The Modulator

In this article, we'll discuss the overarching structure of the transmission side of our communication system, the modulator. The modulator, at its core, takes digital data and encodes it onto an analog waveform so that it can be sent over a transmission line to its destination. Modulating the data can have benefits over just sending digital data, like increased data density and loss tolerance. While there are many digital modulation techniques, the modulator we will be designing here today will make use of Phase-Shift Keying (PSK) and eventually Quadrature Amplitude Modulation (QAM).

For those looking for more information pre-emptively, Wikipedia (Modulation - Wikipedia) is always a wealth of knowledge. #ad

A Basic PSK Modulator

Below is a a very basic way of implementing a Quadrature PSK modulator. It works by creating a sine wave with 4 different phases (0, 90, 180, and 270 degrees) and selecting which one to output based on the digital data to be sent. With this type of modulator we can send 2 bits of data at a time because our modulator has 4 possible output states. However, not all of these components are familiar to most engineers even after finishing a bachelor's degree and I will go in-depth with them in their own pages.