Magnetics play an important role in Ethernet-based local area network (LAN) designs, and especially so as network infrastructure evolves to handle NBASE-T technologies. Integrated connector modules (ICMs) offer ideal solutions for new multi-rate Ethernet LAN device designs.
By Bel Magnetic Solutions NBASE-T
The continued adoption of powerful mobile devices being fed by cloud-based applications streaming rich content, such as HD video, is putting pressure on existing Ethernet networks. One-gigabit (1Gb/s) Ethernet and the associated Cat5e and Cat6 cabling infrastructures are fast becoming a bottleneck in corporate and home networks, which are struggling to keep pace with rising bandwidth demands.
NBASE-T Technology Increases the Speed of Cat5e/Cat6 Cables to 5Gb/s
Due to the high “rip and replace” costs of installed Cat5e and Cat6 cabling infrastructure, 10GBASE-T technology is currently only economically viable for greenfield developments or refurbishments. The introduction of NBASE-T technology, which can increase network speeds of existing Cat5e/Cat6 cables to up to 5Gb/s at lengths up to 100m, means NBASE-T solutions are being widely deployed to provide content creators, broadband consumers, and others a low-cost path to multigigabit speeds.
Since its development in the early 1970s, Ethernet bandwidth has increased dramatically to support the evolving demands of local area computer networks. From the original 10Mb/s, Ethernet speeds have moved through a series of progressions, including Fast Ethernet at 100Mb/s and Gigabit Ethernet at 1Gb/s or 1000BASE-T. Cabling standards have evolved to support these increasing speeds, evolving from coaxial cables to unshielded twisted pair through to Cat5e and Cat6 cables, which comprise much of the installed cable base in today’s offices and campuses. Modern devices and applications, such as wireless access points and servers, along with the explosive growth of video content and cloud applications, are demanding more bandwidth than the 1Gb/s supported by 1000BASE-T.
The 10GBASE-T or 10-gigabit Ethernet standard was defined in the IEEE 802.3ae-2002 standard to specify the networking technologies required to support transmission of Ethernet frames at rates up to 10Gb/s. The roll-out of 10GBASE-T has been more gradual than previous revisions of Ethernet, partially due to the relatively high costs per port of the new technology but mainly because Cat5e/6 cable infrastructure can’t fully support the standard. 10GBASE-T requires an upgraded cable standard — Cat6a — which means that companies would be looking at significant costs to replace existing cable infrastructure.
NBASE-T Alliance Formed in 2014
To address this issue, a number of industry players, including Cisco, Aquantia, NXP, and Intel, formed the NBASE-T alliance in 2014 to introduce specifications for two intermediate transmission speeds: 2.5GBASE-T and 5GBASE-T. The NBASE-T specifications were ratified by the IEEE and released in a new standard, IEEE 802.3bz. The NBASE-T specification includes a downshifting feature, which allows devices to maximize the link speed in real time by stepping down from the ideal link speed of 10G to 5G or 2.5G when the noise in the system is too great. N-BASE-T devices can auto-negotiate to find the best speed for the network, either the NBASE-T rates, slower 100Mb/s and 1Gb/s, or even 10Gb/s if the infrastructure allows.
NBASE-T Supports Power-over-Ethernet
NBASE-T also supports Power-over-Ethernet (PoE), which is fundamental in enterprise deployments, as well as large-building infrastructures, such as airports, shopping malls, and stadiums. All PoE standards are covered and the technology also compensates for the variety of different power spectrums that can be encountered by a device due to varying link speeds within the same cable bundle.
This new standard enables businesses to leverage existing cable investments; Cat5e and Cat6 installations can continue to be used by replacing the devices on either end of the cables, with new ones conforming to the IEEE 802.3bz standard.
Devices connecting to Ethernet cables within homes, offices, and campuses include Ethernet switches, wireless access points, base stations, and security cameras. These devices will include a PHY, a component that implements the Ethernet physical layer portion of the various Ethernet standards: 10GBASE-T, NBASE-T, 1000BASE-T, 100BASE- TX, and 10BASE-T. A block diagram of a typical PHY is illustrated in Figure 1, which shows a device based on the DP83822 10/100 Ethernet PHY transceiver chip by Texas Instruments. The majority of the functionality of the PHY device is digital, with the exception of the “magnetics,” an analogue circuit designed to meet the electrical interfacing requirements of the IEEE 802.3 10/100/1000BASE-T specifications. Magnetics address the key electrical interfacing requirements, including electrical isolation, signal balancing, common-mode rejection, impedance matching, and EMC improvement, and, as such, are critical to the operation of the PHY.
Integrated connector modules (ICMs) incorporate all of the circuitry for the magnetics within a single connector, thereby saving space on the PHY board and avoiding mixing digital and analogue circuitry on the same chip. Transmission speeds of up to 10Gb/s highlight any design flaws or physical imperfections, such as board layout issues and differential pair mismatches, which may lead to electromagnetic interference (EMI) and cause a module to fail electromagnetic compatibility (EMC) requirements.
ICM Critical to Controlling EMI Emission and Susceptibility
In this environment, ICMs are a critical component, as choosing the right LAN magnetic components with proper performance and good EMI suppression is key to controlling EMI emission and susceptibility. As transmission speeds have continued to increase, LAN magnetics have become increasingly complex, so LAN system designers need to choose the right magnetics solutions from well-known magnetics manufacturers.
Existing Cat5e and Cat6 cabling installations are being upgraded to take advantage of the higher speeds afforded by the new NBASE-T specifications. End devices such as switches and network access points (NAPs) are being replaced with NBASE-T equivalents in order to extend the working life of the in-building cabling.
At the faster speeds of NBASE-T, LAN systems are more susceptible to EMI and good design is key to ensuring system performance. LAN magnetics are a critical component when designing out EMI and designers should ensure that they choose a quality ICM from an experienced supplier.
Visit Bel Magnetic Solutions, a Bel group company, to learn more about ICM solutions.