2–6GHz current-reused LNA with transformer-type inductors

In this study, we use the current-reused topology to implement a wideband LNA. We have also successfully designed one kind of center-tapped transformer to replace three couples of inductors in order to save chip area. The transformer is composed of two concentric octagons. The spacing between two concentric octagons can be decreased in order to reduce chip area. The NF is less than 3.6 dB for the WiMAX applications from 2.3 to 5.8GHz. The measured maximum gain (S21) is about 13.5 dB. The measured characteristics are similar to simulated characteristics. This means that accuracy of related EM analyses is acceptable. In the future, the study of test key of the presented concentric-octagon transformer will be done in order to obtain accurate equivalent device parameters and make the simulation of the circuit more accurate.