on-line tools for PLL simulation, power electronics design and thermanl design
http://webench.national.com/
electronics circuit simulation program. uses Spice component models, very suitable for RF simulation.
http://www.aplac.hut.fi/aplac/
General purpose schematic-designer and parts-calculator. Design antennas, LC matching networks, tuned circuits, air and toroidal-core coils, and active filters. Do transmission line calculations, antenna scaling, and all basic electronics calculations.
http://www.fncwired.com/
an Electromagnetic Simulator for design and analysis of high-frequency circuits, distributed filters, transitions, RF packages, waveguides and antennas.
http://www.sonnetusa.com/
a tool used to predict the performance of a radio system.
http://www.cplus.org/rmw/rme.html
a stripline design software written in Ansi-C
http://isi.mtwilson.edu/~david/stripline.html
Highly accurate electromagnetic (EM) simulator. Allows simulation of microstrip and stripline circuits, as well as most printed circuits common to microwave engineering, including filters, patch antennas, and matching networks. Requires Windows NT/2000 or
http://www.amazon.com/exec/obidos/ASIN/1580531849/electronicsin-20
feature-rich and user friendly simulation tool used by leading electronics manufacturers worldwide to design, develop, and test their Communications, DSP, Signal Processing and RF/Analog systems.
http://www.elanix.com/