Analysis and simulation of an MSK modulator in a dynamic temperature environment

An analytical model developed to determine the effects of a dynamic temperature environment on modulator operation is discussed. The model is used in computer simulations in order to assess the modulator performance and identify critical temperature-sensitive modulator components for a variety of typical communication channels. A distortion parameter sensitivity analysis is carried out to define modulator operating temperature ranges such that system performance specifications are met. It is shown that the effects of modulator temperature variation can be characterized in terms of gain and phase imbalances and that gain imbalances produce (1) symbols that are not cosinusoidal and (2) crosstalk between channels. Another finding is that phase imbalance causes a timing error between in-phase and quadrature channel carrier components and the corresponding data sequences. It is stipulated that modulator temperature should be maintained within + or - 20 degrees F of nominal in order to limit maximum BER degradation in the bandwidth-limited, nonlinear channel to approximately 1.1 dB.