# Microwave detection circuit verification

I want to develop a circuit which can detect electromagnetic waves (radio wave, microwaves.)

This circuit will just act as a tamper detect and not physically measure/compute the radiation.

I have designed the circuit using a toroid ring and a few Schottky diodes.

The calculation formulas and schematic diagram are in the attachment.

After testing the circuit, I'm not getting any output.

Hence, I wanted to get the circuit as well as the calculation part of it verified.

Please note that the WAVE_SENSE signal in the design is connected to a 10-bit ADC of a microcontroller.

• Are you expecting the coil to receive microwaves? If so, you can give up on that. It won't work at the frequencies you are interested in. – JRE Apr 30 at 9:46
• Toroids are closed loops, they tend to cancel outside fields. ie. they do not make good antennas. – Aaron Apr 30 at 18:00

1. Your coil won't be responsive at the frequencies you are interested in. I don't have the math to figure it, but I have some experience as a technician with radio frequency circuits. That coil on that core will probably do a dandy job of filtering microwave signals out of your receiver.
2. Those diodes probably won't work at microwave frequencies, either. The BAT43 datasheet only mentions frequencies twice: 1MHz and 45MHz. That diode isn't made for GHz frequencies like you will need to detect microwaves.
• You need a better diode. I have used the BAT63 for a similar project.
• You need an antenna instead of that coil. I used a simple dipole antenna. Just two equal length wires of approximately 1/4 the wavelength of the operating frequency you are interested in.

The circuit that I built used a sort of voltage multiplier to drive a few LEDs to indicate the RF level.

It looked like this:

You could simplify it to this:

Use two wires of about 3 centimeter length as antennas connected to P1 and P2. 3 centimeters is approximately correct for 2.5GHz. That's about 1/4 the wavelength of 2.5GHz.

• Thankyou JRE, Looks like a circuit worth testing. – Pralay Panchwate Apr 30 at 12:21
• @PralayPanchwate: Keep in mind that you can't build this on a solderless breadboard. High frequency stufff does not play nice with solderless breadboards. The BAT63 is purely a surface mount part, and you want to use surface mount parts for the capacitors as well. I used size 0201 SMD capacitors for the 10pF parts. – JRE Apr 30 at 13:14