RF Transmitter Offset-AM Modulation for Spectral Occupancy

The patent applies parameter changes by modifying the amplitude modulation depth from 100% to a reduced level (e.g., 80% or less). This is achieved by adding a DC offset component to the modulated signal, which prevents the signal from reaching zero amplitude. The parameter change resolves the contradiction by maintaining good spectral occupancy while eliminating the phase discontinuities that occur in high efficiency RF power amplifiers when the signal passes through zero.

The patent applies preliminary anti-action by pre-distorting the modulated signal before it enters the non-linear RF power amplifier. A predistortion circuit is used to compensate for the expected non-linear distortion, effectively canceling out the harmful effects. This allows high efficiency class-AB or class-C amplifiers to operate while maintaining signal linearity and preventing spectral regrowth.

The patent applies partial action by using reduced amplitude modulation depth (e.g., 80% or less instead of 100%). This partial modulation approach maintains sufficient signal quality and spectral occupancy while avoiding the extreme conditions that make measurement and implementation difficult. The reduced modulation depth provides a practical operating point where predistortion can be effectively applied without the measurement challenges of 100% modulation.