Media and marketing research firm Arbitron Inc posted better-than-expected quarterly results helped by the marketing of its radio ratings service, and backed its full-year forecast. The company said it has renewed a multi-year contract for its radio ratings and software with Publicis Groupe unit Starcom MediaVest and market research group ZenithOptimedia. Arbitron expects higher margins this year as it has already marketed its Portable People Meter (PPM) service in 48 planned markets and higher revenue with contracted PPM price increases. The company expects to earn $1.90-$2.05 per share on revenue of $419.1-$427 million in 2011. Analysts on average were expecting earnings of $1.97 a share on revenue of $421.3 million, according to Thomson Reuters I/B/E/S. Arbitron’s April-June net income doubled to $7.6 million, or 27 cents a share, from $3.8 million, or 14 cents a share, a year ago. Revenue rose to $95.7 million from $88.3 million a year ago. Analysts on average had expected earnings of 22 cents a share on revenue of $94.9 million. The company said second-quarter revenue was also helped by PPM price increase and PPM ratings contract signed with Univision in November last year.