There are many ways to do impedance matching, including: The computational values are required to set up the type of structure and target component values. In-situ RF lab measurements, along with tuning work, have to be considered for determining the proper final values. Above a few tens of megahertz, theoretical calculations and simulations are often insufficient. The matching task is required for a proper transfer of signal and energy from a 'source' to a 'load.'Īt high radio frequencies, the spurious elements (like wire inductances, interlayer capacitances, and conductor resistances) have a significant yet unpredictable impact on the matching network. Typically these include the antenna to the low-noise amplifier (LNA), power-amplifier output (RFOUT) to the antenna, and LNA/VCO output to mixer inputs. One is the need to match the different impedances of the interconnected blocks. When dealing with the practical implementation of RF applications, there are always some nightmarish tasks. Tried and true, the Smith chart is still the basic tool for determining transmission-line impedances.
A sample matching network of the MAX2472 is designed at 900MHz using graphical methods.
Examples are shown plotting reflection coefficients, impedances and admittances.
Tutorial on RF impedance matching using the Smith chart.
