CT2: Communications Device Theory and Design - Resit Assignment

This document presents a comprehensive solution to a Communications Device Theory and Design assignment, covering a wide array of topics. The solution begins with questions on varactor diodes, including calculations of capacitance under different reverse voltages, and progresses to calculating the EMF generated in a coil with a changing flux density. It then analyzes resonant circuits, comparing their impedance and current characteristics, and calculates the composite noise figure for a two-stage amplifier. The solution also addresses questions on Schmitt triggers, modulation systems (DQPSK and V29 QAM), PCM systems (quantization noise and S/N ratio), and data link flow control protocols (Selective Repeat and Go Back N). Furthermore, the solution delves into flip-flop states, fiber optic dispersion, and the design of synchronous counters using T flip-flops. It includes Boolean expressions and logic gate implementations for a three-sensor alarm system, along with comparisons of HDB3, Manchester, and 4B3T line codes. The document also provides solutions for digital transmission, including HDB3 and 4B3T coding, and explores the advantages of QDPSK over QPSK. Finally, it covers asynchronous, synchronous, and isochronous transmission modes, HDLC protocol, and flow control implementation.