Coupling Factors for Directional couplers:

In general Directional Couplers are provided with the manufacturer's plots across the frequency spectrum for which the Directional coupler is specified. These plots, although very accurate, usually only identify a single measurement of the coupling factor at one specific frequency; therefore calculations are necessary to ascertain the coupling factor at another frequency. The calculations are only accurate within the linear operating frequency spread of the Directional Coupler. An example of a manufacturer's Directional Coupler plot is show above. By clicking here you can open an Excel spreadsheet and by entering the manufacturer's measured Coupling Factor and the associated frequency and then inputting the new frequency of interest the Coupling Factor at this frequency can be calculated. Please note that the calculated Coupling Factor is generally more accurate than can be achieved by bench testing the unit where local interferences could influence or compromise the test environment.