This cellular phone detector schematic circuit can sense the presence of an activated mobile cell phone from a distance of one and-a-half meters.
If a RF signal is detected the circuit will inform you using a sound alarm (beep sound ) and a blinking LED .

In this type of circuit (that use high frequency 0.9-3Ghz ) you can not use an LC circuit for frequency tuning  .
The circuit uses a 0.22μF disk capacitor (C3) to according the RF circuit to ensure the capability of the circuit to capture the mobile phone signal .
This cellular phone detector can detect any activity of a mobile phone : incoming or outgoing SMS , video transmission or voice transmission .
The C3 capacitor must have leads length of 18 mm with 8 mm spacing between leads to obtain the desired frequency .  This small disk capacitor acts as a small gigahertz loop antenna to collect the RF signals  .
The CA3130 operational amplifier IC is used as a current to voltage converter .
This cellular phone detector electronic circuit diagram can be used to verify the presence of an active cellular phone in the tested area .

Cellular phone detector electronic circuit diagram