Investigation on techniques of middle-field ISAR imaging based on rotator mode;

The middle-field ISAR imaging by mending curved phase front is as same as the far-field imaging,but can reduce the requirement of measurement distance greatly,with great engineering meanings.

In the mid-field measurement method,space-magnitude error and space-phase error due to the probe position shift are some special errors.

This paper studied the increase of number of players at the center-field,the improvement of the play,the changes of formation structure and pointed out that the changes of number of players at the center-field was the major factor influencing the development of formation.

The all - round midfield sportsman possesses the ability of utilizing plentiful physical stamina to participate in attack and defence; outstanding pass technology and ouutanding ability to organize; possess the defence ability of forcing the rivals and destroying the rivals attack ;possess the ability of scoring.