Calculator Inputs
Enter any valid calculation group. You can use measured cutoff frequencies, a Q-based estimate, or patch geometry support values.
Example Data Table
| Case | fr (GHz) | fL (GHz) | fH (GHz) | εr | h (mm) | W (mm) | L (mm) | QL | VSWR | Measured BW (MHz) | FBW (%) |
|---|---|---|---|---|---|---|---|---|---|---|---|
| 2.45 GHz WLAN Patch | 2.45 | 2.41 | 2.49 | 4.4 | 1.6 | 38.0 | 29.4 | 28 | 2.0 | 80 | 3.27 |
| GPS L1 Patch | 1.575 | 1.558 | 1.592 | 2.2 | 1.6 | 75.2 | 63.5 | 32 | 2.0 | 34 | 2.16 |
| 5.8 GHz ISM Patch | 5.80 | 5.68 | 5.92 | 3.48 | 0.8 | 17.3 | 12.9 | 22 | 2.0 | 240 | 4.14 |
These are sample engineering scenarios for demonstration and validation checks.
Formula Used
BW = fH − fL
FBW(%) = ((fH − fL) / fC) × 100Here,
fC is the center frequency. If you provide fr, it is used as the reference center.
FBW(%) = ((VSWR − 1) / (QL × √VSWR)) × 100BW = fr × FBW
εeff = (εr + 1)/2 + (εr − 1)/2 × (1 + 12h/W)−1/2
ΔL = 0.412h × ((εeff + 0.3)(W/h + 0.264)) / ((εeff − 0.258)(W/h + 0.8))
Leff = L + 2ΔLf = c / (2Leff√εeff)
W ≈ c / (2fr) × √(2 / (εr + 1))
The measured frequency method is best for tested hardware. The Q-based method is useful during early design, tuning, and comparison stages.
How to Use This Calculator
- Enter measured lower and upper cutoff frequencies to compute real bandwidth from test data.
- Enter resonant frequency, loaded Q, and VSWR to estimate bandwidth before fabrication or tuning.
- Enter substrate and patch dimensions to calculate effective permittivity, fringing extension, and resonance from geometry.
- Use the displayed results section above the form to compare measured and estimated behavior.
- Download the result summary as CSV or PDF for design notes, reports, or client documentation.
FAQs
1. What bandwidth does this calculator report?
It reports absolute bandwidth in GHz and MHz, plus fractional bandwidth in percent. It can also estimate edge frequencies from resonant frequency, loaded Q, and VSWR.
2. Is measured bandwidth better than estimated bandwidth?
Yes. Measured lower and upper cutoff frequencies describe actual hardware performance. The Q-based result is a design estimate and should be verified using simulation or laboratory measurements.
3. Why are εeff and fringing length included?
They help connect bandwidth analysis to patch geometry. Effective permittivity and fringing length improve resonance prediction and support dimension adjustments during antenna design.
4. What VSWR value should I use?
A common threshold is 2:1. Some designs use tighter limits such as 1.5:1 for stricter matching, while wider tolerances may be acceptable for broader operational goals.
5. Can this calculator replace full-wave simulation?
No. It is a fast engineering tool for estimation and comparison. Final antenna behavior still depends on feed structure, ground size, slots, losses, fabrication, and enclosure effects.
6. Why is my measured bandwidth wider than the estimate?
Bandwidth can widen بسبب thicker substrates, matching networks, slots, parasitic elements, lower Q, or test definitions that differ from the simplified resonator estimate.
7. Does loss tangent affect bandwidth?
Yes. Higher loss tangent can reduce efficiency and alter practical response. This calculator shows an approximate dielectric Q so you can quickly judge substrate loss behavior.
8. What units should I enter?
Enter frequency in GHz and all patch dimensions in millimeters. Relative permittivity and loss tangent are unitless, while VSWR is entered as a ratio value greater than one.