A D.C. Superior Court judge yesterday convicted a 15-year-old Southeast Washington youth of the assault and robbery of Rep. Robert H. Michel (R.-Ill.) near the congressman's Capitol Hill home in July.

Judge Joseph M. F. Ryan Jr. also found the youth guilty of assault with intent to commit robbery in connection with a second incident three days later in the same neighborhood.

Ryan said he would sentence the youth Nov. 3. The juvenile faces a maximum penalty of two years confinement in the city's Childrens Center unless the prosecutor moves to extend the term, according to Assistant D.C. Corporation Counsel James J. Stanford.

Michel, 55, was badly beaten and robbed of a gold money clip, $200, his wallet and watch during the assault at 12:45 a.m. July 21 in an alley behind his home in the 30 block of 8th Street SE. A second person, believed involved in the assault, has not been apprehended, Stanford said.

The youth was convicted of the assault charge under a federal law that makes it a separate offense to assassinate, assault or injure a member of Congress.That law was originally proposed following the 1968 assassination of Robert F. Kennedy, then a U.S. senator from New York.