Bernie Ward, 57, who had been a popular talk show host on San Francisco's KGO 810 NewsTalk, was indicted in December, charged with three counts of distributing and receiving child pornography. He pleaded guilty this year to one count of distributing child pornography, the San Jose Mercury News said Thursday.

Ward, the father of four, faced a minimum sentence of five years under federal sentencing guidelines. His attorney said at his arraignment the charges were based on incidents that occurred more than four years before Ward was charged and were part of research for a book on "hypocrisy in America."

An online dominatrix reported him to the authorities after seeing images he had of children, the newspaper said.

Chief U.S. District Judge Vaughn Walker Thursday called Ward "troubled." Ward told the judge he regretted "the harm this has caused my family, my friends, and this community."

Ward is to surrender Friday to begin serving his prison sentence.