Patent ID: 8060045

Claim:
A method for compensating non-linear distortions of high-frequency signals, specifically when observing amplitude modulated signals with a narrow band receiver, comprising the following steps: a) estimating and setting a frequency of a reference oscillator according to an input analogue signal S A ; b) transmitting the analogue signal S A , which is being processed, from sensors through a bandpass filter that cuts off signals with higher harmonic frequencies, to an analogue-digital converter; c) transmitting an output digital signal S D from the analogue-digital converter through the bandpass filter that cuts off higher harmonic components and intermodulation products appearing because of non-linearity of analogue electronic components; d) dividing the output signal from the bandpass filter to two signals, a first signal that is transmitted to a first mixer where it is multiplied by a sine signal from a local oscillator, and a second signal that is transmitted to a second mixer where it is multiplied by a cosine signal from the local oscillator; e) transmitting each of the first and second signals resulting from their multiplications to a low-pass filter that transfers only the signal in baseband and cuts off the part of the signal with double frequency; f) transmitting the first and second signals to a demodulator that calculates the amplitude of interest by means of square amplitude demodulation; g) checking whether at least one of the signals gained after step (f), the output signal of the analogue-digital converter, and the input analogue signal still contains disturbances inside an interesting frequency bandwidth; h) adjusting the frequencies of the reference oscillator and the local oscillator according to the results gained by step (g).