A laboratory minimum shift key modulator

Abstract

Minimum shift keying (MSK) is a modulation format that exhibits some spectral efficiency over currently used spacelink digital modulation techniques such as binary phase shift keying (BPSK) and offset quadrature phase shift keying (OQPSK). The authors present a novel design of an MSK modulator that is well suited for investigating MSK in the laboratory. MSK obtains its advantage over OQPSK through the use of some elaborate timing. One of the costs of this required timing is added complexities in the modulator circuitry. Phase locked loops and an extra phase shift are required to modify a simple OQPSK modulator to perform MSK. Digital timing circuitry, including digital phase shifting, can be used in conjunction with inexpensive laboratory function generators to construct a simple MSK modulator that avoids the complexities of the modified OQPSK design technique. These design techniques are described.<>