Signal Integrity

Browse our library of resources to learn more about pcb design and signal integrity.

Tools for Transient Signal Analysis in Circuit Design You can perform transient signal analysis with any of these circuits with the right simulator. I still remember my first differential equations class. One of the first topics that was discussed was damped oscillator circuits and transient signal response, which arises in many different physical systems. A transient response in an interconnect and on power rails in your PCB is a source of bit errors, timing jitter, and other signal integrity Read Article

What is the Return Current Path in a PCB? Do you know how to determine the return current path in this PCB layout? One of the fundamental aspects of any circuit diagram is the return current path. In a circuit diagram and a schematic diagram, the path that electric current follows to return to the low potential side of a power source should be obvious, but it may not be so obvious in a PCB. To quote the great Eric Bogatin at his PCB West 2019 presentation, the distinction between a Read Article

RF Signal Chain Design for FMCW Chirped Radar Systems If you could hear the output from your chirped radar system, it might sound like a brahminy starling In automotive and UAV radar applications, radar signals are amplified throughout the signal chain. Amplification is critical for ensuring the reflected signal can be accurately detected and for maximizing the range and resolution of your radar system. Although there are some ICs that integrate an entire signal chain into a single package, these Read Article

RF Amplifier Impedance Matching at Microwave and mmWave Frequencies According to MarketWatch, the overall market for RF amplifiers is expected to surpass $27 billion by 2023. So where are all of these RF amplifiers expected to be used? You can thank 5G and the expansion of cellular networks in general for a healthy portion of the expected growth. For the PCB designers out there, RF amplifier impedance matching becomes an important design point, especially with high power amplifiers. Large-signal RF Amplifier Read Article

Cooling Fan Electrical Noise Reduction in Your PCB This GPU will need to pass EMC checks thanks to the presence of these cooling fans Who hasn’t opened up their PC or laptop and taken a long look at its fans and heatsinks? If you’re working with high speed components, high frequency components, or power components, then you’ll need to devise some sort of cooling strategy to remove heat from these components. Unless you want to use the nuclear option and install an evaporative cooling unit or Read Article

Reading Impedance Profiles of High Speed Backplanes Impedance remains a confusing topic in the signal integrity community. By definition, impedance is the ratio of voltage to current. That doesn’t really paint a clear picture to anyone. Getting more specific, the term impedance can mean several things. Step response of broadband reflection coefficient in ohms Impulse response of broadband reflection coefficient in ohms Time domain Z-parameters Frequency domain Z-parameters Signal Integrity Read Article

77 GHz Radar for Automotive PCBs: Routing and Signal Integrity Technology moves quickly these days, and automotive radar has transferred from primarily operating near 24 GHz to 77 GHz shortly after its introduction into new vehicles for object detection. Recent regulation changes have allowed the transition to 77 GHz, which provides a number of benefits. Shorter wavelengths facilitate wider bandwidths, and provide better resolution, smaller device form factors, and longer range. This band just happens to Read Article

Relative Permittivity of PCB Substrates: High-k or low-k dielectrics? The relative permittivity of water makes this pencil appear bent If you’ve paid attention to refraction, then you know something about the physics of relative permittivity. The semiconductor industry has managed to continue scaling to smaller technology nodes by using materials with high dielectric constant (so-called high-k dielectrics), but can you see similar benefits in your PCB with similar substrate materials? What about the use of low-k Read Article

Damping and Reflection Transfer with a Series Termination Resistor Even these transmission lines might require a series termination resistor Trace, source, and load impedance matching are important in boards that contain transmission lines. Whenever the rise time of a signal is much shorter than the round trip propagation time for signals, you should make sure these impedances match in your interconnects. Impedance controlled design and routing can help ensure your traces have consistent impedance, but some Read Article

Pole-Zero Analysis and Transient Analysis in High Speed Design Overshoot and ringing in transient analysis. Image credit. As part of high speed design, transmission line effects in traces and impedance matching normally receive a lot of attention. This is understandable, as switching speed in a digital IC is the primary factor that determines whether termination needs to be considered in a transmission line. However, any RLC circuit can exhibit a transient response, which appears as overshoot or undershoot Read Article

Embedded Optical Interconnects in PCBs for Ultra High Speed Design 5G will be here sooner than you think, creating plenty of new opportunities for PCB designers, manufacturers, and companies that provide optical networking equipment. The huge data transfer rates in 5G networks and in specialized applications like aerospace requires greater use of optical interconnects throughout electronic systems, ultimately requiring conversion to electro-optic systems and fully photonic systems. What can PCB designers do to Read Article

Optical Transceiver Layout for Gigabit and Faster Ethernet Mind your manufacturing process during optical transceiver layout and design The story of PCB layout and channel design for optical transceivers is really a story of high speed PCB design; it requires considering all aspects of high speed design, especially at very high data rates. Data rates reaching 400 Gbps on 10 lanes (that’s 40 Gbps per lane!) are possible over long distances with the right PCB layout and routing techniques. Challenges in Read Article

Silicon Photonics Integration Challenges in PCB Design Silicon photonics will use the same manufacturing processes used in silicon ICs I was honored to meet Richard Soref at a recent IEEE conference and discuss the current state of electronic-photonic integrated circuits (EPICs). The man is often called “the Father of Silicon Photonics”, and for good reason. If you ask him nicely, he’ll tell you how to build all the fundamental logic gates as photonic circuits directly on silicon. Now is a landmark Read Article

Insertion Loss Deviation or Intersymbol Interference Noise? In a previous blog, I discussed how channel quality is quantified by eye patterns [1]. There, it is explained how eye patterns are created from the thru S-parameters only. So, if you are using the thru S-parameters alone, do reflections even matter? Intuitively, it would seem like they don’t matter since they are not directly used to calculate the eye pattern. But, of course reflections matter! Reflections cause signal integrity problems, and I’d Read Article

What Size Decoupling Capacitor Should I Use for My Digital ICs? Are these capacitors sized properly? There is quite a bit of information out there about bypass and decoupling capacitors. Both components are vitally important for maintaining power integrity and signal integrity. When you start looking through the information on this topic, you’ll find that the procedure for sizing a decoupling capacitor for a digital IC is quite simple. Bypassing vs. Decoupling: What’s the Difference? Although you wouldn’t Read Article

Symmetric Stripline Impedance Calculators and Formulas In a previous article, we looked at the inconsistencies that can arise when using different calculators to compute the impedance of surface and embedded microstrip traces. Many of the same issues mentioned in the previous article apply to stripline impedance calculators. Symmetric striplines are easier to address than asymmetric striplines, both numerically and analytically. Here, we’ll give a short comparison of the various impedance formulas Read Article

Embedded System Power Supply Guidelines for Power Integrity This system will require its own power supply and regulation Embedded systems that require a significant amount of processing power and that need to interface with analog components require important embedded system power supply guidelines in order to ensure power and signal integrity. Whether you design your own external power supply, or embed a power supply directly alongside your board, you’ll need to follow some important power integrity Read Article