__UNIT 2:__

__Short answer questions:__

- What is meant by Carson’s rule? Problem on calculation of Bandwidth of FM signal using Carson’s rule.(imp)
- Distinguish between NBFM and WBFM.(imp)
- Problems on instantaneous phase and frequency.
- What is the basic principle involved in Phase discriminator?
- Define capture range and lock range of a PLL.
- Problem on Armstrong method of generation of a WBFM signal?(imp)
- Capture effect and threshold effects in FM (very very imp).
- Problems on carrier swing, frequency deviation, BW, modulation index etc.
- Phasor diagrams of NBFM and AM.
- What is the need for limiter in FM receivers? (Very very imp).
- Find the maximum Frequency deviation of Frequency Modulated signal given by S(t) = 10 cos(1000000 *pi*t + 5 sin(2000*pi*t)).
- A carrier signal 10 cos(8x 10
^{6}πt) is modulated by a modulating signal 5 cos(30x 10^{3}πt) then i. Find the Band width of Frequency Modulated signal assuming k_{f }=15KHz.^{ ii. }Calculate Highest Frequency and lowest Frequency of FM signal. iii. Find Modulation index of FM signal. - Compare Frequency Modulation with Phase Modulation.

__Long answer questions: __

- Explain the operation of balanced slope detector in detail.
- Explain in detail about frequency spectrum of WBFM signal using Bessel functions.
- write in detail about generation methods of FM signal
- Direct method of generation
- Indirect method of generation (Armstrong method).(very very imp)
- What is ratio detector? Explain its working in detail with neat circuit diagram. Explain how ratio detector provides amplitude limiting?
- What is amplitude limiter? Draw its circuit diagram explain its working. Why amplitude limiter is needed in FM receivers justify.(very very imp)
- Compare and contrast foster seeley discriminator with ratio detector.
- What is PLL? What are the applications of PLL? Explain the working of PLL with neat block diagram.(imp)
- How audio frequency signal is demodulated by using PLL? Explain in detail.
- Write about pre-emphasis and de-emphasis circuits in detail. Give the significance of pre-emphasis and de-emphasis.(imp)
- In an FM system if the AF is 500 Hz and its amplitude is 2.4V with a frequency deviation of 4.8 KHz. If the AF voltage is increased to 7.2V then find the modified frequency deviation calculate BW in above two cases.
- Design Armstrong FM generator for the generation of WBFM signal with frequency deviation=75 KHz and using the NB carrier as 100 KHz and second carrier as 10 MHz Find the suitable multiplying factors. Assume the message signal is defined in the range 100Hz-15 KHz.
- Draw the block diagram of single-tone NBFM signal if message signal is.
- Derive an expression for an FM signal with carrier frequency fc and a modulating signal Obtain an expression for its spectrum.
- Why an FM system is preferred over an AM system?

**Unit 2**

**Assignment 2**

- Explain the generation techniques of FM signal using Direct and Indirect methods in detail.
- Explain the working of the following demodulator circuits of FM i. Balanced slope Detector for FM modulation. ii. Foster-Seeley discriminator. iii. Ratio-detector.
- Explain the detection of FM signal using PLL.
- Explain in detail about pre-emphasis and De-emphasis circuits in FM.

**Unit 2**

**Assignment 2 **

- Illustrate the working of PLL using a Block Diagram. Define capture range and Lock range in PLL. 5M.
- Sketch the circuit diagram of Ratio-detector and explain working of it in detail. 5M.
- Sketch the frequency response curves & compare the working of pre-emphasis and De-emphasis circuits in FM communication System.

__TUTORIAL TEST 2__

__Answer any three of the following__

- In an FM system if the AF is 500 Hz and its amplitude is 2.4V with a frequency deviation of 4.8 KHz. If the AF voltage is increased to 7.2V then find the modified frequency deviation calculate BW in above two cases.
- Explain in detail about frequency spectrum of WBFM signal.
- Draw the block diagram of single-tone NBFM signal if message signal is
- Write any four differences between NBFM and WBFM.

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