Design And Group Delay Equalization Of C-band Up-converter

The up-converter is an important part of satellite communication transmission link.It is located between the terminal and the antenna.It uses nonlinear devices to convert If modulated signals into RF signals.The amplitude and phase distortion will occur in the process of frequency conversion,and the group delay can clearly reflect the degree of phase distortion.With the increase of communication modulation and channel transmission capacity,the group delay distortion becomes one of the key factors affecting whether the signal can be correctly received and demodulated during communication.In order to guarantee the quality of communication,the requirement of system group delay index is more and more stringent.In this paper,the concept of group delay and the condition of signal transmission without distortion are introduced through phase shift,and the methods of group delay equalization are introduced: several kinds of transmission all-pass networks and reflecting all-pass networks with different structures are analyzed,and their group delay characteristic functions are derived,their practicability is analyzed.Applying the group delay function to the genetic algorithm,the optimal design of the group delay equalization network is realized by using the algorithm.Then the design and implementation of C-band up-converter in satellite communication link are carried out,a group delay equalization method for pre-equalization network before frequency conversion is used.In order to satisfy the high suppression of local vibration and stray,the s-band and C-band cavity filters are designed,amplifiers and mixers that make up the up-converter are tested and analyzed in practice,and the conclusion that the group delay distortion of complete up-converter is mainly introduced by bandpass filters is drawn.In the end,the group delay equalization network optimized by genetic algorithm is used to equalize the group delay of the up-converter,and the indexes of the frequency conversion channel are measured.The test results show that the introduction of the equalization network significantly improves the group delay distortion of the channel,and does not cause the deterioration of other key indexes.