DEVELOPMENT OF A RECONFIGURABLE IN FREQUENCY LNA THROUGH RF MEMS
J.P. BUSQUÈRE, K. GRENIER, G. BOUCHE, D. DUBUC, P. PONS, R. PLANA, P. ANCEY

Introduction
The first stage of a receiver comprises a Low Noise Amplifier (LNA), whose principal function is to amplify the signal from the antenna while providing a sufficient gain as well as weak noise. In addition to the fact of providing gain and a minimal noise level, a LNA must be able to amplify without distortion signals of great amplitude [1]–[3] and must also present a precise input impedance (in general 50 Ohms).
Nowadays, the multiplication of the standards like in radio frequency communications involves that the receivers must be able to process the data on various frequency bands. However, some circuits like Low Noise Amplifiers (LNA) function only in one precise frequency band [4]. If one wants to then be able to process the data on other frequency bands, it is necessary to add as many circuits as covered bands. Nevertheless, this band multiplicity highly increases the global cost as the space is proportional to the numbers of circuits. The miniaturization of the electronic components thus seems to pass by the use of only one reconfigurable circuit instead of many frequency bands circuits. MicroElectroMechanical components (MEMs) consist in a good solution to improve the miniaturization. These components present indeed very good electric and electromagnetic performances (weak insertion losses, good linearity, no consumption....) [5]. Their use in LNAs is thus particularly attractive.
The first part of this paper deals with the contribution of RF MEMS in the elaboration of a bi-band LNA. Next part is dedicated to the design of the LNA for both 2.45 and 5.5 GHz frequencies. A serial MEMS capacitors part follows, including a light description of the corresponding technological process. Next part will indicate the simulated and measured results of test circuits, which validate the concept of frequency reconfigurability.