Análisis de un Transmisor Digital de HF Basado en la Técnica de Eliminación y Recuperación de Envolvente

Resumen

An HF EER (Envelope Elimination and Restoration) Digital Transmitter simulation is presented in this paper. Effects that increase the IMD (Intermodulation Distortion) levels in an EER system are described and simulated. Basically, the main effects are the limitation of the envelope bandwidth, AMAM distortion and AM-PM distortion at the power amplifier stage, and the delay between the envelope and phase branches. These effects deteriorate the EER Digital Transmitter linearity. By means of this simulation, it is shown the contribution of every effect to the global IMD. The system was tested with a DSB (Double Side Band) signal. As a result, with an envelope bandwidth of 2kHz and a delay between branches smaller than 5 μs, more than 60 dB of intermodulation product rejection was achieved. It has also been developed an algorithm which determines the delay between branches with an error smaller than 0.035o when the signal is a non-modulated tone.