Overview

From APPLIED MICROWAVE & WIRELESS, VOL. 11, NO. 1, JANUARY 1999

This article discusses simulated and measured data for 900 MHz single-stage low noise amplifiers with <1.5:1 input VSWR. Excellent correlation is demonstrated between the simulation and measured data, and potential design and layout problems that may lead to poor circuit performance are discussed. A comparison of amplifier performance on FR4 and higher quality substrate is also given.

RF circuit design is still considered an iterative process in some circles. Many RF circuit designers accept circuit tuning or tweaking as part of the design process, often leading to multiple PCB iterations and increased design time. The ability to produce RF circuits with first time design success can provide a valuable competitive edge.

The specification of an LNA is strongly influenced by the intended application. Consideration must be given to performance, power consumption, linearity and cost. A compromise between these parameters is often necessary. Base station infrastructure applications usually have minimal power constraints so higher LNA power consumption can be tolerated to obtain better linearity. Battery powered equipment applications, however, usually demand lowpower operation.

Component cost is another important consideration, usually forcing a compromise in other parameters such as noise figure and linearity. A low-noise bipolar transistor is cheaper than a GaAs FET, but superior noise performance can be obtained from FET designs. Most portable wireless devices currently use...