Lesson 12 — Phase-Shift Keying (PSK)

Last time, we used a vector of values to modulate the amplitude of the carrier wave, which allowed us to send symbols which could contain more information than a single bit. In binary phase-shift keying (BPSK) we multiply the carrier wave either by 1 or -1. It is common to associate the amplitude of 1 with the binary value 0 and the amplitude of -1 to the binary value 1, which has a simple mapping to the binary XOR operator.

Start with your flow graph from the previous lesson, save a copy with the name BPSK, and then work on the following modifications.

As before, we will use a Vector Source to supply a string of values, only this time our input will be a string of binary digits in a pattern that we will repeat over and over. You can pick whatever pattern you like, but it is helpful to pick something that you can readily recognize in the output [e.g., (0,1,0,1,0,0,1,1,1,1)].

To convert this list of symbols into the values 1 and –1 that we will use to encode, use the Chunks to Symbols block and provide the values (1,-1) as the symbol table.

make the offset range much smaller

need to investigate ways to slowly adjust

This one didn’t work well.

The finished flow diagram

Homework

1. Square the incoming signal to adjust the slider and zero out the frequency difference.

Next time: adjusting .