Versatile Circuit Designs of Digital Modulator and Demodulator

Digital Modulation has a complete scope of appli-cations due to its higher quality communications, compatibility, and security. The digital modulation techniques are being imple-mented in WiFi, RF modules, Bluetooth, and GSM. In this paper, we proposed versatile hardware designs that perform various modulations and demodulations with the same hardware. The generated versatile design can be configured with the control line to give the following modulations and demodulations: Amplitude Shift Keying (ASK), Frequency Shift Keying (FSK), Phase Shift Keying (FSK), Differential Phase Shift Keying (DPSK), Quadrature Phase Shift Keying (QPSK), and Minimum Shift Keying (MSK). The proposed generic design is able to cut down the expenditure of the hardware, as it replaces all the modulation circuits with a single optimized circuit.

I. Introduction

Message signal is a low frequency signal, but a low frequency signal is not suitable for transmission and the signal gets weekend on transmission. To overcome this problem the low frequency message signal is modulated with a high frequency carrier signal. Digital Modulation is the process of converting a message signal, which is in bits, into a waveform that is suitable for transmission over a channel. It changes the properties of the waveform which is called a carrier signal with a modulating signal which contains the data that has to be transmitted. In Modulation, a baseband signal is transmitted into a passband signal. In the receiver end, the modulated signal is then demodulated to get back the original message signal. In demodulation, the passband signal is shifted back to a baseband signal. During the transmission through the channel, the noise is further added to the signal.