RF Micro Devices ( RFMD) saw its shares sink more than 20% Friday after the maker of high-performance radio systems and communications gear offered weak profit estimates. For the third quarter ended Dec. 29, RF said revenue was likely $268 million, of which approximately $254 million is attributable to its historical operations, excluding Sirenza. The company said it saw reduced demand late in the December quarter. Earnings, before items, are estimated at 6 cents to 7 cents a share. Analysts are looking for a profit of 8 cents and a top line of $282 million. RF believes the reduction in demand is temporary and anticipates returning to growth in fiscal year 2009, which begins April 1. Shares of RF were recently sinking $1.12 to $3.90.