Formation of Quadrature Components with Error Estimation for I/Q-Demodulators

The paper investigates the influence of the choice of weighting coefficients on the formation of quadrature components in I/Q demodulators. It proposes methods to improve the accuracy of I/Q demodulation and minimize quadrature errors. Different configurations of 8- and 10-sample I/Q demodulators with open sets of weighting coefficients are considered. Using simulation, it has been shown that certain sets of coefficients can significantly improve the amplitude-frequency characteristics, achieving a bandwidth narrowing of 1.5–1.7 times and better suppression of out-of-band interference. The synthesis of new sets of coefficients for 10-sample I/Q demodulators is also investigated, which leads to improved amplitude-frequency characteristics and reduced phase errors. The equivalence between combinations of two-stage demodulators and their single-stage counterparts is established, providing potential computational efficiency advantages. The proposed 13- and 15-sample equivalent filters demonstrate a high frequency filtering efficiency and zero orthogonalization error, making them a promising alternative to 16-sample demodulators. The obtained results emphasize the importance of choosing weighting coefficients to optimize the performance of I/Q demodulators and contribute to developing more accurate and efficient digital communication systems with increased noise immunity.