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GigaHertz Signal Detector Circuit

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 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.

Related Products: RF ICs Misc

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.

GHz Signal Detector Circuit Diagram

CA 3130 ( IC1) is a CMOS version high speed switching Operational amplifier with gate protected p- channel MOSFET transistors in the inputs. This makes the IC suitable to switch the output high with a current as low as 2 pA. VR is provided for the offset adjustment and bias the internal circuitry of the IC1, so that its output is ordinarily held low. Resistor R3 gives some negative feed back to the amplifier.

When the bursts of microwave impinge on the Loop aerial (L1, it pickup the energy from the radiation and transfer it to the inductor coil (L2) This creates an alternating current in the inductor which passes to the inputs of IC1 through C1 and D1.

Signal diodes D1 and D2 (BAT 43 Shottky Diodes) directs the induced current into the inputs of IC1 and the capacitor C3 provides suitable stabilization of the non inverting input of IC1. Diodes D1 and D2 also perform the function of signal detection. Normally the inputs of IC1 are biased by R1 and C2, and its output is set low by VR. When there is a microwave radiation near the sensor coil, it generates a current that upsets the balance in the inputs of IC1 and its output switches high to drive the switching transistor T1.

Buzzer starts sounding and LED lights indicating the presence of Microwave. Sensor assembly is the important part of the circuit and should be prepared carefully. L2 can be a miniature coil with ferrite core. This can be procured from an old CFL. L1 is the common dipole TV antenna. When the circuit is first powered up, VR needs adjustments to keep the buzzer and LED off. The circuit is immune to other forms of RF radiations but can detect the Giga Hertz signals from an active mobile phone.

Experimentation

There is lot of room for experimentation. To detect different frequencies, experiment with different values of C1, C2, D1, and D2. Also try different types of coils in the place of L2. Try to use a TV signal booster between the dipole and input of circuit.

14 Comments

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  • Sebi

    I’m looking for Bluetooth detecting circuit diagram,can u please help me

  • Raj

    I will try design sensitive signal detector device please help us to me

  • Dinesh83

    could u plz send me a more detail circuit diagram explanation.
    i would like to do a project on this topic
    specially about number of turns L2

  • amit kumar

    please provide me the complete ppt of gigahertz signal detector

  • ANAYAT KHAN

    Assalam-o-alaikum!
    Sir, I like your project and i wish to do it but the problem is that how I can display the frequencies which the detector detects the real problem arises how I count or measure the these frequencies……………
    Sir can you help in that…………….

    • Arun.R.Nair

      Sir,
      I would like to do this project to sense the presence of microwaves emitted during the time of attending a phone call…we are doing a project so as to stop the drivers who using mobiles at time of driving…. I need to know how to display the detected frequency? and what will the range of this particular design? and the whole design of this circuit?.. need your reply as soon as possible….

    • cal

      hi, were you able to do this project topic…i need help i would really appreciate it if you could let me know. you can contact me through this email address.

      Its ROSTOTO@YAHOO.COM

      Thank you in advance!!

  • sindhu

    Im working on a project of mobile bug.can you plzzz suggest me the circuit with a modification near the buzzer by adding a transistor and plzzz mail me the circuit to my ID.reddy.sindhu272@gmail.com

  • sudheer

    could you please send me the details of ic CA 3130, in this ic what is the meaning of “CA” and NE 555 timer ,what is the meaning of “NE”

    • D.Mohankumar

      CA 3130 is the product from Harris Semiconductors. CA represents the product code. NE555 is from NXP Semiconductors. It is the Philips semiconductor product.
      IC coding is based on the company brand code.For details of IC down load from http://www.alldatasheets.com by giving IC number in part name search

    • lindo

      ah sory sir can i use this project as an alignment tool for my satelite dish? can u send or sugest any DIY project for satelite finder

  • el jay

    mr mohan
    could u plz send me a more detail circuit diagram explanation.
    i would like to do a project on this topic

  • D.Mohankumar

    Please specify

  • Samuel Luyimbaazi

    Please give the Art number for the IC

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