MSK Modulation

Minimum Shift Keying (MSK) is an interesting digital modulation that has been applied to communication ranging from Navy submarines at Very Low Frequencies to cellular phones at microwave frequencies.  See the Wikipedia overview article here .  A more recent application of MSK is in amateur radio meteor-scatter communication.   See the 2017 paper by Steven Franke, K9AN, and Joe Taylor, K1JT, appearing in the Jul/Aug issue available here .

MSK can be generated in a variety of ways.  The intent here is to illustrate these methods with a combination of digital logic simulation and analog (transient) time domain simulation in QucsStudio.

The presentations below are arranged as follows: 

(1) Two orthogonal BPSK signals.  This is the earliest approach, which appears in the Collins Radio patent, filed in 1958.

(2)  FM modulating a Voltage Controlled Oscillator.  Using a simulator built-in FM modulator component makes this the simplest simulation of MSK to create and run.

(3)  IQ Quadrature up-conversion by single sideband mixer.  This is a standard approach used in many wireless applications.

(4) Digital method.   This method appears in a patent filed in 1972, also by Collins Radio (Warren Bruene).   The slides are broken into 3 presentations.

(5) Saw filter method (planned).    This consists of two implementations:

  (a)  A transversal filter (tapped delay line) having a fixed bit sequence, and 

(b) A shaping filter allowing an arbitrary data sequence.