Patent ID: 7313175

Claim:
A method for avoiding spurious emissions in an AM transmitter for digital transmission, the method comprising: converting a digital modulation for controlling the AM transmitter into an amplitude signal and a phase-modulated RF signal; compensating for non-linear distortions in an amplitude response and a delay-time characteristic of an amplitude branch using a pre-equalization with inverse shapes by: measuring and storing the amplitude response and the delay-time characteristic of an amplitude branch; determining an inverse transfer function using respective shapes of the measured amplitude response and delay-time characteristic by an inverse Fourier transform; dimensioning an equalizing network for the determined inverse transfer function; and connecting the equalizing network in series upstream of the amplitude branch; adjusting a bandwidth of resonant circuits of an RF branch by suitable selection of a quality of the resonant circuits so as to achieve a linear shape for an amplitude response and delay-time characteristic of the RF branch; and compensating for a propagation time difference between the amplitude branch and the RF branch in a digital modulator by delaying a signal having a smaller propagation time.