Remote RF Unit Introduction And High Temperature Boot Up Defect Analysis

Marketing team feed back that the GSM BTS (Base Station System) product from major vendors already support multi-carrier power amplifier and remote RF head technology on their product to reduce consumable power and operator's capital expenditure per carrier. And some of the products from major competitor also have LTE capability. From this point of view, our major GSM carrier product - CTU2D which launch on 2007 Q3 only can support 2 simultaneous GSM/GPRS/EDGE carrier already out of date. In order to enhance Motorola's competitiveness and recover loosed marketing sharing, we have to design and produce our new product which can support GSM to LTE evolution and apply multi-carrier power amplifier and remote RF unit technology in a very tightened schedule.In the new product pilot stage, around 10% RCTU4 failed at the end of 17 hours vitual customer soaking test due to units can not boot up after power switch. Through deep analysis on remote RF unit theory, virtual customer soaking test theory, power supply management and a lot of lab experiment data, we found the root cause is RCTU4 transceiver board 1.2V power supply enable signal via hole has been shorted to ground thru ferrite inductor body in high temperature environment. A corrective action was then developed using solder mask pen covering the via hole that has short circuit risk to meet new product shipment schedule for FuJian MCC's field trial. Finally, lesson learn has been reviewed on preventive action review board and the RF/analog design guide has been updated accordingly as"Use caution when placing signal via under ferrite inductors".