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 14 tools and 210 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) 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-15 eye diagram. Extracts insertion loss, group delay, and impedance profile, then renders the eye with jitter and ISI.
NEC2 Wire Antenna Simulation
Simulate wire antennas (dipoles, yagis, loops) using the NEC2 method-of-moments engine. Get 3D radiation patterns, gain, impedance, and efficiency across a frequency sweep.
S-Parameter Analysis Pipeline
Upload up to 4 Touchstone files and get insertion loss, return loss, group delay, TDR impedance profile, and passband ripple — all in one automated report.
FDTD Transmission Line Simulator
Full-wave 3D FDTD simulation of microstrip stubs, coupled-line filters, via transitions, and step discontinuities using openEMS. Get 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
Vendor-agnostic NSGA-II optimizer finds Pareto-optimal core and winding designs across 113 cores (EE, ETD, PQ, RM, Toroid) from TDK, Ferroxcube, Magnetics Inc., and Micrometals. 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
Optimize decoupling capacitor selection for PCB power delivery networks. Model plane-pair cavity resonances, specify board geometry and target impedance, then let the genetic algorithm find the optimal capacitor combination to keep Z_PDN below your target across all frequencies.
Satellite & Terrestrial Link Budget
Compute probabilistic link margins using ITU-R propagation models (P.618 rain, P.676 gaseous, P.840 cloud). Enter EIRP, G/T, frequency, and site location. 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 — typed Python client for all 203 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 14 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. 14 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) wraps both endpoints with typed inputs. API tier gives 10,000 calls/month; the MCP server (rftools-mcp on npm) exposes the same catalog to AI agents (ChatGPT, Claude Desktop, Cursor).
What about the 210 calculators — where do those fit in?
The 210 calculators at /calculators solve closed-form problems (Friis link budget, VSWR, Smith chart, trace impedance, etc.) — they run in your browser instantly. The 14 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.