Free RF Simulation Tools — Browser-Based, No Install
Impedance matching, S-parameter analysis, Monte Carlo filter tolerance, satellite link budgets, FDTD, and 9 more — all free, all in-browser, no signup required. Server-side compute for jobs too heavy for instant calculators.
Not sure which simulation tool fits your problem?
Describe what you want to simulate in plain English. The AI assistant picks from all 13 tools and 255 calculators.
rftools.io vs. commercial RF simulation software
Commercial suites like Keysight ADS, Cadence AWR, MATLAB RF Toolbox, and AGI STK cost $10,000+ per seat per year and excel at 3D electromagnetic simulation, nonlinear circuit co-simulation, and production tape-out. rftools.io covers the 80% of RF design questions that fit into closed-form or semi-analytic models: matching synthesis, S-parameter cascading, link budgets, control-loop stability, radiated EMI estimates. Use this when you want an answer in seconds, not minutes.
- Accept .s1p / .s2p / .s3p / .s4p Touchstone files on matching, cascade, and pipeline tools
- Export to Touchstone, SPICE netlist, KiCad schematic, and CSV
- Share scenarios via URL — every tool round-trips its inputs through query params
- Python client (pip install rftools-io) and MCP server for AI agents
Broadband Impedance Matching Synthesizer
Synthesize L, Pi, T, or ladder matching networks for broadband impedance transformation. Enter source/load impedances across a frequency band and get optimized component values with simulated S-parameters. Export results as Touchstone (.s2p) for ADS/Genesys/scikit-rf.
RF Filter Monte Carlo Analysis
Analyse how component tolerances affect your filter's passband ripple and stopband rejection. Run thousands of Monte Carlo trials to get yield and worst-case statistics.
Eye Diagram from S-Parameters
Upload a Touchstone (.s2p) file and generate a PRBS eye diagram. Shows the channel insertion loss and impulse response, then renders the eye with its height, width and jitter measured over the whole bit sequence.
Wire Antenna Simulator (NEC-2)
Solve your own wire antenna with the NEC-2 method of moments: dipoles, Yagis, verticals and loops, element by element. Radiation pattern, gain, impedance, VSWR, efficiency and current distribution, at one frequency or across a sweep, with a multi-objective optimiser on Pro.
S-Parameter Analysis Pipeline
Upload up to 4 Touchstone files and get component values (L, C, R, Q, self-resonance) for a single component, plus insertion loss, return loss, group delay, TDR and passband ripple — all in one automated report.
FDTD Transmission Line Simulator
Solve microstrip stubs, coupled-line filters, via transitions, and step discontinuities across a ladder of named solve modes — from a 2D cross-section in seconds to a fine 3D openEMS field solve. S-parameters, Smith chart, and impedance analysis.
SMPS Control Loop Stability Analyzer
Model switch-mode power supply control loops using small-signal transfer functions. Get Bode plots of T(s), extract phase margin, gain margin, and crossover frequency, then run Monte Carlo trials over component tolerances (L ±20%, C ±20%, ESR ±50%, load ±30%) to compute manufacturing yield.
EMI Radiated Emissions Estimator
Estimate radiated emissions from PCB loops and cables using Paul's analytical DM/CM models. Monte Carlo confidence intervals vs. FCC Part 15 and CISPR 32 limits.
Magnetics & Transformer Design Optimizer
NSGA-II optimizer finds Pareto-optimal core and winding designs across 40 cores (E, ETD, PQ, RM and toroids) and 104 core/material combinations, with TDK and Ferroxcube ferrites and Micrometals iron powder. Minimizes total loss and volume simultaneously — shows the full efficiency-vs-size trade-off frontier.
Radar Detection Performance Monte Carlo
Compute probability of detection (Pd) vs range for pulsed radar systems. Select Swerling target model (0–IV), specify antenna gains, noise figure, pulse parameters, and rain rate. Monte Carlo over RCS fluctuations and system uncertainties produces Pd confidence bands and ROC curves.
PDN Impedance Analyzer & Decoupling Capacitor Optimizer
Choose decoupling capacitors for a PCB power delivery network. Enter the plane pair, the regulator and a flat target impedance, and a genetic algorithm finds the capacitor mix that keeps Z_PDN lowest across the decoupling band, which ends at 0.8 × the board's first cavity mode. Above the band the plane-pair cavity sets the impedance; the plot shows its resonances as one observation port sees them, with every capacitor lumped at that port.
Satellite & Terrestrial Link Budget
Compute probabilistic link margins using ITU-R propagation models (P.618 rain, P.676 gaseous, P.840 cloud) with climate data read from the ITU-R maps at your site. Enter EIRP, G/T, frequency, and site latitude and longitude. Get a full line-by-line budget, availability curve, and Monte Carlo confidence intervals over rain, pointing, and EIRP/G·T uncertainties.
RF Cascade Budget Analyzer
Compute cascaded noise figure, gain, IIP3, and P1dB for an N-stage RF signal chain using Friis formulas. Paste your stage list as JSON, set your system specs, and get a line-by-line cascade table, sensitivity analysis, and Monte Carlo yield statistics across component tolerances.
Interactive Design Tools
Visual, in-browser tools for PCB and signal integrity — no queue, instant results.
PCB Stack-Up BuilderNew
Build layer stacks visually. Compute microstrip, stripline, and differential pair impedance with Hammerstad-Jensen accuracy. Supports FR4, Rogers, and Megtron 6.
Live Data Tools
Real-time data from NOAA, N2YO, and regulatory databases — no queue, instant results.
Satellite Pass Predictor & Link Budget
Predict amateur radio and weather satellite passes with free-space path loss, Doppler shift, and atmospheric loss. 25 satellites including ISS, NOAA APT, and FM repeaters.
S-Parameter Viewer
Upload Touchstone (.s1p, .s2p) files and plot S-parameters as magnitude (dB), phase, or VSWR. Runs entirely in-browser — no upload to any server.
Developer Tools
Integrate rftools.io calculators into your own scripts, notebooks, and applications.
Python Library — rftools
pip install rftools-io — typed Python client for all 255 calculators with batch mode, async support, and a CLI. Ideal for parameter sweeps in Jupyter notebooks.
REST API
POST to /api/py/v1/calculate with any calculator slug and inputs. Returns JSON with computed values. 10,000 calls/month on the API tier.
Interactive Guides
Step-by-step explorable explanations of core RF concepts.
How the Smith Chart Works
Interactive explorable explanation: drag impedance points, watch reflections, and build matching networks step by step.
Frequently asked questions
Are these RF simulation tools really free?
Yes — every tool on this page runs without signup on the free tier. Free jobs share compute with other users and wait in a queue (typical wait under a minute). Pro tier ($9/mo) adds a priority queue and cloud-saved scenarios; API tier ($19/mo) adds REST access. Client-side tools (S-parameter viewer, PCB stack-up builder) always run instantly in your browser.
Do I need to install anything?
No. All 13 tools run in the browser. The heavy simulations (FDTD, Monte Carlo, NEC-2 antenna) execute server-side on our compute cluster and return results to your browser; nothing runs on your machine. You never download or install a binary.
How does this compare to Keysight ADS, Cadence AWR, or MATLAB RF Toolbox?
Commercial RF design suites cost $10,000+ per seat per year and are the right choice for 3D electromagnetic simulation, full nonlinear circuit co-simulation, and production tape-out flows. rftools.io covers the 80% of RF design questions that fit into closed-form or semi-analytic models: impedance matching synthesis, S-parameter cascading, link budgets, control-loop stability, radiated EMI estimates. If your question takes minutes to answer in a commercial tool, it usually takes seconds here.
Can I export to Touchstone (.sNp), SPICE, or KiCad?
Yes. The S-Parameter Pipeline exports to .sNp (1–4 ports). The Impedance Matching Synthesizer imports .s2p files and exports the synthesized match as Touchstone, SPICE netlists, and KiCad schematics. The RF Cascade Analyzer accepts per-stage .s2p uploads. 16 calculators also export KiCad. See each tool page for the full export list.
Is there an API for automation?
Yes. POST to /api/py/v1/calculate with any calculator slug for synchronous results, or /api/py/v1/jobs for async simulation tools. The Python client (pip install rftools-io) wraps both endpoints with typed inputs. The API plan includes 10,000 calls a month; the MCP server (rftools-mcp on npm) exposes the same catalog to AI agents (ChatGPT, Claude Desktop, Cursor).
What about the 255 calculators — where do those fit in?
The 255 calculators at /calculators solve closed-form problems (Friis link budget, VSWR, Smith chart, trace impedance, etc.) — they run in your browser instantly. The 13 tools here solve problems that need iterative or statistical compute (Monte Carlo, FDTD, nonlinear solve, optimization). Use calculators for first-pass sizing; escalate to tools when the problem needs simulation.