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TMO Progress Report 42-134 August 15, 1998 Power Spectrum of MSK-Type Modulations in the
 

Summary: TMO Progress Report 42-134 August 15, 1998
Power Spectrum of MSK-Type Modulations in the
Presence of Data Imbalance
M. K. Simon,1
P. Arabshahi,1
L. Lam,1
and T.-Y. Yan1
Using the amplitude-modulation pulse (AMP) representation of continuous-
phase modulation (CPM) introduced more than a decade ago by Laurent, the power
spectral density (PSD) of minimum-shift-keying (MSK)-type modulations (modu-
lation index equal to one-half) is computed in the presence of data imbalance. The
advantage of this technique is that closed-form expressions can be obtained that
clearly elucidate the partitioning of the spectrum into components due to the effec-
tive AMP pulse shapes and those due to the AMP sequence correlations. As such,
these expressions give insight into the nature of the PSD distortion produced by
the imbalance, i.e., a tilt in the main lobe and a relative unbalance between the
upper and lower side-lobe levels caused by the correlation between the in-phase (I)
and quadrature-phase (Q) components of the complex AMP data sequences and
the correlation between the sequences themselves. It is demonstrated that data
imbalance does not change the rate at which the side lobes roll off. It also is shown

  

Source: Arabshahi, Payman - Applied Physics Laboratory & Department of Electrical Engineering, University of Washington at Seattle

 

Collections: Engineering