Contents

Applied Wave Research, Inc.

TXLine Information

Analyze

Synthesize

Types of Transmission Lines

Microstrip

Stripline

Coplanar Waveguide

Grounded Coplanar Waveguide

Slotline

Dielectric Substrate Materials

Conductivity

Bug Reports


Analyze

The transmission line analysis computes the electrical parameters of the transmission line structure shown in the active tab. The length of the transmission line can also be entered to allow the analysis to compute the electrical length of a section of transmission line.


Synthesize

The width and length of a transmission line can be computed for a desired characteristic impedance and  electrical length. For coplanar waveguide, the width of the gap is synthesized for a user specified center conductor width.


Microstrip

The microstrip analysis option analyzes open microstrip line by means of an empirical formulation. Loss and dispersion can be evaluated. The analysis is based on a set of empirical equations.

Range of Validity

K < 16

0.05 < W/H < 20

T < H/2

T < W/2

where K is substrate dielectric constant, W is strip width, T is strip thickness, and H is substrate thickness.

Accuracy

The static characteristic impedance, effective dielectric constant, and loss calculations are generally accepted as the most accurate empirical formulations available, agreeing with moment-method calculations, within the range of validity, well within 1% when T=0. The dispersion analysis agrees with spectral-domain calculations to 1-2% in effective dielectric constant and characteristic impedance when T=0. Accuracy of the dispersion correction when T is non-zero has not been evaluated.

References

Characteristic impedance and effective dielectric constant:

1. S. March, "Microstrip Packaging: Watch the Last Step," Microwaves, p. 83, Dec. 1981.

2. I. J. Bahl and D. K. Trivedi, "A Designer's Guide to Microstrip Line," Microwaves, p. 174, May, 1977.

Loss:

3. R. Pucel, D. J. Masse, and C. P. Hartwing, IEEE Trans. Microwave Theory Tech., vol. MTT-16, p. 342, 1968.

Dispersion:

4. G. Wells and P. Pramanick, Int. J. Microwave and Millimeter-Wave Computer-Aided Design, vol. 5, p.287, 1995.


Stripline

The stripline analysis option analyzes homogeneous, centered stripline by means of an empirical formulation. Loss is evaluated; since homogeneous stripline is a TEM transmission structure, dispersion analysis is unnecessary. The analysis is based on a set of empirical equations. A factor of 2.0 error in some references has been corrected.

Range of Validity

K: any value

10 > W/H > 0.1

W/T > 2.5

T/H < 0.1

where K is substrate dielectric constant, W is strip width, T is strip thickness, and H is substrate thickness between ground planes.

Accuracy

Characteristic impedance is within 0.5% of numerical results. The resistive loss is accurate to approximately 6%. Dielectric losses are calculated in the same manner as for unguided waves.

References

1. Cohn, S. "Characteristic Impedance of the Shielded Strip Transmission Line," IRE Trans. Microwave Theory Tech., vol. MTT-2, p. 52 (July, 1954).

2. B. C. Wadell, Transmission-Line Design Handbook, Artech House, Norwood, MA 1991.

3. I. J. Bahl and R. Garg, "A Designer's guide to Stripline Circuits," Microwaves, Jan. 1978, p. 90.


Coplanar Waveguide

The CPW (Coplanar Waveguide) option analyzes coplanar waveguides by means of an empirical formulation. The top-surface ground plane is infinite, and no ground plane exists on the underside of the substrate. Loss calculations are included, but not dispersion. The principal advantage of using the equations given in reference 1 is improved accuracy when analyzing coplanar lines with metalization that is relatively thick compared to the slot gap. The impedance and effective dielectric constant are given by the magnitudes of the complex impedance and dielectric constant.

Range of Validity

H >  2(W + 2G)

T <  4.5W

F < Vp/(10(W+2G))

where H is the substrate thickness, G is the gap width, W is the center conductor width, T is the metalization thickness, F is the frequency, and Vp is the phase velocity in the dielectric.

Accuracy

The reference specifies that comparisons with full-wave results show an agreement with less than 5% error for the effective dielectric constant and impedance. The attenuation is typically within 5 - 10% of the full-wave results with a maximum error of 20%.

Reference

1. W. Heinrich, "Quasi-TEM Description of MMIC Coplanar Lines Including Conductor Loss Effects" IEEE Trans. Microwave Theory Tech,  Vol 41, No. 1, January 1993.


Grounded Coplanar Waveguide

The CPW (Coplanar Waveguide) option analyzes coplanar waveguides by means of an empirical formulation. The top-surface ground plane is infinite, and a ground plane exists on the underside of the substrate. Loss calculations and dispersion are not included. The analysis uses a set of empirical equations.

Range of Validity

H >> G

G >> T

where H is the substrate thickness, G is the gap width, and T is the metalization thickness.

Accuracy

The accuracy of these equations has not been well evaluated. Because of the requirement that G<<H, this formulation does not agree well with the microstrip analysis at large values of G.

Reference

1. G. Ghione and C. Naldi, "Parameters of Coplanar Waveguide With Lower Ground Plane," Electronics Letters, vol. 19, p. 734, (Sept. 1, 1983).

2. B. C. Wadell, Transmission-Line Design Handbook, Artech House, Norwood, MA 1991.


Slotline

The slotline option analyzes slotlines by means of an empirical formulation, a closed-form approximation of the results of Cohn's iterative analysis (see refs). The top-surface metalization is infinite, and no ground plane exists on the underside of the substrate. Loss is not calculated and metalization thickness is zero.

Slotline is inherently dispersive; thus, frequency must be entered and dispersion is included. The analysis uses a set of empirical equations, curve-fit to the results of Cohn's iterative analysis.

Range of Validity

For 9.8 < K < 20

 0.02 < G/H < 1

.01* Lambda0 < H < Lambda0 /(4*sqrt(K-1))

For 2.2 < K < 9.8

0.0015 < G/H < 1

.006*Lambda0 < H < .06*Lambda0

T = 0

where H is the substrate thickness, T is the metalization thickness, G is the slot width, and K is the dielectric constant, and Lambda0 is the free space wavelength. Slotline generally requires a high dielectric constant substrate to minimize radiation and the generation of spurious modes.

Accuracy

The effective dielectric constant is within 3% and the characteristic impedance within 6% of Cohn's results. Because slotlines usually use narrow slots, which may not be large compared to the metalization thickness, the lack of any accounting for metalization thickness is a major limitation of these equations.

Reference

1. R. Garg and K. C. Gupta, "Expressions for Wavelength and Impedance of a Slotline," IEEE Trans. Microwave Theory Tech., vol. MTT-24, p. 532, (Aug., 1976).

2. B. C. Wadell, Transmission-Line Design Handbook, Artech House, Norwood, MA 1991. (errors in early printings have been corrected.)

3. S. Cohn, "Slot Line on a Dielectric Substrate," IEEE Trans. Microwave Theory Tech., vol. MTT-17, p. 768, (Oct., 1969).


Dielectric Constant of the Substrate
Dielectric Substrate Materials

The dielectric constant specified is the relative dielectric constant of the substrate material. A table of common dielectric materials is shown below.


Conductivity of the Transmission Line

The conductivity of the transmission line conductors is used in the computation of the loss of the transmission line (for the analysis types that include loss).  A table of common conductor types and conductivities is shown below.


Applied Wave Research, Inc.

MICROWAVE AND ELECTROMAGNETIC CONSULTING AND

SOFTWARE DEVELOPMENT

Applied Wave Research, Inc. is comprised of a small team of highly talented designers and researchers with extensive experience in microwave design, development, testing and software development. We apply the proper balance of practical experience, advanced analysis tools, and theoretical insight that leads to creative and cost-effective solutions to your high frequency design needs.

Microwave CAD Applications

Capabilities

Available Resources

Areas of Expertise

Software Development

How To Contact AWR


Microwave CAD Applications

AWR is continuously developing exciting new applications for the design and analysis of high frequency electronics. The applications range from intuitive and powerful electromagnetic and circuit analysis software, to productivity enhancing utility programs. As a registered user, you will automatically receive new product announcements.


Capabilities

AWR offers practical solutions to your high-frequency electronic design needs. We can help you with:

•	Active/Passive Circuit Design

•	Tradeoff Studies

•	Testing

•	Research and Literature Surveys

•	Computer Software Development

•	Analytic and Computer Methods


Available Resources

We have access to a wide range of tools that allow us to solve your technical problems efficiently and accurately. These tools include:

•	A Proprietary 3-D Electromagnetic Simulator for Planar Circuits

•	A Proprietary Microwave Circuit Simulator

•	Mathematical Analysis Software

•	Access to a Complete Microwave/Millimeter Wave Laboratory

In addition to the above resources, we also have several commercial electromagnetic and circuit analysis software programs available for us to use. Since Our capabilities are being continuously enhanced, please contact us for a more complete list of our capabilites.


Areas of Expertise

The technical staff at AWR has extensive experience in the following technical areas:

•	MMIC and MIC Design

•	Amplifier Design - Low Noise /Gain /Power

•	Electromagnetic Modeling

•	Transition Design/Analysis

•	Microwave Filter Design

•	Nonlinear Circuit Design

•	Statistical Design Methods

•	Active Circuit Stability Analysis

•	Microwave Circuit Measurements

•	Scientific Software Development


Software Development

A primary goal of AWR is the development of powerful and intuitive software applications for the design and analysis of high frequency electronics. We have an excellent environment for the development of advanced  scientific software. Our software development environment utilizes:

•	Object-Oriented Software Design

•	A Complete LAN Based Development Environment

•	State-of-the-Art Development Tools for Programming, Testing and Quality Assurance

•	Extensive Libraries of Proprietary and Third-Party Software Components

•	Rapid Application Development Capability for Graphical Interfaces

•	Extensive experience in numerical software development and graphical user interface development

AWR can develop custom software solutions including complete applications, customized versions of existing applications, algorithms and subroutines.


How to Contact AWR

Applied Wave Research can be contacted at the following:

Applied Wave Research, Inc.

2210A Graham

Redondo Beach, CA 90278

Phone: (310) 370-1714

Fax:     (310) 793-6500

E-Mail:  pekarek@appwave.com

Please E-Mail registration material to:  reg@appwave.com

At the time that this software was published, AWR was in the process of finding a new location. If we cannot be contacted at the above phone number or address, then e-mail us at  pekarek@appwave.com and we will send you updated information. If you are a registered user of this software, then we will automatically notify you of any changes.


TXLine Information

You are using TXLine version 1.1. copyright Applied Wave Research Inc. 1996. Please contact AWR for information on new versions of this software. If you are a registered user with your current e-mail address registered with us, we will automatically notify you of any updates. Thank you for using TXLine.


Bug Reports

If you find any bugs in the software, or if you have any problems or comments about the software, please send an e-mail describing the problem to:

  pekarek@appwave.com

We will do our best to correct any problems that are discovered and we will make updated versions available to all users.