Howard Johnson is an electrical engineer, known for his consulting work and commonly referenced books on the topic of signal integrity, especially for high speed electronic circuit design. He served as the chief technical editor for Fast Ethernet and Gigabit Ethernet standardisation, [1] and was recognized by the IEEE as an "Outstanding Contributor" to the IEEE P802.3z Gigabit Task Force. [2]
Johnson earned his Bachelor of Science in Electrical Engineering (1978), Masters of Electrical Engineering (1979), and PhD (1982) from Rice University. His dissertation was titled The design of DFT algorithms.
Johnson has significantly raised awareness of analog effects at work in high speed digital electronic systems.
In modern digital systems, it is common for digital designs to be subject to analog effects, even if they operate at a relatively low clock frequency. Circuits operating at lower clock rates can behave as high speed digital systems if there is sufficient high frequency content in the signal edges (when transitioning between digital logic levels) relative to the distance traveled across a printed circuit board. As a result of improvements in semiconductor process, faster edge rates of even "low technology" electronic components can be sufficient to make the system effectively high speed and thus subject to havoc caused by unanticipated analog effects.
A good example is his illustration of the matrix of rising edges that result from different combinations of skin-effect and dielectric loss [3] which illustrates PCB design problems one encounters at microwave frequencies.
Johnson was also active in the development of two Institute of Electrical and Electronics Engineers (IEEE) standards that govern Ethernet, IEEE 802.3 Fast Ethernet and IEEE 802.3 Gigabit Ethernet.
Johnson has written three books:
Johnson also ran a monthly column at EDN (magazine) entitled Signal Integrity, which was later moved to a blog format.
He signed off with his last post "Seek inspiration" on 24 June 2013.
Ethernet over twisted-pair technologies use twisted-pair cables for the physical layer of an Ethernet computer network. They are a subset of all Ethernet physical layers.
A signal generator is one of a class of electronic devices that generates electrical signals with set properties of amplitude, frequency, and wave shape. These generated signals are used as a stimulus for electronic measurements, typically used in designing, testing, troubleshooting, and repairing electronic or electroacoustic devices, though it often has artistic uses as well.
Category 5 cable (Cat 5) is a twisted pair cable for computer networks. Since 2001, the variant commonly in use is the Category 5e specification (Cat 5e). The cable standard provides performance of up to 100 MHz and is suitable for most varieties of Ethernet over twisted pair up to 2.5GBASE-T but more commonly runs at 1000BASE-T speeds. Cat 5 is also used to carry other signals such as telephone and video.
Pulse-amplitude modulation (PAM) is a form of signal modulation where the message information is encoded in the amplitude of a series of signal pulses. It is an analog pulse modulation scheme in which the amplitudes of a train of carrier pulses are varied according to the sample value of the message signal. Demodulation is performed by detecting the amplitude level of the carrier at every single period.
In computer networking, Fast Ethernet physical layers carry traffic at the nominal rate of 100 Mbit/s. The prior Ethernet speed was 10 Mbit/s. Of the Fast Ethernet physical layers, 100BASE-TX is by far the most common.
In computer networking, Gigabit Ethernet is the term applied to transmitting Ethernet frames at a rate of a gigabit per second. The most popular variant, 1000BASE-T, is defined by the IEEE 802.3ab standard. It came into use in 1999, and has replaced Fast Ethernet in wired local networks due to its considerable speed improvement over Fast Ethernet, as well as its use of cables and equipment that are widely available, economical, and similar to previous standards. The first standard for faster 10 Gigabit Ethernet was approved in 2002.
In the seven-layer OSI model of computer networking, the physical layer or layer 1 is the first and lowest layer: the layer most closely associated with the physical connection between devices. The physical layer provides an electrical, mechanical, and procedural interface to the transmission medium. The shapes and properties of the electrical connectors, the frequencies to broadcast on, the line code to use and similar low-level parameters, are specified by the physical layer.
Electronic test equipment is used to create signals and capture responses from electronic devices under test (DUTs). In this way, the proper operation of the DUT can be proven or faults in the device can be traced. Use of electronic test equipment is essential to any serious work on electronics systems.
This is an index of articles relating to electronics and electricity or natural electricity and things that run on electricity and things that use or conduct electricity.
The media-independent interface (MII) was originally defined as a standard interface to connect a Fast Ethernet media access control (MAC) block to a PHY chip. The MII is standardized by IEEE 802.3u and connects different types of PHYs to MACs. Being media independent means that different types of PHY devices for connecting to different media can be used without redesigning or replacing the MAC hardware. Thus any MAC may be used with any PHY, independent of the network signal transmission media.
Differential signalling is a method for electrically transmitting information using two complementary signals. The technique sends the same electrical signal as a differential pair of signals, each in its own conductor. The pair of conductors can be wires in a twisted-pair or ribbon cable or traces on a printed circuit board.
The 10 Gigabit Ethernet Alliance (10GEA) was an independent organization which aimed to further 10 Gigabit Ethernet development and market acceptance. Founded in February 2000 by a consortium of companies, the organization provided IEEE with technology demonstrations and specifications. Its efforts bore fruit with the IEEE Standards Association (IEEE-SA) Standards Board's approval in June 2002 of the IEEE 802.3 standard.
Signal integrity or SI is a set of measures of the quality of an electrical signal. In digital electronics, a stream of binary values is represented by a voltage waveform. However, digital signals are fundamentally analog in nature, and all signals are subject to effects such as noise, distortion, and loss. Over short distances and at low bit rates, a simple conductor can transmit this with sufficient fidelity. At high bit rates and over longer distances or through various mediums, various effects can degrade the electrical signal to the point where errors occur and the system or device fails. Signal integrity engineering is the task of analyzing and mitigating these effects. It is an important activity at all levels of electronics packaging and assembly, from internal connections of an integrated circuit (IC), through the package, the printed circuit board (PCB), the backplane, and inter-system connections. While there are some common themes at these various levels, there are also practical considerations, in particular the interconnect flight time versus the bit period, that cause substantial differences in the approach to signal integrity for on-chip connections versus chip-to-chip connections.
The physical-layer specifications of the Ethernet family of computer network standards are published by the Institute of Electrical and Electronics Engineers (IEEE), which defines the electrical or optical properties and the transfer speed of the physical connection between a device and the network or between network devices. It is complemented by the MAC layer and the logical link layer.
40 Gigabit Ethernet (40GbE) and 100 Gigabit Ethernet (100GbE) are groups of computer networking technologies for transmitting Ethernet frames at rates of 40 and 100 gigabits per second (Gbit/s), respectively. These technologies offer significantly higher speeds than 10 Gigabit Ethernet. The technology was first defined by the IEEE 802.3ba-2010 standard and later by the 802.3bg-2011, 802.3bj-2014, 802.3bm-2015, and 802.3cd-2018 standards. The first succeeding Terabit Ethernet specifications were approved in 2017.
10 Gigabit Ethernet is a group of computer networking technologies for transmitting Ethernet frames at a rate of 10 gigabits per second. It was first defined by the IEEE 802.3ae-2002 standard. Unlike previous Ethernet standards, 10GbE defines only full-duplex point-to-point links which are generally connected by network switches; shared-medium CSMA/CD operation has not been carried over from the previous generations of Ethernet standards so half-duplex operation and repeater hubs do not exist in 10GbE. The first standard for faster 100 Gigabit Ethernet links was approved in 2010.
Terabit Ethernet or TbE is Ethernet with speeds above 100 Gigabit Ethernet. 400 Gigabit Ethernet and 200 Gigabit Ethernet standards developed by the IEEE P802.3bs Task Force using broadly similar technology to 100 Gigabit Ethernet were approved on December 6, 2017. In 2016, several networking equipment suppliers were already offering proprietary solutions for 200G and 400G.
Electronic engineering is a sub-discipline of electrical engineering which emerged in the early 20th century and is distinguished by the additional use of active components such as semiconductor devices to amplify and control electric current flow. Previously electrical engineering only used passive devices such as mechanical switches, resistors, inductors, and capacitors.
25 Gigabit Ethernet and 50 Gigabit Ethernet are standards for Ethernet connectivity in a datacenter environment, developed by IEEE 802.3 task forces 802.3by and 802.3cd and are available from multiple vendors.
IEEE 802.3bz, NBASE-T and MGBASE-T are standards for Ethernet over twisted pair at speeds of 2.5 and 5 Gbit/s. These use the same cabling as the ubiquitous Gigabit Ethernet, yet offer higher speeds. The resulting standards are named 2.5GBASE-T and 5GBASE-T.