Impedance matching can be done by using a broadband as well as a narrowband solution. In case of a narrowband and frequency dependent matching solution, one can make use of reactive components (capacitors and inductors).
A very useful tool in WinRFCalc is the L-Match calculator.
In case you are required to create a broadband matching network, the solution can only be found by making use of resistors. In resistive matching network designs, there are no inductive and/or capacitive components, making the matching network inherently broadband and frequency independent.
When the source and load impedance to be matched are known you can easily make use of the resistive attenuator calculator, otherwise when you only know the VSWR you have to improve than the VSWR improvement calculator is your tool.
You can select the appropriate calculator through the attenuator switchboard you see below.