgrade of other networks. The MRJ21 miniature PC board connector developed by Tyco Electronics, shown in Figure 1, offers fully shielded and positive retention screw jack hardware. This connector can be applied to almost all network hardware devices. These networking hardware devices have traditionally come with standard stacked modular jack products or 50-pin RJ-21 connector products (Figure 2). Original equipment manufacturers (OEMs) producing Ethernet switches, network cabinets, routers, digital jumpers, DSLAMs, and similar products can modify their designs to accommodate the new MRJ21 connector.

Comparison of MRJ21 and RJ-21 connectors

Figure 1 MRJ21 Micro PC Board Connector

Connector Design Package Efficiency

Figure 2 Comparison of MRJ21 and RJ-21 connectors showing newer design packaging efficiencies

In addition to allowing networks to operate properly in Gigabit Ethernet environments, the MRJ21 connector is more compact than previous modular jack and RJ-21 designs. Higher density solutions for networking I/O interfaces have been devised. And through corresponding tests and verifications, not only can the synchronous transmission of the Gbit Ethernet system be reliably completed, but also power transmission can be performed through the Ethernet (PoE or PoLAN).

For hardware designers, the increase in connector density means that the I/O interface density can be increased by 1.5 to 3 times compared to the original stacked RJ-45 modular jack. Compared with the RJ-21 connector, the size of the MRJ21 connector is reduced by 2/3. In addition, the right-angled socket is 50% shorter than the standard stacked jack, as shown in Figure 3.

Crosstalk values for MRJ21 connector interface

Figure 3 Comparison of MRJ21 and RJ-21 connectors

Today, people can use 16 MRJ21 connectors to form 96 GbE interfaces or 192 10/100 interfaces on standard copper sheets. This also means that its Gbit Ethernet interface density is doubled compared to RJ-45 connectors, which allows each 1RU panel to generate a total of up to 48 pluggable interfaces. This reduces or simplifies the number of wiring harnesses in the terminal block. This is very attractive to original equipment manufacturers, equipment installers and users.

Figure 4 represents the crosstalk values for each of the six interfaces in a typical MRJ21 assembly. The curve (PS ELFEXT) on the figure a represents the far-end crosstalk value change curve of the first pair of connector interfaces 1, the second pair of connector interfaces 1, the third pair of connector interfaces 1 and the fourth pair of connector interfaces 1. The curves in figure b respectively represent the variation curves of near-end crosstalk values of the first pair of connector interfaces 1 , the second pair of connector interfaces 1 , the third pair of connector interfaces 1 and the fourth pair of connector interfaces 1 .

For networking hardware OEMs, the advantages of this packaging are obvious. In addition to packing more I/O interfaces into a given box design, the MRJ21 connector offers other design improvements. For example, the MRJ21 connector has electrical characteristics that can suppress alien line crosstalk to meet or exceed the specified category 5e cable requirements, and it has complete shielding performance to suppress its electromagnetic interference. In addition, the use of a screw socket provides the necessary positive locking function.

Figure 4 Crosstalk value of each of the 6 interfaces in the MRJ21 component

As interface density increases, OEMs have options to improve the functionality or features of their devices. And other advantages are provided to users in the form of spare interfaces so that users can expand or upgrade their networks. With spare interfaces, users or equipment installers can connect more devices or devices on the network, thereby achieving the purpose of further reducing costs, as shown in Figure 4.

2. MRJ21 connector structure design
As system designers are interested in a high level of technological advancement, several MRJ21 connectors with different configurations have been introduced to meet various application requirements in the Gigabit Ethernet environment and networking fields. These configurations include single-port MRJ21 (choice of panel ground and non-panel ground, through-hole solder, and press-fit, both of which have the same board layout and same size) and dual- and quad-port MRJ21s with integrated magnetics Connector components.

MRJ21 interconnects have been designed to be simpler and have lower crosstalk noise levels than RJ-45 and RJ-21 interconnects. It minimizes the possibility of causing alien crosstalk and creates a method of noise compensation that does not require the myriad of proprietary RJ-45 interconnects. These design features can maintain continuity and excellent link electrical characteristics, making interconnect devices more suitable for gigabit applications.

The structural design of the connector

Figure 5, RJ-45 interconnect device interface

Network system installers using MRJ21 connectors and cable assemblies are also seeing improved performance. First, the switch’s cable management has been further improved because it requires only one cable (compared to six cables required in Gigabit Ethernet or 10/100/1000 applications). And in 10/100 applications, the number of cables is also reduced from 12 to 1. Moreover, the only cable is about 30% smaller than the cross-sectional area of the corresponding six 4-pair cables. In addition, due to the increased density of the PCB board, the resulting I/O interconnection device has a smaller form factor, and the visibility of the sensitivity display on the hardware is also greatly improved. Overall costs to end equipment users may also be further reduced.

MRJ21 Micro PC Board Connector

Figure 6 Structural design diagram of MRJ21 connector

After using the MRJ21 connector in infrastructure cabling, equipment manufacturers and service providers can expect additional advantages. In addition, a dedicated study of the four associated cost savings (labor, space, time and maintenance) also shows that MRJ21 cable devices can provide many potential cost-saving opportunities.

In labor cost studies, it has been estimated that using MRJ21 connectors can save $3.50 to $14 per interface in direct installation costs compared to traditional RJ-45 based cables. The study also showed that the space occupied by MRJ21 connectors installed in the above equipment can save about $4.50/interface per year, because the data center can occupy less space. In the high-cost and important application environment of this study, the savings in the area occupied by the equipment can reach more than 50%.

In addition, the study concluded that the time required to connect the data center is about 1/6 of the time spent on traditional wiring. Finally, the study demonstrated significantly less downtime for switch replacement or restoration of functionality.

Figure 4 Crosstalk value of each of the 6 interfaces in the MRJ21 component

As interface density increases, OEMs have options to improve the functionality or features of their devices. And other advantages are provided to users in the form of spare interfaces so that users can expand or upgrade their networks. With spare interfaces, users or equipment installers can connect more devices or devices on the network, thereby achieving the purpose of further reducing costs, as shown in Figure 4.

2. MRJ21 connector structure design
As system designers are interested in a high level of technological advancement, several MRJ21 connectors with different configurations have been introduced to meet various application requirements in the Gigabit Ethernet environment and networking fields. These configurations include single-port MRJ21 (choice of panel ground and non-panel ground, through-hole solder, and press-fit, both of which have the same board layout and same size) and dual- and quad-port MRJ21s with integrated magnetics Connector components.

MRJ21 interconnects have been designed to be simpler and have lower crosstalk noise levels than RJ-45 and RJ-21 interconnects. It minimizes the possibility of causing alien crosstalk and creates a method of noise compensation that does not require the myriad of proprietary RJ-45 interconnects. These design features can maintain continuity and excellent link electrical characteristics, making interconnect devices more suitable for gigabit applications.

RJ-45 interconnect device interface

Figure 5, RJ-45 interconnect device interface

Network system installers using MRJ21 connectors and cable assemblies are also seeing improved performance. First, the switch’s cable management has been further improved because it requires only one cable (compared to six cables required in Gigabit Ethernet or 10/100/1000 applications). And in 10/100 applications, the number of cables is also reduced from 12 to 1. Moreover, the only cable is about 30% smaller than the cross-sectional area of the corresponding six 4-pair cables. In addition, due to the increased density of the PCB board, the resulting I/O interconnection device has a smaller form factor, and the visibility of the sensitivity display on the hardware is also greatly improved. Overall costs to end equipment users may also be further reduced.

MRJ21 connector structure design drawing

Figure 6 Structural design diagram of MRJ21 connector

After using the MRJ21 connector in infrastructure cabling, equipment manufacturers and service providers can expect additional advantages. In addition, a dedicated study of the four associated cost savings (labor, space, time and maintenance) also shows that MRJ21 cable devices can provide many potential cost-saving opportunities.

In labor cost studies, it has been estimated that using MRJ21 connectors can save $3.50 to $14 per interface in direct installation costs compared to traditional RJ-45 based cables. The study also showed that the space occupied by MRJ21 connectors installed in the above equipment can save about $4.50/interface per year, because the data center can occupy less space. In the high-cost and important application environment of this study, the savings in the area occupied by the equipment can reach more than 50%.

In addition, the study concluded that the time required to connect the data center is about 1/6 of the time spent on traditional wiring. Finally, the study demonstrated significantly less downtime for switch replacement or restoration of functionality.

Advances in I/O Interconnect Devices

One of the most advanced I/O application areas for next-generation modular jacks is 10/100 Base-T transmission, Gigabit Ethernet, and Power Ethernet integration. The essence of 10/100 Base-T transmission and Gbit Ethernet is basically the same thing. It’s just that transferring power through an Ethernet connector is a relatively new problem, and the interconnects used in such applications require careful consideration.

Transmitting high-speed signals through a network is a challenge in itself, and adding the burden of low-power devices to the network places new challenges on an interconnect system.

First, because transmitting high-speed signals over a network that already carries the signal itself is prone to interference, it is extremely important to protect the signal contacts from interference that may occur in the lower power regions of the interconnection system. Some designers may choose to properly filter the interconnect leads on the board to reduce interference. However, this increases the complexity of the circuit board processing in the manufacturing process, increases the corresponding cost and requires more effort.

Yet another option is to use an integrated or combined MRJ21 connector. The combined MRJ21 connector can realize 10/100/1000 Base-T transmission, and can also use PoE pins. The combination of integrated magnetics and power management eliminates the need for time-consuming and costly board-level solutions.

Integrated magnetics provide some of the following essential functions:
(1) Provide the DC insulation requirements proposed in IEEE 802.3 and IEC 60950;
(2) Provide the anti-electromagnetic interference (EMI) function of the normal mode;
(3) The DC power supply can be applied to the PoE field by using integrated magnetic components.

When the MRJ21 crimp gang connector switch is applied to Ethernet, the advantages of power devices with network support can be further extended throughout the network.

One of the important attributes of the MRJ21 ganged magnetics connector is its flexibility. The connector can be designed as non-PoE or with PoE function. With this design approach, network systems transitioning from 10/100 and GbE 802.3af-compliant PoE is much easier.

in conclusion:
Product development seems to have gotten easier in recent years, further proving the role of I/O interconnects and taking them to the next level. These next-generation I/O connectors can provide higher packaging density and performance, not only to improve their shipping and handling conditions, but also to further improve their manufacturing process. As such, it affects not only OEMs, but also installers and users of equipment. Most importantly, the application of these new I/O interconnect devices can not only make Gbit Ethernet and active Ethernet easier to implement, but also further improve network functions and work efficiency.