The angle modulation & demodulation module will deal with the angle modulation techniques currently used in modern analog and digital communications systems. An analog or digital information signal will be conveyed on to a carrier signal whose instantaneous angle or frequency varies according to the variation of the original information signal. The module will offer the advantage of increased signal to noise ratio without increases in transmitter power. Specifically, Phase Modulation (PM) and conventional Frequency (FM) will be studied as well as modulation and demodulation techniques.
RECOMMENDED EXPERIMENTS
1. Phase Modulation
- Time & spectrum displays of 400 Hz sine wave
- Bessel lines
- Time & spectrum displays for NRZ, PAM, PSK, QPSK and M-array PSK
2. Correlation of PM and FM
- Generate PM with an FM modulator
- Generate FM with a PM modulator
3. Analog FM
- Spectrum, Bessel lines
- Narrow & wide band FM
4. Digital FM
- spectrum displays for NRZ, PAM and M-FSK
- CPFSK and non-CPFSK
5. FM Detectors
- ratio & zero crossing
- frequency discriminator
6. FM Demodulation For Strong Signal & Noise
- SNR0 dependence on SNR1
- Pre-emphasis, de-emphasis
7. FM Demodulation For Weak Signal & Noise
- FM threshold effect
- performance at the threshold
- click noise
8. PLL as an FM Detector
- Effect of loop parameters on performance
- Effect of noise on PLL
TECHNICAL SPECIFICATIONS
The angle modulation & demodulation module will consist of the following main blocks:
- Phase Modulator
- Vco
- Rf Switch
- Ratio Detector
- Frequency Discriminator
- Zero Crossing Detectors
- Pre-Emphasis
- De-Emphasis
- Integrator
- Differentiator
- Limiter
-Pll
