gigahertz signal detector circuit

Posted on Feb 5, 2014

This circuit is useful to detect microwave (gigahertz signal) sources like microwave oven, satellite communication devices, Mobile phones etc. It gives audio visual indications when it detects the Microwaves in the Gigahertz band. Microwave is the form of EM radiation with frequencies between 2 GHz and 300 GHz. Microwave oven uses UHF around 3 GHz

gigahertz signal detector circuit
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in the S band. Mobile phones and Satellite devices generally use 2 to 3. 5 Gigahertz signals. The circuit exploits a few simple scientific facts about EM radiations and Magnetic induction. Electromagnetic radiation has both electrical and magnetic field components which oscillate in phase perpendicular to each other to the direction of energy propagation. If an inductor coil with a parallel capacitor is placed in the path of EM radiation, the capacitor stores electrical energy and inductor stores energy in the magnetic field induced by the coil windings. The magnetic field induces a current in the inductor through` Skin Effect`. This phenomenon is exploited in the circuit to detect the energetic microwave radiations. A pickup coil (L2) with a capacitor (C2) forms the signal detector which resonates in response to the microwave radiation and generates a minute voltage (around 2 milli volts) along the signal diodes D1 and D2. Since the voltage generated by the sensor assembly is too weak, a differential amplifier (IC1) is used to amplify the signal. CA 3130 (IC1) is designed as a differential amplifier with balanced inputs set by R1 and the sensor assembly. The pickup coil is directly coupled to the inverting and non inverting inputs of IC1, so that a minute current in the pickup coil can generate a potential difference across the inputs of IC1 and its output switches high. CA 3130 ( IC1) is a CMOS version high speed...

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