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Open source RF signal generator features WiFi

Jun 12, 2017 — by Eric Brown 2,384 views

An Arduino-Due based “ERASynth” RF signal generator starts at $499, and offers WiFi and a multiloop integer-N PLL for better performance and reduced noise.

Istanbul, Turkey based startup ERA Instruments has successfully funded its open spec ERASynth RF signal generator on Crowd Supply, having raised over $30,000. The ERASynth offers some features found on much more expensive commercial RF signal generators, including WiFi and a multiloop integer-N PLL, says ERA Instruments. The device is available through June 16 selling for $499 (10MHz to 6GHz) or $749 (250kHz to 15GHz) for the ERASynth+ model, with shipments due Sep. 21. The product also stands out with its open schematics and open source firmware and GUI software.

(click images to enlarge)

The ERASynth runs Arduino and web GUI source code on an Arduino Due board based on the Atmel SAM3X8E Cortex-M3 MCU. The compact, 145 x 100 x 20mm system provides WiFi with the help of an Espressif ESP8266 wireless module.

RF signal generators like the ERASynth can be used as a signal source for any radio frequency testing, such as measuring the gain of an amplifier or testing SDR (software defined radio) applications. The ERASynth can also serve as an “agile LO source” for up- and down-converters, or as a clock source for ADCs and DACs, says ERA Instruments.


Potential customers are said to include makers, students, educators, and researchers. Even professional RF engineers with access to higher end equipment may be interested in the device’s portability and open source nature, says the company.

ERASynth (left) and block diagram
(click images to enlarge)

Most under-$1,000 RF signal generators are limited to USB access instead of the WiFi and serial, and USB connections found on the ERASynth. More importantly, they are typically limited to “a single fractional PLL IC with integrated VCO,” says ERA Instruments. “While fractional-N PLL are great for generating frequencies with fine frequency resolution, they suffer from a phenomenon called ‘integer boundary spurs’ (IB spurs)” that can be as large as -30 dB, says the company.

By comparison, ERASynth’s multi-loop architecture “eliminates IB spurs by varying the reference in fine steps while keeping the main loop in integer-N mode,” says ERA Instruments. “This architecture not only diminishes IB spurs but also helps reduce phase noise.”

The base-level ERASynth has a typical phase noise rating of -120 dBc/Hz while the higher-frequency ERASynth+ is rated at -125 dBc/Hz. Both devices have a -60 to +15 dBm amplitude range and a 100 µs frequency switching time.

ERASynth detail view (left) and web GUI
(click images to enlarge)

The entry level ERASynth integrates a ±0.5 ppm TCXO (temperature compensated crystal oscillator) reference while the ERASynth+ has a higher performance ±25 ppb OCXO (oven-controlled crystal oscillator) reference. (If, like us, you’re not up on your oscillators, you may want to check out this helpful comparison. )

One reason you don’t see WiFi on most RF signal generators is the risk of signal contamination. However, ERA Instruments claims the problem has been solved thanks to extensive partitioning “to protect sensitive areas from the outside world and from the other noisy areas on the board itself.”

Other features include serial (mini-USB) and micro-USB interfaces, a 5-12V power input, and a WiFi antenna connector. You also get REF IN and REF OUT connectors, a trigger input, an RF out interface.

There were relatively few details on the Arduino code, web GUI source code, and RS-232 command set except that the web GUI includes an HTTP server, and all source code will be posted on GitHub. There are no plans to provide mobile apps, but the software can run on smartphone browsers. The hardware will be offered with an undetermined permissive license.

Further information

The ERASynth is available on Crowd Supply through June 16 for $499 for (10MHz to 6GHz) or $749 (250kHz to 15GHz), with shipments due Sep. 21. More information may be found on the ERASynth Crowd Supply page and ERA Instruments website.

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