In an apparent effort to placate an aroused Federal Communication Commission and soften possible sanctions the FCC could impose. CBS-TV will broadcast an apology today for misleading the viewing public on telecasts of four "Heavyweight Championship of Tennis" matches between 1975 and 1977.

A statement by Gene F. Jankowski, president of the CBS Broadcast Group, will be aired today at 1:25 p.m., at the conclusion of CBS's "Network Challenge of the Sexes" program (WMAR-TV-2). It is expected to follow the lines of an internal memo Jankowski sent to the CBS organization March 27, expressing "disappointment and chagrin at the negligence in the handling of these events that resulted in the public being misled" and assured "new procedures that we feel will guard against repetition of these occurrences."

CBS faces potentially costly and embarrassing penalties for having falsely billed "challenge matches" between Jimmy Connors and four opponents as "winner-take-all," and for failing to acknowledge on the air promotional considerations provided by Caesars Palace, the Las Vegas hotel where there of the matches were played.

The FCC has given the network until April 17 to show that it has implemented procedures to prevent similar abuses in the future. The commission is expected to make its final determination in the year-old case within a week thereafter and has the power to require yearly renewal of the licenses of the five stations owned and operated by CBS, a sanction it has never before imposed.