Formula Used
Closed-form equations provide a practical starting point. Inset gaps and discontinuities change final impedance. Verify critical designs with electromagnetic simulation.
How to Use
- Select a complete, inset-only, feed-line, or reverse mode.
- Enter frequency, target impedance, and preferred dimension unit.
- Select a substrate preset or provide custom material values.
- Choose automatic or manual patch dimensions.
- Select an edge-resistance method and enter feed geometry.
- Set fabrication resolution, tolerance, and sensitivity sweep limits.
- Submit the form and review warnings before fabrication.
- Export results as CSV, PDF, CAD notes, or print output.
Example Data
| Parameter | Example value | Purpose |
|---|---|---|
| Frequency | 2.45 GHz | Common wireless design frequency |
| Target impedance | 50 Ω | Standard RF feed impedance |
| Substrate | FR-4 | Low-cost prototype material |
| Relative permittivity | 4.4 | Controls electrical dimensions |
| Substrate thickness | 1.6 mm | Affects bandwidth and feed width |
| Loss tangent | 0.02 | Estimates dielectric attenuation |
| Copper thickness | 0.035 mm | Typical one-ounce copper |
Substrate Comparison
| Material | Typical εr | Typical loss tangent | General use |
|---|---|---|---|
| FR-4 | 4.4 | 0.020 | Low-cost prototypes |
| RO4003C | 3.55 | 0.0027 | Low-loss RF boards |
| RO4350B | 3.48 | 0.0037 | Microwave circuits |
| RT/duroid 5880 | 2.20 | 0.0009 | High-performance antennas |
| RT/duroid 6010 | 10.2 | 0.0023 | Compact microwave designs |
| Alumina | 9.8 | 0.0001 | High-stability ceramic circuits |
Frequently Asked Questions
What does inset depth control?
Inset depth controls the patch feed-point resistance. Moving inward usually lowers resistance. The centre approaches a current maximum.
Why is fifty ohms commonly selected?
Many RF systems use fifty-ohm sources and cables. Matching reduces reflected power. It also simplifies testing.
Can I enter simulated edge resistance?
Yes. Select the simulation-derived method. Enter the simulated edge resistance value.
Why can the inset equation fail?
The target resistance cannot exceed edge resistance. That condition makes the square-root ratio invalid. Use another matching method.
Does inset gap width matter?
Yes. The gap introduces discontinuity capacitance. Narrow gaps can shift the best match.
Are the calculated dimensions final?
No. They are analytical starting dimensions. Full-wave simulation should refine critical designs.
What does fabrication rounding show?
It rounds inset depth to your manufacturing resolution. The calculator then recomputes resistance. This reveals practical matching error.
Why include conductor roughness?
Rough copper increases high-frequency conductor loss. The estimate applies a roughness correction. Real laminates may differ.
What does the sensitivity sweep show?
It shows resistance across multiple inset positions. The curve reveals matching sensitivity. Use it for tolerance planning.
Can this calculate an offset feed?
The offset field supports geometry validation. The simple resistance equation assumes centred feeding. Offset feeds need stronger simulation.
How accurate is the loss estimate?
It is a first-order engineering estimate. Connector and radiation losses are excluded. Measurement provides the final answer.