The Waves module for the Ambient Energy Monitor (Rev. 1 compatible) is an integrated RF energy harvesting add-on capable of detecting and measuring electromagnetic energy in the frequency range 80 MHz up to 4 GHz, covering most frequency bands used for modern analog and digital communication. Rev. 1 of the Waves module features 3 SMA connectors to connect antennas with overlapping gain bandwidth to the module, and an additional SMA connector to hook up an antenna for harvesting purposes.
The RF detection system is based on the CCC 2015 Rad1o badge design, a development kit for SDR (Software Defined Radio) with a frequency range of 50 MHz up to 4 GHz. This in turn is an extension of the HackRF One design. For RF measurement purposes, the Rad1o badge design has been simplified to a generic superheterodyne receiver with IQ demodulator, allowing the removal of the image rejection filter at the input. The RF front end of the Rad1o badge has been inherited: MAX2616 LNA, MAX2871 VCO and LTC5510 mixer. In addition, an Analog Devices ADL5513 RMS meter and 10 MHz crystal filter were added for RF amplitude measurement with high frequency selectivity. The LF front end consists of an AD7705 ADC.
The second part implements an actual RF energy harvesting system, using an RFD102A integrated RF to DC converter, a precision electronic load, and an ADC.
Revision 2 brings a few changes: the AD7705 was swapped for the AD7689 because its superior driver, ground reference has been improved, USB support for status, programming and power added, a switched mode power supply for ultra low noise analog power rail improvement, and a complete redesign of the RF harvester front end with 90 dB dynamic range.
March 2018 update: it was found that in AEM Waves Rev. 2.0 the SPI series resistors R7 .. R10 are causing problems when bootloading the microcontroller. If problems are experienced bootloading the board, these resistors can be (temporarily) bridged with a jumper (0 ohm resistor). It should be noted that the faster rise times will significantly increase EMI generated by SPI communication, however.
To burn the Optiboot bootloader into the microcontroller, get it from the AEM github repository, then burn it with avrdude as follows:
$ avrdude -c jtag2isp -p atmega2560 -P usb -vv -Uflash:w:stk500boot_v2_mega2560.hex -U lfuse:w:0xFF:m -U hfuse:w:0xD8:m -U efuse:w:0xFD:m -U lock:w:0xFF:m
The Bill of Materials for all versions of the board is attached below.