GSM BTS Duplexer Voltage Alarm Analysis And Improvement

In the field of digital mobile communications, GSM is currently the most maturesystem with the largest market share. From2009, Tianjin plant became the only BTSmanufacturer of Motorola within the global scope. We take orders and demands fromall over the world. It is very important to maintain the quality of products and fulfillthe commitment to customers with100%on-time delivery on the condition thatproduction is running under full capacity. However, in the virtual customer testing, itis found that a large number of cabinets have the flaw of BTS duplexer voltage alarm.The failure rate is around10%. This problem has a great impact on the productionefficiency and the test capacity. If the problem cannot be resolved in short time, wehave to stop production and delay the shipment. Obviously it will bring great loss toour company.Firstly, the trend of GSM BTS development and the feature of Motorola BTS areoutlined. Then, the technical specification, testing environment and method ofduplexer are introduced. The importance of the duplexer to ensure the BTS workingin good status is presented. By deep analysis of BTS testing principle and duplexervoltage alarm trigger logic, the root cause is confirmed that27V input power circuiton VSWR detection board has design reliability issue. Finally, we find the solution isto enlarge the resistance in the27V input circuit and re-select the fuse with improvedblowout current. By a lot of experimental data, it is shown that the improved designcan effectively enhance the product reliability.With the application of the improved circuit design, all BTS pass the test andmeet quality requirement. Also, we spread this positive result from EGSM900toPGSM900and DCS1800duplexer modules.