Computer and Communication Network Engineering

Simulation of a Digital Ultra High Frequency Communication System with High Power. Since the early days of electronics, as advances in technology were taking place, the boundaries of both local and global communication began eroding, resulting in a world that is smaller and hence more easily accessible for the sharing of knowledge and information. The pioneering work by Bell and Marconi formed the cornerstone of the information age that exists today and paved the way for the future of telecommunications. [1] Traditionally, local communication was done over wires, as this presented a cost-effective way of ensuring a reliable transfer of information. However, for long-distance communications, transmission of information over radio waves was needed. Although this was convenient from a hardware standpoint, radio-waves transmission raised doubts about the corruption of the information; transmission was often dependent on high-power transmitters to overcome weather conditions, large buildings, and interference from other electromagnetic sources. The various modulation techniques offered different solutions in terms of cost-effectiveness and quality of received signals but until recently, they were still largely analog. Frequency modulation and phase modulation presented certain immunity to noise, whereas amplitude modulation was simpler to demodulate. However, more recently with the advent of low-cost microcontrollers and the introduction of domestic mobile telephones and satellite communications, digital modulation has gained in popularity. With digital modulation techniques come all the advantages that traditional microprocessor circuits have over their analog counterparts. Any shortfalls in the communications link can be eradicated using software. Information can now be encrypted, error correction can ensure more confidence in received data, and the use of Digital Signal Processing (DSP) can reduce the limited bandwidth allocated to each service [2]. As with traditional analog systems, digital modulation can use amplitude, frequency, or phase modulation with different advantages. As frequency and phase modulation techniques offer more immunity to noise, they are the preferred scheme for the majority of services in use today. The transition from analog communication to digital has advanced the use of QPSK. Digital processing is used to remove phase and frequency errors. This dissertation demonstrates the simulation of a complete radio-communication system using the Quadrature Phase Shift Keying (QPSK) modulation and demodulation, with the tool HP-ADS of Agilent Technologies.