Radio ReceiverGroup-1 ADC, SEM-IV

Kavi Pandya - 131020Maninder Sambhi - 131024Prarthana Padia - 131035Prem Shah - 131036

Antenna and GroundAntenna

● made of copper wire(open or isolated)● length - 6m or more ● follows TLTB Law (the Longer, the Better)● not to be placed near electronic devices● act as voltage generator because of resistance & capacitance(C1)● C1 length of antenna∝

Ground● used for better reception● receiver ground connected to ground via copper wire● copper wire connected to plumbing pipe of length 80cm ● connection made with ring and a screw with bolt

Oscillatory Circuit(This parallel LC Circuit acts as oscillator circuit as charging of capacitor reduces magnetic field of inductor and vice-versa which results in an infinite sinusoids. It consists of variable capacitor and fixed inductor.)

It has two functions to perform in Radio Receiver :i)Band-Pass Filter/Separate the signal of required Station from Others – Antenna receives various signals both required and unrequired. To separate out the required signal we tune the capacitor to the same frequency(resonant) as that of the required signal.●

ii)Amplify the signal and proceed to rectifier – The gain of Band-Pass filter is multiplied with the tuned signal thus amplifying the input signal.Input of Oscillator Circuit :α(V1 + m1(t))Cos(w1t) + α(V2 + m2(t))Cos(w2t) + ….. + α(Vi + mi(t))Cos(wit)Output of Oscillator Circuit :If we need the signal with frequency at w4, so we tune the capacitor accordingly and get:kα(V4 + m4(t))Cos(w4t)α – attenuation and k – band-pass gain. Thus Oscillator acts as band-pass filter(allowing only signal at frequency w4 to pass) and amplifier(as the output signal is multiplied by the gain of band-pass filter)

RectifierAM Signal Detector:The rectifier performs the function of eliminating and obtaining the original signal from the amplified one received from the transmitterThe AM signal detector (rectifier) comprises of a diode capacitor and the headphone resistance. The output obtained is an envelope of the AM signal containing only original signal: Gain*(mit)cos(wit)Here, the product of the capacitance and the headphone resistance should be approximately equal to 50 microsecondsThe headphones are used here to convert the electrical signal into sound that can be heard. The original signal obtained after passing through the rectifier can be heard through the headphones which are of 3 kU resistance.Here the original output is obtained when the AM signal of the station to which the receiver is tuned is brought on its input.

LF Audio AmplifierNeed: To enhance the sound reproduction on the receiver’s end.

Components significance:C4: Used because it obtains the voltage negative feedbackR2: Adjusts the transistor optimal reproductionR3: Used because it obtains the current negative feedbackC5: Prevents the AM signal carrier

Use of R3, C4 increases Stability, reduces Distortion and widens the reception band. But for this, the trade-off is reduction in amplification.

This Audio (LF) amplifier adjusts the gain.Let output voltage= Vo,Vo=KifKKmKbαVm(t)

If α increases, Kb needs to be reduced. This could be managed by the Audio amplifier.

Reference1.http://www.mikroe.com/old/books/rrbook/rrbook.htm