Agilent 5990-9346EN Stressing 1 GbE Receivers on the Physcial Layer - Application Note c20141103 [9] free download

File name 5990-9346EN Stressing 1 GbE Receivers on the Physcial Layer - Application Note c20141103 [9].pdf

Keysight Technologies Stressing 1 GbE Receivers on the Physical Layer Application Note More eficient and effective tests with a new generation of test instruments Introduction 1000Base-T Ethernet, and the technical challenges it creates for design and test The standard for the 1000Base-T Ethernet (IEEE 802.3ab) describes data rates of 1 Gb/s over a star topology, over up to 100 meters of Category 5 (or better), unshielded, balanced, twisted-pair, copper cable. To make the 1000BASE-T physical layer standard as compatible as possible with existing standards, it reuses aspects of the existing IEEE 100BASE-TX, 100BASE-T4, and 100BASE-T2 standards. In particular, the 125 Mbaud baseband signaling from 100BASE-TX, the use of all four twisted pairs simultaneously for full duplex transmission from 100BASE-T4, and the 5-level pulse amplitude modulation (PAM5) from 100BASE-T2. This enables dual-speed 100/1000 Ethernet physical layer implementations to reuse existing infrastructures. Cherry-picking elements from existing standards also helped reduce the time taken to develop the newer standard. Baseband signaling at a modulation rate of 125 Mbaud over each twisted pair matches the GMII clock rate of 125 MHz, as used for 100BASE-TX, and results in a symbol period of 8 ns. Each twisted pair also uses ive-level (-2, -1, 0, +1, +2), Pulse Amplitude Modulation (PAM5) to transmit 2-bits per symbol. The resulting data rate of 250 Mb/s in one direction over each twisted pair achieves a combined data rate of 1000 Mb/s. Furthermore, by using canceller symbols and magnetic hybrids (for echo cancellation), 1000BASE-T can optionally transmit and receive simultaneously on each twisted pair, to achieve full-duplex transmission at 2000 Mb/s. 03 | Keysight | Stressing 1 GbE Receivers on the Physical Layer - Application Note The design implications for 1000BASE-T receivers Gigabit Ethernet promises a cost effective migration to 1000BASE-T for installations that are already running 10/100Base-T over Category 5 cabling. However, because these installations were originally only speciied to 10Base-T or 100Base-T, this is also a potential weakness. Inadequate cabling can introduce distortions, attenuation, noise (including cross-talk and echoes that have not been properly removed by the hybrids), and propagation delay, and delay skew between the different twisted pairs. Distortion Attenuation Noise Delay TDX RDX T R