RF Engineer Network

Free RF design reference

RF Engineer Network

A free, engineering-grade RF design reference for working engineers and students: the equations, the worked numbers and the reasoning behind each design choice.

Start with the RF Design guideBrowse the calculators
  • 17topic hubs
  • 20part Radio Architectures series
  • 10free calculators
Spectrum analyzer view of a 20 MHz channel above the noise floor Power spectral density in dBm/Hz against frequency offset in MHz, 10 dB per division. A flat-topped 20 MHz channel sits at minus 110 dBm/Hz with adjacent-channel skirts 40 dB lower (ACLR 40 dB). The receiver noise floor is at minus 168 dBm/Hz: the thermal floor kT of minus 174 dBm/Hz plus a 6 dB noise figure. The channel is 58 dB above that floor. −80 −90 −100 −110 −120 −130 −140 −150 −160 −170 −180 −190 −50 −40 −30 −20 −10 0 10 20 30 40 50 REF −80 dBm/Hz 10 dB/div RBW 100 kHz kT −174 dBm/Hz NF 6 dB Channel 20 MHz SNR 58 dB ACLR 40 dB S11 −19.1 dB offset from carrier (MHz) dBm/Hz
A 20 MHz channel 58 dB above the receiver noise floor: kT at 290 K is −174 dBm/Hz, and a 6 dB noise figure lifts the floor to −168 dBm/Hz.
Start here

A learning path in six steps

Read these in order. Each step uses the units and ideas from the one before it.

Full learning roadmap
  1. RF fundamentals dBm to watts scale and a sine wave showing wavelengthStep 1

    RF Fundamentals

    Units, wavelength, power, Q and parasitics.

  2. dBm scale from -30 dBm to +50 dBm with the +3 dB and +10 dB power rulesStep 2

    dB, dBm, dBW and dBc

    Decibel units, a conversion table and a converter.

  3. S-parameters two-port network with incident and reflected waves and the S11 and S21 definitionsStep 3

    S-Parameters

    Incident and reflected waves, S11, return loss and VSWR.

  4. RF noise trace with a 6 dB noise figure above the -174 dBm/Hz thermal limitStep 4

    Noise in RF Systems

    Thermal noise, noise figure and sensitivity.

  5. RF linearity intercept plot with IM3 slope 3 meeting the fundamental at OIP3Step 5

    Linearity and Distortion

    Compression, harmonics and intermodulation.

  6. Superheterodyne receiver chain with running noise figure from the Friis formulaStep 6

    Radio Architectures

    Put the blocks together into complete receivers and transmitters.

Topic hubs

Every topic, from first principles to finished radio

The RF Design guide maps the whole subject. Each hub below collects the articles, worked examples and calculators for one area.

RF design Smith chart showing an L-match from a 15 minus j20 ohm load to 50 ohms at 1 GHzStart here: the pillar guide

RF Design: The Complete Guide

A complete guide to RF design: definition, design flow, figures of merit, a worked receiver example and a map of every section.

 RF fundamentals dBm to watts scale and a sine wave showing wavelengthHub

RF Fundamentals

The basics of RF engineering: units, wavelength, power, Q, skin effect and parasitics, and why lumped models fail at RF.

 Transmission line standing wave with a 100 ohm load on a 50 ohm line, VSWR 2.0Hub

Transmission Lines and Impedance Matching

Line theory, terminations, reflection, VSWR, microstrip, CPW, stripline, waveguides, the Smith chart and matching networks.

 RF noise trace with a 6 dB noise figure above the -174 dBm/Hz thermal limitHub

Noise in RF Systems

Thermal, shot, flicker and phase noise in RF circuits, with the articles on noise figure and sensitivity.

 RF linearity intercept plot with IM3 slope 3 meeting the fundamental at OIP3Hub

Linearity and Distortion

How the power-series model explains compression, harmonics and intermodulation, with links to every linearity topic.

 RF amplifier output power and gain versus input power with OP1dB and PsatHub

RF Amplifiers

RF amplifier types and datasheet specifications, with links to every amplifier design and selection page.

 RF filter response comparing 5-pole Chebyshev and Butterworth low-pass designsHub

RF Filters

How resonator Q sets filter loss, how to size filter order for rejection, and where LC, ceramic, SAW, BAW and cavity filters fit.

 Oscillator phase noise curve from the Leeson modelHub

Oscillators and Frequency Synthesis

How feedback oscillators start and settle, what the Barkhausen criteria require, and how references, VCOs and PLLs fit together.

 RF mixer output spectrum with IF, sum and harmonic productsHub

Mixers and Frequency Conversion

How an RF mixer multiplies a signal by a local oscillator to shift its frequency, and the specifications used to compare mixers.

 Superheterodyne receiver chain with running noise figure from the Friis formulaHub

Radio Architectures: 20-Part Series

Index to the series, with an architecture comparison table and reading paths for students and engineers.

 Wilkinson power divider schematic beside its S-parameter responseHub

RF Passive Components

Couplers, dividers, attenuators, circulators, switches and detectors: the parts between the active stages of a radio.

 Antenna array polar pattern of an 8-element half-wavelength arrayHub

Antennas and Propagation

How antennas turn guided signals into radiated waves, and how antenna gain and path loss decide what reaches the receiver.

 16-QAM constellation diagram at 20 dB SNR with 10 percent EVMHub

Modulation for RF Designers

AM, FM and PM, then ASK, FSK, PSK, QAM, PAM and OFDM, plus ACLR and constellation diagrams.

 VNA style S21 and S11 sweep of a series RLC in a 50 ohm lineHub

RF Measurement and Test

RF test equipment and good measurement practice, with links to every measurement guide on the site.

 RF simulation of S11 for one and two section quarter-wave impedance matchingHub

RF Design Tools and Simulators

RF simulators compared, free design software, harmonic balance and EM simulation, and Python with scikit-rf.

 Microstrip impedance calculator curves versus W/h for three substratesHub

RF Calculators

Every RF calculator on the site in one place, with the formula behind each.

 Free-space path loss versus distance for Wi-Fi, radar, 5G, LoRa, GNSS and satellite linksHub

RF Design by Application

RF design for SDR, IoT, GNSS, radar, 5G and satellite links, and how their priorities differ.

 RF engineering career skills as rising steps from fundamentals to radio systemsHub

Learning RF Design and Careers

Careers in RF engineering, a learning roadmap, recommended books, interview questions and the glossary.
Series

Radio Architectures, in 20 parts

A complete course on how radios are built, from the superheterodyne receiver to mmWave arrays and how to measure the result. Read it in order or jump to a part.

Series index and reading paths
  1. Pt 01Understanding radio architectures
  2. Pt 02Receivers, LOs and mixers
  3. Pt 03Intermodulation and intercept points
  4. Pt 04Receiver sensitivity
  5. Pt 05ADCs and receivers
  6. Pt 06Transmitter architectures
  7. Pt 07Power amplifier classes and efficiency
  8. Pt 08PA linearization: feedforward, DPD, Doherty
  9. Pt 09RF filters
  10. Pt 10PLLs, frequency synthesis and phase noise
  11. Pt 11DACs and the transmit signal chain
  12. Pt 12Zero-IF receivers, DC offset and I/Q imbalance
  13. Pt 13Direct RF sampling and SDR
  14. Pt 14Front-end modules, duplexers and switches
  15. Pt 15Link budgets
  16. Pt 16Modulation, EVM and PAPR
  17. Pt 17Antennas and propagation
  18. Pt 18MIMO, beamforming and phased arrays
  19. Pt 19mmWave radio architectures
  20. Pt 20Measuring radio performance
Tools

Free RF calculators

Each calculator sits on a page that explains the formula behind it.

All calculators
dB / dBm converterdBm, dBW, mW and W VSWR and return lossVSWR, RL, |Γ|, mismatch loss Cascaded noise figureFriis cascade: NF, gain, IP3 Microstrip impedanceHammerstad and Wheeler Link budgetReceived power and link margin Free-space path lossFSPL vs distance and frequency Pi and T attenuatorsMatched resistor values Impedance matchingL, Pi and T networks Coplanar waveguideCPW and GCPW gap and impedance Patch antennaWidth, length and inset feed
Popular guides

Reader favourites

New to RF?

Follow the roadmap from the maths you need to a first system calculation, and keep the glossary open while you read.

How to learn RF designWireless terms glossary
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