AM-PM conversion introduced by weakly nonlinear circuits

This paper is related to a novel model for the AM–PM conversion characterization of systems. By means of nonlinear transfer function analysis, AM–PM conversion is obtained as a phase statement of compression and desensitization, thus immunity against electromagnetic interference of radio systems can be evaluated when the signal undergoes fading or when it is received with interfering oscillations. The model is used to obtain the AM–PM conversion introduced by a feedforward amplifier. The results show that the maximum compensation of third-order intermodulation does not necessary coincide with the minimum AM–PM conversion condition.     

Retrieval of Atmospheric Water Vapor Density With Fine Spatial Resolution Using Three-Dimensional Tomographic Inversion of Microwave Brightness Temperatures Measured by a Network of Scanning Compact Radiometers

Quantitative precipitation forecasting is currently limited by the paucity of observations on sufficiently fine temporal and spatial scales. Three-dimensional water vapor fields can be retrieved with improved spatial coverage from measurements obtained using a network of scanning microwave radiometers. To investigate this potential, an observation system simulation experiment was performed in which synthetic examples of retrievals using a network of radiometers were compared with results from the Weather Research and Forecasting model at a grid scale of 500 m. These comparisons show that the 3-D water vapor field can be retrieved with an accuracy of better than 15%-20%. A ground-based demonstration network of three compact microwave radiometers was deployed at the Atmospheric Radiation Measurement Southern Great Plains site in Oklahoma. Results using these network measurements demonstrated the first retrieval of the 3-D water vapor field in the troposphere at fine spatial and temporal resolutions.     

Comparison of different high-linear LNA structures for PCSapplications using SiGe HBT and low bias voltage

Different high-linearity low noise amplifier (LNA) structures have been designed, simulated and compared, providing good performance results concerning noise figure, bandwidth, power gain, intermodulation and gain compression, when a low-level voltage supply is used. The structures were designed to be used in personal communication systems (PCSs), operating at 1900 MHz using a SiGe heterojunction bipolar transistor (HBT) and 2.4 V bias polarisation