The Polar Application Note library includes a comprehensive resource of information on signal integrity and loss. Use the search engine below to locate your subject of interest.

PCB fabrication considerations for lossy transmission lines

The high speed board industry is increasingly considering loss testing, or modelling of PCB losses. For a PCB fabricator the considerations necessary for building repeatable lossy transmission lines are different from those necessary for lossless (impedance controlled) lines. This note considers some of the factors that determine loss and the Polar products designed to assist in modelling and fabricating boards for very high speed transmission.

Economics of PCB impedance test and the hidden cost of reducing rise time

From the early days of impedance controlled PCBs OEMs and PCB fabricators have expressed the need to test on short traces and test using fast rise times and in appropriate situations this can be true, but in the headlong push for speed the hidden running costs are often overlooked in the rush for risetime. This note looks at the real costs of testing short traces with fast rise time TDRs and provides some useful rules of thumb for choosing measurement techniques and equipment.

Laminates, losses & the Si9000e – choosing a PCB laminate

New "mid market" core and prepreg materials offer increased high speed performance and more standard processing methods than more exotic laminates and have presented the designer with a bewildering array of choices from ease of processing through to reliability requirements and onwards to signal integrity capability. This note explains how to use the Si9000e to make the best choice of laminate materials when trading cost versus signal integrity performance.

Signal integrity – design and test

Signal integrity theory

Using the Si9000.

RIE loss / attenuation measurement method and PCB manufacture

This application note provides a brief introduction to RIE (Root Impulse Energy) testing, one of 4 PCB material loss (attenuation) measurement methods shortly to be published by IPC. RIE testing is aimed at the PCB manufacturing shop floor to provide an easily deployed and relatively straight-forward method of monitoring the high frequency performance of PCBs to ensure they stay within an acceptable loss budget.

Vias, stubs and minimizing their visibility to high speed signals

Many of our PCB design customers ask us about modelling plated through hole (PTH) vias with respect to impedance. However, from a signal integrity standpoint, unconnected via stubs have a far larger effect on the signal than the geometry of the via itself. This note explains how the Polar Si9000 can help you check if, at your desired bit rate or operating frequency, you need to take steps to reduce or remove the effects of via stubs. 

An introduction to forward and reverse crosstalk

Crosstalk is the unwanted coupling of energy between two or more adjacent lines. The electromagnetic fields between two closely coupled lines interact with each other and will affect the behaviour of the signals on both lines. This note discusses near and far-end crosstalk and includes formulas that will enable the maximum peak effect to be predicted.

Nickel-gold plating copper PCB traces

Nickel plating of copper PCB traces, widely practised in the microwave industry, is acceptable on short lengths of pad to accommodate gold plating; plating the whole trace length is generally not a good idea. This application note explains the effect that nickel will have on high frequency transmission lines.

Locating Critical Tracks on PCB Inner Layers

From susceptibility to electrical interference to control of track cross-sectional dimensions — this note provides several good reasons why you shouldn’t put critical tracks on the surface layer of a PCB.

Transmission line testing — VNA or TDR?

Sometimes board fabricators are asked to test PCB transmission lines at a given frequency.  In some cases boards are tested using a Vector Network Analyser (VNA) and in others a Time Domain Reflectometer (TDR); both instruments should offer similar readings. This note sets out to explain expected differences in measurement results, and points out where differences are due to incorrect test setup rather than any material problem.

Polar recommended signal integrity reading

For those who would like more information on signal integrity issues, this note contains a list of books recommended by Polar.

Critical length of transmission lines - Dr. Eric Bogatin

This new application note gives a clear and easy to read explanation of the critical length of a transmission line.  Written for Polar by Dr. Eric Bogatin this article is an ideal place to broaden your knowledge of PCB transmission line behaviour.  If you like this you will also find a broad range of PCB signal integrity related training materials on the Bogatin Enterprises website. www.bogent.com 

Effect of risetime on the TDR measurement of impedance

This application note is intended to give guidance to those making impedance measurements on industry standard 6 inch long coupons. The note will show that in this situation the use of risetimes shorter than 200ps will yield no advantage and in fact may prove more difficult to use.

Laminates, losses & the Si9000e – choosing a PCB laminate

New "mid market" core and prepreg materials offer increased high speed performance and more standard processing methods than more exotic laminates and have presented the designer with a bewildering array of choices from ease of processing through to reliability requirements and onwards to signal integrity capability. This note explains how to use the Si9000e to make the best choice of laminate materials when trading cost versus signal integrity performance.

Surface roughness effect on PCB trace attenuation / loss

Designers and fabricators are increasingly concerned with the effects on PCB transmission line losses of the surface roughness of the copper layers within a stackup. With the Si9000 versions 9.01 and above you can include values for surface roughness in frequency dependent calculations. Charting dielectric losses along with conductor losses and attenuation values that include compensation for surface roughness can help isolate the contributions of the different loss mechanisms. 

Modelling and testing broadside-coupled differential pairs without ground

From a modelling standpoint the broadside-coupled differential pair without ground is like a paired wire transmission line. This structure does not appear directly in the Si8000/9000 field solver; this application note discusses how to use one of the standard Si8000/9000 structures to predict the finished impedance and suggests a method of testing for this differential structure.

Modelling and testing differential pairs without ground

From a modelling standpoint the differential pair without ground is like a paired wire transmission line. Although this structure does not appear in the Si8000/9000 field solver this note shows how to use one of the standard Si8000/9000 structures to predict the finished impedance and suggests a method of testing for this differential structure.

Displaying s-parameters with Smith charts on the Si9000

The Si9000 v7 and later allows graphical representation of s-parameters S₁₁ and S₂₁ via a Smith Chart, a tool widely used for graphic solution of transmission-line networks. This note briefly discusses how reflection and transmission coefficients S₁₁ and S₂₁ of a typical 50 Ohm controlled impedance structure, represented as a transmission line, are graphed by the Si9000.

Ground plane thickness in Si9000 frequency dependent calculations

This application note describes how the Si9000 PCB Transmission Line Field Solver fully takes into consideration power plane thickness in frequency dependent calculations.

Introduction to s-parameters

The Si9000 extracts RLGC matrices and 2-Port (single-ended) or 4-Port (differential) s-parameters and rapidly plots transmission line information for the structure under design. This application note provides a simple introduction to the concepts of s-parameters, or scattering parameters, which describe the "scattering", reflection and transmission of travelling waves when a linear network is inserted into a transmission line.

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