Output design considerations in wireless portable through-the-earth communications system using current injection

Through-The-Earth (TTE) wireless communication systems are very useful in confined areas, tunnels or mines where electromagnetic waves suffer from high attenuation. This attenuation is introduced by the dissipative media that forms the channel so low frequency signals are mandatory in the communication resulting in a poor antenna/system efficiency. Up to date designed amplifiers use class A, B or AB stages, making the overall efficiency even worse. This paper presents to the wireless designers the design of an efficient output topology around a switching class-S amplifier which maintains efficiency in spite of a widely varying load. A working prototype based in the proposed design is evaluated in terms of efficiency for the whole range of loads and used frequencies.