The workspace window of the schematic editor contains components and transmission lines for use when adding schematic elements to a project. Once added to the current schematic, users can edit a transmission line's properties by either double-clicking on the desired element in the schematic window, or right-clicking on the desired element and selecting Edit Properties.

Each transmission line property editor includes element-specific settings, as well as the following general options:

- Name: user-defined component identifier.
- Label Position: placement of a component's label.
- : determines which information is visible in a component's label.
- Enabled State: sets a component as either active or inactive. Inactive components are either open or short.

## Ideal Transmission Lines

## Substrate

## Microstrip Line

## Microstrip Step

## Microstrip Tee

## Microstrip Bend

## Microstrip Dispersion Models

The **Kirschning/Jansen** model calculates the frequency dependent characteristic line impedance, $Z_L(f)$, and frequency dependent effective permittivity, $\epsilon_r(f)$, using formulas from [5].

$\epsilon_r(f)$ is said to have an accuracy better than 0.6% for $0.1 \leq \frac {W} {H} \leq 100$, $1 \leq \epsilon_r \leq 20$, and $0 \leq \frac {H} {\lambda} \leq 0.13$ for frequencies up to 60 GHz and substrate thicknesses up to 25 mm.

$Z_L(f)$ is said to be valid for $0 \leq \frac {H} {\lambda} \leq 0.1$, $0.1 \leq \frac {W} {H} \leq 10$, and $1 \leq \epsilon_r \leq 18$.

In accordance with reference information, the valid ranges for this model are described as $1 \leq \epsilon_r \leq 20$, $0.1 \leq \frac {W} {H} \leq 100$, and $0 \leq \frac {H} {\lambda} \leq 0.13$, where $W$ is the microstrip line width, $H$ is the substrate dielectric thickness, and $\lambda = \frac {c} {f}$.

The **Hammerstad/Jensen** model calculates the frequency dependent characteristic line impedance, $Z_L(f)$, and frequency dependent effective permittivity, $\epsilon_r (f)$, using formulas from [1].

In accordance with reference information, the valid ranges for this model are described as $1 \leq \epsilon_r \leq 128$ and $0.01 \leq \frac {W} {H} \leq 100$, where $W$ is the microstrip line width and $H$ is the substrate dielectric thickness.

The **Kobayashi** model calculates the frequency dependent effective permittivity, $\epsilon_r (f)$, using formulas from [6].

This calculation of $\epsilon_r (f)$ is said to provide accuracy better than 0.6% for $0.1 \leq \frac {W} {H} \leq 10$ and $1 \leq \epsilon_r \leq 128$ with no frequency limits. Also, $Z_L (f) = Z_0$.

In accordance with reference information, the valid ranges for this model are described as $1 \leq \epsilon_r \leq 128$ and $0.1 \leq \frac {W} {H} \leq 10$, where $W$ is the microstrip line width and $H$ is the substrate dielectric thickness.

The **Yamashita** model calculates the frequency dependent effective permittivity, $\epsilon_r (f)$, using formulas from [7].

This calculation of $\epsilon_r (f)$ is said to provide accuracy better than 1% for $2 \leq \epsilon_r \leq 16$, $0.06 \leq \frac {W} {H} \leq 16$, and $0.1 \; GHz \lt f \lt 100 \; GHz$. Also, $Z_L (f) = Z_0$.

In accordance with reference information, the valid ranges for this model are described as $2 \leq \epsilon_r \leq 16$ and $0.06 \leq \frac {W} {H} \leq 16$, where $W$ is the microstrip line width and $H$ is the substrate dielectric thickness.

## Microstrip Loss Calculations

Microstrip loss is calculated as a summation of dielectric and conductor losses according to

\begin{equation} \alpha = \alpha_d + \alpha_c \end{equation}where $\alpha$ is the total attenuation constant, $\alpha_d$ is the attenuation due to dielectric losses, and $\alpha_c$ is the attenuation due to conductor losses.

**Dielectric loss** is calculated according to

where,

$\epsilon_r =$ the relative permittivity of the substrate’s dielectric material

$\epsilon_r (f) =$ the frequency dependent effective permittivity of the microstrip

$\lambda = \frac {c} {f}$ is the wavelength

$\delta_d =$ the loss tangent of the substrate’s dielectric material

Users should note that if $\delta_d = 0$, then $\alpha_d(f) = 0$.

**Conductor loss** is calculated according to [2]. Loss due to surface roughness is incorporated into the calculation by applying a correction factor to the conductor’s skin resistance, $R_s$, such that [1][2]:

where $\Delta$ is the rms surface roughness and $\delta$ is the conductor’s skin depth.

Users should note that if the substrate’s conductivity equals 0 or the substrate’s conductor thickness equals 0, then $\alpha_c = 0$.

## References

- E. Hammerstad and O. Jensen, “Accurate Models for Microstrip Computer-Aided Design,” Symposium on Microwave Theory and Technique, pp. 407-409, June 1980.
- R. Garg, I. Bahl, and M. Bozzi, Microstrip Lines and Slotlines, 3rd ed. Boston, MA, USA: Artech House, 2013, pp. 165 - 169.
- E. Hammerstad, "Computer-Aided Design of Microstrip Couplers with Accurate Discontinuity Models," Symposium on Microwave Theory and Techniques, pp. 54–56, June 1981.
- M. Kirschning, R. H. Jansen, and N. H. L. Koster, “Measurement and Computer-Aided Modeling of Microstrip Discontinuities by an Improved Resonator Method,” IEEE MTT-S International Microwave Symposium Digest, pp. 495–497, May 1983.
- M. Kirschning and R. H. Jansen, “Accurate Model for Effective Dielectric Constant of Microstrip with Validity up to Millimeter-Wave Frequencies,” Electronics Letters, vol. 8, no. 6, pp. 272–273, Mar. 1982.
- M. Kobayashi, “A Dispersion Formula Satisfying Recent Requirements in Microstrip CAD,” IEEE Transactions on Microwave Theory and Techniques, vol. 36, no. 8, pp. 1246–1250, Aug. 1988.
- E. Yamashita, K. Atsuki, and T. Ueda, “An Approximate Dispersion Formula of Microstrip Lines for Computer Aided Design of Microwave Integrated Circuits,” IEEE Transactions on Microwave Theory and Techniques, vol. 27, pp. 1036–1038, Dec. 1979.