Two different designs of a low-noise amplifier (LNA) at 5 GHz are presented in this paper. The first design uses lumped elements for implementing the matching networks. The second design utilizes distributed element matching networks using microstrip lines. It is shown that the design using lumped element matching networks has difficulties to achieve high performance at a frequency of above 5 GHz and that distributed matching circuits are more adequate compared to the lumped element solution. Experimental results confirm the simulation results based on the LNA design with distributed matching networks

An ultra-wideband (UWB) 3.1-4.8 GHz low-noise amplifier (LNA) employing two-section reactive input and output matching networks is presented in this paper. The amplifier is optimized for the minimum noise figure over the entire bandwidth and for maximum flat power gain. lf implemented in a narrowband system, the LNA can be matched for the optimal noise figure using simple one-section reactive input and output matching networks. However, if a wideband operation is required, the issue must be solved with other techniques. It is shown that with appropriate broadband matching techniques, Bands Group 1 ultra-wideband typical specifications can be achieved using a 5.25 GHz LNA. As a first step the design methodology focuses on noise figure optimization and continues with the optimization of the power gain. The nonidealities of the broadband matching networks implemented with microstrips are analyzed and their effects on the LNA performances are presented. The printed circuit board (PCB) manufacture process variations are included in the simulation setup. The substrate used is a double layer PCB with the Rogers material RO43508. The simulated LNA using microstrip matching networks achieved a noise figure smaller than 2.3 dB over the entire band and a flat power gain of 15.8 ± 0.14 dB.

An ultra-wideband (UWB) 3.1-4.8 GHz radio front-end consisting of three frequency multiplexed antennas and a low-noise amplifier (LNA) is presented in this paper. Using one antenna for each sub-band and an LNA designed for maximum-flat power gain provides equal performance within the entire frequency band. Frequency multiplexing is used to combine the antennas for multi-band UWB. The LNA is optimized for wideband operation and minimum noise figure. The LNA design employs dual-section input and output matching networks. The antennas, the frequency multiplexing network, the matching networks and the bias circuit of the LNA are all implemented using microstrip lines.

In this letter, bias networks with three different radio frequency chokes for ultra-wideband systems have been studied. The bias network with a butterfly stub results in not only the broadest band, but also the highest robustness. Resonances generated within the DC path of the bias network are investigated and explained. Both simulation and experimental results show that microstrip bias networks for ultra-wideband systems can be optimized to avoid or reduce the resonance phenomena.