Design Of The Miniature Repeater And Its Modules For WCDMA

Nowadays, the miniaturization of microwave circuit is getting more and more important in many electronic equipments such as radar, Electronic Warfare, and communication and so on. Miniaturization is not just small, it also means consistency, integration, low cost and high dependability.According to the trend of microwave circuit's miniaturization, integration and low cost, we design the RF circuits which are the most important part of a repeater for WCDMA using the minute microstrip film technics. The works in this paper can be summarized as follows:1. A Lange coupler is designed, this coupler has many excellent characteristics such as small size, high isolation, low in/out return loss and wide bandwidth, and it can be used in many kinds of microwave circuits.2. A quasi-elliptic microstrip bandpass filter with high selectivity is designed. A new method to design a filter which is to connect the filters in series in order to obtain a high restrain is presented. This method can also shorten the design cycle and reduce the load of debugging.3. A new scheme of designing a microstrip duplexer which combines Lange coupler and bandpass filter is presented. This microstrip duplexer has many excellent characteristics such as small size, high selectivity. Furthermore, compare with other microstrip duplexers consisting of power divider and bandpass filter mentioned in many other papers (such as reference [2] [3]), our duplexer has higher isolation between the up-link and the down-link.4. A balance amplifier combines Lange coupler and amplifier is designed, then we design a frequency selected amplifier module using the high selectivity bandpass filter and the balance amplifier mentioned above, from the test results we can see that this module not just has low noise, high gain and high linearity, but also is small size.5. At the end of this paper we design a WCDMA miniature repeater which consists of the microstrip duplexer and the frequency selected amplifier module mentioned above. From the test results we can see this repeater's performance almost accord with the system's requirement except the down link's restrain to the uplink. From the temperature test results we can see this repeater's indexes are steady in a large temperature range, thus this repeater has good temperature characteristic and high reliability.