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RF Calculators

RayRF ships an RF Calculators panel for quick analytical estimates. The calculators are synthesis tools: they give you a starting geometry before you commit to a full FDTD run. Open the panel with Ctrl + R or from the RF Calculators button at the top of the Edit tab.

Microstrip

Width, characteristic impedance, effective Er, and electrical length of a single trace over a ground plane. The cross-section diagram on the right updates as you type.

Differential pair

Differential and common-mode impedance from trace width, spacing, dielectric height, and Er. Useful for impedance-matched diff pairs on multi-layer PCBs.

Other calculators

  • GCPW. Grounded coplanar waveguide width, gap, and impedance.
  • Stripline. Symmetric and offset.
  • Patch. Rectangular patch antenna W and L from frequency, dielectric height, and Er.
  • lambda Calc. Free-space and guided wavelength in any medium.
  • CPW. Ungrounded coplanar waveguide.
  • Embedded MS. Microstrip embedded in a multi-layer stack.
  • lambda 0 free. Wavelength in unbounded media.
  • lambda / 4 xfmr. Quarter-wave transformer for impedance matching between Z1 and Z2.
  • Smith chart. Interactive matching with L, C, and transmission-line stubs.

Pull from stackup

Each calculator with a substrate parameter has a Pull from stackup checkbox. Tick it and the calculator reads height, Er, and loss tangent from the active project's stackup. Untick to type values in directly. This is the quickest way to keep the calculator and the simulated geometry in sync while you iterate.

Expression evaluator

Every calculator has a small expression line at the bottom. Type any Python-style arithmetic (2.5 * 1e9 / 4, sqrt(50 * 75)) and press Enter to evaluate. Useful for adapting calculator output without leaving the panel.

Calculator vs simulation
The calculator gives an analytic, closed-form estimate that ignores edge effects, finite ground planes, fringing fields, and feed parasitics. Use it to seed a starting geometry, then let the FDTD sim refine. Do not expect the calculator W and the patch on the canvas to match exactly. They should not.

Step-by-step breakdown

The link at the bottom right of each calculator (Step-by-step breakdown on RayRF) opens a longer companion page on the website with the formulas, derivations, and the typical accuracy band of each model.