Multi-Carrier GMSK Modulator

  • Jouko Vankka
  • Kari Halonen
Chapter
Part of the The Springer International Series in Engineering and Computer Science book series (SECS, volume 614)

Abstract

In conventional base station solutions, the transmitted carriers are combined after the power amplifier (PA), as shown in Figure 11.1. This chapter describes an architecture where a multi-carrier GMSK modulated IF signal is up converted to RF by two mixers and bandpass filters (BPFs) as shown in Figure 13.1. This saves a huge number of analog components, many of which require production tuning. Consequently, an expensive and tedious part of the manufacturing will be eliminated. The proposed multi-carrier GMSK modulator does not use an analog I/Q modulator, therefore the difficulties of adjusting the dc offset, the phasing and the amplitude levels between the in-phase and quadrature phase signal paths are avoided. A single linearized multi-carrier power amplifier replaces a bank of individual amplifiers whose high-power outputs are conventionally combined by using selective cavities. Hence, power losses inherent to cavity-filter combiners are avoided which results in space and cost savings as well as greater reliability. The GMSK modulation method used in the GSM 900 and the DCS 1800 is a constant envelope modulation scheme. As a number of these GMSK carriers are combined to produce a multi-carrier signal, the beneficial properties are lost. Because of the strongly varying envelope of the composite signal, very stringent linearity requirements are imposed on the wideband D/A converter, up conversion mixers and the PA.

Keywords

Power Level Power Control Word Length Clock Frequency Read Only Memory 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

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Copyright information

© Springer Science+Business Media New York 2001

Authors and Affiliations

  • Jouko Vankka
    • 1
  • Kari Halonen
    • 1
  1. 1.Helsinki University of TechnologyFinland

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