Westbay Compufilt v2
Line Interference Analysis. EMI Suppression Filter Modelling
Westbay Compufilt, first introduced in 1994, has been fully updated for V2.0, with the introduction of many new features. The principle of Compufilt is to provide ready built models of Feedthrough, Mains (Line), and PCB filters, to allow insertion loss versus frequency characteristics to be plotted. A range of pulse shapes can also be applied to filter circuits, allowing behaviour in data circuits and to transient events to be modelled. A fully-featured Search Wizard is also available to provide a filter circuit and component values to match particular performance requirements.
style filter models are provided: capacitor, L-C filter, C-L filter,
Ferrite Bead, Pi filter and T filter. There is a choice of eight Source
Circuits and six Load Circuits. Inductors can have self-resistance and
self-capacitance. Inductors can have a Core Characteristic assigned,
allowing inductance and resistance to be frequency-variable. A Saturation
Characteristic can also be defined, allowing inductance to be varied with
Seven Mains (or
Line) filter models are provided, ranging from the basic inlet filter with
a sngle Cx capacitor, bigfilar inductor and pair of Cy capacitors, through
to a two stage filter with two sets of inductors, two pairs of Cy
capacitors and three Cx capacitors. Both differential mode and common mode
insertion loss is calculated. The differential mode circuit can have the
full range of Source and Load circuits, whilst the common mode circuit can
have resistive or capacitive coupling and loading, reflecting real
Six Printed Circuit Board filter models are provided, being C, L-C, C-L, inductor, Pi filter and T filter. They differ from the Feedthrough models in that the capacitors have self-inductance, which dominates the performance at high frequencies. All the inductor and capacitor characterisations provided by the Feedthrough models are also available.
Feedthrough, PCB and Mains configurations will cover many filter circuit
needs, the Custom Circuit Modeller offers the opportunity to define many
other styles. It consists of seven series and six shunt elements,
interspersed with one another. Each element can be a choice of R, L, C,
C-R, L-R, L-C or L-R-C. The standard range of source and load circuits is
Filters are normally characterised in a 50 ohm source and load system,
although insertion loss levels vary considerably with other source and
load conditions. Compufilt not only allows any value of source and load
resistance to be specified, but allows other circuits to be
Sweeps facility offers an excellent means of investigating filter
performance variations under varying operating conditions. Factors such as
Source and Load impedance will often not be precisely known, and it
is useful to look at worse case performance by varying these factors over
Filters are often used on data lines, carrying digital signals for
example. Higher data rates can include frequencies close to that of the
interference band, and in these circumstances it is necessary to know the
effect of the filter on the signal. Capacitive filters tend to slow the
rising edge of a pulse, and if the capacitance is large enough, to
attenuate the signal. The switching threshold can also be
It is often required to match a filter to a set of insertion loss requirements, or an increase in a margin between observed currents and specification limits perhaps. The Filter Search Wizard leads the user through a series of stages to make the process of finding a suitable filter more straightforward, collecting data as it progresses.
Users of Westbay Compufilt will often want to reference filter manufacturers' data, and to assist that process, Compufilt incorporates a database of manufacturers' web addresses. This can be viewed and edited within the program, and a simple in-built browser enables rapid connection to the company's site. (Please note that Microsoft Internet Explorer 4 or later needs to be installed on your system for the in-built Browser to operate).
A 'Tools' facility gathers together a range of inductance and capacitance calculations, dB conversions and other useful information, for the convenience of the user.
This is a free of charge program that can be copied and installed as required. It provides unlimited modelling of Feedthrough Capacitors, and unlimited access to the URL Database and Web Browser. All other circuit models can also be accessed, with restrictions on source and load circuits and component values. Compufilt Lite can be downloaded.
Windows 95 or later. 20Mb of Hard Disk space.
Westbay Compufilt is a trademark of Westbay Technology
Westbay Technology Ltd, Main Street, Baycliff, Ulverston, Cumbria LA12 9RN, England
Tel: 01229 869 798 (from the United Kingdom) Tel: +44 1229 869 798 (International) Contact by e-mail