Carrier Synchronization Techniques For Unbalanced Qpsk Signals-Part I

Carrier Synchronization Techniques For Unbalanced Qpsk Signals-Part I

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IEEE TRANSACTIONS ON COMMUNICATIONS, VOL. COM-26, NO. 9, SEPTEMBER 1978 1325 Carrier Synchronization Techniques for Unbalanced QPSK Signals-Part I WALTER R. BRAUN, MEMBER, IEEE, AND WILLIAM c. LINDSEY, FELLOW, IEEE Abstract-This paper uses MAP estimation techniques to obtain carrier reconstruction circuits for unbalanced QPSK signals. In addition, the performance analysis -of these circuits is carried out to the extent that a loop design can proceed. Optimal weighting coefficients in the receiving system are identified as functions of the I-Q power and data rate splits. Finally, numerical results are presented in order to demonstrate the utility of the theory developed. This signal design will be used in the development of the Tracking and Data Relay Satellite System (TDRSS) and the Navigation Satellite Timing and Ranging Global Positioning System (NAVSTAR GPS). 1. INTRODUCTION A N UNBALANCED QPSK (UQPSK) signal format is a QPSK signal where the two quadrature components of the carrier have unequal power and are modulated with independent binary data streams of different rates. This transmission scheme is most useful when data of two different sources possibly varying rates have to be transmitted in the same fre- quency band. This signal design will be used in the development the Tracking and Data Relay Satellite System (TDRSS) and the Navigation Satellite Timing and Ranging Global Positioning System (NAVSTAR GPS). Carrier synchronization techniques UQPSK signals in which the power split in the in-phase and (I-Q) channels is variable and I-& arm data rates are also variable are therefore of interest. In fact, certain signal design concepts the TDRSS require carrier reconstruction from an unbal- anced QPSK waveform inwhich thepowerratio imbalance, say X, is variable between zero and six dB. It is also well known that a Costas or squaring loop cannot provide a coherent carrier reference for a balanced QPSK signal. Therefore, it is important to be able to predict the “optimum” carrier recon- struction technique varying power split rates between the inphase and quadrature channels of the signal and compare optimum method performance of a Costas loop tracking the high power, high data ratechannel only. It is also of interest to this with that of conven- tional receivers for balanced QPSK, viz., the fourth power type, etc. Intuitively, some form hybrid loop will arise as a con- sequence of the desire to track an unbalanced QPSK signal as Paper approved by the Editor Communication Theory of the IEEE Communications Society for publication after presentation at the International Conference on Communications, Chicago, IL, June 1977. Manuscript received February 28, 1977; revised May 3, 1977. This work was sponsored by NASA’s Goddard Space Flight Center, Greenbelt, MD, under Contract NAS 5-23591.
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This note was uploaded on 05/11/2011 for the course ELECTRONIC 005 taught by Professor Haghbin during the Spring '10 term at Sharif University of Technology.

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Carrier Synchronization Techniques For Unbalanced Qpsk Signals-Part I

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