Amplitude Modulation Network Design and Simulation for Analog Telecommunications Applications

Abstract

This paper presents amplitude modulation network design and simulation for analog telecommunications application. The design  consists of three sections; a novel Amplitude modulator (Multiplier) which was designed using the logarithmic and anti-logarithmic  amplifiers, the audio signal oscillator made up of phase-shift oscillator and the Radio frequency (RF) signal oscillator made up of Hartley  oscillator. The complete system was simulated using Multisim software version 14.2 and modulation index calculated at under  modulation, 100 percent modulation and over modulation which were compared with other literature where the complete AM modulator  was designed using a diode as the multiplier, wien bridge circuit as the Audio signal Oscillator and colpitt oscillator as the RF signal Oscillator. Results show that the designed network 1 has output voltages 0.993mV at 100mV, X-Input and 10mV Y-Input to 6.223V at 2.5V  at both X and Y input before decreasing to 5.974V at 3V XInput and 2V Y-Input, greater than the network 2 from literature. Also the  modulation index (ɸ1) with values 0.56, 0.60, 1.00, 1.75, 2.15 as against (ɸ2) 0.4915, 0.6938, 0.9956, 1.4725 and 1.8042, while depth of  modulation of this study (ß 1 ) has higher values of 56%, 60%, 100%, 175%, and 215% than modulation depth values of 49.15%, 69.38%,  99.56%, 147.25% and 180.42%, Except at 700mV message and 1V carrier amplitude where (ß 2 ) is higher than (ß 1 ), when compared with  literature was found to be better than that of network 2. Overall, the designed AM modulator (Network 1) was found to be superior in  performance in terms of Output Voltages and modulation Index. Also it is in line with standards with little deviation due to component  variation. Recommendations were also made for further improvements to functionality.