Advanced differential impedance calculator facilitates design and production of latest-generation PCBs
Advanced differential impedance calculator facilitates design and production of latest-generation PCBs
Keywords Calculator,Controlled impedance
Polar Instruments has launched an advanced differential controlled impedance calculator (Plate 1). Developed in direct response to industry demands for a means of evaluating the impedance of differential PCB trace structures, the new CITS 25 calculator tool is a true 32-bit application that runs under Windows 95, 98 and NT, and uses powerful field solving techniques. Intended for PCB designers and manufacturers involved in the creation of high technology boards handling ultra-fast analog or digital signals, the calculator enables users to easily obtain the PCB trace dimensions needed to secure a specific impedance and a cost-effective production yield.
A free evaluation copy of the CITS25 calculator with limited functionality will soon be available for download from Polar's Web site at http://www.polar.co.uk,and a full working version is available from the company for a small charge.
The CITS25 follows on from the outstanding success of Polar's first controlled impedance calculator, which met with considerable acclaim from PCB manufacturers when it was introduced in 1996. Since then, the company has co-ordinated an extensive research programme involving academics from two of the UK's leading universities, aimed at extending the performance of the first single-ended impedance calculator to include differential PCB traces. The algorithms used by the CITS25 are extremely sophisticated, utilising field solving by boundary finite element analysis (which involves predicting the surface charge distribution of a trace,and then using Green's function to obtain the charge distribution in the dielectric, for subsequent evaluation of capacitance and impedance). The net effect is that users can now calculate the characteristic impedance of three-dimensional structures such as complex conductor paths quickly and easily,by modelling the cross-section of the trace configuration, with no constraints on trace geometry.
Plate 1 Polar Instruments' new CITS25 differential controlled impedance calculator
The calculator runs under Windows on any standard PC-compatible computer equipped with a colour monitor,although a reasonably powerful model is recommended, owing to the considerable"number crunching" involved. A mouse-driven graphical user interface makes operation simple users merely point and click on the appropriate PCB trace icon, and key-in a few fundamental process details, such as the thickness and dielectric constant of the materials being used. The calculated PCB trace impedance is displayed instantly, allowing the effect of minor changes to parameters such as trace positioning or board thickness to be previewed very easily. Results can be output to a printer, for subsequent inclusion in manufacturing process reports or customer documentation, and can be saved for future review.
The calculator accommodates all standard PCB fabrication technologies, including differential surface, coated surface and embedded edge-coupled microstrip, symmetric and asymmetric edge-coupled stripline, and symmetric broadside-coupled stripline. It also handles single-ended surface, coated surface and embedded microstrip, and symmetric and asymmetric stripline constructions.
The CITS25 differential impedance calculator is totally complementary to Polar's CITS500 differential controlled impedance test system, which enables PCB manufacturers to quickly and easily verify the impedance attributes of single-ended and balanced traces. The company also produces a range of impedance-matching microstrip probes for both single-ended and differential measurements, and has just launched an innovative new 50 ohm variable pitch probe called the IP-50V which is instantly adjustable to any pitch in the range 0.1 to 0.3 in., making it ideal for PCB manufacturers handling a mix of boards with different signal-to-ground conductor spacings.
For further information please contact: Andy Burkhardt, Polar Instruments Ltd, Garenne Park, St Sampson,Guernsey GY2 4AF, UK. Tel: +44 (0) 1481 53081; Fax: +44 (0) 1481 52476; E-mail: polar@itl.net http://www.polar.co.uk
