Emissions Control Techniques for MSS Handset Transmitters

Standards development work during the 1990's for LEO and GEO MSS handsets has been very contentious over the issue of acceptable and realisable conducted transmitter emission limits. Compromised standards eventually were agreed for LEO operation in the 1610 to 1626.5 MHz band and were drafted to protect adjacent MSS services and GNSS composed of GPS and GLONASS systems. Development work continues for the adjacent band above 1626.5 MHz and this is also very contentious. Early transmitters introduced for the Iridium LEO MSS and presented in this paper were straight forward designs and are shown to be compliant with the LEO standards for MSS. This paper also presents more advanced transmitter architectures that reduce complexity, improve efficiency and still provide the necessary conducted emissions control. These techniques can be used for GEO MSS handset transmitters as well as LEO MSS handsets. The paper suggests the performance possible for GEO and LEO MSS handsets and helps set attainable performance useful in subsequent standard development.