RF calculators
Closed-form transmission-line and antenna calculators for sizing a starting geometry before a full FDTD run. They live in a floating overlay in the Edit tab, and the same math is available headless through rayrf calc.
The overlay
Open the overlay with Ctrl+R on the Edit tab, or with the RF Calculators (Ctrl+R) button in the Stackup section header. Both toggle the same floating panel.
The panel floats over the canvas. Drag it by its title bar, and resize it from any edge or corner. A grid of buttons across the top selects the calculator, and the body shows that calculator's inputs, its solved outputs, and a live cross-section preview that redraws as you type. When a value leaves a formula's validity window, an amber warning appears under the form stating the bound and what to change. The calculators are read-only analytic tools, so they stay available when a project is open read-only.
Where a calculator has both an impedance and a width, the two solve for each other. Edit Z0 and it sizes the width, edit the width and it reports Z0. The solved-for field carries a violet highlight.
Pull from stackup
Each calculator that takes a substrate has a Pull from stackup checkbox. Tick it, pick a Top and a Ref conductor layer, and the calculator fills the substrate height and epsilon_r from the active project between those layers, then locks those two fields. When more than one dielectric slab sits in the gap, the epsilon_r is a thickness-weighted average and the detail line lists the blend. Untick to type the substrate values in directly. See Stackup and layers for how layers are defined.
Calculators
Eleven calculators ship, in this order. Each solves the closed form named in its walkthrough. Wavelengths are reported as free-space lambda0 and guided lambda_g.
| Calculator | Inputs | Returns |
|---|---|---|
| Microstrip | h, epsilon_r, and Z0 or W | the other of Z0/W, epsilon_eff, wavelengths |
| GCPW | gap S, h, epsilon_r, and Z0 or W | the other of Z0/W, epsilon_eff |
| Stripline | plate spacing b, epsilon_r, copper t, and Z0 or W | the other of Z0/W (IPC-2141A) |
| Patch antenna (inset feed) | frequency, h, epsilon_r, feed target Z0 | patch W and L, inset depth, feed line width |
| lambda Calc (guided wavelength) | frequency, and in PCB mode h, epsilon_r, trace W | lambda0, guided lambda_eff, lambda/4 |
| CPW | gap S, h, epsilon_r, and Z0 or W | the other of Z0/W, epsilon_eff (no bottom ground) |
| Differential pair | h, epsilon_r, spacing S, frequency, and Zdiff or W | the other, plus Z0 even/odd, Zcommon |
| Embedded MS | W, h, epsilon_r, cover height h2, cover epsilon_r, frequency | Z0, epsilon_eff, wavelengths |
| lambda0 free (free-space wavelength) | frequency | lambda0, half, quarter |
| lambda/4 xfmr (quarter-wave transformer) | Z1, Z2, frequency, h, epsilon_r | Zt = sqrt(Z1 Z2), length lambda_g/4, and microstrip widths W1, Wt, W2 |
| Smith chart | R, X, system Z0 | Gamma magnitude and phase, VSWR, return loss, mismatch loss |
The patch calculator sizes a rectangular patch and its inset feed. It reports the inset depth that transforms the radiating-edge resistance to the target impedance, and the width of the microstrip feed line at that impedance. When the target exceeds the edge resistance no inset matches it, and the calculator says so.
The expression strip
A single expression line sits at the bottom of the panel. Type arithmetic (+ - * / ** and parentheses, numbers only) and press Enter to evaluate. The two buttons take the square root and cube root of the current result, so sqrt(Z1*Z2) is entered as 50*75 then the root button. A rejected expression shows err.
Step-by-step breakdown
Each calculator footer links to Step-by-step breakdown on RayRF, which opens the matching walkthrough at rayrf.com/calculators for that structure with the formula, its derivation, and the accuracy band of the model.
CLI equivalent
rayrf calc <kind> runs the same formulas headless and prints a table, or --json for a machine-readable report. The kinds are microstrip, stripline, cpw, gcpw, diff, embedded, patch, lambda, lambda-diel, qwt, and smith. Inputs are given in GHz, mm, and ohms. Omit --w and pass --z0 to solve a width from a target impedance.
rayrf calc patch --er 4.4 --h 1.6 --freq 2.45
rayrf calc qwt --z1 50 --z2 75 --freq 2.4 --er 3.66 --h 0.5The full flag list for calc is on the CLI reference.