Integrating AD8318 RF power meter with Arduino Uno

Hello all,

I have been using Arduino for school projects for about a year now. I am pretty comfortable with the basics of the Arduino syntax. I am currently in the middle of a mechanical engineering senior design project. As a part of a system of things we are making for this project, one component involves recognizing the signal strength of radio frequencies.

Due to this, I purchased the AD8318 RF power meter. According to the data sheet it can receive the RF signals and convert them into a corresponding output voltage from 0 to 5 volts. I am however having trouble getting any sort of reading from the device to the Arduino. I have attached a picture of how I connected the RF power meter to the Arduino. The VCC went the 5V pin, ground to ground, 1st Vout to A0 pin, and 2nd Vout to A1 pin.

After I have the device connected to the Arduino. I have a basic code to analogRead both of the voltage out pins. I’d assume these pins should be set as OUTPUTS, but I have tried setting the pins as INPUTS as well. The analogRead or analogWrite values are being printed to the serial monitor so I can watch if they change based on incoming RF signals.

I have a 3.5 GHz SMA antenna connected to the female SMA of the RFin for the power meter. I also have a 315 MHz RF transmitter key fob that I am using to send RF signals to the AD8318.

The values that I am reading in the serial monitor do not change no matter how close or far I transmit the RF signals to it. I am very ignorant of how to design this circuit and/or code to detect the frequencies from the RF key fob transmitter and convert it into an output voltage. Any help or tips in the right direction would be very appreciated. Thanks in advance!

Here is the datasheet for the AD8318 for reference:

ad8318-converted-edited.pdf (24.4 KB)

Don't declare analog pins as Inputs or Outputs in setup(). Having arduino, you have a voltmeter, keeping basic sketch "analog out serial" running, you could do a basic troubleshooting. Put a jump wire to analog pin associated with analogRead() in the code, and try to measure voltages (it's easy to convert ADC binary to milliVolts) all around the main AD8318 IC. Try not to short any pins, better to touch neighboring R or C components, they bigger spaced. Come back and post results, mVolts and pins of IC as a table.

3.5 GHz SMA antenna

That won't work well, if at all. For 315 MHz, use about 24 cm of long wire, which is 1/4 wavelength. Better, use a "sleeve type" balanced dipole made from shielded cable with an SMA connector. Plenty of design info on the web.

That power meter chip has a minimum power level of -60 dbm in a 50 ohm load. You will be struggling to get that much from a keyfob as they use an inefficient microstrip antenna inside the fob , and the transmit power is only around 10 mw. The power meter is designed to be connected to the RF source you want to measure directly via coax cable, not via an antenna , as the power meter is a broadband untuned amplifier which will pick up anything.