PENGEMBANGAN TRANSMISI PERANGKAT KERAS SISTEM MODULASI DIGITAL 8-QUADRATURE AMPLITUDE MODULATION ( 8-QAM ) MENGGUNAKAN MODULASI FM (FREQUENCY MODULATION)

Abstract

Quadrature Amplitude Modulation is a type of digital modulation that modulating information signal with biner form to sinusoidal carrier signal. This modulation technique uses phase and amplitude changing of carrier signal with constant frequency. There are many types of QAM such as 8-QAM, 16-QAM, 64-QAM etc. The grouping is depended on total bit in one symbol. On 8-QAM system, one symbol representate three bit data. This final project develope previous final project so transmitting 8-QAM signal between modulator and demodulator is designed using wireless system. 8-QAM signal is transmitted using frequency moduation. FM modulator is set to work on frequency 87 MHz, so it doesn’t disturb broadcasting radio from other comercial FM transmintter. Frequency moduation is choosed because it is better than amplitude modulation suffering interferention. From testing result, 8-QAM signal can be transmitted perfectly and it’s received with 25 μs delay time. Transmitted FM signal still can be received well altough not on Line of Sight condition with distance 10 m between transmitter and receiver. Delay time 70 μs between modulator input and demodulator output is caused of component delay accumulation and transmitting signal by FM transmitter. Keyword : Modulation, 8-QAM, FM Transmition