A U.S. appeals court on Friday upheld a lower court’s decision to clear Qualcomm Inc in a patent lawsuit by ParkerVision Inc, allowing it to escape a $173 million verdict for infringement. Trading in ParkerVision shares was halted on the Nasdaq after the price fell 50 percent to 23 cents. ParkerVision had accused Qualcomm of infringing its patents beginning in 2006 over a means to convert radio frequency signals, and incorporating its technology in products sold for use in mobile devices such as smartphones.