Formula Used
This calculator estimates substrate thickness from antenna frequency by first converting
the frequency to hertz. It then finds free space wavelength. The basic equation is
wavelength equals light speed divided by frequency.
The effective permittivity estimate is:
eeff = ((er + 1) / 2) + ((er - 1) / 2) × 1 / sqrt(1 + 12 / whr).
Here, er is dielectric constant. whr is width to height ratio.
Guided wavelength is calculated as free space wavelength divided by square root of
effective permittivity. Substrate thickness is then calculated as guided wavelength
multiplied by the selected thickness ratio. A common practical band is also shown
from 0.003 to 0.05 of guided wavelength.
How To Use This Calculator
Enter the target antenna frequency first. Select the correct frequency unit.
Add the dielectric constant of the substrate material. Then set the width to
height ratio. Use the default thickness ratio for quick estimates. Increase or
reduce it for your own design rule.
Keep manual effective permittivity set to no for automatic estimation. Select yes
when a field solver or datasheet gives a better value. Enter copper and mask
thickness values when you want a stack estimate. Press the calculate button.
The result appears above the form and below the header.
Example Data Table
| Frequency |
Er |
Ratio |
Approx Thickness |
Typical Use |
| 915 MHz |
4.4 |
0.02 |
3.12 mm |
Low band prototype |
| 2.45 GHz |
4.4 |
0.02 |
1.17 mm |
Wireless module study |
| 5.8 GHz |
3.38 |
0.02 |
0.58 mm |
Compact antenna board |
Frequency Based Substrate Thickness Design Guide
Antenna substrate thickness affects size, bandwidth, losses, and repeatability.
A thin substrate can support compact layouts. It may also reduce unwanted surface
waves. A thicker substrate can improve bandwidth. It can also create stronger
fringing fields. This calculator gives a practical starting point before detailed
electromagnetic simulation.
Why Frequency Matters
Frequency controls wavelength. Higher frequency means shorter wavelength.
Because many antenna dimensions are fractions of wavelength, thickness often
becomes smaller as frequency rises. A board that works at a lower band may be
too thick for a higher band. The same material can behave differently when
frequency changes.
Role Of Dielectric Constant
Dielectric constant changes wave speed inside the structure. A larger value
shortens the guided wavelength. That can reduce the calculated substrate
thickness. It can also increase stored energy in the substrate. Designers must
balance compact size against efficiency and bandwidth.
Effective Permittivity
Microstrip fields are not fully inside the dielectric. Some fields travel in air.
Therefore effective permittivity is usually lower than the substrate dielectric
constant. The calculator estimates this value from dielectric constant and width
to height ratio. You can also enter a manual value from measurement or simulation.
Thickness Ratio Choice
The thickness ratio defines the selected fraction of guided wavelength. Small
ratios produce thin boards. Larger ratios produce thicker boards. A practical
range is included for comparison. It is not a final rule for every antenna.
Feed type, copper thickness, losses, and enclosure effects can change the best
value.
Engineering Use
Use this page for early calculations, comparison tables, and documentation.
Export the result when you need a record for review. The CSV file helps with
spreadsheets. The PDF file helps with design notes. Always verify the final
antenna using measurement, matching checks, and layout review.
FAQs
What does this calculator estimate?
It estimates antenna substrate thickness from frequency, dielectric constant, effective permittivity, and a selected guided wavelength ratio.
Is the result a final manufacturing value?
No. It is an early design estimate. Final values should be checked with simulation, datasheets, tolerance studies, and measured antenna performance.
What is effective permittivity?
Effective permittivity represents the combined field behavior in substrate and air. It is commonly used for microstrip style antenna calculations.
Why enter width to height ratio?
The ratio helps estimate effective permittivity. It describes how the conductor width compares with substrate height in a simplified microstrip model.
What thickness ratio should I use?
A value near 0.02 gives a reasonable starting point. Use smaller or larger values based on bandwidth, loss, size, and fabrication limits.
Can I use manual effective permittivity?
Yes. Use manual mode when you have a trusted value from a simulator, measurement, stackup supplier, or published design reference.
Why include copper and mask thickness?
They help estimate total stack thickness. This is useful for documentation, enclosure spacing, tolerance checks, and simple mechanical planning.
What do CSV and PDF downloads contain?
They contain the main inputs and calculated outputs. Use them for quick reports, records, review sheets, or further spreadsheet analysis.