A new calculator for measuring delay and capacitance per unit length and characteristic impedance.
One of today’s primary challenges of the technological progress is the development of the scientific foundations for further improvement of the elements and structures of the computer technology. The areas of research targeted at boosting performance of the computing devices include such issues as the improvement of the design of the multilayer printed circuit boards (MLB) as the main structural and contact elements in modern computing systems. Some issues are at the forefront of research, such as an efficient simulation of the MLB communication lines and the development of hardware and software that are used to put the simulation results into practice.
Despite intensive research on various aspects of problems related to multilayer printed circuit board (MLB) communication line simulation, some open scientific tasks in the spheres of development and improvement of computing elements and devices still exist.1,2 Such issues are associated with analysis and synthesis of the MLB communication lines for high-performance computing systems for the subnanosecond time range, including special switched meander delay line structures, as well as development of software applications to support new pre-design simulation techniques for multilayer PCBs with the flexible topology of communication lines.1,2
This article addresses issues related to the development and organization of production of hardware and software tools for debugging microprocessor systems and programs, which are a part of the hardware-software complex. Each type of communication line has an individual set of design electrical parameters from a common set of parameters that determines the quality (integrity) of pulse signals during the exchange of information in printed transmission lines. The key parameters to be measured are the extrinsic electrical parameters of the communication lines.3,4
The extrinsic electrical parameters of the communication lines are as follows:
FIGURE 1 shows the design of a printed circuit board with the meander communication lines.
Figure 1. Structure of a PCB with meander delay lines.
The scheme given in FIGURE 2 illustrates the examples of data input for processing in the XML format (the eXtensible Markup Language describes a document and partially describes the behavior of computer programs) individually for the microstrip transmission lines with consideration for the topology of a microstrip line. The microstrip line topology is shown in FIGURE 3
where
W = the signal strip width;
h = height of a rise of a printed track over the support layer;
t = thickness of the conductive layer;
εr = the relative permittivity of a substrate.
Figure 2. Wiring diagram of a network analyzer (calculator) to measure the communication line parameters (WA – wave adapter).
Figure 3. The microstrip line topology.
The design electrical parameters of a microstrip line are as follows:
Steps for calculating the characteristic impedance of a microstrip structure:
The Z0 calculation error in the working range is not greater than 2%.
Comparison of calculations made using the calculator with those made using HyperLynx is shown in FIGURE 4.
Figure 4. Comparison of calculated values using the calculator vs. HyperLynx.
The geometry of a microstrip line in a dielectric medium is shown in FIGURE 5.
Figure 5. The geometry of a microstrip line in a dielectric.
W = the signal strip width;
h1 = the height of a rise of the dielectric over the signal strip;
h2 = the height of a rise of the printed track over the lower backup layer;
t = thickness of the conductive layer;
εr = specific relative permittivity of the substrate.
The design electrical parameters of a microstrip line:
Steps for calculating the characteristic impedance of a microstrip structure in a dielectric medium:
Figure 6. Comparison of calculated values using the calculator vs. HyperLynx for a microstrip structure in a dielectric medium.
centered printed track. For copper ρ = 0.0176 Ohm·mm2/m.
Differential Microstrip Line
The topology of a differential microstrip line in a dielectric medium is shown in FIGURE 7.
Figure 7. Differential microstrip line topology.
Calculation of the signal strip width (W) at a given differential characteristic impedance (Z0 diff) and a given distance between the coupled lines (the Synthesis Mode).
The width of a strip is calculated by using an iterative method (FIGURE 8).
Figure 8. Comparison of calculated values using the calculator vs. HyperLynx for a differential microstrip structure.
Symmetrical Strip Line (h1 = h2)
The geometry of a microstrip line in a dielectric medium is shown in FIGURE 9
Figure 9. Strip line geometry (h1 = h2).
where
W = the signal strip width;
h1 = the height of a rise of the printed track over the upper support layer;
h2 = the height of a rise of the printed track over the lower backup layer;
t = thickness of the conductive layer;
εr = specific relative permittivity of the substrate.
H = h1+h2+t – distance between the support planes.
The design electrical parameters of a stripline are as follows:
Steps for calculating the characteristic impedance of a symmetrical strip structure (h1=h2=h):
The Z0 calculation error in the working range is no greater than 1.5%.
The comparison of Z0 calculations using the calculator with those using HyperLynx for a symmetrical strip line is shown in FIGURE 10.
Figure 10. Comparison of calculated values using the calculator vs. HyperLynx.
The calculated values obtained using the calculator are practically in close agreement with those obtained using HyperLinx at h – the height of a strip line (Figure 10).
Asymmetrical Strip Line (h1≠ h2)
The characteristic impedance of an asymmetrical strip line is calculated as a parallel connection of two characteristic impedances of the symmetrical strip structures (Eq. 9, 10) having a different distance between the reference planes H1=2h1 и H2=2h2:(Eq. 14)
Differential Stripline on the Narrow Side of a Conductor
The geometry of a differential microstrip line in a dielectric medium is shown in FIGURE 11.
Figure 11. Geometry of a differential stripline on the narrow side of a conductor.
Steps for calculating the differential characteristic impedance of a strip structure on the narrow side of a conductor:
Differential Symmetrical Stripline on the Wide Side of a Conductor (Analysis Mode and Synthesis Mode)
The geometry of a differential microstrip line on the wide side of a conductor is shown in FIGURE 12.
Figure 12. Geometry of a differential stripline on a wide side of a conductor.
Steps for calculating the differential characteristic impedance of a strip structure on the wide side (the Analysis Mode):
The primary function of the measuring device calculator is to perform a quick measurement of the delay per unit length, capacitance per unit length and characteristic impedance of the printed test-transmission lines on the MLB in mass production.
The calculator functions as a self-contained measuring device, and is capable of measuring the delay per unit length, capacitance per unit length and characteristic impedance of the printed test transmission lines of the multilayer PCBs. The major expected parameters of the characteristic impedance measuring device are in TABLE 1.
Table 1. The Basic Parameters of the Characteristic Impedance Meter
The proposed methods, algorithms and equations, as well as the comparative evaluation of the calculator methods, suggest this domestic device is capable of measuring the key parameters of the communication lines in high-speed computing systems. Compared to the import devices of the same type known in Russia, the calculator has certain advantages and can be used when designing the domestic computing systems.
1. S.A. Sorokin, Theoretical and Methodological Fundamentals of the Printed Circuit Board Design for High Performance Computer Applications, Moscow, MIREA, 2017.
2. A.V. Parfenov and S.M. Chudinov, “Trends in the Development of Computer Technologies,” Nauchnye Vedomosty BelSU, no. 16 (237), issue 39, 2016.
3. D.M. Malinichev, S.A. Sorokin and S.M. Chudinov, “Research and Selection of the PCB Transmission Line Parameters for Computer Systems,” Voprosy Radioelektroniki, OT series, vol. 11, 2015.
4. D.M. Malinichev, S.A. Sorokin and S.M. Chudinov, “Selection of Cross Section for the Transmission Lines in Computers,” Voprosy Radioelektroniki, OT series, vol. 11, 2015.
5. A.A. Amosov, Yu.A. Dubinsky and N.P. Kopchenova, “Computational Techniques for Engineers,” Vysshaya Shkola, 1994, ISBN 5-06-000625-5.
This email address is being protected from spambots. You need JavaScript enabled to view it.. , is chief designer of NIIVK; This email address is being protected from spambots. You need JavaScript enabled to view it.; and is a post-graduate student of NIIVK; This email address is being protected from spambots. You need JavaScript enabled to view it..
is professor and scientific adviser to the general director of NIIVK (Scientific Research Institute of Computer Systems);